Ch 96 hepatic vascular anomalies Flashcards
List the tributaries of the portal vein from caudal to cranialList the tributaries of the portal vein from caudal to cranial
- Mesenteric veins (drain the intestines and form the cranial mesenteric vein)
- Caudal mesenteric vein
- Splenic vein (with left gastric vein)
- Gastroduodenal vein (dogs)
Portal Vein
- portal vein divides into right and left portal branches
- right portal vein: caudate and the right lateral liver lobe
- left portal vein: left medial and lateral and quadrate
- central portal vein(from left branch) to the right medial lobe
In cats the portal vein divides into right, central, and left branches.
Hepatic Artery
- right lateral, right medial, and left branches. The presence of additional branches varies
- In another 50% of dogs the right medial branch arises from the left hepatic artery and supplies only the right medial lobe
How many hepatic veins do dogs usually have?
Which is the largest?
5-8 hepatic veins
The left hepatic vein is the largest and most cranial
drain into the abdominal portion of the caudal vena cava
Embryology
The abdominal venous system originates from umbilical, vitelline, and cardinal veins during embryonic development.
Vitelline veins:
- Carry blood from the yolk sac to the embryonic heart.
- They form a venous plexus > hepatic sinusoids.
- right vitelline vein > caudal vena cava
- left vitelline vein atrophies.
- anastomoses between vitelline veins form the portal vein.
Umbilical veins:
- Carry blood from the allantois to the sinus venosus.
- left umbilical vein channel for placental blood to the liver,
- most blood bypasses the liver directlt to heart via the ductus venosus, a shunt connecting it to the right vitelline vein.
Cardinal veins:
- Three pairs (caudal, subcardinal, and supracardinal) contribute to caudal vena cava.
- supracardinal veins > azygos and hemiazygos veins.
What embryonic vessels give rise to:
- The hepatic sinusoids
- Hepatic portion of the vena cava
- Portain vein
The vitelline vessels
What is the ductus venosus?
A venous shunt between the left umbilical vein and the cranial segment of the right vitelline vein (which become the hepatic vena cava)
Portocaval and Portoazygos Shunts
- Developmental errors > abnormal connections between the cardinal and vitelline systems = extrahepatic portocaval and portoazygos shunts
- Extrahepatic and right or central intrahepatic portocaval shunts may result from persistent connections
- Theory; toy breeds shunts results from concurrent portal microvascular underdevelopment that increases intrahepatic portal resistance, forcing vestigial anomalous vessels to remain open
Patent Ductus Venosus
- ductus venosus is a fetal blood vessel that connects the umbilical vein to the portal sinus, allowing blood to bypass the liver.
- it originates opposite the umbilical vein and ends at the left hepatic vein.
Closure after Birth:
- Normally functionally closes 2-6 days after birth and undergoes structural closure within 3 weeks.
- Delayed closure > Irish Wolfhounds, 65% patent at 4 days old, though all had closed by day 9.
- Hemodynamic factors, such as reduced umbilical venous flow, likely influence closure.
Mechanisms of Closure:
- Smooth muscle contraction, driven by endothelin, cytochrome P-450, thromboxane A₂, and prostaglandins, regulates closure.
- Corticosteroids and indomethacin can accelerate closure in infants.
Persistent Ductus Venosus:
- unknown cause
- from increased sinusoidal pressure due to congenital portal hypoplasia
- chemical imbalances affecting endothelin.
What are the three broad categories of hepatic vascular disease?
- Congenital PSS
- “primary hypoplasia of the portal vein” PVH (PVH with portal hypertension and PVH without portal hypertension. PVH without portal hypertension was previously termed microvascular dysplasia)
- Disturbances in portal outflow
PSS
Portosystemic shunts can either be congenital or acquired in nature
Congenital Portosystemic Shunts
- commonly occurs as a single intrahepatic or extrahepatic vessel that provides direct vascular communication between the portal venous supply and the systemic venous circulation (caudal vena cava or azygos veins)
- 66% to 75% of congenital single PSSs are extrahepatic.
- intrahepatic PSSs are found in larger breed dogs, most extrahepatic PSSs are seen in smaller breeds
- spleno-caval, left gastro-phrenic, left gastro-azygous and right gastric vein account for 94%
- portocaval, portoazygous, cranial mesenteric, caudal mesenteric to caudal vena
Acquired Portosystemic Shunts
- (20%) most commonly occur secondary to chronic portal hypertension; increased portal pressures result in opening of vestigial fetal blood vessels.
- also cirrhosis, PVH with portal hypertension , and arteriovenous malformations
- means for handling the increase in hydrostatic pressure present
- usually multiple, tortuous, and extrahepatic
- connect a portal tributary directly to the renal vein or the caudal vena cava near the kidneys,
Where do acquired shunts most commonly enter the systemic circulation?
What are some causes of acquired shunts?
At the renal vein or the vena cava near the renal vein
Causes:
- Hepatic fibrosis
- PVH with portal hypertension
- Hepatic AV malformations
What % of dogs and cats with PVH-MVD have a concurrent congenital PSS?
Dogs 58%
Cats 87%
What breeds are overrepresented for PVH-MVD?
Cairn terrier, Maltese, Yorkie
Portal Vein Hypoplasia
PVH with hypertension
- characterized by intraabdominal portal hypertension, a patent portal vein, and a lack of cirrhosis on liver biopsy.
- underlying cause unknown > speculated intrahepatic microscopic vascular malformation
Primary hypoplasia of the portal vein without portal hypertension (PVH-MVD)
- microscopic malformation of the hepatic vasculature
- characterized by small intrahepatic portal vessels, often associaed with some fibrosis
- occur as an isolated disease or with congenital PSS
Hepatic Arteriovenous Malformations
- multiple high-pressure arterial and low-pressure venous communications are present within the liver
- usually congenital in nature.
- Typically a branch of the hepatic artery communicates directly with the portal vein(tens to hundreds)
- high-pressure system that causes hepatofugal blood flow and arterialization of the portal vein.
- multiple extrahepatic shunts open to decompress the portal system.
Pathophysiology
Hepatic Encephalopathy
- occurs when more than 70% of liver function is lost
- pathogenesis largely unknown and quite complex
- altered liver cannot perform its role in metabolism or substance clearance, permitting toxic substances to enter the systemic circulation
- > 20 different compounds found in excess in the circulation when liver function is impaired, including ammonia, aromatic amino acids, endogenous benzodiazepines, gamma-aminobutyric acid (GABA), glutamine, short-chain fatty acids
- substances may
1. impede neuronal and astrocyte function, causing cell swelling,
1. inhibition of membrane pumps or ion channels
1. elevation in intracellular calcium concentrations,
1. depression of electrical activity,
1. and interference with oxidative metabolism
1. altered permeability of the blood-brain barrier
Clinical signs
- variable, most suggestive of neuroinhibition.
- Excitatory activity such as seizures, aggression, and hyperexcitability also occur
list compounds found in excess in the circulation when liver function is impaired (7)
more than 20 identified…
- ammonia (decreases ATP availability; increases neuronal and cellular excitability; increases glycolysis; can cause brain edema)
- aromatic amino acids (Decrease dopamine neurotransmitter synthesis; alter neuroreceptors)
- endogenous benzodiazepines (Neural inhibition through hyperpolarization)
- gamma-aminobutyric acid (GABA) (Neural inhibition by hyperpolarizing)
- glutamine (Alters BBB amino acid transport)
- short-chain fatty acids (Decrease microsomal Na+,K+-ATPase in brain)
- Bile acids (alter cell membrane permeability; make BBB more permeable to others)
BASEGAG
Ammonia
- trigger a sequence of metabolic events
- produced by gastrointestinal flora
- converted in the normal liver to urea and glutamine by the urea cycle.
- excitotoxic and associated with an increased release of glutamate (excitatory neurotransmitter).
- Overactivation of the glutamate receptors, (NMDA), has been implicated as one of the causes of hepatic encephalopathy–induced seizures
- chronic liver impairment in PSS, results in alterations in neuronal responsiveness and energy requirements
- Treatments that decrease ammonia concentrations, seem to reduce signs of hepatic encephalopathy.
- Ammonia concentrations do not always correlate with signs > suggesting that other suspected neurotoxins are also very important in the pathophysiology
Coagulation Disorders
- Coagulation abnormalities in patients with liver failure are multifactorial, depending on the interaction of the coagulation, anticoagulation, and fibrinolytic systems.
- Spontaneous hemorrhage is uncommon
- Suggested causes of coagulopathy in liver failure include decreased factor synthesis, increased factor utilization, increased fibrinolysis and tissue thromboplastin release, synthesis of abnormal coagulants (dysfibrinogenemia), decreased platelet function and numbers, vitamin K deficiency (particularly in bile duct obstruction), and increased production of anticoagulants
- Approximately 43% of the dogs with congenital PSS had hypercoagulable thromboelastography results
What breeds are predisposed to exhepatic PSS?
Yorkies, Norweigan Terrier, Havanese, Maltese, Dandie Dinmont Terrier, Pugs, Min Schnauzer
commonly seen in small- or toy-breed
Intrahepatic PSS is overrepresented in larger breed dogs
irish Wolfhounds, retrievers (Labrador, Golden), Australian Cattle Dogs, and Australian Shepherds
What genes have been detected to have an increased expression in intrahepatic and extrahepatic shunts?
Intra: WEE1
Extra: VCAM1
What breed is represented for PVH with hypertension accounting for 27% of cases?
Doberman
Cairn Terriers and yorkies for PVH-MVD
History
- single congenital PSS present with signs of chronic or acute illness at a young age (1 month to 2 years)
- Multiple acquired extrahepatic shunts and PVH-MVD are usually diagnosed in older animals
- “failure to thrive” since birth
- intermittent episodes of dullness, lethargy, or “bizarre” behaviors (41% to 90%; including stargazing, head pressing,
- history of anesthetic intolerance
- history of dysuria (20% to 53%)
- polyuria and polydipsia
- Abdominal effusion is seen in 75% of dogs with hepatic arteriovenous malformations
polyuria and polydipsia potential causes
- poor medullary concentration gradient because of low blood urea nitrogen (BUN) concentration,
- increased renal blood flow,
- increased adrenocorticotropic hormone (ACTH) secretion with associated hypercortisolism,
- psychogenic polydipsia
Clinical Signs and Examination Findings
Portosystemic Shunts
- clinical signs are milder in dogs with portoazygos or portophrenic shunts. These shunts are likely compressed by the diaphragm during respiration or with gastric distention after meals, resulting in improved portal perfusion
- shunts that inserted caudal to the liver were more likely to result in clinical signs
central nervous system
- lethargy, ataxia, unresponsiveness, pacing, circling, blindness, seizures, and coma.
gastrointestinal
- vomiting, diarrhea, anorexia, pica, and, gastrointestinal bleeding
- Preoperative gastrointestinal hemorrhage, may occur in 30% of large-breed dogs with intrahepatic PSS
- Ptyalism is extremely common in cats (75%)
urinary systems
- present with signs of lower urinary tract disease
- formation of ammonium urate calculi are common and can be associated with secondary bacterial urinary tract infections
- calculi were documented in up to 36%
- Glomerular filtration rate (GFR) and renal volume are increased in 81%
congenital defects
- Cryptorchidism
- heart murmurs
- Copper-colored irises inappropriate for the breed
Clinicopathologic Findings
- microcytic, normochromic, nonregenerative anemia
- hypoalbuminemia (50%),
- reduced BUN (70%),
- hypocholesterolemia
- hypoglycemia
- Mild to moderate increases in serum liver enzyme activities (uncommon values >4x the high end of the reference)
- ammonium biurate crystalluria
- hyposthenuric or isosthenuric
- bladder stones 30-36%
- Hyperammonuria from the deficient hepatic urea cycle + hyperuricacidemia from a deficiency uric acid cycle > excessive ammonia and urate excretion by the kidneys.
- These compounds can precipitate into crystals or stones in the kidney or bladder
Liver Function Testing - BA
suggestive; however, no blood tests are definitively diagnostic
- Bile acids are produced in the liver, stored in the gallbladder, released into the intestines for fat digestion, and then reabsorbed and recirculated.
- Their levels are influenced by gallbladder contraction, intestinal transport, and liver function.
- In PSS, bile acid levels remain persistently high due to improper circulation.
- Increased postprandial bile acids are highly sensitive indicators of PSS, but variations exist (can be up to 100% sensitive)
- Some animals show elevated levels without liver disease, such as Maltese dogs
- False positives can occur due to liver disease, certain medications, or gastrointestinal disorders,
- false negatives may result from delayed intestinal absorption, gallbladder dysfunction, or maldigestion.
liver function - ammonia
- when bile acid results are inconclusive
- Blood ammonia originates from the gastrointestinal tract and is converted into urea by the liver.
- conversion is impaired, leading to increased ammonia levels.
- Baseline ammonia levels are less sensitive 62-88% of PSS cases.
- False positives and negatives occur
- Sensitivity improves with postprandial ammonia testing.
ammonia tolerance test
- administering ammonium chloride and measuring the body’s ability to clear it
- highly sensitive (95-100%) for PSS
- should be avoided in animals with already high ammonia levels.
- Ammonia test results are influenced by diet, handling, and lab processing.
What is the sensitivity of the ammonia tolerance test for hepatic insufficiency?
85-100%
preoperative hyaluronic acid concentrations
- significantly higher than those of healthy Beagle dogs
- suspected mechanism of preattenuation increase was reduced hepatic clearance secondary to poor intrahepatic portal blood flow, which improves after shunt closure
- may be useful in evaluating successful attenuation of congenital PSS
PT or activated partial thromboplastin time (aPTT)
- loss of approximately 65% to 80% of factors needs to occur before prolongation in PT or activated partial thromboplastin time (aPTT) results.
- spontaneous bleeding is very rare
- prolonged aPTT (>20 seconds)
- prolonged PT (>9 seconds).
histopathology
- most common include bile duct proliferation, hypoplasia of intrahepatic portal tributaries, hepatocellular (lobular) atrophy, arteriolar proliferation or duplication, lipidosis and cytoplasmic vacuolar changes
- histologic features associated with a poor prognosis included fibrosis, biliary hyperplasia, and necrosis.
- Significant histologic improvement is not expected in dogs or cats that undergo partial attenuation of congenital PSS, even if those animals improve clinically
- Dogs with noncirrhotic portal hypertension often have more significant fibrosis extending into the parenchyma, particularly along the portal tracts or even bridging to other portal areas or central veins
Diagnostic Imaging
Abnormalities on survey abdominal radiographs that are suggestive of, but not diagnostic for, PSS include microhepatia (60% to 100% of dogs and 50% of cats with PSS) and bilateral renomegaly.
Abdominal Ultrasonography
- detecting radiolucent uroliths in dogs and cats
- ecreased number of hepatic and portal veins, a subjectively small liver, and an anomalous vessel
- Extrahepatic shunts are more difficult to diagnose than intrahepatic PSS
- Multiple extrahepatic shunts are even harder to find and are typically located near the left kidney.
- variation in reported accuracy
- sensitivities 68% to 95%
- specificity 67% to 100%
- operator and experience dependent.
- color-flow and pulse-wave Doppler imaging may detect changes in flow direction
- extrahepatic PSSs have hepatopetal flow through the portal vein
- Ultrasound-guided percutaneous splenic injection of agitated saline > microbubbles
Scintigraphy
- (99mTc mebrofenin) and using transcolonic or transsplenic administration
- If a PSS is present, radioisotope often reaches the heart within 4 seconds after administration
- 100% sensitive and specific for diagnosis of shunting
Computed Tomographic Angiography
and MRI and portovenogram
- gold standard
- noninvasive, fast, and accurate
- Dual-phase computed tomographic angiography provides a complete evaluation of portal and hepatic vasculature
- valuable for preprocedural planning
- provided information about various tributary vessels that could be overlooked during surgical exploration
MRI
- magnetic resonance angiography provides a three-dimensional, preoperative image of the shunt
- more expensive than good CT
Portovenography
- Operative mesenteric portography
- at the time of laparotomy with a portable fluoroscope (C-arm).
- Sensitivity 85%, 91%, and 100% in dorsal, right lateral, and left lateral recumbency
- improved with use of digital subtraction
Differential Diagnoses
hypoglycemia,
hydrocephalus,
atlantoaxial subluxation,
idiopathic epilepsy,
gastrointestinal parasitism, hypoadrenocorticism,
protein-losing enteropathy
primary hepatopathies
Medical Management
Bacterial translocation or decreasing bacterial byproduct absorption (ammonia)
- Cleansing enemas
- Oral lactulose: 0.5–1.0 mL/kg PO q6-8hr (results in entrapment of luminal ammonia in the form of ammonium and a decrease in colonic bacterial numbers)
- ab?
Coagulopathy (symptomatic; postoperative)
- Fresh frozen plasma: 10–15 mL/kg over 2–3 hr
- Vitamin K1: 1.5–2.0 mg/kg SC
Gastrointestinal ulceration (intrahepatic, AVM)
- Omeprazole: 1.0–2.0 mg/kg/d PO
Seizure control
- Benzodiazepines (controversial) > Diazepam is not recommended for animals with hepatic encephalopathy or other causes of liver failure
- Phenobarbital (16 mg/kg IV divided into four doses for loading over 12–24 hr). Maintenance: 20–30 mg/kg/d PO
- Propofol: 0.5–1.0 mg/kg IV bolus; CRI at 0.05–0.1 mg/kg/min (controversial)
- Keppra: 20 mg/kg (≤60 mg/kg) PO or IV every 8 hr (there is limited evidence to support this)
Decrease cerebral edema
- Mannitol: 0.5–1.0 g/kg bolus over 20–30 min
Nutritional support
- Moderate protein restriction: 18%–22% for dogs and 30%–35% for cats
Hepatoprotective therapy
- chronic conditions that are unable to be fixated [e.g., MVD]
- SAMe: 17–22 mg/kg/d PO (hepatoprotective, antioxidant, and antiinflammatory properties)
- Ursodeoxycholic acid: 10–15 mg/kg/d
Glucose should be supplemented in intravenous fluids
Prognosis With Medical Management Alone
- varied outcomes.
- Some dogs developed progressive liver fibrosis.
- In a study of 27 dogs, MST 9.9 months, with intrahepatic shunts having worse outcomes. 51.8% euthanized within a year (encephalopathy).
- Dogs with extrahepatic PSS had better survival
- Another study of 27: 89% medically treated died (median survival >2.3 years), compared to 21.6% of surgically treated dogs (MST not calculated).
- Long-term prognosis is generally better for dogs with primary portal vein hypoplasia (PVH-PVD), with 92% surviving
surgery remains the preferred treatment for congenital PSS when feasible.
Beardall 2023 – surgical ligation vs medical management for CEPSS
complete ligation 46/64 (71.9%) → 16/20 (80.0%) complete resolution of clinical signs
vs 4/10 (40.0%) partial attenuation
- complete ligation → longer MST (not reached) vs medical (1730d)
- PANS in 1/64 – minor, self-resolving
- portal hypertension 5/62 (8.1%): 2/16 (12.5%) partial, 3/46 (6.5%) complete ligation
- 1/2 partial ligation with portal hypertension euthanased
- outcome: good-excellent 20/20 (100%) complete, 9/10 (90.0%) partial, 19/32 (59.3%)
medical
Wallace 2022 – surgical attenuation → better long term outcome vs medical for dogs ≥5y old
JAVMA
survival time longer with surgical attenuation
- 7.3% peri-op mortality
- shorter survival associated with: non-sx, HE at dx, higher neutrophil count
- medical management → more common continued clinical signs and medical tx
Serrano 2022 – diet, lactulose and metronidazole combinations for control of pre-sx clinical signs
- diet + lactulose → decreased clinical scores – not seen with diet alone or diet + metro
- addition of metro → no additional benefit
- medical management → decreased fasting ammonia
Preoperative Medical Stabilization
- cachectic, encephalopathic, or unstable should be managed medically before sx (min. 2 weeks)
- treat hypoalbuinaemia
- preoperative anticonvulsant therapy remains a debated topic (retrospective study with levetiracetam, no seizure post op when give > controlled studies are needed)
- generalized seizures that are not controlled by routine medical management should be placed on phenobarbital
anaesthetic
- avoid agents metabolized by the liver, highly protein bound, or hepatotoxic
- opiod (remifentanyl)
- propofol
- Hypothermia should be anticipated
- CVC ideal
How much plasma is required to increase albumin by 1g/dL?
45ml/kg
Surgical Treatment for Congenital Portosystemic Shunts
single congenital PSS
- partial or complete acute occlusion with ligatures or more gradual attenuation with ameroid constrictors, cellophane bands, or hydraulic occluders.
- Most animals will not tolerate acute complete occlusion
- Gradual attenuation is preferred to reduce the risk for postoperative complications
- should be attenuated as close to their insertion sites as possible so that blood flow from all tributaries of the shunt is redirected
- diaphragm may be opened if more exposure is needed
- portal vein lies within the mesoduodenum ventral to the hepatic artery and is identified by retracting the duodenum to the left.
What options are there if you cannot find the shunt vessel in surgery?
Intraop mesenteric portovenography
Portal catheterisation
Intra-op Doppler ultrasound
Extrahepatic Portocaval Shunts
- often terminate on the caudal vena cava cranial to the renal veins at the level of the epiploic foramen
- epiploic foramen can be exposed by gently retracting the duodenum ventrally and to the left.
- In normal: no large vessels entering the caudal vena cava between the right renal and hepatic veins
- Rarely located within the caudal abdomen (e.g., colonocaval shunts)
Gastrophrenic or splenophrenic shunts
- travel along the lesser or greater curvature of the stomach and ventral surface of abdominal portion of the esophagus
- become enveloped in the fascia transversalis of the diaphragm’s central tendon
Portoazygos Shunts
- usually traverse the diaphragm along its crura at the aortic hiatus or through the esophageal hiatus
- may be necessary to enter the omental bursa by tearing through the ventral leaf
- stomach is retracted cranially
- examine the dorsal bursal recesses for abnormal vessels that penetrate the diaphragmatic crura.
Multiple Acquired Portosystemic Shunts
commonly seen near the kidneys and within the intestinal mesentery but can occur anywhere in the abdomen
What is a normal baseline portal pressure?
8-13cmH2O (6-10mmHg)
Degree of shunt attenuation:
- max portal pressure 17-24cmH2O (12.5-17.6mmHg)
- max change in portal pressure 9-10mmH2O (6.6-7.35mmHg)
- max decrease CVP 1cmH2O, (0.74mmHg)
Measuring Portal Pressure
Operative Mesenteric Portography
- When a shunt cannot be located during surgery
- Before abdominal closure the surgeon should obtain a liver biopsy sample to rule out other hepatic diseases
- Overdose of iodinated contrast materials can lead to hypotension, arrhythmias, cardiac arrest, and contrast-induced renal failure
- Identification of congenital PSS with operative mesenteric portography depends on patient positioning
- Some clinicians use operative mesenteric portography to evaluate intrahepatic portal development. A portogram is obtained before surgical attenuation and during complete temporary occlusion
- the absence of arborizing intrahepatic vasculature on preligation portograms was correlated with a greater occurrence of postoperative complications
What is the maximum amount of contract that can be used during mesenteric portvenography?
1200mg iodine/kg
Overdose - hypotension, arrhythmias, cardiac arrest, renal failure
Ameroid Constrictors
- inner ring of casein surrounded by stainless steel sheath.
- Casein = hygroscopic substance that swells as it slowly absorbs body fluid, reducing the ring’s internal diameter by 32%.
- stimulates a fibrous tissue reaction that causes gradual shunt occlusion within 2 to 5 weeks after placement.
- attenuation is most rapid during the first 3 to 14 days
- thrombus formation could result in more rapid obstruction of partially attenuated shunts
- size based on shunt diameter; preferably internal diameter larger than the shunt (5-9mm
- gas sterilized and therefore should not be used until 12 to 24 hours after sterilization to allow residual ethylene oxide to be released from the casein
- Measurement of portal or central venous pressures is unnecessary with ameroid constrictor placement as long as the shunt has not been attenuated at the time of surgery.
Cellophane Bands
- from regenerated cellulose or from thin films made of polyester or olefin
- reports rarely define the material with which the bands are made, making comparison of postoperative results difficult.
- 1 × 10-cm strip is folded longitudinally into thirds
- securing the ends together with three or four large surgical clips placed from alternating directions
- cellophane bands cause fibrous tissue reaction and gradual shunt occlusion
- used to attenuate shunt to less than 3 mm in diameter, complete occlusion was demonstrated in dogs and cats that underwent cellophane banding without intraoperative attenuation
- Synthetic materials used to make the thin film bands in these later studies may cause greater inflammatory reaction
- reduced inflammatory response in cats
Real cellophane has a microscopic fiber pattern with striations, will burn like paper. There is no bubbling, blistering or melting
Hydraulic Occluders
- silicone and polyester cuff connected by tubing to a vascular access port
- small amount of sterile saline is injected through the port every 2 weeks
- closure not depend on fibrous tissue formation
Suture Ligation
- Nonabsorbable synthetic monofilament (e.g., polypropylene) is recommended in cats because of the risk for shunt recanalization
- Failure of silk suture has also been reported in a dog
- shunt is temporarily occluded with a Rumel tournique > evaluated for evidence of portal hypertension
- rapid increase in portal pressure of at least 4 cm H2O.
- If necessary, a portogram can be performed to verify
- a surgeon’s throw is tied on the ligature, and the ligature is gradually tightened. With each incremental decrease in shunt diameter, the animal is evaluated
if revision required
- leave a polypropylene suture with long ends
- At that time the suture is elevated, and hemostatic clips are placed across the two ends to compress the shunt while portal pressures are evaluated.
- obviates the need for dissection around the vessel.
Determining the Degree of Shunt Attenuation
- Nonencephalopathic dogs can often tolerate complete shunt ligation
- up to 86% of animals require partial attenuation
- A second surgical procedure to occlude a partially ligated shunt is therefore not recommended unless clinical signs reoccur.
portal and central venous pressures
- maximum portal pressure of 17 to 24 cm H2O (12.5 to 17.6 mm Hg), maximal change in portal pressure of 9 to 10 cm H2O (6.6 to 7.35 mm Hg),
- maximal decrease in central venous pressure of 1 cm H2O (0.74 mm Hg)
- arterial pressure maximum of 5 mm Hg or 15% or less, and the heart rate should not increase dramatically
- not be used as the sole criteria for degree of shunt attenuation because blood pressures may vary with the depth of anesthesia, hydration status
visual inspection
- pallor or cyanosis of the intestines
- increased intestinal peristalsis,
- cyanosis or edema of the pancreas
- increased mesenteric vascular pulsations.
what % of dogs does liver function return to normal after a single partial ligation?
70%
What are the broad options of treatment of an intrahepatic shunt?
- Extravascular ligation (usually of shunt or draining hepatic vein, occassionally of feeding portal branch) > under ultrasonic guidance, To improve exposure of the vessels, the surrounding parenchyma can be removed with suction
- Intravascular ligation (not really one anymore)
- Intravascular coiling
Shunts of the Left Division: Extravascular Approach
- left hepatic vein is responsible for draining the left hepatic division.
- Shunts often appear as dilated vessels between the left lateral and medial liver lobes.
- treated by ligating the shunt or the hepatic vein.
- Complete ligation of the left hepatic vein may cause temporary hepatic congestion but does not have long-term effects on hepatic function in healthy dogs.
- If the shunt or hepatic vein is not identifiable, attenuation of the left portal vein branch may be necessary.
Surgical Dissection Approach:
- transecting the left triangular ligament.
- left hepatic vein is usually visible where it meets the caudal vena cava, but the rest is surrounded by hepatic tissue.
- Tissue removal may be done by crushing or suctioning
- forceps are used to apply sutures or constriction devices like a cellophane band or ameroid constrictor.
- If the vessel is too short or thick, an ameroid constrictor may not be feasible.
Dissection of the Ductus Venosus:
- ductus venosus is typically found between the left lateral liver lobe and the caudate lobe before entering the left hepatic vein.
- or through the left lateral liver lobe.
- Dissection involves transecting the left triangular ligament
- The terminus of the ductus venosus is bluntly dissected near its entry into the left hepatic vein
Dissection of the Left Portal Vein:
- left liver lobes are retracted cranially to expose the hilus (medial and lateral separated)
- If the lobar hepatic artery and biliary duct obstruct, double-ligate and transect
- Dissection of the left lateral portal vein branch may require cutting through the hepatoduodenal ligament.
- A peritoneal window is created over the portal branch
Shunts of the Right Division: Extravascular Approach
- Right divisional shunts are usually detected by identifying the enlarged portal vein branch and by palpation of a soft, compressible area within the affected liver lobe
- Most hepatic veins of the central and right divisions are completely encompassed within hepatic tissue > shunts of these divisions are often treated surgically by ligation of the supplying portal vein branch or by intravascular techniques.
Indirect Suture Passage
- If the right portal vein branch cannot be directly dissected safely, a suture can be passed around it indirectly by dissection of the main and left portal veins
Shunts of the Central Division: Extravascular Approach
- portal vein branch supplying the shunt is often too close to the main or left portal vein to permit dissection.
- surgical repair is usually limited to intravascular approaches.
- Because these are fraught with potential complications, referral for intravascular coiling is preferred.
Intravascular Approaches
- liver can tolerate up to 20 minutes of blood flow occlusion
- practically limited to 10 to 15 minutes to avoid effects of prolonged hypotension and intestinal ischemia
Postoperative Management After Portosystemic Shunt Attenuation
- maintained on intravenous fluids
- blood glucose
- monitored for hypoglycemia, hypothermia, delayed anesthetic recovery, hemorrhage, seizures, and signs of portal hypertension.
- A protein-restricted diet and lactulose are continued after surgery until liver function improves.
- Frequently animals can be weaned off lactulose within 4 to 6 weeks.
- Bile acids and a biochemical panel are evaluated 2 to 3 months after the surgery.
- function is normal, medical management is discontinued> slowly weaned over 2 to 3 months after surgery, removing one treatment at a time (antibiotics, then lactulose, then diet)
- In many patients, bile acid concentrations do not return to reference ranges (<10 µmol/L and <15 µmol/L for preprandial and postprandial samples, respectively); therefore assessment may be based on clinical response
- moderately increased, medical management is continued, and animals are rechecked 5 to 6 months after surgery
- Normalization of bile acid not correlated with long-term outcome
- persistently increased bile acid concentrations ok as long as routine biochemical parameters improve and clinical signs are well controlled
What are the reported post-op complications (11)?
- Hypogylcaemia 44%, 29% of which are refractory to dextrose
- Haemorrhage and anaemia
- Portal hypertension 2-14% with acute ligation
- Seizures and encephalopathy 3-18% dogs, 8-22% cats
- thrombus
- arrythmia
- peritonitis,
- bacterial hepatitis,
- sepsis
- sudden death
- recurrence of clinical signs
Hypoglycemia
- reported in 44% of dogs
- Toy breeds are most commonly affected. Initial treatment should include intravenous boluses of 25% to 50% dextrose and initiation of oral
- 29% of affected dogs, hypoglycemia is refractory to intravenous dextrose
Hemorrhage and Anemia
- Intraoperative and postoperative hemorrhage are uncommon
- acute anemia can be seen postoperatively in dogs
- Changes in coagulation usually do not cause clinical bleeding and normalize after shunting resolves and liver function improves
- Portal hypertension may result in hemorrhage because of gastrointestinal or incisional bleeding.
- use of gastroprotectants postoperatively, particularly in patients that have undergone intrahepatic shunt attenuation.11,125 Use of lifelong antacid therapy (omeprazole 0.5 to 1.5 mg/kg/d) in dogs with intrahepatic PSS
Portal Hypertension
- 2% to 14% of patients undergoing acute suture ligation
- less common in patients undergoing gradual shunt occlusion
- Portal hypertension can be exacerbated by overhydration, vocalization, defecation, and large meals
Clinical signs
- hypovolemic shock
- abdominal pain,
- abdominal distention (ascites)
- diarrhea or vomiting
tx
- supported with oxygen, warmth, intravenous crystalloids
- omeprazole
- analgesics,
- systemic antibiotics.
- evaluated for hypotension and DIC
- clotting times are prolonged, fresh frozen plasma or fresh whole blood
- Ligature removal immediately with severe clinical signs > DIC or nonresponsive hypotension.
- Spironolactone or furosemide for chronic ascites
- ascites may be a precursor of multiple acquired shunt formation
Seizures and Encephalopathy
- 3% to 18% of dogs and 8% to 22% of cats
- Seizures may occur up to 80 hours after surgery and are not associated with hypoglycemia, hyperammonemia, or attenuation technique
- Lethargy, facial twitching, ataxia, muscle fasciculation, blindness, and abnormal vocalization are often apparent before generalized seizure activity.
cause
- unknwon
- decreases in endogenous inhibitory central nervous system benzodiazepines agonist levels or imbalances in excitatory and inhibitory neurotransmitters
tx
- Hypoglycemia and electrolyte disorders should be ruled out
- midazolam or diazepam (0.5 mg/kg IV).
- Levatiracetam,
- Phenobarbital, because of its lower lipid solubility, may take up to 30 minutes to reach therapeutic concentrations
- propofol (4 to 8 mg/kg) and maintained under anesthesia on a propofol continuous rate infusion (0.1 to 1.0 mg/kg/min)
- Intravenous levetiracetam and rectally instilled lactulose are continued.
- Mannitol (1 g/kg over 20 minutes) is administered intravenously every 6 hours to reduce intracranial swelling.
- Partial or total parenteral nutrition
- propofol is discontinued after 12 to 24 hours > trial
- some animals may require 72 hours of anesthesia to resolve seizure activity
- In general, half of affected dogs die or are euthanized and those that survive often continue to have visual deficits and other neurologic problems for weeks to years.
What other derangement can occur with post-op hypoalbuminaemia?
Hyponatraemia - cause unknown
What are potential causes of recurrence or persistence of clinical signs post-attenuation (5)?
Continued flow through original shunt
Presence of a second shunt
Multiple acquired shunts
Congenital PVD
Unrelated disease
Animals with clinical signs or biochemical changes should have repeat imaging. Surgical intervention is recommended for patients with a second congenital shunt or clinical signs related to persistent flow through the original shunt.
What are the reported periop mortality rates for extrahepatic PSS?
Intrahepatic?
Extrahepatic:
- Suture: 2-32%
- Ameroid: 7%
- Cellophane: 6-9%
- Good-to-excellent outcome in 78-94%
Intrahepatic:
- Suture: 6-23%
- Ameroid: 0-9%
- Cellophane: 27%
- Probability of long term survival withou recurrence 60-61% at 1yr, 55-56% at 2-4yr
most common death within 1 month is severe persistent neurologic signs
long-term outcomes
Comparing long-term outcomes is difficult because of variations in follow-up times and standards for satisfactory outcome
- good to excellent outcomes were noted in 78% to 94%
- Most dogs continued to have mildly increased bile acid concentrations.
- Outcomes are better in patients that undergo complete shunt attenuation.95 In one study, 35% of animals were euthanized an average of 43 months after partial shunt ligation because of clinical recurrence of signs
- Some dogs that have undergone partial ligation cannot tolerate complete ligation in a subsequent surgery because of portal hypertension
- Good to excellent outcomes were noted in 70% to 89% of dogs with intrahepatic portosystemic shunts that underwent ameroid constrictor placement, 76% to 100%
Predicting Outcome Based on Preoperative or Postoperative Findings
- Anaemia - poorer long-term outcome
- Increased BUN assoc with a decreased short-term survival
- Increased WBC/neutrophils assoc with decreased survival and unsuccessful long-term outome
- Higher pre-op albumin and TP assoc with better short term survive for intrahepatic PSS
- Extrahepatic ameroid: for every decreased in albumin by 1g/dL, odds of continued shunting increased 3.76 times. For every increase of albumin by 1, odds of unsuccessful outcome decreased by 0.4times
- Breeds not predisposed to shunts are more likely to have unusual or inoperable shunt
- Nonencephalopathic dogs can often tolerate complete shunt ligation
Degree of Shunt Attenuation
- portal pressures before ligation and during temporary occlusion and change in portal pressure after ligation were not correlated with long-term outcome
- those that tolerate complete acute ligation usually have a better outcome and are less likely to develop multiple acquired shunts
- some studies show no difference in the long-term outcome when comparing complete and partial ligation
What is the perioperative mortality and prognosis in cats?
Ameroid: 0-4.5% mortality
Cellophane: 0-22%
Suture: 4-20%
Good-to-excellent outcome in:
- Ameroid: 33-75%
- Cellophane: 57-80%
- Suture: 56-75%
Generalised seizures in 8-28% and central blindness in up to 44% (usually resolves within 2 months)
What % of dogs will have AV malformations in 2 lobes?
20 %
most often found in the right or central divisional lobes
Surgical Treatment of Hepatic Arteriovenous Malformations
- Multiple acquired extrahepatic PSSs are also evident
- surgical treatment of hepatic arteriovenous malformations is resection of the affected lobe
- Some authors recommend preplacement of Rumel tourniquets for temporary inflow occlusion
- If the appropriate artery has been occluded, portal pressure should decrease.
Complications
- hemorrhage,
- portal hypertension,
- systemic hypotension,
- bradycardia,
- thrombus formation.
What pertreatment is required prior to ligation of hepativ AV malformation?
Pretreatment with atropine or glycopyrrolate to prevent reflex bradycardia (Branham reflex)
What is the prognosis for hepatic AV malformations?
- Perioperative survival 75-91%
- Long-term outcome fair or good in 38-57%
- 75% continue to require dietary or medical management (continue to have multiple acquired shunts)
What introducing vessel is used for intrahepatic and amenable extrahepatic shunts and for AV malformation?
PSS: Jugular vein
AV malformations: femoral artery
Percutaneous Transjugular Coil Embolization
- Portal pressures should be assessed before intervention, as ~5% of dogs have a portal-caval pressure gradient.
- Procedure:
Initial Access & Vessel Selection:
- A guide wire is inserted via the jugular vein into the cranial vena cava, right atrium, and caudal vena cava.
- A catheter is advanced to identify the shunting vessel (hepatic vein to portal vein).
- Contrast angiography confirms vessel anatomy and shunt location.
Stent Placement & Coil Embolization:
- measure the size of the intraabdominal vena cava during positive-pressure ventilation
- A self-expanding nitinol stent is deployed in the caudal vena cava to prevent coil migration.
- The catheter is advanced through the stent into the shunting vessel.
- places thrombogenic coils into the shunt, monitored under fluoroscopy.
- Coils are added until portal pressure reaches a safe level (~7 mmHg increase, not exceeding 15 mmHg final pressure).
Outcomes & Considerations:
- Coil embolization immediately reduces shunt flow, allowing a clot to form and occlude the vessel.
- Additional coils may be required later if liver function does not improve (~18% of cases).
- In rare cases (~3%), temporary balloon occlusion is used if portal perfusion remains high.
- If portal pressure changes are not excessive, complete shunt attenuation can be achieved using coils, vascular plugs, or covered stents.
What is the goal in regards to portal pressures for intravascular coiling?
- Increase the portal pressure by 7mmHg, but not higher than a final portal pressure of 15mmHg
- Coils are added until the mouth of the shunt is coered or the portal pressure is no greater than 10cmH2O (7mmHg) above baseline or a final pressure of approx 20cmH2O (15mmHg)
What medication should patients with intrahepatic shunts recieve for the rest of their lives?
Omeprazole to reduce the risk of GI ulceration
- With addition of lifelong antacids, mortality dropped from 25% to 3.2%
Complications
- fewer than 15% had perioperative complications
- coil migration (reduced by caval stent)
- excessive bleeding at jugular catheter site,
- aspiration
- PANS (6%).
- mortality rates are approximately 5% (gastrointestinal bleeding, cardiac arrest, or euthanasia because of neurologic sequelae)
- gastrointestinal bleeding (long-term mortality rate of 30%, which was due to gastrointestinal disease/ulceration in 50% of the dogs that died > significantly reduced using antacids)
- Portal hypertension has not been a problem (likely due to the fact that shunt attenuation occurs postsinusoidally) > also reduces the likelihood of restoring complete hepatic portal flow without some degree of shunting (trade-off between risk and benefit)
- persistence of abnormal clinical, biochemical, and scintigraphic evaluations common
Hepatic Arteriovenous Malformation Cyanoacrylate Glue Embolization
- Cyanoacrylate glue embolization may be used to occlude the anomalous vascular communications under fluoroscopic guidance
- Within a few seconds of infusion, the glue polymerizes and occludes the small communications
- All tributaries must be occluded to resolve the condition > careful evaluation of hepatic arterial perfusion after initial embolization is important to avoid incomplete occlusion
- venous occlusion of hepatic arteriovenous malformation is now being investigated (safer than arterial)
Complications (rare).
- Nontarget vascular embolization of vessels may occur I.e. portal circulation, acquired shunts, pulmonary, gastroduodenal artery, or other branches of the hepatic artery)
- second embolization and partial hepatectomy required
- survival rate was 100%
- most dogs require lifelong medical management because of continued shunting through multiple acquired PSSs.
Hepatofugal flow (ie, flow directed away from the liver)
What can be added to cyanoacrylate glue to aid with embolisation procedures?
1:1 or 1:2 ratio with Ethiodol - makes mixture radioopaque and slows polymerisation
Powdered tantalum - additional radioopacity
Multiple Acquired Extrahepatic Portosystemic Shunts
- animals with chronic portal hypertension dt MVD, cirrhosis, AVM, acute or gradual attenuation of congenital PSS
- often present with ascites (transudate), gastrointestinal hemorrhage, and signs of hepatic encephalopathy.
tx
- controlling the clinical signs of hepatic encephalopathy
- slowing the progression of the liver disease
- Ligation of the individual shunts is not considered effective because they are relieving the portal hypertension (unless cause of underlying liver disease is resolved)
- Survival times in animals undergoing caval banding is similar to those treated medically
- prognosis is poor (though mnat are asymptamostic of devveloped atyer single PSS ligation)
Enlargement of the hepatic artery is present in dogswith a
congenital extrahepatic portosystemic shunt and is
independent of shunt insertion into the systemic circulation
In humans, hepatic arterial blood flow changes in response to the
reduction in portal blood flow. The so-called hepatic arterial buffer
response (HABR) is an intrinsic regulatory mechanism,
Clinical outcomes for 20 cats with congenital extrahepatic
portosystemic shunts treated with ameroid constrictor ring
attenuation (2002–2020)
Janas 2024
Retrospective case series
long term clinical outcome was excellent in 15/18, good in 1/18 cats, and poor in 2/18 cats that were available for follow up.
complications 5/20 (25%)
including blindness (two cats), ascites (one cat), head pressing (one cat),
and seizures and death (one cat)
was excellent or good for 16/18 cats (88.9%) available for follow up
Surgical attenuation of EHPSS with an ARC can result in resolution of clinical signs and biochemical abnormalities in the majority of
cats. The perioperative complication rate for feline patients with EHPSS attenuated
with an ARC was lower than reported historically
Postoperative seizures
have been reported in 8–33% of cats undergoing gradual
attenuation with an ARC or thin film band and 22% of cats
undergoing acute partial or complete ligation
postoperative blindness resolved within
2 weeks in both affected cats
Evaluation of different blood tests in dogs with
extrahepatic portosystemic shunts to assess shunt
closure after surgical treatment
Devriendt 2022
Clinical prospective study.
Animals: 20 client-owned dogs with EHPSS
Transsplenic portal scintigraphy was performed to determine EHPSS closure 3 months postoperatively
When assessing a single blood parameter, Fasting ammonia had the highest specificity
(100%) with 81.5% sensitivty, whereas Serum hyaluronic acid and lidocaine/monoethylglycylxylidide had the highest sensitivity (96.9% and 96.2%, respectively - 81% specificity) for determining shunt closure postoperatively.
ammonia
In dogs with FA concentrations within normal
limits, further blood tests will be of added value as negative cases may be encountered. The findings of this studyconfirm that increased FA concentrations postoperatively
are suggestive of persistent shunting
SBA
do not seem of added value after surgical
attenuation. This has also been suggested in previous studies.13,14 Although SBA concentrations are reported to
decrease significantly after successful gradual attenuation or complete ligation of EHPSS,14,15 it is currently
unclear to what extent they should decrease or if different cutoff values need to be established in order to use SBA
concentrations as a measure of surgical attenuation.
In clinical cases, having a blood test that reaches a sensitivity of 100% to determine shunt closure would be ideal. In that case persistent shunting could be ruled out
without further imaging required. If persistent shunting is present, to the contrary, additional imaging is always advised to differentiate persistent shunting through the original EHPSS or due to development of MAPSS
ameroid constrictors or thin film banding
secured with stainless steel staples were used in this study,
persistent shunting through such small tributaries can also
be missed using CTA because of streaking artifacts
In conclusion, both SHA and the L/MEGX test have a
high sensitivity to detect EHPSS closure. Test performances
can be improved by combining these tests with
each other or with traditional tests such as FA or postprandial
SBA.
high sensitivity (Snout)
- chance of positive test when disease is present
- false positives due to other dz
- highly likely to give a positive result when disease is present (good screening)
- thus negative test likely to occur on those without dz
- only consdiers animals with disease,
high specificity (Spin)
- chance of a negative test when the disease is not present
- highy likely to give a negative result in an animal without disease
- thus, if positive result, very likely animal has the disease (good confirming test)
Surgical treatment and outcome
of intrahepatic shunts in 12 cats
Lavinia Economu 2022
A retrospective case series
Seven cats were diagnosed with a left divisional shunt, three with a central divisional shunt and two with a right
Three > complete acute suture
attenuation, eight cats underwent partial suture attenuation, four of which received complete suture ligation at a
second surgery, and one cat underwent partial attenuation with a thin film band.
Six cats (50%) developed postattenuation
neurological signs (PANS) after first surgery and two cats (17%) died or were euthanased due to severe PANS
long term excellent in five cats (63%),
dissected extravascularly immediately cranial to the liver at insesion at cranial vena cava
Contrast-enhanced ultrasonography is a feasible technique
for quantifying hepatic microvascular perfusion in dogs
with extrahepatic congenital portosystemic shunts
Masahiro Tamura1
Short- and long-term outcomes of
polyethylene band attenuation of
congenital extrahepatic portosystemic
shunts in dogs: 60 cases (2010-2020)
Glenn 2022
Post-operative complications occurred in 10 of 60 dogs (16.7%),
four major and six minor, with a peri-operative mortality of 6.7%. Persistent shunting was identified in
nine of 53 dogs (17%)
Long-term outcomes were “excellent” (26) or “good” (8) in 81.8% of dogs and “poor” (8) in
18.2%. At the time of follow-up, 30 of 44 (68.2%) dogs were not receiving any medical treatment
In conclusion, polyethylene band attenuation of CEHPSS
resulted in “good” to “excellent” long-term outcomes with low
peri-operative mortality. It is comparable to previous reports
of TFBs with the benefit of being pre-sterilised and pre-folded
from a consistent and widely available source
Only two reports have evaluated noncellulose
material for thin film banding (polyolefin), both
reported good long-term outcomes (Nelson & Nelson 2016,
Otomo et al. 2020).
This is within the published range of 9% to 47% persistent shunting with cellophane band attenuation
Intercostal thoracotomy for surgical attenuation of portoazygos extrahepatic
portosystemic shunts in three dogs: surgical technique and short-term
outcomes
G Casha * and C Jones 2022
NZVJ
right-sided intercostal thoracotomy was performed. The location of the thoracotomy was
patient-specific and located cranial to the diaphragm, either at the point of PAS insertion into
the azygos vein or one rib-space caudal to the insertion
Problems arise when vessels are attenuated prior to
their final insertion, as distal tributaries may still
enter cranial to the attenuation site, resulting in persistent
portosystemic shunting
Or et al. (2016a) identified that all PAS cross the diaphragm
to terminate within the thorax. This prompted
ongoing debate as to whether PAS attenuation should
be performed via an intra-abdominal or an intra-thoracic
approach.
Laparoscopic portosystemic shunt attenuation in 20 dogs (2018-2021)
Edoardo Pogg1 2022
laparoscopic PSS attenuation (TFB) in 20 dogs
- conversion 5/20 (25%)
- complications: self-limiting portal hypertension 3/20
- can be performed in dogs, in particular for a CEPSS located in the epiploic foramen (3 or 4 port technique)
severe portal hypertension requiring revision 1/20
- good outcome in all dogs after resolution of complications
- right paramedian approach for epiploic foramen, otherwise left paramedian
Percutaneous shunt vessel embolisation with Amplatzer vascular plugs II
and IV in the treatment of dogs
with splenophrenic shunts: four cases
(2019-2022)
Y. Kawamura 2023
There were no major procedure-related complications. No dogs developed post-ligation seizures or signs of portal hypertension. In addition, improvements in ammonia values were observed in all cases.
C linical Significance: Percutaneous splenophrenic shunt embolisation using Amplatzer vascular plugs II and IV is technically feasible in dogs, and assessed by intra-procedure angiography, a single plug
completely obstructed blood flow in all dogs.
AVP > increase density and flow disturbance and result in rapid occlusion
Ten minutes after balloon occlusion, there was no change in
heart rate, portal vein pressure or arterial blood pressure measured
from the dorsalis pedis artery. In both cases, angiography
confirmed the diameter of the shunting vessel and that the vessel
was of sufficient length to allow placement of an AVP
Dogs with congenital extrahepatic portosystemic shunts that have persistent shunting after surgery
have a higher prevalence of urolithiasis
Burger 2023
25 client-owned dogs that underwent gradual attenuation of a cEHPSS, of which 19 had a closed cEHPSS and 6 developed multiple acquired portosystemic shunts (MAPSS) following surgery
1 of 19 (5%) dogs with closed cEHPSS and 4 of 6 (67%) dogs with MAPSS had urolithiasis at long-term follow-up. Three (50%) dogs with MAPSS developed new uroliths.
Dogs that developed MAPSS following cEHPSS surgery are at greater risk of urolithiasis compared to those with closed cEHPSS. Furthermore, ammonium urate uroliths might dissolve (partially) if portosystemic shunting ceases to exist.
Postattenuation neurologic signs after surgical correction
of congenital portosystemic shunts in cats: A narrative
review
Ronan A. Mullins 2023
incidence: PANS: 14.3-62.0%, PAS 0-32.0%
- risk factors: lower grade intra-op postocclusion mesenteric portovenography,
- not associated: shunt morphology, signalment, method/degree of attenuation,
presence of pre-op neuro signs
- no evidence/support for the use of prophylactic anti-epileptics
- px for recovery variable, dependent on severity of signs
- cats surviving to discharge (PANS: 66.7-100%, PAS 25.0-100%)
→ possible long-term survival
- persistence/recurrence of neuro signs not uncommon
White 2017 – anatomy of shunts in dogs and cats
morphology: dogs: spleno-caval, left gastro-phrenic, left gastro-azygous and right gastric
vein account for 94%
cats: spleno-caval, left gastro-phrenic, left gastro-caval, left gastro-azygous
- first 3 → 92% of shunts
- proposed development of majority of shunts developing as a result of preferential blood
flow → subsequent formation of shunt from essentially normal portal vasculature
Implications of shunt morphology for the surgical management of extrahepatic portosystemic shunts
RN White
2018
revealing five distinct shunt types: left gastrophrenic, right gastrocaval (types Ai, Aii and Aiii), splenocaval, colocaval and left gastro-azygos
confirmed four consistent sites of communication between the anomalous shunting vessel and the systemic venous system:
1. the caudal vena cava at the level of the epiploic foramen;
2. the left phrenic vein at the level of the oesophageal hiatus;
3. the azygos vein at the level of the aortic hiatus;
4. caudal vena cava or iliac vein at the level of the 6th or 7th lumbar vertebrae.
Percutaneous transvenous coil embolization
of congenital intrahepatic portosystemic shunts in small- and toy-breed dogs: 20 cases (2015–2021)
Solari 2022
retrospective
Complication and survival rates in this cohort were similar to or better than those reported in previous studies evaluating PTCE and open surgical techniques for treatment of IHPSS in dogs.
Intra- and postoperative complication rates were 20% (4/20) and 5% (1/20), respectively, and included hypotension, bradycardia, hypercapnia, ventricular premature contractions, hypothermia, and regurgitation.
all dogs survived to discharge. Clinical signs resolved in 95% (19/20) of the dogs a median of 21 days after the procedure. One- and 2-year survival rates were 92%. Three dogs had died by the time of data collection; 2 of these dogs died of causes related to the IHPSS
Longterm outcome and quality of life of dogs
that developed neurologic signs after surgical treatment of a congenital portosystemic shunt: 50 cases (2005–2020)
Carrera 2022
- for those that survive >30 days
- 30/50 (60%) PAS and 20/50 had other neuro signs; 24/50 (48%) resolved neuro signs by discharge
- 15/30 PAS dogs had recurrence of seizures
- 50% new neuro signs after discharge
- > 6 month survival 45/50 (90%)
- outcome: 27/33 (82%) owner-assessed QOL ‘high’
- 67% of neuro signs (other than seizures) present at discharge resolved within 1 month
- blindness or vision impairment less likely to resolve
Twenty-nine (88%) dogs were alive at the time of questionnaire completion a mean of 1,986 days (SD, 1,237 days) postoperatively, whereas 4 (12%) dogs had died or been euthanized
Half of the dogs with postattenuation seizures had a reoccurrence.
Postattenuation neurologic signs after surgical attenuation of congenital portosystemic shunts in dogs: A review
Mullins 2022
most commonly occur
within 7 days postoperatively
theories of etiology:
CNS derangement:
- altered metabolism – decreased endogenous benzodiazepines (theory is that a decrease in systemic concentrations of endogenous benzodiazepines derived from the gastrointestinal tract occurs after shunt attenuation,fails to explain the occurrence of PANS after partial ligation and delayed attenuation techniques >Administration of benzodiazepines has also proven unreliable
- increased manganese
- not associated with post-op hyperammonemia (occurs with normal levels, absence of preoperative HE in some dogs and the refractory nature of PANS in comparison to preoperative HE suggest an alternative etiology than postoperative continuation of HE)
- adapted to a state of altered metabolism and that a change in this
altered metabolic state postattenuation precipitates PAS
- concurrent brain disease
- acquired brain disease – no strong evidence for ischemic/hypoxic injury
- peri-op hypoglycemia (occurs when normal, hypoglycaemic-induced brain lesions?)
- peri-op electrolyte disturbances – unclear
- post-op portal hypertension – no evidence in support
- infections disease – not identified
PANS incidence 1.6-27.3%, post-attenuation seizures (PAS) 0-18.2%
risk factors: immediate pre-op HE, increasing age, potentially breed, shunt morphology (more with extrahepatic than intra)
- not associated: method/degree of attenuation ( The incidence of PAS after suture ligation 0%-18.2%, TFB 1.8%-18.2% and and AC placement is 0%- 13.0%), pre-op neuro signs/seizures,
sx or ga time, post-op change in Na or serum osmolality
prophylactic antiepileptics do not prevent PANS
Tx
- generalised PAS often refractry to tx
- propfol > good for PAS
- no evidence for levetiracetam
survival:
- 30-day 0-100 with PANS, 0-75% with PAS
- PANS mortality associated with generalised seizure activity
- px factors for positive survival: pre-op seizures, focal seizures only
- survivors → long term survival with resolution of majority of PANS signs
Incidence and risk factors for neurological signs after
attenuation of a single congenital portosystemic shunt
in 50 cats
Rhiannon Strickland 2021
Congenital portosystemic shunts in 50 cats included 40 extrahepatic
and 10 intrahepatic shunts. Postattenuation neurological signs were recorded
in 31 (62%)
Five of 31 cats with PANS did not survive to discharge
Preoperative levetiracetam did not prevent
Serum hyaluronic acid, a marker for improved liver perfusion after
gradual surgical attenuation of extrahepatic portosystemic shunt
closure in dogs
N. Devriendta
there was a significant difference between the
median sHA concentration in dogs with closed EHPSS vs. those with persistent shunting
sHA is a promising
non-invasive biomarker that can help to determine liver perfusion after surgical attenuation of EHPSS.
Hyaluronic acid is locally metabolised and, when it reaches the blood via the lymphatic system, it is rapidly catabolised, mainly by
hepatic sinusoidal endothelial cells. Consequently, increased serum (s)HA concentrations in dogs with PSS can be an indication of decreased clearance
secondary to decreased liver perfusion.
Long-term clinical outcomes of dogs with single congenital
extrahepatic portosystemic shunts attenuated with thin
film banding or ameroid ring constrictors
Aki Otomo 2020
- TFB (polyolefin fibre = polypropylene) placed to result in no attenuation
- no difference in survival to discharge (TFB 95.3%, AC 97.4%)
- post-op seizures: 10/123 (8.1%) overall, TFB 10.6%, AC 2.6% - not different
- incidence not associated with levetiracetam administration
- ongoing clinical signs at follow up: overall 22%
- TFB 19.0%, AC 21.6% - not different
- similar long-term outcomes with low post-op morbidity and mortality
non–cellulose-based TFB led to short- and
long-term outcomes similar to ARC
Neither reimaging nor revision surgery
was performed in any dog, so persistent shunting could not be confirmed.
Liver function tests in dogs with congenital portosystemic shunts
and their potential to determine persistent shunting after surgical
attenuation
Nausikaa Devriendt
Reported success of surgical attenuation is often based on clinical outcome alone, which may correlate poorly with the degree of persistent shunting
fasted ammonia and ammonia tolerance tests are relatively commonly used after
surgical attenuation; however, theycan give falsenegative results for persistent residual shunting.
SBA are frequently measured
postoperatively, but results do not always correlate with complete PSS closureand can both give false positive and false negative results
increased SBA are not uncommon in dogs with completed PSS closure.
unknown to what extent a congenital PSS needs to be
attenuated in order to result in a good life expectancyand QoL
Based on the available literature, as an
initial screen, the
findingofan increased fasted ammoniaaftersurgical
attenuation should raise a strong suspicion of persistent residual
shunting
Bile acids are
principally reabsorbed by the ileum and carried via the portal
vein to the liver, where active transport into the bile occurs. During
this enterohepatic circulation, >95% of the bile acids are removed
from the portal blood by hepatocytes and recycled back into the
biliary system
The measurement of paired SBA is a commonly performed
liver function test in dogs suspect for PSS. To diagnose PSS, the
sensitivity of increased postprandial SBA was reported to be 100% (other liver dz??)
Health-related quality of life following surgical attenuation of congenital portosystemic shunts versus healthy controls
P. Bristow 2019
cohort of dogs treated with suture attenuation and compare results with those obtained from a healthy control cohort
The median long-term health-related quality of life score was excellent for both intrahepatic and extrahepatic shunt cases and similar to that of control dogs. The long-term portosystemic shunt clinical sign scores for both intrahepatic and extrahepatic congenital portosystemic shunt dogs were significantly worse than
Effect of prophylactic treatment with levetiracetam
on the incidence of postattenuation seizures in dogs
undergoing surgical management of single congenital
extrahepatic portosystemic shunts
Ronan A. Mullins 2019
The overall incidence of PAS was low (8%).
Prophylactic treatment with LEV does not afford protection
against development of PAS. Surgically treated dogs should continue to be monitored
closely during the first 7 days postoperatively for seizures
30 day survival 23/75 (30.7%)
Evaluation of different methods of securing cellophane bands for
portosystemic shunt attenuation
Joffe 2019
recommended 4-layer TFB with medium polymer locking ligation clip or titanium
ligation clip to secure TFB
Serrano 2019 – review of treatments
- quality of evidence low with high risk of bias
- no strong evidence for ameroid vs TFB vs PTCE
- ameroid constrictor → superior outcome vs TFB for achieving shunt closure
Outcomes of cellophane banding or percutaneous transvenous coil
embolization of canine intrahepatic portosystemic shunts
J. Brad Case 2018
Dogs treated with CB sustained more minor postoperative
complications and were hospitalized longer than dogs treated with PTCE. The 1-year
and 2-year survival rates were 89% for the CB group and 87% and 80% for the PTCE
group, respectively. The proportion surviving at 5 years was 75% and 80% for CB
dogs and PTCE dogs, respectively.
Conclusion: CB and PTCE are associated with similar short-term and intermediateterm
survival. PTCE is a minimally invasive alternative to CB via celiotomy. However,
CB allows concurrent abdominal procedures requiring the same approach.
Spies 2024 – medium-large breed (>15kg) dogs with extrahepatic PSS, n=63
- median age 21.9m (9-36.8); Golden Retriever most common (17/63)
- morphology: portocaval 17/63, splenocaval 15/63; PVH in 18/63
- complications: short term: 14/45 (35.6%); 3/45 (6.7%) shunt-related death
- outcome: 15/40 survivors discontinued meds, 9/40 reduced meds
- medically managed → 18/18 maintained on original medication
- revision for persistent shunting/clinical signs 4/45
- similar outcomes/clinical features to small breed CEPSS
Lipscomb 2023 – complete polypropylene ligation vs partial TFB for CPSS
- 57/110 (51.8%) complete ligation, 53/110 (48.1%) partial
- PANS: 6/57 (10.5%) complete vs 7/53 (13.2%) partial
- surgical mortality: 2/57 (3.5%) complete vs 3/53 (5.7%) partial
- peri-op mortality, incidence of PANS, incidence of multiple acquired shunts, post-op
clinical shunt score and QOL score not different between groups
- partial attenuation → higher number of unchanged bile acid concentration after sx,
more likely to remain on hepatic diet +/- medical management,
higher number of revision sx
- 60% persistent shunting
- “no reason to deny complete acute shunt closure to a patient that can tolerate it”
Lipscomb 2023 – second sx portovenogram after partial attenuation with polypropylene or TFB
- second procedure previously routine at this institution for dogs that do not tolerate
complete attenuation at first surgery
- intra-op portovenogram at 3 months → 9/12 (75%) TFB → complete shunt closure
vs 2/12 (16.7%) polypropylene
- multiple acquired shunts in 2/12 TFB – with patent original shunt
Anglin 2022 – multiple acquired PSS in 72 dogs
- MST for MAPSS-related death (23/72 dogs): 580d (156-1363)
- MAPSS-related death associated: bWt, albumin concentration at first and last recheck
cholesterol, total solids, glucose at last recheck
- not associated with previous PSS surgery
- no medical management or no signs of depressed mentation at initial presentation
→ lower risk of MAPSS-related death - survival not associated with MAPSS-related death or otherwise
