Chapter 95 - Liver and Biliary Flashcards
What is the proportion of R:L liver in dogs?
R:L is 3:2
List the lobes, (sublobes) and [processes] of the liver
Left (lateral and medial), right (lateral and medial), quadrate, caudate [caudate and papillary]
Describe the ligaments of the liver
Coronary ligament - porta hepatis to diaphragm
Right triangular ligaments - right medial and lateral to the diaphragm
Left triangular ligament - left lobes to the diaphragm
Hepatorenal ligament - caudate process to the right kidney
Hepatogastric ligament - papillary process to the lesser curvature of the stomach
Hepatoduodenal ligament - papillary process to the duodenum
Describe the major arterial blood supply to the liver
Hepatic artery - branch of the coeliac artery, arterial blood, provides 20% of the blood flow and 50% of the oxygen, at the porta it branches into 2-5 to penetrate different lobes (left, right lateral, right middle, cystic) but can be variable
Describe the portal blood supply to the liver
Provides 80% of blood flow and 50% oxygen
Continuation of the cranial mesenteric and caudal mesenteric veins, gastroduodenal (not in cats) and splenic v also contibute prior to entry into the porta
In the liver, divides into right and left (then into central, lateral, medial and quadrate)
Right - caudate process and right lateral lobe
Central - right medial and papillary
Lateral - left lateral
Medial - left medial
Quadrate - quadrate
Describe the venous system of the liver
6-8 hepatic veins empty into the CVC
Right is most caudal, left is most cranial (almost at the diaphragm)
Describe the passage of bile through the liver
Bile is formed by hepatocytes and secreted into bile canaliculi, these enter interlobar ducts, then lobar ducts which become 2-8 hepatic ducts as they exit the parenchyma
The hepatic ducts converge with the cystic duct into the common bile duct which then enters the duodenum and the major duodenal papilla
The cystic duct leads to the gall bladder
Describe the major duodenal papilla, and discuss the differences in cats
Small mound present on the mesenteric surface of the duodenum, 3-6cm aboral to the pylorus, it passes within the duodenal wall for 1-2cm
Sphincter of oddi is a small circumferential muscle surrounding the opening (not in cats)
In cats, the common bile duct joins with the pancreatic duct before entering the major duodenal papilla
Discuss the minor duodenal papilla and species differences
Minor duodenal papilla is 2cm aboral to the major
The accessory pancreatic duct enters here and provides most pancreatic excretions in the dog
In the cat, only 20% have an accessory pancreatic duct, most enters at the major with the conjoined common bile duct
List the functions of the liver
- Synthesis of plasma proteins
- Carbohydrate and lipid metabolism
- Coagulation factor synthesis
- Modifying immune function
- Bile and hormone synthesis
- Storage of vitamins, fat, glycogen and metals
- Clearance of toxic metabolites
What is bile composed of
Bile acids
bilirubin
cholesterol
phospholipids
water
bicarbonate
What are the function of bile sats
Emulsify fats and aid in their digestion
Bind endotoxin and prevent absorption
WHat % of acute liver resection is tolerated in dogs
70%
Death was caused by portal hypertension rather than liver failure
Describe liver regeneration
Peaks within 3 days, near complete compensatory hypertrophy and hyperplasia occurred by 6d following 70% hepatectomy, can take 6-10 weeks
Describe the hepatic arterial buffer response
When portal perfusion reduces, this results in lack of washout of adenosine (a potent vasodilator) which triggers a compensatory increase in arterial perfusion from the hepatic artery
How can portal embolization assist in partial hepatectomy?
Embolization of the portal vein for the affected lobe results in increased portal blood flow to the contralateral side and hypertrophy
Decribe the etiology of gall bladder mucocele
Hypersecretion of mucus leads to accumulation of thick, gelatinous bile
Can be present in the common bile duct and hepatic ducts
Can then lead to EHBTO and possible rupture
Reduced ejection fractions of bile may contribue
Genetic predispositions may be present
Cushings and hypothyroidism may contribute
What is the sensitivity for US diagnosis of GBM rupture?
86%
How frequently is infection detected in GBM?
3-75%…
How frequently is rupture of GBM identified?
23-60%
What is the mortality rate following GBM surgery?
16-40% in the textbook
What factors negatively affect hepatic regeneration?
diabetes mellitus, pancreatectomy, malnutrition, male gender, older age
Where does trauma cause bile leakage most commonly?
Hepatic ducts and common bile duct, rarely gall bladder
The sudden, rapid cranial movement of the liver cf the duodenum can cause tearing
Bile trauma is very rare in cats
What are the most common causes of EHBO?
Dogs: pancreatitis, pancreatic neoplasia, GBM, cholngitis, cholelithiasis
Cats: pancreatitis, cholangiohepatitis, cholecystitis, cholelithiasis, neoplasia
Describe the anatomical and pathophysiological effects of bile outflow obstruction
Anatomical: AUS reveals CBD within 24-48h
Dilation of the lobar and interlobar hepatic ducts by day 4-6
Pathophysiology: hypotension, decreased myocardial contractility, acute renal failure, coagulopathies, GI haemorrhage, delayed wound healing
What are the causes of the pathophysiological effects of EHBO?
Not completely understood but believed to be endotoxin mediated
- absence of bile salts results in overgrowth of bacteria in the intestine
- reduced hepatic clearance of endotoxin results in endotoxemia
- endotoxin is a potent vasoconstrictor causing renal disease
- GI bleeding may occur due to endotoxin ischemia and increased acid
- Decreased healing in abdominal wounds
Describe bile peritonitis
Bile salts enter the peritoneum and their hyperosmolality causes significant fluid shifts resulting in dehydration and shock. If bacteria are present, septic peritonitis also occurs which is profoundly worse.
What % of choleliths are visible on radiographs?
Dogs - 50%
Cats - 80%
Describe percutaneous contrast ultrasound-guided cholecystography
Contrast is injected into the gall bladder under ultrasound guidance and passage into the duodenum is documented in the same AUS
Describe the appearance on AUS of a GBM
immobile, stellate or striated appearance of the gall bladder contents
Describe hepatobiliary scintigraphy for diagnosis of EHBO
IV injection of compounds which should accumulate in the intestines within 3 hours
List the main procoagulants produced by the liver
Coagulation factors, fibrinogen, vitamin k, thrombopoetin
List the main anticoagulants produced by the liver
protein C, protein S
Removal of activated coagulation factors and fibrinogen degradation products
What % of dogs with naturally occuring liver disease have derangements on coagulation testing?
Approx 50%
What % of dogs and cats with hepatobiliary disease have positive liver and bile culture?
Dogs: 5% liver
Cats: 14% liver
Cultures were more likely positive with surgical liver sampling (17%) than with needle biopsy (4%)
Bile is more likely to culture positive than liver (30% v 7% in the same patient)
What are the options for control of extensive hepatic haemorrhage?
- Control CVP at <5mm H20
- Occlusion of liver inflow
- Occlusion of liver inflow and outflow
Describe the pringle maneuver
Allows rapid occlusion of liver inflow
Occludes the hepatic artery and the portal vein
Approached through the epiploic foramen into the omental bursa
Can only be applied for <20min
Ongoing haemorrhage may be due to backflow through hepatic veins or from the gastroduodenal vein
Describe hepatic artery ligation in hepatic tumours
Hepatic tumours rely on the hepatic artery supply (95%) cf normal liver (20%) which relies on portal vein
Permanent hepatic artery ligation can be considered in inoperable tumours or intractable neoplasia haemorrhage
All dogs require antibiotics to prevent necrotic gangrenous necrosis
What is the accuracy of hepatic FNA and trucut?
FNA concurred with biopsy in 48%
Trucut concurred with biopsy in 48-83%
Require at least 3-12 portal triads
Need to sample at least 2 liver lobes
What are the risks of liver tru-cut biopsy?
Minor complication in 22% (PCV drop >10%, no intervention)
Major complications in 6% (required blood, death)
Dogs with thrombocytopenia or prolonged coag times were at most risk
What is the conversion rate of lap liver biopsy?
2-4%
What are the surgical options for partial hepatic lobectomy?
Blunt dissection with electrocautery, hemoclips or ligation; vessel sealing devices; TA staplers; encircling suture devices; harmonic scalpels
Describe the most common causes of acute mortality following liver lobe resection
Haemorrhage - inappropriate surgery, coagluopathies
Liver failure - reduction of functioning liver to below requirements
Portal hypertension - consider monitoring portal pressures in extensive resections, consider staged resection or create a portocaval shunt
What is the maximum acute liver excision %?
70%
Right lateral and caudate - 28%
Right medial and quadrate - 28%
Left lateral and medial - 44%
What are some interventions available for non-resectable tumours?
- Percutaneous tumour ablation with radiofrequency, microwave, laser thermal, cryoablation and ethanol
(Usually only suitable for fewer and smaller tumours) - Intravascular techniques like intra-arterial chemotherapy, transarterial embolization, chemoembolization
- aim to increase local chemotherapy delivery (10-50x), reduce systemic toxicities, reduce tumour blood supply and oxygen, improve local tumour control
What are the most common lab abnormalities in biliary disease?
Increase ALP, ALT, bilirubin, cholesterol, GGT, leucocytes
Reduced albumin
Abnormal coagulation can occur and is highly variable
How can you confirm biliary abominal effusion?
Bilirubin in the abdominal fluid is at least 2x the serum bilirubin
What options exist to surgically treat EHBO?
Cholecystectomy
Cholecystotomy
Cholecystoenterostomy
Choledochal stenting
Cholecystotomy tube
Choledochotomy
Describe the process of a lap chole
- Four port technique: subumbilical cannula, left craniolateral, 2 x right lateral
OR SILS port - Retract the gall bladder cranially
- Identify and dissect around the cystic duct with right-angle forceps
- Ligate the cystic duct and artery proximal and distal to trasection site with intracorporeal or extracorporeal suture, ligasure or hemoclip
- The gall bladder is then dissected free from the liver with ligasure
- Placed into a specimen retrieval bag
- Gall bladder punctured in bag if necessary and contents suctioned to allow removal through the port
What complication can occur if cholecystojejunosotmy is performed instead of cholecystoduodenostomy?
Lack of bile in the duodenum results in lack of inhibition of gastric acid secretion
Duodenal ulceration can occur due to hyperacid stomach contents
What are some possible complications following cholecystoduodenostomy?
Haemorrhage, incisional dehiscence, stricture of the stoma, ascending cholangitis, gastric ulceration
List some indications for choledochal stenting
Reversible EHBO
Palliation for non-reversible EHBO
To support repair of CBD rupture and repair
Temporary drainage of the biliary system prior to surgery
Describe choledochal stenting
- Antimesenteric duodenotomy
- Identification of the major duodenal papilla
- Passage of a red rubber catheter that is large but does not fill the entire duct
- Several fenestrations can be cut prior to placement
- The stent should be inserted past the level of obstruction
- Leave 2-4cm of stent within the duodenum
- Suture stent to the duodenal submucosa with either absorbable (temporary) or nonabsorbable (permanent)
- Removal of the stent in 2-4m post resolution is advised if it does not pass in the stool to prevent risk of obstruction and ascending infection
Which liver lobe is most likely to become torsed?
Left lateral
What is the proposed etiopathogenesis of cholelithiasis in dogs and cats
Choleliths are usually composed of calcium carbonate or calcium bilirubinate
Potential causative roles for cholestasis and infection but not proven
In dogs, ligation of the CBD resulted in cholelith formation within days, but none in cats
Mucin overproduction (like in GBM) can slo lead to binding of cholelith components and formation
Formation of choleliths has not been reported following cholecystectomy, suggesting a role for the gall bladder wall
