PSS and oncology Flashcards
What is the normal portal blood flow?
What happens with a portosystemic shunt?
- Normal
- GI tract/spleen –> portal vein –> liver –> hepatic veins –> caudal vena cava
- PSS
- Abnormal communication between portal and systemic vasculature
- Products of intestinal digestion bypass liver
What are the various malformations that can occur within the liver?
- PSS
- Patent ductus venosus
- Portal vein hypoplasia
- Hepatic arteriovenous malformations
What is patent ductus venosus?
Failure of closure results in left intrahepatic shunt
What are the 2 types of portal vein hypoplasia?
- With portal hypertension
- Without portal hypertension
- Occurs in 58% of dogs and 87% of cats with macroscopic shunts
What are hepatic arteriovenous malformations?
- Intrahepatic
- Multiple high pressure arterial to low pressure venous malformations
- Blood bypasses capillary beds
What are the various classifications of portosystemic shunts?
Which is the most common?
- Extrahepatic vs. intrahepatic
- Congenital vs. acquired
- Single vs. multiple
- 66-75% of all PSS in small animals are congenital, single, and extrahepatic
What is the classic signalment for extrahepatic congenital shunts?
- Small dogs and cats
- Yorkies, Shih Tzus, Maltese, mini poodles, mini Schnauzers, pugs
- Most patients <2yrs at time of presentation
What is the classic signalment for intrahepatic congenital shunts?
- 25-33% of congenital shunts
- Large breed dogs
- Labrador retrievers
- Australian shepherds
- Old English sheep dogs
What do multiple acquired portosystemic shunts occur secondarily to (most commonly)?
Portal hypertensions
What is the medical management for PSS?
- Lactulose
- Diet:
- Restricted protein
- Soy proteins
- Antibiotics
- Metronidazole
- Neomycin
- Ampicillin
What is the mechanism for using lactulose as medical management for PSS?
- Promotes acidification of colonic contents (traps ammonia)
- Cathartic effect decreases colonic transit time (minimizes ammonia production and absorption)
How does diet change help medically manage PSS?
- Reduced protein content
- 18-22% for dogs
- 30-35% for cats
- Soy proteins associated with greater improvement in clotting factors and lower ammonia production
What is the mechanism behind antibiotics helping PSS?
Decreases colonic bacterial load
T/F: Medical management is indicated for at least 2 weeks prior to any surgery for PSS
TRUE
Which body systems are most affected by PSS?
- Coagulopathies/general
- GI
- CNS
- Urinary
What is the pathogenesis of coagulopathies in response to PSS?
- Decreased factor synthesis
- Increased factor use
- Increased fibrinolysis release
- Decreased vit K production
- Spontaneous hemorrhage uncommon
What are the general changes associated with PSS?
Failure to thrive
Weight loss
Intolerance to ax/sedation
What are the GI signs associated with PSS?
- Anorexia
- Vomiting
- Diarrhea
- Ptyalism in cats
- PICA
- Melena (intrahepatic shunt)
What are the CNS signs associated with PSS?
- Head pressing
- Blindness episodes
- Ataxia
- Stupor
- Aggression
- Dullness
- Seizures
- Weakness
- Depression
What are the urinary signs associated with PSS?
- PU/PD
- Cystitis
- Hematuria
- Pollakiuria
- Urolithiasis
- Urethral obstruction
What clinical signs and PE findings are unique to cats with PSS?
- Ptyalism
- Copper colored irises
- Aggressive behavior
What biochemical changes would one expect to see in a patient with a liver shunt?
- Increased pre- and post-prandial bile acids
- Shunting of resorbed bile acids from portal to systemic circulation
- Increased ammonia (fasting or with ammonia tolerance test)
- Shunting from portal to systemic circulation
What biochem tests are indicators of liver function vs. parenchymal disease?
- Decreased hepatic synthesis
- Decreased BUN
- Hypercholesterolemia
- Hypoalbuminemia
- Hypoglycemia
- Hepatic cell injury
- Normal to increased liver enzymes
- Decreased hepatic synthesis
- Decreased protein C activity
What are the various imaging modalities for diagnosing liver shunts? Which is the gold standard?
- Plain rads
- Portography
- Ultrasound
- Nuclear scintigraphy
- CT angiography–gold standard (humans, but also recommended for dogs/cats)
What radiographic changes are found in patients with liver shunts?
- Microhepatica
- Bilateral renomegaly
- Does not provide definitive diagnosis
What is portography? What is in a patient with liver shunts?
- Injection of iodinated contrast via mesenteric vein
- Mostly performed intra-op to confirm shunt ID
- Allows visualiation of shunting vessel
- Rarely performed outside of a surgical setting
What can be seen on ultrasound in patients with liver shunts?
- Very operator experience dependent
- Intrahapatic easier to ID than extrahepatic
- Findings
- Decreased hepatic and portal veins
- Subjectively smaller liver
- +/- anomalous vessel
- Decreased portal vein:aorta size (EHPSS)
What is seen on nuclear scintigraphy in patients with liver shunts?
- Technetium pertechnate 99
- Trans-colonic–shunt vs. microvascular dysplasia
- False positive possible
- Trans-splenic–100% sensitive; more likely to diagnose shunt # and location
- Shunt fraction calculated
- < 15% normal
- PSS = 60-80%
- Trans-colonic–shunt vs. microvascular dysplasia
What is seen on CT angiography in patients with liver shunts?
- Gold standard
- Dual-phase better than single
- Allows completion evaluation of portal and hepatic vasculature
- Images can be reconstructed to maximize visualization of shunt morphology
What are the various surgical options for liver shunt occlusion?
- Suture ligation
- Suture attenuation
- Ameroid constrictor
- Cellophane banding
What is the acute ligation/attenuation technique when occluding extrahepatic liver shunts?
- Open approach or laparoscopic procedure suture ligation
- Minimally invasive approach with coils or ductal occluders
How does suture attenuation work when occluding extrahepatic liver shunts?
- Vessel partially occluded with ligature
- May completely occlude due to fibrosis
- Additional surgery may be required
- Portal pressures must be measured
What is the ameroid constricter technique for occlusion of extrahepatic liver shunts?
- Casein ring surrounded by outer stainless steel sheath
- Slow absorption of abdominal fluid = gradual closure of ring (?)
- Fibrotic reaction also contributes to shunt attenuation
- Various sized rings
Howw does cellophane banding occlude extrahepatic liver shunts?
- Slow occlusion secondary to inflammatory reaction
- Cellophane is folded and loosely wrapped around shunting vessel
- Secured with 3-4 hemoclips
- No attenuation of shunt at time of sx
- Lower success in cats for complete occlusion
Why do we measure portal pressures and why is it important?
To avoid portal hypertension
T/F: Vessel occlusion/attenuation must occur as close to the caudal vena cava as possible
TRUE
Which surgical procedures should always include measurements of portal pressure?
Suture ligation and attenuation
What are the intraoperative signs of portal hypertension?
- Hypermotility of intestinal loops
- Pale/ashen discoloration of intestines
- Increased mesenteric arterial pulsation
- Cyanosis of pancreas
What signs would you expect to see post-op in a patient that is experiencing portal hypertension?
- Hypovolemic shock
- Hypothermia
- Weak pulses
- Abdominal pain and swelling
- Vomiting/diarrhea
What complications can occur secondary to chronic portal hypertension?
- Multiple acquired shunts
- Macrovascular shunt
- Cirrhosis
- Idiopathic
- Hepatic AV malformation
What complications are associated with shunt ligation/attenuation?
- Acute complications
- Portal hypertension
- Seizures
- Portal vein thrombosis
- Hypogycemia
- Hemorrhage
- Electrolyte disturbances–iatrogenic hyponatremia
- Chronic complications: recurrence of signs
What is the prognosis for dogs and cats following PSS surgery?
- Extrahepatic PSS
- Good to excellent in 78-94% of patients
- Intrahepatic PSS
- Good to excellent in 50-89% of patients
- Cats
- 75% post-op complications
- Longterm outcome: good to excellent in 30-80% of patients
Surgery is the most important component of treatment for solid animals with what type of tumors?
Solid
What is the best chance of curative surgery?
The first attempt
What is the role of surgery in cancer treatment?
- Obtaining a diagnosis via biopsy
- Curative sx/longterm tumor control
- Palliation of clinical signs
- Debulking surgery prior to adjunctive therapy
- Prevention/reduction of risk recurrence
- Ancillary procedures
- Vascular access port placement
What is a vascular access port placement?
- Vascular access port put into jugular and secured, then connected to disk implanted under skin
- Can be used as a permanent catheter for undergoing longterm radiation or getting frequent IV treatments
What is the gold standard for diagnosing neoplasia?
BIOPSIES
What are the indications for incisional biopsies?
- Sampling large superficial lesions
- Careful surgical planning is necessary due to perceived difficulty with curative surgery (size and location of lesion)
- Less invasive sampling techniques have not yielded a diagnosis
What are the pros/cons of incisional biopsies?
- Will require a second procedure
- May create communication between neoplastic and normal tissue (seeding)
- Can be done when there are multiple small nodules in areas like the liver, where morbidity associated with definitive surgery without a diagnosis would be unacceptable
What are the indications for excisional biopsies?
- Should only be considered when:
- Gingival lesions
- Lesion is known to be benign
- Lesion is small (< 5mm)
- Treatment would not be altered by tumor type
- Re-excision possible without great morbidity
What are the pros/cons of excisional biopsies?
- Removes tumor along with surrounding tissue
- Allows removal of small, non-invasive masses in single procedure
What are the various approaches to removing a mass?
- Intracapsular (rarely if ever indicated)
- Marginal/cytoreductive
- Wide
- Radical
When are marginal/cytoreductive excisions indicated?
- Lipomas and benign masses
- Malignant lesion-goal is microscopic disease
When are wide excisions indicated?
- Removal of 2-3cm normal tissue 3-D (metric approach)
- Removal of 2-3cm normal tissue laterally and 1 fascial plane deep (metric/barrier hybrid)
- Mast cell tumors (high grade)
- Sarcomas
- Vaccine-associated sarcomas
When are radical excisions indicated?
Removal of an entire compartment
Amputation, hemipelvectomy
What are the important principles of oncotic surgery?
- Ability to close wound should not influence aggressiveness if intent is to cure
- Minimize handling of tumor
- Do not penetrate tumor capsule
- Protect normal tissues
- Ligate blood supply as early as possible
- Increase in circulating tumor cells peri-operatively
- Excise biopsy tract
- Excise LN if indicated
- Lavage tissues, change gloves and instruments, lavage again before closing
- AVOID USE OF DRAINS
Why is it important to understand the flow of lymphatics when working up a patient with malignancy?
- Local draining LN should be aspirated prior to surgery for cytology if possible
- Local LN excision is prognostic for multiple cancer types
- Mammary carcinoma
- Mast cell tumors
- Apocrine gland adenocarcinoma
- Sentinel LN mapping
- Radioactive material and NS or fluoroscopy to tract LN that drain a mass
What types of tumors can be most readily diagnosed from a cytology sample?
- Mast cell tumors
- Melanoma
- Lymphoma
- For all others interpret cautiously
- Inflammation may resemble malignancy
- If not diagnostic, pursue biopsy
What information is important to receive on a histopathology report to help guide further treatment and to provide a prognosis?
- Tumor or other
- Benign vs. malignant
- Histologic type
- Grade
- Margins
What is body mapping?
- Masses on external aspect of body part
- Should measure masses and draw on body map on PE
- Body map = profile of an animal, w/ RL, LL, and DV
- Can track masses to evaluate change over time
What is palliative surgery?
- No curative intent
- Improve quality of life, won’t extend life
- Disease processes might be slowed with adjuvant therapy
What are some examples of palliative surgery?
- Splenectomy or liver lobectomy for hemangiosarcoma
- Amputation for OSA
- Partial cystectomy for TCC
