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Small animal surgery I > PSS and oncology > Flashcards

PSS and oncology Flashcards

1
Q

What is the normal portal blood flow?

What happens with a portosystemic shunt?

A
  • 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
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2
Q

What are the various malformations that can occur within the liver?

A
  • PSS
  • Patent ductus venosus
  • Portal vein hypoplasia
  • Hepatic arteriovenous malformations
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3
Q

What is patent ductus venosus?

A

Failure of closure results in left intrahepatic shunt

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4
Q

What are the 2 types of portal vein hypoplasia?

A
  • With portal hypertension
  • Without portal hypertension
    • Occurs in 58% of dogs and 87% of cats with macroscopic shunts
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5
Q

What are hepatic arteriovenous malformations?

A
  • Intrahepatic
  • Multiple high pressure arterial to low pressure venous malformations
    • Blood bypasses capillary beds
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6
Q

What are the various classifications of portosystemic shunts?

Which is the most common?

A
  • Extrahepatic vs. intrahepatic
  • Congenital vs. acquired
  • Single vs. multiple
  • 66-75% of all PSS in small animals are congenital, single, and extrahepatic
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7
Q

What is the classic signalment for extrahepatic congenital shunts?

A
  • Small dogs and cats
    • Yorkies, Shih Tzus, Maltese, mini poodles, mini Schnauzers, pugs
  • Most patients <2yrs at time of presentation
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8
Q

What is the classic signalment for intrahepatic congenital shunts?

A
  • 25-33% of congenital shunts
  • Large breed dogs
    • Labrador retrievers
    • Australian shepherds
    • Old English sheep dogs
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9
Q

What do multiple acquired portosystemic shunts occur secondarily to (most commonly)?

A

Portal hypertensions

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10
Q

What is the medical management for PSS?

A
  • Lactulose
  • Diet:
    • Restricted protein
    • Soy proteins
  • Antibiotics
    • Metronidazole
    • Neomycin
    • Ampicillin
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11
Q

What is the mechanism for using lactulose as medical management for PSS?

A
  • Promotes acidification of colonic contents (traps ammonia)
  • Cathartic effect decreases colonic transit time (minimizes ammonia production and absorption)
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12
Q

How does diet change help medically manage PSS?

A
  • Reduced protein content
    • 18-22% for dogs
    • 30-35% for cats
  • Soy proteins associated with greater improvement in clotting factors and lower ammonia production
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13
Q

What is the mechanism behind antibiotics helping PSS?

A

Decreases colonic bacterial load

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14
Q

T/F: Medical management is indicated for at least 2 weeks prior to any surgery for PSS

A

TRUE

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15
Q

Which body systems are most affected by PSS?

A
  • Coagulopathies/general
  • GI
  • CNS
  • Urinary
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16
Q

What is the pathogenesis of coagulopathies in response to PSS?

A
  • Decreased factor synthesis
  • Increased factor use
  • Increased fibrinolysis release
  • Decreased vit K production
  • Spontaneous hemorrhage uncommon
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17
Q

What are the general changes associated with PSS?

A

Failure to thrive

Weight loss

Intolerance to ax/sedation

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18
Q

What are the GI signs associated with PSS?

A
  • Anorexia
  • Vomiting
  • Diarrhea
  • Ptyalism in cats
  • PICA
  • Melena (intrahepatic shunt)
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19
Q

What are the CNS signs associated with PSS?

A
  • Head pressing
  • Blindness episodes
  • Ataxia
  • Stupor
  • Aggression
  • Dullness
  • Seizures
  • Weakness
  • Depression
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20
Q

What are the urinary signs associated with PSS?

A
  • PU/PD
  • Cystitis
  • Hematuria
  • Pollakiuria
  • Urolithiasis
  • Urethral obstruction
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21
Q

What clinical signs and PE findings are unique to cats with PSS?

A
  • Ptyalism
  • Copper colored irises
  • Aggressive behavior
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22
Q

What biochemical changes would one expect to see in a patient with a liver shunt?

A
  • 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
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23
Q

What biochem tests are indicators of liver function vs. parenchymal disease?

A
  • Decreased hepatic synthesis
    • Decreased BUN
    • Hypercholesterolemia
    • Hypoalbuminemia
    • Hypoglycemia
  • Hepatic cell injury
    • Normal to increased liver enzymes
  • Decreased hepatic synthesis
    • Decreased protein C activity
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24
Q

What are the various imaging modalities for diagnosing liver shunts? Which is the gold standard?

A
  • Plain rads
  • Portography
  • Ultrasound
  • Nuclear scintigraphy
  • CT angiography–gold standard (humans, but also recommended for dogs/cats)
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25
Q

What radiographic changes are found in patients with liver shunts?

A
  • Microhepatica
  • Bilateral renomegaly
  • Does not provide definitive diagnosis
26
Q

What is portography? What is in a patient with liver shunts?

A
  • 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
27
Q

What can be seen on ultrasound in patients with liver shunts?

A
  • 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)
28
Q

What is seen on nuclear scintigraphy in patients with liver shunts?

A
  • 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%
29
Q

What is seen on CT angiography in patients with liver shunts?

A
  • 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
30
Q

What are the various surgical options for liver shunt occlusion?

A
  • Suture ligation
  • Suture attenuation
  • Ameroid constrictor
  • Cellophane banding
31
Q

What is the acute ligation/attenuation technique when occluding extrahepatic liver shunts?

A
  • Open approach or laparoscopic procedure suture ligation
  • Minimally invasive approach with coils or ductal occluders
32
Q

How does suture attenuation work when occluding extrahepatic liver shunts?

A
  • Vessel partially occluded with ligature
  • May completely occlude due to fibrosis
  • Additional surgery may be required
  • Portal pressures must be measured
33
Q

What is the ameroid constricter technique for occlusion of extrahepatic liver shunts?

A
  • 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
34
Q

Howw does cellophane banding occlude extrahepatic liver shunts?

A
  • 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
35
Q

Why do we measure portal pressures and why is it important?

A

To avoid portal hypertension

36
Q

T/F: Vessel occlusion/attenuation must occur as close to the caudal vena cava as possible

A

TRUE

37
Q

Which surgical procedures should always include measurements of portal pressure?

A

Suture ligation and attenuation

38
Q

What are the intraoperative signs of portal hypertension?

A
  • Hypermotility of intestinal loops
  • Pale/ashen discoloration of intestines
  • Increased mesenteric arterial pulsation
  • Cyanosis of pancreas
39
Q

What signs would you expect to see post-op in a patient that is experiencing portal hypertension?

A
  • Hypovolemic shock
  • Hypothermia
  • Weak pulses
  • Abdominal pain and swelling
  • Vomiting/diarrhea
40
Q

What complications can occur secondary to chronic portal hypertension?

A
  • Multiple acquired shunts
    • Macrovascular shunt
    • Cirrhosis
    • Idiopathic
    • Hepatic AV malformation
41
Q

What complications are associated with shunt ligation/attenuation?

A
  • Acute complications
    • Portal hypertension
    • Seizures
    • Portal vein thrombosis
    • Hypogycemia
    • Hemorrhage
    • Electrolyte disturbances–iatrogenic hyponatremia
  • Chronic complications: recurrence of signs
42
Q

What is the prognosis for dogs and cats following PSS surgery?

A
  • 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
43
Q

Surgery is the most important component of treatment for solid animals with what type of tumors?

A

Solid

44
Q

What is the best chance of curative surgery?

A

The first attempt

45
Q

What is the role of surgery in cancer treatment?

A
  • 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
46
Q

What is a vascular access port placement?

A
  • 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
47
Q

What is the gold standard for diagnosing neoplasia?

A

BIOPSIES

48
Q

What are the indications for incisional biopsies?

A
  • 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
49
Q

What are the pros/cons of incisional biopsies?

A
  • 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
50
Q

What are the indications for excisional biopsies?

A
  • 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
51
Q

What are the pros/cons of excisional biopsies?

A
  • Removes tumor along with surrounding tissue
  • Allows removal of small, non-invasive masses in single procedure
52
Q

What are the various approaches to removing a mass?

A
  • Intracapsular (rarely if ever indicated)
  • Marginal/cytoreductive
  • Wide
  • Radical
53
Q

When are marginal/cytoreductive excisions indicated?

A
  • Lipomas and benign masses
  • Malignant lesion-goal is microscopic disease
54
Q

When are wide excisions indicated?

A
  • 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
55
Q

When are radical excisions indicated?

A

Removal of an entire compartment

Amputation, hemipelvectomy

56
Q

What are the important principles of oncotic surgery?

A
  • 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
57
Q

Why is it important to understand the flow of lymphatics when working up a patient with malignancy?

A
  • 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
58
Q

What types of tumors can be most readily diagnosed from a cytology sample?

A
  • Mast cell tumors
  • Melanoma
  • Lymphoma
  • For all others interpret cautiously
    • Inflammation may resemble malignancy
  • If not diagnostic, pursue biopsy
59
Q

What information is important to receive on a histopathology report to help guide further treatment and to provide a prognosis?

A
  • Tumor or other
  • Benign vs. malignant
  • Histologic type
  • Grade
  • Margins
60
Q

What is body mapping?

A
  • 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
61
Q

What is palliative surgery?

A
  • No curative intent
  • Improve quality of life, won’t extend life
    • Disease processes might be slowed with adjuvant therapy
62
Q

What are some examples of palliative surgery?

A
  • Splenectomy or liver lobectomy for hemangiosarcoma
  • Amputation for OSA
  • Partial cystectomy for TCC

Small animal surgery I (25 decks)

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