Lecture 15: Surgery of the Liver (Exam 3) Flashcards
Define hepatectomy
Removal of the entire liver
Define partial hepatectomy
Removal of a portion of the liver
Define lobectomy
Often used to refer to the removal of a single (or multiple) liver lobes w/out perform a total hepatectomy
What are the preop concerns
- Hypoalbuminemia (below 2g/dl)
- Coagulopathies
- Anemia
- K+ abnorms
- Anorexia
- Hypoglycemia
- Massive ascites (lots of fluid in the stomach)
What type of bacteria normally reside in the liver
Aerobic & anaerobic
When are ax used in liver sx
Px w/ severe hepatic dx that are undergoing hepatic surgery
What are the two afferent blood supplies
- Portal system (low pressure)
- Arterial system (high pressure)
Describe the portal vein in the liver
- Drains the stomach, intestines, pancreas, & spleen
- Supplies 4/5ths of the blood that enters the liver
Describe the proper hepatic arteries
- Provides the remainder of the afferent blood supply
- These are branches of the common hepatic artery may # btw/ two & five
When dissecting around the pylorus what should be avoided
Damaging the common bile duct
What are the diff types of liver biopsy techs
- Percutaneous & fine needle (blind & ultrasound guided)
- Laparoscopic
- Guillotine method
- Punch
- Partial lobectomy
How is tissue core biopsies obtained in percutaneous bx
- Tru cut biopsy
- Large bore needle
- Automated bx device
Who should automated bx device not be used on & why
Cats b/c of the potential mortality associated with/ the shock wave caused by triggering the device
Where are percutaneous core bx performed on the liver & why
- Left lateral lobe
- Min the chance of lacerating the bile ducts or gallbladder (both are on the right side)
Why is taking bx only on the left lateral lobe a significant limitation
B/c lesions may be present in only a few of the liver lobes
What is a disadvantage of percutaneous liver bx
False neg results are far more common than false positive results
Summarize the guillotine liver bx method
- Place a loop of suture around the margin of a liver lobe
- Pull the ligature tight so it crushes through the hepatic parenchyma before tying it
- Use a blade to take out the mass
Summarize a punch biopsy
- Hemostatic foam
- 6mm min
- Bx where norm & abnorm meet
Summarize a partial lobectomy
- Make a line of separation btw/ norm & what has to be removed
- Incise the liver capsule along the site
- Bluntly fracture the liver & expose the parenchymal vessels
- Ligate large vessels & electrocoagulate small bleeders
What are portosystemic vascular anomalies (Portosystemic shunts)
- Allow norm portal blood draining to pass directly into the systemic circulation w/out first passing through the liver
- Portocaval shunts are a specific vascular anomaly (portal vein to caudal vena cava)
What are extrahepatic shunts
- Vascular anomalies located outside the hepatic parenchyma
- Can be congenital extrahepatic portosystemic shunts (CEPSSs) or acquired
Where are congenital intrahepatic portosystemic shunts (IHPSSs) located
In the liver
What is hepatic microvascular dysplasia (HMD)
Small or absent intrahepatic portal vessels & portal arteriolar hyperplasia associated w/ microscopic shunting of blood through the liver w/out a macroscopic portosystemic shunt
What are the broad general categories of shunts
- Congenital or acquired
- Intrahepatic or extrahepatic
Describe congenital extrahepatic shunts
- Single anomalous vessels that allows abnormal blood from the portal vein directly to the systemic circulation
- Accounts for nearly 63% of single shunts in dogs
- Also occurs in cats
- Usually small thin dogs
Describe congenital extrahepatic shunts in cats
Large single vessel that empties directly into the pre hepatic vena cava
Describe intrahepatic portosystemic shunts
- Usually congenital (35% of single shunts in dogs)
- Singular shunts that occur b/c the ductus venosus fails to close after birth
- May arise when other portal to hepatic vein or caudal vena cava anastomoses exist
What is most commonly associated with/ multi extra hepatic shunts
Chronic severe hepatic dx (not surgical candidates)
T/F: HMD is surgical
False it is nonsurgical
What types of shunts are small breed & large breed dogs more likely to have
- Small: extrahepatic shunts
- Large: IHPSSs
When should congenital PSS be considered in young animals
When there is prolonged response to ax agents or tranquilizers that require hepatic metabolism for clearance
Describe nuclear scintigraphy
A useful noninvasive screening tool for dxing congenital or acquired shunts to distinguishes them from HMD
Describe the medical management for the liver
- Surgery appears to be the tx of choice
- Medical management of px w/ congenital PSS has a mortality rate of 48%
What is the surgical tx of PSSs
- Only px w/ congenital PSS are surgical candidates
- Goal: is to ID & occlude (acutely cut off circulation) or attenuate (slowly over time cut off circulation) the abnormal vessels
What are the three methods of surgical occlusion or attenuation in PSSs
- Ameroid constrictor
- Cellophane banding
- Ligation
What is this
Ameroid ring
What does cellophane banding cause
- Initial acute inflammatory response
- Chronic low grade foreign body tissue reaction
Why can ligation be fatal
Often leads to portal hypertension which may be fatal
What is good to know about sx options
- If multi shunts be sure to bx the liver
- Ameroid should fit on the vessel w/out compromising the lumen
- Avoid using too large of an ameroid b/c the weigh ot the device may cause the vessel to kink (obstruct flow prematurely)
- Warn owners that ligation of IHPSS is difficult b/c the shunts are often hard to ID @ sx
What are cavitary hepatic lesions
Usually cysts or abscesses
What are hepatic abscesses
Localized collections of pus in the hepatic parenchyma
What are hepatic cysts
Closed fluid filled sacs lined by secretory epithelium
What is the sx procedures for cavitary hepatic lesions
- Generally by partial hepatectomy
- Omentalized
Describe omentalization
- ID a segment of the omentum that will extend into the cyst cavity
- Remove as much of the wall of the cyst as possible
- Spread the omentum over the remaining cyst & adjacent liver
- Tack it gently in place to the remaining cyst capsule
Describe hepatic lobe torsion
- Occurs when a liver lobe twists around it axis
- Rare in dogs & cats
- Torsion of the left lateral or medial appear to be the most common
- Cause is unknown (congenital failure or rupture of the hepatic lig)
What occurs b/c of a hepatic lobe torsion
- Venous obstruction
- Increased hydrostatic pressure
- Ascites
- Thrombosis
- Lobe will eventually necrose
