Chapter 95 - Liver and Biliary

Question 1

What is the proportion of R:L liver in dogs?

Answer 1

R:L is 3:2

Question 2

List the lobes, (sublobes) and [processes] of the liver

Answer 2

Left (lateral and medial), right (lateral and medial), quadrate, caudate [caudate and papillary]

Question 3

Describe the ligaments of the liver

Answer 3

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

Question 4

Describe the major arterial blood supply to the liver

Answer 4

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

Question 5

Describe the portal blood supply to the liver

Answer 5

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

Question 6

Describe the venous system of the liver

Answer 6

6-8 hepatic veins empty into the CVC
Right is most caudal, left is most cranial (almost at the diaphragm)

Question 7

Describe the passage of bile through the liver

Answer 7

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

Question 8

Describe the major duodenal papilla, and discuss the differences in cats

Answer 8

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

Question 9

Discuss the minor duodenal papilla and species differences

Answer 9

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

Question 10

List the functions of the liver

Answer 10

• 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

Question 11

What is bile composed of

Answer 11

Bile acids
bilirubin
cholesterol
phospholipids
water
bicarbonate

Question 12

What are the function of bile sats

Answer 12

Emulsify fats and aid in their digestion
Bind endotoxin and prevent absorption

Question 13

WHat % of acute liver resection is tolerated in dogs

Answer 13

70%
Death was caused by portal hypertension rather than liver failure

Question 14

Describe liver regeneration

Answer 14

Peaks within 3 days, near complete compensatory hypertrophy and hyperplasia occurred by 6d following 70% hepatectomy, can take 6-10 weeks

Question 15

Describe the hepatic arterial buffer response

Answer 15

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

Question 16

How can portal embolization assist in partial hepatectomy?

Answer 16

Embolization of the portal vein for the affected lobe results in increased portal blood flow to the contralateral side and hypertrophy

Question 17

Decribe the etiology of gall bladder mucocele

Answer 17

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

Question 18

What is the sensitivity for US diagnosis of GBM rupture?

Answer 18

86%

Question 19

How frequently is infection detected in GBM?

Answer 19

3-75%…

Question 20

How frequently is rupture of GBM identified?

Answer 20

23-60%

Question 21

What is the mortality rate following GBM surgery?

Answer 21

16-40% in the textbook

Question 22

What factors negatively affect hepatic regeneration?

Answer 22

diabetes mellitus, pancreatectomy, malnutrition, male gender, older age

Question 23

Where does trauma cause bile leakage most commonly?

Answer 23

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

Question 24

What are the most common causes of EHBO?

Answer 24

Dogs: pancreatitis, pancreatic neoplasia, GBM, cholngitis, cholelithiasis
Cats: pancreatitis, cholangiohepatitis, cholecystitis, cholelithiasis, neoplasia

Question 25

Describe the anatomical and pathophysiological effects of bile outflow obstruction

Answer 25

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

Question 26

What are the causes of the pathophysiological effects of EHBO?

Answer 26

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

Question 27

Describe bile peritonitis

Answer 27

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.

Question 28

What % of choleliths are visible on radiographs?

Answer 28

Dogs - 50% Cats - 80%

Question 29

Describe percutaneous contrast ultrasound-guided cholecystography

Answer 29

Contrast is injected into the gall bladder under ultrasound guidance and passage into the duodenum is documented in the same AUS

Question 30

Describe the appearance on AUS of a GBM

Answer 30

immobile, stellate or striated appearance of the gall bladder contents

Question 31

Describe hepatobiliary scintigraphy for diagnosis of EHBO

Answer 31

IV injection of compounds which should accumulate in the intestines within 3 hours

Question 32

List the main procoagulants produced by the liver

Answer 32

Coagulation factors, fibrinogen, vitamin k, thrombopoetin

Question 33

List the main anticoagulants produced by the liver

Answer 33

protein C, protein S Removal of activated coagulation factors and fibrinogen degradation products

Question 34

What % of dogs with naturally occuring liver disease have derangements on coagulation testing?

Answer 34

Approx 50%

Question 35

What % of dogs and cats with hepatobiliary disease have positive liver and bile culture?

Answer 35

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)

Question 36

What are the options for control of extensive hepatic haemorrhage?

Answer 36

1. Control CVP at <5mm H20 2. Occlusion of liver inflow 3. Occlusion of liver inflow and outflow

Question 37

Describe the pringle maneuver

Answer 37

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

Question 38

Describe hepatic artery ligation in hepatic tumours

Answer 38

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

Question 39

What is the accuracy of hepatic FNA and trucut?

Answer 39

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

Question 40

What are the risks of liver tru-cut biopsy?

Answer 40

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

Question 41

What is the conversion rate of lap liver biopsy?

Answer 41

2-4%

Question 42

What are the surgical options for partial hepatic lobectomy?

Answer 42

Blunt dissection with electrocautery, hemoclips or ligation; vessel sealing devices; TA staplers; encircling suture devices; harmonic scalpels

Question 43

Describe the most common causes of acute mortality following liver lobe resection

Answer 43

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

Question 44

What is the maximum acute liver excision %?

Answer 44

70% Right lateral and caudate - 28% Right medial and quadrate - 28% Left lateral and medial - 44%

Question 45

What are some interventions available for non-resectable tumours?

Answer 45

1. Percutaneous tumour ablation with radiofrequency, microwave, laser thermal, cryoablation and ethanol (Usually only suitable for fewer and smaller tumours) 2. 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

Question 46

What are the most common lab abnormalities in biliary disease?

Answer 46

Increase ALP, ALT, bilirubin, cholesterol, GGT, leucocytes Reduced albumin Abnormal coagulation can occur and is highly variable

Question 47

How can you confirm biliary abominal effusion?

Answer 47

Bilirubin in the abdominal fluid is at least 2x the serum bilirubin

Question 48

What options exist to surgically treat EHBO?

Answer 48

Cholecystectomy Cholecystotomy Cholecystoenterostomy Choledochal stenting Cholecystotomy tube Choledochotomy

Question 49

Describe the process of a lap chole

Answer 49

- 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

Question 50

What complication can occur if cholecystojejunosotmy is performed instead of cholecystoduodenostomy?

Answer 50

Lack of bile in the duodenum results in lack of inhibition of gastric acid secretion Duodenal ulceration can occur due to hyperacid stomach contents

Question 51

What are some possible complications following cholecystoduodenostomy?

Answer 51

Haemorrhage, incisional dehiscence, stricture of the stoma, ascending cholangitis, gastric ulceration

Question 52

List some indications for choledochal stenting

Answer 52

Reversible EHBO Palliation for non-reversible EHBO To support repair of CBD rupture and repair Temporary drainage of the biliary system prior to surgery

Question 53

Describe choledochal stenting

Answer 53

- 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

Question 54

Which liver lobe is most likely to become torsed?

Answer 54

Left lateral

Question 55

What is the proposed etiopathogenesis of cholelithiasis in dogs and cats

Answer 55

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