3.2 Hepatic, Biliary & Pancreatic Disorders

Hepatic, Biliary, and Pancreatic Diseases

Disorders of the hepatobiliary system and pancreas are highly prevalent on the PANCE. Successful candidates must master hepatitis serologic panels, understand the physiological basis of cirrhosis complications, and differentiate biliary disorders based on physical exam findings and diagnostic testing.

Viral Hepatitis and Serological Panels

Viral hepatitis is hepatocyte inflammation caused by hepatotropic viruses. Hepatitis A (HAV) and E (HEV) are transmitted via the fecal-oral route, causing acute, self-limiting disease that never transitions to chronic states. Hepatitis B (HBV), C (HCV), and D (HDV) are bloodborne pathogens transmitted parenterally or sexually and can lead to chronic liver disease, cirrhosis, and hepatocellular carcinoma. Hepatitis B serology interpretation is high-yield. Hepatitis B surface antigen (HBsAg) is the first marker to appear during acute infection and its persistence beyond six months defines chronic infection. Hepatitis B surface antibody (anti-HBs) indicates protective immunity, which is acquired via vaccination or natural clearance. Hepatitis B core antibody (anti-HBc) is a marker of exposure to the natural virus; IgM anti-HBc denotes acute or recent infection (and is the sole marker positive during the "window period" when HBsAg is cleared but anti-HBs is not yet detectable), while IgG anti-HBc denotes chronic infection or past recovery. Hepatitis B e-antigen (HBeAg) is a marker of active viral replication and high infectivity. Hepatitis C is screened using anti-HCV antibodies, but confirmation requires quantitative HCV RNA polymerase chain reaction (PCR) testing. Acute or chronic infection is treated with direct-acting antivirals (DAAs) which are curative.

Cirrhosis and Portal Hypertension Complications

Cirrhosis represents end-stage hepatic fibrosis with regenerative nodules, leading to portal hypertension and synthetic dysfunction. The major complications include:

• Ascites: Fluid accumulation in the peritoneal cavity due to portal hypertension-induced splanchnic vasodilation, which triggers renin-angiotensin-aldosterone system (RAAS) activation and sodium retention. First-line management includes dietary sodium restriction (<2 g/day) and dual diuretics. The standard regimen combines spironolactone (an aldosterone antagonist) and furosemide (a loop diuretic) in a 100:40 mg ratio to maintain normal potassium balance. Refractory ascites requires large-volume paracentesis; if more than five liters of fluid are removed, intravenous albumin (6-8 g/L of fluid removed) must be administered to prevent post-paracentesis circulatory collapse.
• Hepatic Encephalopathy: Neuropsychiatric dysfunction caused by toxic metabolites (primarily ammonia) bypassing liver clearance due to portosystemic shunting. It presents with confusion, sleep disturbances, and asterixis (a flapping tremor elicited by wrist dorsiflexion). First-line treatment is lactulose, which is metabolized by colonic bacteria into organic acids that lower colonic pH, converting absorbable ammonia (NH3) into non-absorbable ammonium (NH4+) and facilitating its excretion via osmotic diarrhea. Rifaximin, an oral non-absorbable antibiotic, is added for refractory cases to decrease ammonia-producing gut flora.
• Esophageal Varices: Dilated collateral veins in the distal esophagus at risk of rupture. Primary prophylaxis is achieved with non-selective beta-blockers (propranolol or nadolol), which cause splanchnic vasoconstriction and reduce portal inflow. Active variceal hemorrhage is a medical emergency managed with intravenous octreotide (a somatostatin analog that induces splanchnic vasoconstriction), prophylactic ceftriaxone, and emergent endoscopic variceal ligation (EVL).

Biliary Tract Pathology: Acute Cholecystitis

Acute cholecystitis is gallbladder inflammation caused by cystic duct obstruction, typically by a gallstone. It presents with constant, severe right upper quadrant (RUQ) pain radiating to the right shoulder, fever, leukocytosis, and a positive Murphy sign (inspiratory arrest during deep palpation of the RUQ). The initial diagnostic test of choice is RUQ transabdominal ultrasound. Classic ultrasound findings include gallbladder wall thickening (>3 mm), pericholecystic fluid, gallstones, and a sonographic Murphy sign. If the ultrasound is equivocal but clinical suspicion remains high, the gold standard diagnostic test is hepatobiliary iminodiacetic acid (HIDA) scan. Non-visualization of the gallbladder on HIDA scan indicates cystic duct obstruction and confirms acute cholecystitis. Treatment is intravenous fluids, antibiotics, and laparoscopic cholecystectomy.

Acute Pancreatitis

Acute pancreatitis is an inflammatory disorder of the pancreas, most commonly caused by gallstones and chronic alcohol consumption. Other causes include hypertriglyceridemia (>1000 mg/dL), medications (e.g., thiazides, valproic acid), and trauma. It presents with severe, sharp epigastric pain that characteristically radiates to the back and is partially relieved by sitting upright and leaning forward. Diagnosis requires at least two of the three following criteria:

1. Typical epigastric abdominal pain radiating to the back.
2. Serum lipase or amylase elevated >=3 times the upper limit of normal (lipase is preferred due to superior sensitivity and specificity).
3. Characteristic findings on contrast-enhanced computed tomography (CECT) or magnetic resonance imaging (MRI). Early prediction of severity and mortality is determined using scoring systems such as the Ranson criteria or the APACHE II score. Ranson criteria evaluate parameters at admission (age >55, WBC >16k, glucose >200, LDH >350, AST >250) and during the first 48 hours (hematocrit drop >10%, BUN rise >5, calcium <8, PaO2 <60, base deficit >4, fluid sequestration >6L). A score >=3 indicates severe disease. The cornerstone of management is early, aggressive intravenous volume resuscitation (ideally with Lactated Ringer's), pain control, and pancreatic rest (NPO).