Gastroenterology (including Hepatology)
Core concepts
Read liver biochemistry by pattern: hepatocellular (ALT/AST rise out of proportion to ALP) versus cholestatic (ALP and GGT rise). Cirrhosis complications: variceal bleeding (band ligation, terlipressin, prophylactic antibiotics), ascites (diagnostic tap; serum-ascites albumin gradient ≥11 g/L means portal hypertension), spontaneous bacterial peritonitis (ascitic neutrophils >250 cells/mm³; cephalosporin plus albumin), hepatic encephalopathy (lactulose plus find the precipitant), hepatorenal syndrome. Hepatitis B serology: HBsAg = current infection, anti-HBs = immunity, anti-HBc IgM = acute or recent, HBeAg = high replication; isolated anti-HBc means remote infection, window period or occult infection. Inflammatory bowel disease: ulcerative colitis is continuous from the rectum and mucosal; Crohn's is skip lesions, transmural, granulomatous, with perianal disease; smoking worsens Crohn's but protects against ulcerative colitis. Coeliac disease: IgA tissue transglutaminase with a total IgA (IgA deficiency causes false negatives), villous atrophy, dermatitis herpetiformis. Pancreatitis: gallstones and alcohol; do not give prophylactic antibiotics; feed early in mild disease.
Traps
Misreading a cholestatic picture as hepatocellular. Missing Wilson's disease or haemochromatosis in a young patient with liver disease. Giving NSAIDs in inflammatory bowel disease or in cirrhosis with ascites. Assuming a normal ALP excludes biliary obstruction.
Rule of thumb
Ascitic fluid with a SAAG ≥11 g/L indicates portal hypertension (cirrhosis, cardiac failure, Budd-Chiari); a SAAG <11 g/L suggests peritoneal disease such as tuberculosis, malignancy or pancreatic ascites.