Gastrointestinal System
Esophagus and stomach
Achalasia: progressive solid-then-liquid dysphagia with a bird's beak on barium swallow and loss of the myenteric plexus; raises squamous cell carcinoma risk. Esophageal cancer: progressive dysphagia and weight loss - squamous cell with smoking and alcohol, adenocarcinoma with Barrett esophagus. Peptic ulcer disease: Helicobacter pylori eradication or NSAID-related injury; duodenal ulcers classically improve with eating while gastric ulcers may not. Mallory-Weiss tear: retching followed by hematemesis. Variceal bleeding: portal hypertension; treat with octreotide, antibiotics, and endoscopic banding.
Bowel
Small bowel obstruction: crampy pain, vomiting, distension, high-pitched then absent bowel sounds, air-fluid levels. Ileus: diffuse and quiet abdomen without a transition point. Appendicitis: periumbilical pain migrating to the right lower quadrant with psoas or obturator signs. Diverticulitis: left lower quadrant pain, fever, leukocytosis; avoid colonoscopy acutely. Ulcerative colitis: continuous disease from the rectum, bloody diarrhea, pseudopolyps. Crohn disease: skip lesions, transmural inflammation, fistulas, granulomas, perianal involvement.
Liver and pancreas
Hepatocellular pattern: AST/ALT predominant; cholestatic pattern: ALP and GGT predominant. An AST/ALT ratio above 2 suggests alcohol-related liver disease. Acute pancreatitis: epigastric pain radiating to the back with lipase more than 3 times the upper limit of normal; gallstones and alcohol are the most common causes; treat with fluids and early feeding. Ascites: serum-ascites albumin gradient of 1.1 g/dL or more indicates portal hypertension; below 1.1 suggests peritoneal carcinomatosis or tuberculosis.
Rule of thumb
Fever, right upper quadrant pain, jaundice, and altered mental status (Reynolds pentad) mean ascending cholangitis - antibiotics alone are not enough; biliary drainage is urgent.