Gastrointestinal System and Nutrition
Core concepts
Sort abdominal pain by location, onset, and associated symptoms. Epigastric pain radiating to the back with lipase greater than three times the upper limit of normal is acute pancreatitis; treat with aggressive fluids, analgesia, and early enteral feeding. Right upper quadrant pain after fatty meals with a positive Murphy sign is cholecystitis, and right upper quadrant ultrasound is the first test. Fever, jaundice, and right upper quadrant pain define cholangitis, which needs biliary drainage by ERCP plus antibiotics. Periumbilical pain migrating to the right lower quadrant suggests appendicitis.
Upper gastrointestinal bleeding from ulcers is managed with resuscitation, a proton pump inhibitor, and endoscopy; variceal bleeding adds octreotide and prophylactic ceftriaxone with band ligation.
Inflammatory bowel disease: ulcerative colitis is continuous from the rectum with bloody diarrhea; Crohn disease is transmural with skip lesions, fistulae, and perianal disease.
Cirrhosis complications are heavily tested: ascitic fluid with a polymorphonuclear count of 250 or more means spontaneous bacterial peritonitis, treated with ceftriaxone plus albumin; encephalopathy is treated with lactulose; hepatorenal physiology follows.
Nutrition essentials: refeeding syndrome is driven by hypophosphatemia after rapid carbohydrate reintroduction in a malnourished patient; fat-soluble vitamins are A, D, E, and K.
Traps
- Ordering CT before ultrasound in suspected cholecystitis.
- Forgetting prophylaxis against variceal hemorrhage and spontaneous bacterial peritonitis in cirrhotic patients.
- Missing celiac disease in a patient labeled with irritable bowel syndrome.
Rule of thumb
Ascitic fluid with 250 or more neutrophils per microliter defines spontaneous bacterial peritonitis even with a negative culture; treat and give albumin to reduce renal failure.