Small-bowel bleeding

Acute upper gastrointestinal bleeding arises proximal to the ligament of Treitz and presents with hematemesis or melena, most often from peptic ulcer disease or bleeding gastroesophageal varices. Management sequences resuscitation, restrictive transfusion, IV proton pump inhibitor therapy, and, when varices are suspected, octreotide plus antibiotic prophylaxis, all before upper endoscopy within 24 hours, which is both diagnostic and therapeutic.

Acute lower gastrointestinal bleeding is hematochezia from a source distal to the ligament of Treitz, most often diverticular, that requires simultaneous resuscitation and localization because a brisk upper source can masquerade as the same presentation. Colonoscopy after rapid bowel preparation is the first-line diagnostic and therapeutic study in stable patients, while CT angiography localizes active bleeding in unstable or rapidly bleeding patients before catheter embolization or surgery.

Peptic ulcer disease is a mucosal break in the stomach or duodenum caused chiefly by Helicobacter pylori infection or NSAID use, diagnosed by upper endoscopy with biopsy of gastric ulcers to exclude malignancy. Treatment eradicates H. pylori when present, stops the ulcerogenic drug, and heals the ulcer with a proton pump inhibitor, while its complications of bleeding, perforation, and obstruction drive most of its morbidity.

Crohn disease is a chronic transmural inflammatory bowel disease that can affect any segment from mouth to anus in skip lesions, most classically the terminal ileum, and is confirmed by ileocolonoscopy showing cobblestoning, skip areas, and non-caseating granulomas on biopsy. Management follows an ordered sequence of glucocorticoid or budesonide induction followed by immunomodulator or biologic maintenance, with surgery reserved for fixed complications rather than cure.

Nonsteroidal anti-inflammatory drugs (NSAIDs) relieve pain, fever, and inflammation by inhibiting cyclooxygenase (COX)-1 and COX-2, and that single mechanism predicts every major toxicity: gastric ulceration, platelet dysfunction, and hemodynamic renal injury. First-line agents are naproxen or ibuprofen (or topical diclofenac for knee or hand osteoarthritis) at the lowest effective dose for the shortest duration, with a proton pump inhibitor such as omeprazole 20 mg once daily added for patients at increased gastrointestinal risk.

Carcinoid syndrome is the clinical syndrome of episodic flushing, secretory diarrhea, and late right-sided valvular heart disease caused by serotonin and other vasoactive amines escaping hepatic first-pass metabolism, almost always because a well-differentiated neuroendocrine tumor has spread to the liver or arises outside the portal circulation. Diagnosis rests on an elevated 24-hour urinary 5-HIAA with tumor localization by somatostatin-receptor PET, and management combines somatostatin analogues for symptom control and antiproliferative effect with tumor-directed therapy and peri-procedural crisis prevention.

Celiac disease is an immune-mediated small-intestinal enteropathy triggered by dietary gluten in genetically predisposed individuals, presenting with malabsorptive diarrhea, iron-deficiency anemia, or dermatitis herpetiformis. Diagnosis requires IgA tissue transglutaminase serology with a total IgA level while the patient still eats gluten, confirmed by duodenal biopsy showing villous atrophy, and the only treatment is a strict lifelong gluten-free diet.