Chronic mesenteric ischemia

Acute mesenteric ischemia is an abrupt drop in small-bowel blood flow, most often superior mesenteric artery embolism, presenting as severe abdominal pain out of proportion to an unimpressive early examination. CT angiography confirms the diagnosis, and survival depends on immediate resuscitation, antibiotics, and anticoagulation followed by urgent revascularization or resection before infarction and peritonitis develop.

Ischemic colitis is the most common form of gastrointestinal ischemia, caused by a nonocclusive low-flow state in colonic microvessels that classically injures the watershed splenic flexure and rectosigmoid junction. Most cases are mild and self-limited with supportive care, but segmental CT thickening with peritoneal signs, pneumatosis, or gangrene demands emergent surgery rather than antibiotics alone.

Abdominal aortic aneurysm is focal dilation of the abdominal aorta to 3 cm or more, usually degenerative and often asymptomatic until rupture. Management is risk-factor control and surveillance for small aneurysms and elective repair at 5.5 cm (men) or with rapid growth or symptoms; rupture is a catastrophic emergency.

Chronic pancreatitis is irreversible fibro-inflammatory destruction of the pancreas that produces abdominal pain along with exocrine and endocrine insufficiency, most often from long-term alcohol use in adults and cystic fibrosis in children. Diagnosis rests on CT or MRI showing calcifications and ductal change, and management combines alcohol and tobacco cessation, staged analgesia, pancreatic enzyme replacement, and endoscopic or surgical drainage for ductal obstruction.

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.

Atherosclerosis is a chronic inflammatory, lipid-driven disease of the arterial wall in which plaques narrow arteries and can rupture to cause acute thrombosis. It underlies coronary, cerebrovascular, and peripheral artery disease, and management is aggressive risk-factor control, high-intensity statins, and antiplatelet therapy, with revascularization for specific lesions.

Peripheral artery disease is atherosclerotic narrowing of the limb arteries, most often causing exertional claudication and, when advanced, chronic limb-threatening ischemia. It is a strong marker of systemic atherosclerosis, diagnosed by the ankle-brachial index, and managed with aggressive risk-factor control, antiplatelet therapy, exercise, and revascularization for severe disease.

Irritable bowel syndrome is a functional disorder of gut-brain interaction diagnosed clinically by Rome IV criteria, recurrent abdominal pain related to defecation, stool frequency, or stool form, without alarm features. Management is subtyped by stool pattern, with fiber and dietary change first, then IBS-C secretagogues or IBS-D antidiarrheals and antibiotics, and low-dose tricyclics or antispasmodics for pain.

Colorectal cancer is an adenocarcinoma that arises through the adenoma-carcinoma sequence and presents differently by location, with right-sided tumors causing occult bleeding and iron-deficiency anemia and left-sided tumors causing obstruction and hematochezia. Colonoscopy with biopsy confirms the diagnosis, TNM staging on CT chest/abdomen/pelvis with CEA guides treatment, and management ranges from surgical resection alone for localized disease to adjuvant FOLFOX for node-positive colon cancer, neoadjuvant chemoradiation for rectal cancer, and molecularly targeted systemic therapy for metastatic disease.