Small Bowel

Etiologies

• SMA embolism (50%): from LA (AF). LV (I EF). or valves; SMA most prone to embolism

• Nonocdusive mesenteric ischemia (25%): transient intestinal hypoperfusion due to

I CO, atherosclerosis, sepsis, drugs that i gut perfusion (pressors, cocaine, dig. diuretic)

• SMA thrombosis (10%): usually at site of atherosclerosis, often at origin of artery

• Venous thrombosis (10%): due to hypercoagulable states, portal hypertension.

malignancy, inflammation (pancreatitis, peritonitis), pregnancy, trauma, surgery

• Focal segmental ischemia of the small bowel (5%): vascular occlusion to small segments of the small bowd (vasculitis, atheromatous emboli, strangulated hernias. XRT)

Clinical manifestations

• Sudden onset of abdominal pain out of proportion to abdominal tenderness on exam

• Abdominal distension w/o pain (usually with nonocdusive disease); nausea vomiting

• Gl bleed due to mucosal sloughing (right colon is supplied by superior mesenteric artery)

• "Intestinal angina": postprandial abdominal pain & early satiety may occur wks to mos before the onset of acute pain in Pts w chronic mesenteric ischemia Physical exam

• May be unremarkable, or may only show abdominal distention or occult blood in stool

• Bowel infarction suggested by peritoneal signs (diffuse tenderness, rebound, guarding)

Diagnostic studies

• Diagnosis relies on high level of suspicion; rapid diagnosis essential to avoid infarction

• Laboratory evaluation: may be normal;' WBC; T amylase and LDH;

metabolic acidosis and * lactate (late)

• Imaging studies plain radiograph: normal prior to infarction, "thumbprinting" & ileus in later stages abdominal CT: early signs nonspecific; colonic dilatation, bowel wall thickening.

pneumatosis of bowel wall; best test to detect mesenteric vein thrombosis CT angiogram: more sensitive than CT alone, less invasive than standard angio angiography: gold standard; potentially therapeutic; indicated if suspect occlusion Treatment

• Volume resuscitation, optimization of hemodynamics, discontinue pressors if possible

• Broad spectrum antibiotics (amp gent MNZ) for infarction, sepsis

• Intraarterial infusion of thrombolytic agent for acute arterial embolism

• Anticoagulation for arterial and venous thrombosis and embolic disease

• Intraarterial infusion of papaverine (vasodilator) for nonocdusive mesenteric ischemia

• Surgery: embolectomy for acute arterial embolism; revascularization for acute superior mesenteric arterial thrombosis; resection of infarcted bowel

Prognosis

• Mortality 20-70%; dx prior to infarction strongest predictor of survival

Ischemic Colitis Definition and pathophysiology

• Non-ocdusive disease 2° to As in systemic circulation or anatomic fxnal As in local mesenteric vasculature

• Most common ischemic bowel syndrome

• "Watershed" areas (splenic flexure and recto-sigmoid) are most susceptible Clinical manifestations, diagnosis, and treatment

• Disease spectrum: reversible colopathy (35%). transient colitis (15%). chronic ulcerating colitis (20%). stricture (10%). gangrene (15%). fulminant colitis (<5%)

• Usually p/w cramping LLQ pain with ® FOBT or overtly bloody stool; fever and peritoneal signs should raise clinical suspicion for infarction

• Diagnosis: r o infectious colitis; consider flexible sigmoidoscopy or colonoscopy if sx persist and no alternative etiology identified (only if peritonitis not present)

• Treatment: bowel rest. IV fluids, broad spectrum abx, serial abd. exams; surgery for infarction, fulminant colitis, hemorrhage, failure of medical Rx. recurrent sepsis, stricture

• Resolution w in 48 h with conservative measures occurs in over 50% of cases

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