Intestinal Ischemia¶

Michael Koenig

Acute Mesenteric Ischemia¶

Sudden onset ↓ or absence of blood flow to the small intestines
Mesenteric Arterial Occlusion:
- Arterial Embolism: Associated with cardiac arrhythmias (atrial fibrillation), valvular disease, endocarditis, ventricular aneurysm, aortic atherosclerosis, and aortic aneurysm
- Arterial thrombosis: Most commonly from atherosclerotic disease; can also be 2/2 abdominal trauma, infection, or dissection
Venous thrombosis:
- Associated w/ hypercoagulable states, malignancy, prior abdominal surgery, abdominal mass venous compression, intra-abdominal inflammatory processes
Non occlusive mesenteric ischemia:
- Intestinal hypoperfusion and vasoconstriction; associated with decreased cardiac output, sepsis, vasopressor use

Early: Abdominal pain is most common symptom, abdominal distension
Abdominal tenderness is not prominent early (“pain out of proportion to the exam”)
Arterial occlusion: Sudden onset, severe periumbilical pain, nausea, and emesis
Venous thrombosis: More insidious onset abdominal pain, waxing and waning
Nonocclusive mesenteric ischemia: variable location and severity of abdominal pain; often overshadowed by a precipitating disorder
Late: As transmural bowel infarction develops, abdomen becomes distended, bowel sounds become absent, and peritoneal signs develop

Type and Screen, Lactic acid, BMP, CBC
Imaging: KUB: Normal in > 25% of cases
Ileus w/ distended bowel loops, bowel wall thickening, ± pneumatosis intestinalis
Free intraperitoneal air immediate abdominal exploration
CT Angiography: no oral contrast, obscures mesenteric vessels, ↓ bowel wall enhancement
Focal or segmental bowel wall thickening, intestinal pneumatosis, portal vein gas, porto-mesenteric thrombosis, mesenteric arterial calcification, mesenteric artery occlusion

General: IVFs, NPO, hemodynamic monitoring and support (try to avoid vasoconstricting agents), anticoagulation, broad-spectrum antibiotics, pain control
If develops peritonitis or evidence of perforation on CT EGS consult for surgery
Mesenteric arterial embolism: Embolectomy vs. local infusion of thrombolytic agent
Mesenteric arterial thrombosis: Surgical revascularization vs. thrombolysis with endovascular angioplasty and stenting
Venous thrombosis: Anticoagulation; possible thrombolysis if persistent symptoms
Nonocclusive occlusion: Treat underlying cause, stop vasoconstriction meds, consider intra-arterial vasodilator infusion

↓ blood flow to intestines, typically caused by atherosclerosis of mesenteric vessel
High-grade mesenteric vascular stenoses in at least two major vessels (celiac, SMA, or IMA) must be established

Conservative management if asymptomatic: smoking cessation and secondary prevention to limit progression of atherosclerotic disease
Nutritional evaluation
Revascularization (open vs. endovascular) is indicated if symptoms are present
Mesenteric angioplasty and stenting is first-line therapy
Goal is to prevent future bowel infarction

Sudden, transient reduction in blood flow to colon
Typically at “watershed” areas, such as the splenic flexure and rectosigmoid junction
Most often nonocclusive (95% of cases) and affects older adults
Risk factors: ACS, hemodialysis, shock, aortoiliac instrumentation, cardiopulmonary bypass, extreme exercise (marathon running)

Rapid onset, mild cramping abdominal pain, associated with urge to defecate, hematochezia
Tenderness present (typically over left side)

Lactic acid (nonspecific but elevated), LDH, CPK, CBC (leukocytosis), BMP (metabolic acidosis)
KUB; if peritonitis or signs of severe ischemia → surgery
CT A/P with IV contrast (and oral contrast if patient can tolerate)
Consider CTA A/P if suspicion for vascular occlusion
Colonoscopy confirms diagnosis.
Edematous, friable mucosa; erythema; and interspersed pale areas; bluish hemorrhagic nodules representing submucosal bleeding
Segmental distribution, abrupt transition between injured and non-injured mucosa

General: IVFs, bowel rest, antibiotics (Zosyn vs CTX/flagyl)

Ischemic Colitis Management
	Classification	Management
Mild	No risk factors (see below)	Supportive care and observation Antibiotics can be stopped if no ulceration
Moderate	1-3 risk factors	Same as mild ischemia if no vascular occlusion Systemic anticoagulation +/- vascular intervention if mesenteric occlusion
Severe	> 3 risk factors, peritoneal signs, pneumatosis, pneumoperitoneum, gangrene or pancolonic ischemia on colonoscopy	Consult EGS for abdominal exploration and segmental resection
Risk factors: male, SBP <90, HR >100, WBC>15k, Hgb <12, Na <136, BUN >20, LDH >350, isolated right-sided colonic involvement, abdominal pain with rectal bleeding