Intestinal Ischemia (Acute Mesenteric Ischemia)

Diagnosis
–History and Physical.
-Risk Factors:
-DDx and Etiology:
-A very high index of suspicion is needed for timely diagnosis. Time is bowel. Timely dx is key to avoiding bowel infarction which can occur within hours.
-Labs: Often normal or nonspecific early on. Later often shows leukocytosis, acidosis, elevated HCT (from hemoconcentration).
Order: CBC, CMP, LDH, lactate, FOBT, lipase, phosphate, D-dimer. Lactic acidosis is a late finding found in only 50% patients. FOBT is positive in ~75% patients.
-CT angiogram (arterial phase imaging): is the recommended non-invasive imaging modality of choice for the diagnosis of visceral ischemic syndromes because of its 95%–100% accuracy. It shows the architecture of the vessels, the extent of stenosis or occlusion/thrombi in mesenteric vessels and helps in the assessment of options for revascularization. It also clearly shows bowel wall structure and reveals any bowel wall thickening, dilation of the colon, pneumatosis/portal venous gas, etc. CTA can be done quickly vs. MRA which is slow and doesn’t give as good an image.
–CT abdomen with contrast is acceptable if you can’t get CT angiogram.
-KUB – Usually normal early before infarct. Look for “thumbprinting”, ileus, pneumatosis in later stages.
–Mesenteric angiography is the gold standard and is potentially therapeutic; indicated if you suspect occlusion. Used after a plan for revascularization has been chosen
Treatment
–IVFs – Fluid resuscitation (to increase perfusion). Limit use of vasopressors.
–Broad-spectrum antibiotics – that covers enteric flora. E.g. Zosyn.
–Consult surgery ASAP so they are aware and give input early. If peritoneal signs develop, emergent surgery to resect the necrotic bowel is indicated.
–Anticoagulation – In the hospital, use heparin drip.
-Pain Management – Morphine / Hydromorphone
-Ischemia due to vasospasm, not an occlusion: Consider catheter-directed infusion of a vasodilator (like Papaverine) into the SMA to help the spasm.
“-For AMI caused mesenteric artery occlusion:
–SMA embolism: consider fibrinolytic; if no quick improvement, proceed to surgical embolectomy if possible, o/w aortomesenteric bypass
–SMA thrombosis: percutaneous or surgical revascularization
-For AMI 2/2 to nonocclusive causes: correct underlying cause (especially cardiac)
-Consider angioplasty/stent vs. surgical revascularization in cases of chronic mesenteric ischemia if: 2 vessels or occlusion of SMA, supportive clinical hx, & other etiologies for abd pain excluded
-Prognosis: Mortality 20 to 70% if bowel infarcted; dx prior to infarction strongest predictor of survival” Pocket Medicine.