Small Bowel Disorders: Chronic Intestinal Ischemia and Acute Intestinal Ischemia
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Small Bowel Disorders: Chronic Intestinal Ischemia and Acute Intestinal Ischemia

Angiography is the test of choice and allows identification of the cause of ischemia, which is important for the selection of a treatment method. Emboli are treated surgically by embolectomy, thrombotic disease requires arterial bypass, whereas vasoconstriction responds to vasodilators.

Ileus and Chronic Intestinal Pseudo-Obstruction

• Both conditions represent small-bowel hypomotility causing a picture of small-bowel obstruction in the absence of a mechanical cause. Symptoms are similar to those of a mechanical obstruction except for the presence of diminished or absent bowel sounds consistent with hypomotility.

• Ileus is an acute reversible syndrome seen most commonly after abdominal surgery or with infections, electrolyte abnormalities, and certain medications.

• Chronic intestinal pseudo-obstruction is chronic irreversible intestinal dysmotility that is caused by myopathies or neuropathies affecting the small intestine. Common causes include diabetes mellitus, thyroid disease, systemic sclerosis, Parkinson’s disease, and viral infections such as Epstein-Barr virus.

• Ileus is diagnosed by abdominal imaging, although differentiation from mechanical obstruction can be challenging and may require additional tests. Management of ileus consists of reversing the cause and providing symptomatic relief through nasogastric suction and abstaining from oral intake. Temporary support with intravenous (IV) fluids and occasionally TPN is necessary.

• The diagnosis of chronic pseudo-obstruction is suggested by the recurrent nature of the bowel obstruction in the absence of a specific reversible cause. Manometric studies are necessary to make a definitive diagnosis. Identifying the etiology of chronic intestinal pseudo-obstruction often requires full thickness biopsy of the bowel. Management is challenging and focuses on ensuring adequate nutritional intake through TPN in advanced cases. Promotility agents are not particularly effective, whereas venting gastrostomy can be useful to remove secretions.

Chronic Intestinal Ischemia

• A chronic reduction in arterial perfusion of the small bowel that is caused by the presence of occlusive atherosclerotic lesions, and less frequently by vasculitis. Considering the extensive collateral flow, ischemia can only be clinically significant if two of the three major arteries (celiac, superior mesenteric, inferior mesenteric artery) are affected.

• The most common presentation of chronic intestinal ischemia is recurrent postprandial abdominal pain (visceral angina) leading to food aversion and weight loss in the absence of any other explanation. An upper abdominal bruit can be heard in most cases. Finding of occluded arteries by angiography establishes the diagnosis. Less invasive testing such as duplex ultrasound scan and magnetic resonance angiography (MRA) can be very helpful. Treatment requires revascularization through stenting, endarterectomy, grafting, or bypass surgery. The long-term success rate is good.

Acute Intestinal Ischemia

• Acute occlusion of a visceral arterial branch because of embolization, thrombosis, or arterial spasm. Occasionally, it is caused by a sudden drop in blood pressure.

• Presents with sudden onset of excruciating periumbilical pain without any significant findings on physical examination unless bowel perforation is present. Bowel infarction is suspected when lactic acidosis is found.

• Angiography is the test of choice and allows identification of the cause of ischemia, which is important for the selection of a treatment method. Emboli are treated surgically by embolectomy, thrombotic disease requires arterial bypass, whereas vasoconstriction responds to vasodilators. Any suspicion of bowel infarction requires urgent surgery and resection of the infarcted bowel.

• Despite aggressive interventions, the overall mortality is approximately 70%, which increases to 90% if bowel infarction occurs.

 

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