Intestinal ischemia resident survival guide
Synonyms and keywords: Mesenteric ischemia, bowel ischemia

# Overview
Intestinal ischemia are a heterogeneous group of diseases characterized by hypoxia of the small bowel and/or colon, which most commonly arises from occlusion, vasospasm, and/or hypoperfusion of the mesenteric vasculature.

# Classification

## Acute Mesenteric Ischemia
Acute mesenteric ischemia (AMI) includes superior mesenteric artery embolism (SMAE) (50%); nonocclusive mesenteric ischemia (NOMI) (20% to 30%); superior mesenteric artery thrombosis (SMAT) (15% to 25%); and superior mesenteric vein (SMV) thrombosis (5%).  It is most commonly associated with compromise of the blood flow in the superior mesenteric artery (SMA) distribution affecting all, or portions of, the small bowel and right colon.

## Chronic Mesenteric Ischemia
Chronic mesenteric ischemia (CMI) is usually referred to intestinal angina, where the splanchnic circulation is insufficient in meeting the functional demands of the gut, but there is no loss of tissue viability.

## Colonic Ischemia
Colonic ischemia (CI) is the most common vascular disorder of the gut that includes reversible ischemic colopathy, transient ulcerating ischemic colitis, chronic ulcerating ischemic colitis, colonic stricture, colonic gangrene, and fulminant universal ischemic colitis.

# Causes

## Life Threatening Causes
Intestinal ischemia can be a life-threatening condition and must be treated as such irrespective of the underlying cause.

## Common Causes
- Arterial embolism
- Arterial thrombosis
- Hypercoagulable states
- Non-occlusive ischemia
- Cardiogenic shock
- Vasculitis
- Vasoconstrictors: Cocaine, ergot, vasopressin, or norepinephrine.
- Venous thrombosis

# Management
The algorithm is based on the American Gastrointestinal Association guidelines for management of intestinal ischemia in adults.

## Management of Acute Mesenteric Ischemia

### Management of Mesentric Venous Thrombosis

### Management of Major and Minor Embolus

### Management of Thrombus Occlusion and Nonocclusive Mesenteric Ischemia

## Management of Chronic Mesenteric Ischemia

## Management of Colonic Ischemia

# Do's
- A high index of suspicion in elderly patients with risk factors for intestinal ischemia is imperative for making a prompt diagnosis.
- Rapid diagnosis is essential to prevent the catastrophic events associated with delay in immediate treatment leading to intestinal infarction.
- Aggressive hemodynamic support, monitoring in intensive care unit, correction of metabolic acidosis, initiation of broad spectrum antibiotics, and placement of a nasogastric tube for gastric decompression take priority over specific treatment.
- Hemodynamic stabilization should be achieved prior to arteriography.
- Stool cultures for Salmonella, Shigella, Campylobacter, Yersinia, E-coli O157:H7, and assay for stool toxins of Clostridium difficile should be considered in the appropriate clinical situation.
- Do aim at the prevention of future embolic events, typically with the long term use of warfarin.

# Dont's
- Don't treat patients with severe diarrheal dehydration using 5% dextrose with 1/4 normal saline, as using solutions with lower amounts of sodium (such as 38.5 mmol/L in 1/4 saline with 5% dextrose ) would lead to sudden and severe hyponatremia with a high risk of death.
- Dont administer systemic anticoagulants to prevent thrombus formation or propagation in patients who are actively bleeding.
- Dont use opioids, anticholinergic and antidiarrheal agents in patients with severe colitis because of the potential to precipitate further complications.