Acute abdomen

# Overview
Acute abdomen refers to a sudden, severe pain in the abdomen that is less than 24 hours in duration.  It is in many cases an emergency condition requiring urgent and specific diagnosis, and the treatment usually involves surgery.

# Classification

## Peritonitis
Acute abdomen is occasionally used synonymously with peritonitis.  This is not incorrect; however, peritonitis is the more specific term, referring to inflammation of the peritoneum.  It is diagnosed on physical examination as rebound tenderness, or pain upon removal of pressure rather than application of pressure to the abdomen. Peritonitis may result from several diseases, notably appendicitis and pancreatitis.

## Ischemic Acute abdomen
Vascular disorders are more likely to affect the small bowel than the large bowel.  Arterial supply to the intestines is provided by the superior and inferior mesenteric arteries, (SMA and IMA respectively) both of which are direct branches of the aorta.
The superior mesenteric artery supplies:
- Small bowel
- Ascending and proximal 2/3 of the transverse colon
The inferior mesenteric artery supplies:
- Distal 1/3 of the transverse colon
- Descending colon
- Sigmoid colon
Of note, the splenic flexure, or the junction between the transverse and descending colon, is supplied by the most distal portions of both the inferior mesenteric artery and superior mesenteric artery. It is referred to medically as a watershed area, or an area especially vulnerable to ischemia during periods of systemic hypoperfusion, such as in shock (medical).
Acute abdomen of the ischemic variety is usually due to:
- A thromboembolism from the left side of the heart, such as may be generated during atrial fibrillation, occluding the SMA.
- Nonocclusive ischemia, such as that seen in hypotension secondary to heart failure may also contribute, but usually results in a mucosal or mural infarct, as contrasted with the typically transmural infarct seen in thromboembolus of the SMA.
- Primary mesenteric vein thromboses may also cause ischemic acute abdomen, usually precipitated by hypercoagulable states such as polycythemia vera.

# Causes

## Life Threatening Causes

## Common Causes
- Acute appendicitis
- Acute peptic ulcer and its complications
- Acute cholecystitis
- Acute pancreatitis
- Acute intestinal ischemia
- Diabetic ketoacidosis
- Acute diverticulitis
- Ectopic pregnancy with tubal rupture
- Acute peritonitis
- Bowel perforation with free air or bowel contents in the abdominal cavity
- Acute ureteral colic
- Bowel volvulus

## Causes by Organ System

## Causes in Alphabetical Order

# Diagnosis

## History and Symptoms
Patients with an Ischemic type of acute abdomen present with symptoms of:
- Diffuse abdominal pain
- Bowel distension
- Bloody diarrhea

## Physical Examination

### Abdomen
In cases of ischemic acute abdomen, bowel sounds will be absent.

## Laboratory Findings
In cases of ischemic acute abdomen, laboratory tests reveal:
- Neutrophilic leukocytosis, sometimes with a left shift assessed through a complete blood count
- Increased serum amylase.

## CT
A CT scan can provide a differential diagnosis between simple and complex pathologies causing the Acute abdomen.  The scan can also provide evidence to the doctor whether surgical intervention is necessary.

## Other Imaging Findings
In cases of ischemic acute abdomen, abdominal radiography will show many air-fluid levels, as well as widespread edema.

# Treatment

## Surgery
Acute ischemic abdomen is a surgical emergency.  Typically, treatment involves removal of the region of the bowel that has undergone infarction, and subsequent anastomosis of the remaining healthy tissue.