Pneumatosis intestinalis

Overview
Pneumatosis intestinalis is a sign on x-ray which is highly suggestive for necrotizing enterocolitis. The literal meaning is gas in the bowel wall, as opposed to in the lumen which is normal.


 * Pneumatosis intestinalis (PI) is defined as the presence of gas in the bowel wall.
 * PI is associated with numerous conditions, ranging from benign to life threatening.

Benign causes include

 * Pulmonary: Asthma, Bronchitis, Emphysema, Cystic fibrosis
 * Systemic disease: Scleroderma, Systemic lupus erythematosus
 * Intestinal causes: Enteritis, Peptic ulcers, Bowel obstruction, Adynamic ileus, Inflammatory bowel disease, Diverticulitis
 * Iatrogenic: Postsurgical anastomosis, Endoscopy
 * Medications: Corticosteroids, Chemotherapeutic agents, Lactulose
 * Organ transplantation
 * Primary pneumatosis: Idiopathic, Pneumatosis cystoides intestinalis

Life-threatening causes

 * Intestinal ischemia
 * Mesenteric vascular disease
 * Intestinal obstruction (especially strangulation)
 * Colitis
 * Ingestion of corrosive agents
 * Toxic megacolon
 * Trauma

Two theories on pathogenesis of

 * Mechanical theory: gas dissects into the bowel wall from either the intestinal lumen or the lungs via the mediastinum due to some mechanism causing increased pressure.
 * Bacterial theory proposes that gas-forming bacilli enter the submucosa through mucosal rents or increased mucosal permeability and produce gas within the bowel wall.

Imaging Findings

 * Although PI can be seen on abdominal radiographs, CT is the most sensitive imaging test for identification of PI.
 * On both radiographs and CT, PI usually appears as a low-density linear or bubbly pattern of gas in the bowel wall. It can be a combination of both linear and bubbly bowel-wall gas. There also may be circular collections of gas in the bowel wall.
 * Viewing CT images with lung windows may accentuate the detection of PI, especially in the colon.
 * Circular form of PI is usually benign and most often seen with pneumatosis cystoides intestinalis (PCI).
 * Linear or bubble-like PI can be due to both benign and life-threatening causes, and its radiographic or CT appearance alone does not allow differentiation between them.
 * The presence of additional findings such as bowel wall thickening, absent or intense mucosal enhancement, dilated bowel, arterial or venous occlusion, ascites, and hepatic portal or portomesenteric venous gas increases the possibility of PI due to a life-threatening cause.
 * PI that is confined to a portion of the small or large bowel within a specific vascular distribution also increases the likelihood that ischemia is the cause of PI.
 * Intraperitoneal or retroperitoneal free air can be seen with PI due to life-threatening or benign causes.

Case Examples
Case #1

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