PNEUMATOSIS INTESTINALIS

Pneumatosis (cystoides) intestinalis (PI) is defined as multiple gas-filled cysts in the gastrointestinal tract wall (1, 2, 3). The cysts may be located in the subserosa, submucosa, and rarely, the muscularis layer (1, 4). They may be single or multiple and vary in size from microscopic to several centimeters in diameter (4). They are usually lined by mixed inflammatory cells, macrophages, or foreign body giant cells (1, 3, 4) with no communication between the air spaces and the bowel lumen (5, 6). PI is a radiographic finding and not a diagnosis. PI is considered an ominous finding in ischemia, particularly if it is associated with portomesenteric venous gas (1, 6). The majority of cases of PI occur in the jejunum and ileum, with 6-10% of cases involving the colon (6).

Two forms of PI are recognized: primary and secondary (4, 5, 7, 8) Primary pneumatosis intestinalis (15% of cases) is a benign idiopathic condition and patients are usually asymptomatic. These cysts are incidentally discovered on radiography or endoscopy. The secondary form (85% of cases) is associated with obstructive pulmonary disease, as well as obstructive and necrotic gastrointestinal diseases (6, 8).

PI is a rare condition, although the exact prevalence is unknown. No sex or race predominance is reported (6). Exact pathogenesis of PI is not known and many theories explaining the process of PI have been put forth; the most prominent among them are mechanical, bacterial, and pulmonary mechanisms (7, 8).

More than fifty causative factors have been identified that result in PI (1, 7). The breadth of pathologic conditions associated with PI formations suggests that its development is a multifaceted phenomenon (2). Common causes are summarized in Table 1

Table 1.
Common causes of pneumatosis intestinalis
1. Necrotizing enterocolitis
2. Ischemia and infarction
3. Emphysematous gastritis
4. Bowel obstruction
5. Trauma of child abuse
6. Crohn’s disease
7. Immunotherapy
8. Steroid therapy
9. Chemotherapy
10. AIDS enterocolitides
11. Pulmonary disease

Plain X-ray film findings of PI include air within the walls of the GI tract. The patterns of the radiolucencies seen may be linear, curvilinear, small bubbles, or collections of larger cysts (5, 7) Pneumoperitoneum or pneumoretroperitoneum can be seen secondary to cyst rupture (6, 7, 8, 9).

PI on barium enema is visualized as a circumscribed attenuation pattern in the contrast column. When the cysts protrude into the lumen, they may mimic polyps or carcinomas on barium enema studies (2, 3, 7, 8). Gas enters the bowel wall because of direct trauma. Enhanced gut permeability to gas can be induced by defects in the mucosa, the gut’s immune barrier (intramural lymphoid tissue), or both (2).The current case is interesting because it is the first published patient with PI after direct repetitive colon trauma.

PI appearance on ultrasound includes circumferential, bright, echogenic foci in the bowel wall.

Computed tomography (CT) with a wide lung parenchyma window is the best imaging modality for establishing the diagnosis of PI. It has greater sensitivity than plain film or ultrasound (6, 7). CT can distinguish PI from intraluminal air or submucosal fat. A thickened bowel wall with contrast enhancement may suggest ischemia in the setting of PI. Dilated bowel loops and abnormal fluid levels suggest an obstructive cause

When a foreign body causes PI, a careful history and physical examination should be followed by a biplanar radiograph of the abdomen to determinate not only the exact position of the foreign body (or bodies) but also to assess the presence of free air to exclude perforation (10) The most common reason for rectal foreign bodies is autoeroticism; other causes include criminal assault and medical diagnostic indications (10).