eMedicine Specialties > Radiology > Gastrointestinal

Pneumatosis Intestinalis

Author: Sameer K Goyal, MD, Post Graduate Instructor, Staff Physician, Department of Radiology, Nassau University Medical Center
Coauthor(s): David I Weltman, MD, Consulting Staff, S & D Medical, LLP; Director, Department of Radiology, Southside Hospital; Dvorah Balsam, MD, Chief, Division of Pediatric Radiology, Nassau University Medical Center; Professor, Department of Clinical Radiology, State University of New York at Stony Brook
Contributor Information and Disclosures

Updated: Aug 13, 2009

Introduction

Background

Pneumatosis intestinalis, defined as gas in the bowel wall, is often first identified on abdominal radiographs or computed tomography (CT) scans. It is a radiographic finding and not a diagnosis, as the etiology varies from benign conditions to fulminant gastrointestinal disease. Pneumatosis intestinalis is considered an ominous finding in ischemia, especially in association with portomesenteric venous gas. The disease is seen in other conditions, including chronic obstructive pulmonary disease, connective tissue disorders, infectious enteritis, celiac disease, leukemia, amyloidosis, and acquired immunodeficiency syndrome (AIDS); it is also found in association with organ transplantation, steroid use, and chemotherapy.^1,2,3,4,5,6

Pneumatosis intestinalis occurs in 2 forms. Primary pneumatosis intestinalis (15% of cases) is a benign idiopathic condition in which multiple thin-walled cysts develop in the submucosa or subserosa of the colon. Usually, this form has no associated symptoms, and the cysts may be found incidentally through radiography or endoscopy. When the cysts protrude into the lumen, they may mimic polyps or carcinomas, as shown on barium enema studies. This primary form is often termed pneumatosis cystoides intestinalis.⁷ The secondary form (85% of cases) is associated with obstructive pulmonary disease, as well as with obstructive and necrotic gastrointestinal disease.

Recent studies

Khalil et al reported on computed tomographic and surgical findings in patients with pneumatosis intestinalis from 2003 to 2008. The authors noted that after its diagnosis, the specific pathogenesis must be identified because the appropriate therapy is related to the underlying cause, which is sometimes difficult to ascertain. They advise that surgical treatment be considered urgent in symptomatic patients who have an acute abdomen, signs of ischemia, or bowel obstruction and that, in asymptomatic patients, the underlying disease be treated first.⁸

McCarville et al studied the radiology reports at St. Jude Children's Hospital from 1994 through 2006 and identified 12 boys and 4 girls with pneumatosis intestinalis, 11 of whom were hematopoietic stem cell transplant recipients. Their study suggested that male children may be at increased risk of benign pneumatosis intestinalis; the incidence of benign pneumatosis may be proportional to the number of hematopoietic stem cell transplants; the degree of intramural distention may correlate with the number of bowel segments involved; and patients with free air may have a longer time to resolution of benign pneumatosis.⁹

Morris et al retrospectively reviewed the diagnosis and management of pneumatosis intestinalis in 97 patients who were diagnosed with pneumatosis by CT. The location of pneumatosis was the colon in 46% of cases; small bowel in 27%; stomach in 5%; and both small and large bowel in 7%. Fourteen patients also had portal venous gas; 6 of these patients subsequently died. In 52% of cases, the pneumatosis was managed nonoperatively; in 33%, surgical management was used; and in 15%, care was futile. Overall mortality was 22% (16% operative, 6% nonoperative, 87% futile). Patients who died had a higher mean APACHE II score (25 vs 11, P <.001).¹⁰

Pathophysiology

Several etiologies have been suggested for pneumatosis intestinalis. The formation of pneumocysts results from the interaction of multiple factors, such as mucosal integrity, intraluminal pressure, bacterial flora, and intraluminal gas. Mucosal disruption may be caused by bowel wall trauma, obstruction, ischemia, or inflammation, allowing bacteria or gas to invade the bowel wall. A bacterial origin of the gas is suggested by the high concentration of hydrogen within the cysts. Steroids, immunosuppressants, and chemotherapeutic agents also are thought to lead to pneumatosis through increased mucosal permeability.

Disease entities associated with pneumatosis intestinalis can be divided into the following 3 general categories:

• Necrotic gastrointestinal disease
• Nonnecrotic gastrointestinal disease
• Pulmonary diseases

Bowel necrosis leading to pneumatosis is seen in necrotizing enterocolitis (NEC), mesenteric ischemia, and caustic ingestions. In neonates, pneumatosis is usually secondary to NEC and indicates a later stage of the disease. NEC is seen almost exclusively in premature infants and is associated with bowel ischemia caused by bacterial invasion and hyperosmolar feeds. Mesenteric vascular occlusion leads to ischemic damage of the mucosa, which allows luminal gas and bacteria to invade the bowel wall. Corrosive agents, including lye, acids, and formaldehyde, also may lead to mucosal disruption and pneumatosis.

In the absence of bowel necrosis, many gastrointestinal diseases resulting in obstruction or ulceration can lead to pneumatosis intestinalis. Pneumatosis can be seen in pyloric stenosis and Hirschsprung disease in children, as well as in bowel obstruction in adults. The increased pressure proximal to the obstruction forces intraluminal gas into the bowel wall. Pneumatosis can be present in Crohn disease and ulcerative colitis because of a combination of mucosal ulceration, stenotic segments that increase the luminal pressure, and bacterial invasion. Pneumatosis has also been associated with collagen vascular disease and celiac sprue. Abdominal trauma may lead to mucosal disruption; pneumatosis has been found secondary to motor vehicle accidents, child abuse, and endoscopy.

Immunosuppression is one of the more common causes of pneumatosis. It has been suggested that steroid therapy and immunosuppressed states lead to the depletion of Peyer patches, resulting in loss of structural integrity of the bowel wall. Pneumatosis has been reported to occur after solid organ and bone marrow transplantation. Concomitant infection in these patients increases the risk of pneumatosis intestinalis. Graft-versus-host disease can lead to enterocolitis and pneumatosis in the absence of necrosis.

The most common associated infections include those resulting from cytomegaloviruses, rotaviruses, Clostridium difficile, and human immunodeficiency virus (HIV) enterocolitis.

Finally, severe obstructive pulmonary disease may result in pneumatosis. Rupture of pulmonary blebs in obstructive lung disease may cause air to dissect through the retroperitoneum, into the mesentery, and, finally, to the bowel subserosa and submucosa.

Frequency

United States

Pneumatosis intestinalis is a rare condition, although the exact prevalence is unknown. It is seen in 80% of cases of necrotizing enterocolitis.

Mortality/Morbidity

• In patients with pneumatosis intestinalis, the prognosis depends on the overall clinical picture. The wide range of possible causes, as described above, should first be considered.
• Pneumatosis is an ominous radiographic finding in patients suspected of having bowel ischemia, and surgery should be performed in patients who are not responding to nonoperative treatment, especially those with signs of perforation, peritonitis, or abdominal sepsis.
• Necrotizing enterocolitis has a mortality rate of about 30%, and as many as 50% of patients may require surgery for perforation.

Age

The incidence of pneumatosis intestinalis is highest in neonates because of the condition's association with necrotizing enterocolitis; however, pneumatosis intestinalis may occur in any age group. Primary pneumatosis intestinalis typically occurs in adults.

Anatomy

Primary pneumatosis intestinalis, which usually affects the descending colon, consists of cystic gas collections.

Secondary pneumatosis typically involves the small intestine, but it may occur throughout the gastrointestinal tract, and the collections are linear or curvilinear. Secondary pneumatosis is most frequently seen in the small bowel, but it can involve the colon, stomach, and esophagus as well.

Microvesicular gas collections, defined as 10-100 mm cysts or bubbles within the lamina propria, are predominantly associated with primary (benign) pneumatosis intestinalis, whereas linear or curvilinear gas collections seen parallel to the bowel wall are found in secondary pneumatosis. Therefore, linear gas collections are usually an ominous sign.

Presentation

Primary pneumatosis is often asymptomatic. Rarely, patients may experience symptoms secondary to the cysts. Signs and symptoms include diarrhea, bloody stools, abdominal pain, abdominal distention, and constipation. The physical findings are usually unremarkable.

In neonates, the elderly, and immunosuppressed patients, pneumatosis may be a sign of underlying disease. In these patients, the most life-threatening causes of secondary pneumatosis intestinalis, including bowel necrosis, should be investigated. The decision to proceed with surgical intervention is based on a combination of radiographic findings, laboratory markers, and clinical examination findings.

Preferred Examination

Pneumatosis intestinalis is usually identified on plain radiographs of the abdomen. Occasionally, submucosal cysts may be identified during endoscopy. The cysts, which may appear similar to polyps, may be examined at biopsy for signs of inflammation.

Gas may collect peripherally in the lumen of the bowel, around fecal or contrast material. This gas can simulate pneumatosis and is usually depicted on CT scans. Rarely, emphysematous ureteritis may simulate pneumatosis of the descending or sigmoid colon on plain radiographs. Colitis cystica profunda is an extremely rare disease in which mucin-filled cysts form in the wall of the rectum.

Differential Diagnoses

Other Problems to Be Considered

Colitis cystica profunda
Emphysematous ureteritis
Gas in the lumen of the bowel

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