Pneumatosis cystoides intestinalis is a condition characterized by gas cysts in the wall of the gut and sometimes in the mesentery. When the process is limited to the large intestine, the term pneumatosis coli is used. Cysts vary in size from microscopic to several centimeters in diameter.
Pneumatosis may be primary or secondary. About 15% of cases are primary and idiopathic; the cysts are submucosal and usually are limited to the left colon. Secondary pneumatosis comprises 85% of cases. Cysts are subserosal and may be located anywhere in the gastrointestinal tract or its mesentery.
The mechanism of cyst formation may not be the same in all patients. In some, anaerobic bacterial fermentation of carbohydrates leads to excess production of hydrogen gas, which enters the intestinal wall by diffusion. Some patients have greatly diminished activity of methanogenic bacteria, which normally consume or metabolize hydrogen. Patients with impaired pulmonary function are less able to excrete excessive hydrogen gas through the lungs, and they are more prone to develop pneumatosis. Cysts are maintained because additional hydrogen is generated with each meal, thus replacing gas that may have diffused into the bloodstream since the previous meal. High breath hydrogen levels have been reported in pneumatosis patients even during fasting.
Symptoms of pneumatosis intestinalis
Symptoms are absent or nonspecific. In secondary pneumatosis, symptoms are due to the underlying disease. In the primary form, patients may complain of abdominal discomfort, distention, diarrhea with mucus, or passing of excessive amounts of gas. Rarely, perforation of a cyst, hemorrhage, obstruction, or malabsorption may bring benign pneumatosis to medical attention. Fulminant pneumatosis is associated with acute bacterial infection of the bowel wall. Such patients are toxic and may have underlying impaired immunologic defenses. Gas may also be seen within the intestinal wall late in intestinal infarction. Pneumoperitoneum is sometimes present.
Treatment of pneumatosis intestinalis
Treatment of secondary pneumatosis intestinalis is directed toward the underlying disease. Resolution of cysts can be accomplished in either primary or secondary pneumatosis by having patients breathe oxygen by mask for several days interrupted only at mealtime. Response to hyperbaric oxygen is more rapid. Recurrence of cysts after oxygen treatment reflects continued production of hydrogen, and in these patients it is necessary to reduce the amount of gas being generated. The amount of substrate can be controlled by dietary manipulation, and the fecal flora can be suppressed by antibacterial agents such as ampicillin or metronidazole. Surgical resection of bowel involved with benign primary pneumatosis is rarely required, but underlying disease may need operative treatment in the secondary form of this condition. Fulminant pneumatosis is treated surgically, but the mortality rate is high.