Pneumatosis Intestinalis and Colocolic Intussusception Complicating Crohn's Disease

Pneumatosis intestinalis (PI), a well-recognized manifestation of necrotizing enterocolitis, is characterized by the presence of gas in the submucosal or subserosal compartments of the bowel wall. It may occur anywhere along the gastrointestinal tract, in both linear and cystic forms (pneumatosis cystoides intestinalis) (1). Although its pathogenesis remains unclear, both bacterial and mechanical theories have been put forward, largely based on the clinical entities known to be associated with PI (2). Rarely seen beyond the newborn period, PI has been reported in a few adults with Crohn's disease (CD) (3–5). However, its significance and subsequent management remain unclear. In this report, we provide the first description of PI complicating CD in the pediatric age group. CASE REPORT A male infant was transferred to our hospital at 5 weeks of age with intractable diarrhea. He had been in a hospital for severe dehydration and metabolic acidosis as a consequence of persistent liquid stools since birth. The perinatal history was negative, with a birth weight of 3.46 kg at term. Each attempt at enteral feeding resulted in an exacerbation of the diarrhea. No enteric pathogens were identified. Findings in upper endoscopy and in analysis of multiple biopsy specimens were normal on light and electronic microscopy. Antienterocyte antibodies were repeatedly negative. Although mucosa in an initial complete colonoscopy appeared macroscopically normal, moderate acute and chronic inflammation was noted in the sigmoid colon and rectal specimens. A diffuse eosinophilic infiltrate was observed more proximally. Multiple formula changes did not resolve the diarrhea, and the patient was given an elemental formula (Neocate, Scientific Hospital Supplies, Gaithersburg, MD, U.S.A.). Total parenteral nutrition was initiated at the time of admission and remained an important source of fluids and caloric supplementation up to the time of discharge (at 172 days). When the patient was 5 months of age, a perianal abscess developed requiring surgical drainage and intravenous antibiotics. Findings in a thorough immune work-up were normal, including the nitroblue tetrazolium test (NBT), quantitative immunoglobulin and complement assays, lymphocyte subset and activation markers, lymphocyte response to mitogens, phagocytic function, and human immunodeficiency virus serology. At discharge, the patient was gaining weight and having 4 to 6 stools per day; half of his calories had to be administered parenterally. Two months after discharge, the patient had rectal bleeding and fever. Another colonoscopy revealed a deep linear ulcer at the rectosigmoid junction. Analysis of biopsy specimens revealed chronic inflammatory changes, compatible with, but not specific for inflammatory bowel disease. An upper gastrointestinal series and follow-through were normal. A diagnosis of probable CD was made, and the patient was discharged receiving therapy with oral sulfasalazine and steroid enemas. At 11 months of age, he was readmitted with fever and bloody diarrhea. Peripheral eosinophilia suggested a hypersensitivity reaction to sulfasalazine, and the medication was discontinued. No abscess was found during abdominal ultrasound. However, multiple hyperechoic foci representing air in small vessels dispersed throughout both lobes were noted during oblique sonogram of the liver. An abdominal plain radiograph revealed the presence of intramural air in the colon, confirming PI. Although physical examination was normal, the patient received nothing by mouth and was administered intravenous corticosteroids and antibiotics. After 48 hours, the radiographs normalized, and the patient was discharged home with oral prednisone (1 mg/kg per day). One month later, he was brought to the outpatient clinic with dehydration, failure to thrive, and bloody diarrhea, while continuing to receive oral corticosteroids daily. Plain radiographs of the abdomen showed the reappearance of PI. Another colonoscopy showed macroscopic cystic masses at the level of the splenic angle. Deep mucosal and submucosal granulomas were now seen histologically, confirming the diagnosis of CD colitis. Azathioprine (1 mg/kg per day) was added along with prednisone. His course was complicated by Candida parapsilosis septicemia, requiring amphotericin B. Subsequently, bilious vomiting along with palpable bowel loops in the left lower abdominal quadrant were noted. Abdominal ultrasound and computed tomographic scan suggested a colocolic intussusception. During laparotomy, the intussusception was reduced, and diffuse serosal colonic and mesenteric PI was found. No ischemic bowel or vascular abnormalities were noted. The small bowel was spared, as was the section of colon directly involved in the intussusception, probably because of compression of the cysts by the surrounding bowel wall. His postoperative course was favorable, with radiologic resolution of PI. Azathioprine and enteral feeding were resumed, and the dosage of prednisone was tapered. Nevertheless, another colonoscopy 1 month later revealed the recurrence of cystic PI, from the rectum to the hepatic angle. The diarrhea improved with administration of oral metronidazole, and he was discharged (on day 107). At this writing, after 1.5 years of follow-up, the patient has persistent diarrhea, intermittently severe enough to require rehydration with intravenous fluids. However, PI has not recurred, and total parenteral nutrition has been discontinued successfully. DISCUSSION Pneumatosis intestinalis is an uncommon condition, the pathogenesis of which remains unclear. Current theories suggest that it is the result of several interrelated causes: mechanical, bacterial and dietary (2,6). Intramural gas most likely arises from the bacterial fermentation of malabsorbed carbohydrates or by gas-producing organisms (7). Regardless of the underlying source, the gas can enter through breaks in the mucosa or penetrate an intact mucosa as a result of high pressures, as in the case of intestinal obstruction or excessive distension. In our patient, cystic PI was thought to be the cause of the intussusception, rather than the obstruction's provoking the PI. Outside of necrotizing enterocolitis in premature infants, PI is rare in the pediatric age group. In one large series of cystic PI (8), only 8% of 919 patients were less than 20 years of age. There is thus limited information available regarding the pathogenesis, predisposing conditions, diagnosis, and management of PI in childhood. Most pediatric patients beyond the newborn period are immunocompromised, either because of a congenital immunodeficiency, cancer, acquired immune deficiency syndrome, or immunosuppression medications, often with concomitant gastrointestinal infections (cytomegalovirus, rotavirus, Clostridium difficile) (9–14). No consensus has been reached on the significance, prevalence, and management of PI complicating CD. In 1959, Rienhoff and Collins (15) first reported regional enteritis associated with PI. The pathogenesis of PI in CD is thought to be multifactorial, not dissimilar from that hypothesized for immunocompromised patients (3–5). Transmural inflammation gives rise to mucosal breaks, theoretically providing an entry point for luminal air. The host's endogenous gut flora is implicated as the principal gas producer. Bacterial overgrowth along with increased peristalsis and intraluminal pressure necessary to force luminal contents through stenotic areas, provide the mechanical force for air entry into the bowel wall (4). Our patient had no strictures, and PI was observed in the absence of macroscopic ulcers. Glucocorticoid use appears to be an important contributing factor (3), as was true in the present case. Steroids deplete lymphoid tissue, facilitating intramural gas accumulation. It is uncertain whether PI is a reliable indicator of severity in CD. It recurred in our patient despite clinical stabilization. Therefore, treatment decisions must be based on the entire clinical picture, not simply the radiographic or endoscopic findings. The presence of hepatic portal venous gas (HPVG), with or without PI, is usually considered an ominous prognostic sign. This generally occurs in acutely ill patients, most frequently in newborns with necrotizing enterocolitis. Heng et al. (1) found that up to 75% of adult patients with HPVG had bowel infarction, and 10 of 12 patients with the combination of PI and HPVG died within 48 hours. However, benign or uncomplicated causes of HPVG have been described in patients with inflammatory bowel disease after therapeutic or diagnostic procedures, such as barium enema and colonoscopy (16,17). It has also been identified in patients with CD in the absence of iatrogenic manipulation (18,19). In all cases, except that of one patient receiving high-dose steroids, the course was uneventful, with or without medical management, and surgery was avoided. However, concomitant PI was not found radiographically in these reports, unlike the present case. Several medical treatment options have been recommended, based on the various theories on the pathogenesis of PI. By reducing the bacterial load and subsequent gas production, antimicrobial agents, specifically metronidazole, has been reported to provide symptomatic relief (20). However, the dose and duration of therapy have not been standardized. Others have suggested the use of oxygen therapy, either normobaric or hyperbaric, to dissolve intramural gas (21). High concentrations of oxygen wash nitrogen gas out of the circulation, creating a diffusion gradient between tissue and the blood, deflating the cysts. Treatment with an elemental diet decreases fermentable substrate in the colon, leading to resolution of cysts and symptoms (22). When a normal diet was resumed, the cysts recurred. Finally, in patients with toxemia, those who had complications of PI (obstruction, intussusception, or volvulus) or those with underlying causes associated with a high mortality rate, generally require surgery (1,2,9,13,23). Crohn's disease must be considered one of the pediatric conditions associated with PI beyond the newborn period. As with any disease entity, the clinician must determine the clinical significance of PI in each patient to make appropriate therapeutic decisions. In the absence of complications, we suggest that these patients can be successfully treated medically.

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