Pneumatosis intestinalis may occur in many different situations. The etiology actually favours iatrogenic conditions (surgery, endoscopy, enteric tube placement, positive pressure ventilation), immunodepression, collagen vascular disease and infectious agents[2,4,5,7,8
]. The jejuno-ileal bypass has accounted for some cases of PI; this condition is generally considered benign with a favourable outcome, supporting the concept that “surgical indication is not indicated under the usual circumstances”[9
]. The published experiences on this topic, generally in the form of single cases or small series of patients, refer to reports from the 1970s[9-15
], when this type of bariatric surgery was adopted in many centres. PI occurred any time during the first postoperative phase (mean delay 5 mo, range 1-20 mo)[7
] and patients recovered spontaneously in the majority of cases[9,11
Although responsible for a small number of cases, the “model” of jejuno-ileal bypass is well within the supposed pathogenetic mechanisms of PI, because these patients really present several predisposing factors. The first is ascribed to surgery alone with the consequent modification in bowel pressure[16
]. Another factor may be related to the marked obesity, as PI has been described in obese patients without a history of abdominal surgery[9
]. The type of reconstruction of bowel continuity also seems to play a central role; increased colonic gas secondary to fermentation of undigested lactose may reflux into the excluded segment of the small bowel. This occurs in particular when an ileum-sigmoid anastomosis has been performed, so favoring, because of abnormal pressure, the dissolution of gas into the bowel wall. This mechanism may be augmented by the concomitant bacteria overgrowth, most likely anaerobic, in the bypassed small bowel segment, so assigning the etiology of PI a mechanical - infectious process[12
]. Our case tends to support this hypothesis. PI involved only the bypassed small bowel where the two mechanisms, high pressure and bacterial overgrowth, were more significant. An anastomosis had been built between the defunctionalized ileum and the sigmoid, the excluded small bowel was significantly dilated, with a clear discrepancy of size compared with that of the functioning bowel, and it was edematous. Histology showed a severe mucosal injury with marked inflammation and signs of a remodeling reactive process.
Pneumoperitoneum is a complication of PI, but not an automatic indication for surgery. An increasing list of conditions relating to pneumoperitoneum without peritonitis are now recognized[17,18
], PI being the most common. These cases have a benign progression without laparotomy[17-22
]. They are the prevalent situations where no transmural perforation exists: as a consequence, no peritoneal contamination results from the rupture of the intramural sterile blebs. According to these considerations, the demonstration of PI in a patient with pneumoperitoneum may allow us to avoid the need for a laparotomy[19
]. This assumption must be accepted with caution in our opinion. The presence of PI is not enough to consider pneumoperitoneum as a benign condition in every case, with a good spontaneous outcome. Surgical indication must rely above all on the clinical data; neither CT nor the amount of free air are reliable guides for therapy[20
]. A negative abdominal examination could exclude signs of peritonitis, but clinical signs may be minimal or absent, for example in immunodepressed patients, or difficult to discover, as in obese patients. These two situations clearly define an increased risk of a delayed diagnosis of peritonitis, which can present with an ominous course in these frail patients. In our patient, peritonitis was not clear at the time of admission owing to the marked obesity of the patient, but the general signs of septic compromise (hypotension, oliguria, leukocytosis, high PCR value) suggested the clinical relevance of the radiological images. Laparotomy became urgent within a few hours. A complete perforation was discovered in the defunctionalized bowel without extravasation of enteric content, but the presence of gram-positive bacteria in the peritoneal fluid together with the histological demonstration of inflamed peritoneal serosa confirmed the contamination from the intestinal lumen. In the context of a fibrinous peritonitis a simple suture of the perforation might be advised, but this was not our choice because the bowel appeared very dilated and inflamed. The possibility of saving the proximal and distal segments, which were macroscopically normal, directed us towards performing the resection of the pathological bowel.
The histological examination of the resected bowel showed obvious pathological aspects of the PI with typical submucosal cysts surrounded by granulomatous reaction; the peculiarity of the case is the discovery of focal areas of mild dysplasia confirmed by the immunohistochemical evaluation with p53 and p16. These findings have never been reported before. Owing to the rare indication for surgery in these patients, an exhaustive histological evaluation of the pathologic bowel is rare but generally marked by an intact, pale and sometimes transparent mucosa[7
]. These changes, together with the unusually long time between the intestinal bypass and the discovery of PI in our patient, support the hypothesis of a long standing remodeling process, promoting the concept of a preneoplastic condition. This possibility, together with the rare occurrence of malignant lymphomas developing in the excluded intestine[23
], leads us to advise a long term follow up. When surgery is indicated for this complication, complete resection of the tract with pneumatosis, if technically possible in symptomatic patients, appears to us to be advisable.