Pneumoperitoneum is almost indicating a perforated abdominal viscus requiring urgent surgical intervention. Spontaneous or non-surgical pneumoperitoneum is a rare clinical condition. We describe an adolescent girl who was diagnosed as chronic intestinal pseudo-obstruction syndrome (CIPOS) presented with repeated episodes of pneumoperitoneum secondary to pneumatosis intestinalis. A 16-year-old female patient without any previous medical or surgical history was transferred to our hospital due to repeated episodes of abdominal distension for one year. Her other associated symptoms included dull periumbilical pain, non-bilious vomiting, occasionally diarrhea, secondary amenorrhea and bodyweight loss from 38 kilograms to 33 kilograms in one year (<the 3rd percentile). A plain film of abdomen showed severe bowel dilation and pneumoperitoneum (Fig. 1). Clinically, she had neither fever nor peritoneal signs. Plain radiograph. Massive free air under diaphragm (arrows). Diagnosis of this patient was difficult. The possibility of bowel perforation was first considered but several clues were against this idea. Laboratory data including hemogram and serum biochemistry were all in normal ranges. There was also no bacterial growth in the large amount of ascites. Subsequently, the water-soluble whole gastrointestinal series did not show any perforation or obstructive lesion but extremely slow transit time more than 24 hours (Fig. 2). Endoscopies were also performed with no specific pathological finding. Bowel dilatation and slow transit of contrast in small bowel series without any perforation or obstruction. Interestingly, signs of pneumatosis intestinalis (PI) were noted in the subsequent plain film (Fig. 3) and computed tomography (CT) scans (Fig. 4). Diagnosis of bacterial overgrowth syndrome was also established by lactulose breath hydrogen test. Pneumoperitoneum secondary to pneumatosis intestinalis due to severe ileus and bacterial overgrowth were highly suspected. In order to reach a final diagnosis, laparoscopic examination with full-thickness ileal biopsy and appendectomy was carried out. Smaller ganglion cells and moderately increased acetyl-cholinesterase were found in the small intestinal pathology. Signs of pneumatosis intestinalis in the plain film (arrows). Computed tomography of abdomen. Intraluminal air dissecting the bowel wall and making evidence of pneumatosis intestinalis (arrows). In summary, from the above clinical presentations and pathological report, a primary neuropathic form of chronic intestinal pseudo-obstruction syndrome (CIPOS) was diagnosed after other secondary causes had been excluded. After diagnosis, the patient was managed conservatively with total parenteral nutrition and efforts to recover oral feeding tolerance gradually. Prokinetics were added and bacterial overgrowth syndrome was treated by intravenous metronidazole. The patient was under long-term home parenteral nutrition support. Pneumoperitoneum developed intermittently in the two and a half years' follow-up period. Both non-surgical pneumoperitoneum and CIPOS are rare conditions, especially in children. In pathogenesis, the symptoms of CIPOS were generated by failure of the intestinal pump in the absence of gut-occluding lesions, leading to abnormal intestinal tract peristalsis and finally nutritional disorders.1,2 The condition may be a primary disorder of enteric neuromusculature or secondary to a variety of pathological conditions.2 Distinct from adults, children with CIPOS predominantly have the primary form, whereas adults most often present with the secondary form.3 Two-thirds of patients have disease onset within the first month of life and 80% by 1 year of age.4,5 Our case was previously healthy until 15 years of age and she had the very late onset form of the condition. Establishing diagnosis in such patient is difficult. The diagnosis of CIPOS is usually accomplished by careful exclusion of other diseases. Contrast studies are useful for excluding the mechanical obstructive lesion.6 The distended bowel loops and slow transit time are usually observed in CIPOS patients. Although a variety of presentations of CIPOS have been reported, pneumoperitoneum is still rare. PI is not a diagnosis but a radiological finding caused by underlying diseases.7 The intramural gas was proposed to diffuse from the intraluminal bowel gas or the bacterial production of gas. Gut permeability to gas would be further enhanced after bacteria invading and destructing the mucosa barrier.7 When the mucosal barriers of the gastrointestinal tract are compromised and blood supply of the gastrointestinal tract is relatively decreased after intraluminal pressure is increased, PI becomes more likely. In our case, it is perceived that severe intestinal distension and bacterial overgrowth allow intraluminal air to dissect through the bowel wall and cause recurrent episodes of pneumoperitoneum. The diagnosis of CIPOS via surgical exploration should be avoided.1 Surgery may predispose the patient to develop later adhesions. Recently, laparoscopy was used to obtain biopsies and reduce the risk of adhesion.2,8 Laparotomy would be reserved for performing an enterostomy or ruling out bowel obstruction and should not be undertaken only for obtaining biopsies.1 Based on the tissue examination, CIPOS can be classified into three major entities: neuropathies, mesenchymopathies, and myopathies.2 In our case, smaller ganglion cells with moderately increased acetylcholinesterase activity were found in the small intestinal pathology and the neuropathic form was most favored. In pediatric cases, immature and small ganglion cells are often present.9 However, neither hypoganglionosis nor submucosal giant ganglia were found; therefore, neither Hirschprung's disease nor intestinal neuronal dysplasia could be further subclassified. At present, medical treatment in pseudo-obstruction has limited success.10 Nutritional support is the rule of thumb and enteral feeding should always be preferred to parenteral nutrition. When enteral feeding is not enough or intolerable, parenteral nutrition should be employed. However, total parenteral nutrition can cause major morbidity and mortality in its long-term use. Intestinal transplantation is the only definite curative treatment for the CIPOS patient after failure of medical and surgical treatment.1 Overall, the prognosis of CIPOS is poor. We would like to thank Dr Chia-Hsiang Chu for further care and follow up of this patient.