gastric or duodenal perforations due to peptic ulcer are the most common causes of pneumoperitoenum . however , surgery is not required in cases of pneumoperitoneum where there is no evidence of visceral perforation caused by a physiological process . this status , termed spontaneous pneumoperitoneum ( sp ) , is reported to occur in 1423% of all patients with pneumoperitoneum [ 1 , 2 ] . generally , sp is not complicated by peritonitis , is benign and can be treated conservatively . in addition , pneumoperitoneum without peritonitis is a rare phenomenon which creates a management dilemma for the treating surgeon . the diagnosis of sp is difficult ; thus , sp patients may undergo unnecessary surgery . the dilemma in the treatment of sp lies in deciding between a laparotomy and a conservative line of management . so far , various reports with causes of sp have been discussed , and they have not been clear yet . in our case , although computed tomography ( ct ) showed free air in the abdomen , the perforation of the digestive tract was not recognized during the exploratory laparotomy . the aim of this report is to present a case of sp of undetermined origin , and to discuss the possible etiology . an 82-year - old japanese male patient was referred to our hospital due to constipation and abdominal pain for 3 days . the patient 's medical history included distal gastrectomy for gastric ulcer ( 20 years previously ) and community - acquired pneumonia ( 3 weeks previously ) . the laboratory data showed an abnormal white blood cell ( wbc ) count of 16,500/l ( normal range : 3,9009,800 ) , and a procarcitonin level of 0.26 ng / ml ( normal range : < 0.05 ) . abdominal ct revealed a large amount of feces in the colon and rectum , and free air in the abdomen ( fig . three hours after coming to the hospital , emergency exploratory laparotomy was subsequently performed but revealed no evidence of perforation or ischemic changes in the digestive tract ( fig . 2 ) . finally , because the cause of the pneumoperitoneum could not be identified , the operation was completed by placing a closed drain in the abdomen . pneumoperitoneum without peritonitis is a rare phenomenon which creates a management dilemma for the treating surgeon . as a result of this diagnostic dilemma gantt et al .   suggested that the origin of sp indicated intra - thoracic , intra - abdominal , gynecological , and iatrogenic causes . the intra - thoracic causes include barotrauma pneumothorax , bronchoperitoneal fistula , pneumomediastinum , and mechanical ventilation . the intra - abdominal causes include abdominal emphysematous cholecystitis , spontaneous bacterial peritonitis , intestinal cystic pneumatosis [ 10 , 11 , 12 , 13 , 14 , 15 ] , and liver abscess . the gynecological causes include rupture of pyometra . intestinal cystic pneumatosis was first described by du vernoi   in 1783 and documented in greater detail by bang   in 1876 . several theories have been suggested based on different observations , including the penetration of luminal gas through the bowel mucosa into the bowel wall after mucosal injury , pulmonary gas released from the ruptured alveoli dissecting the vascular channels in the mediastinum and tracking through the retroperitoneum into the mesenteric root , gas production of some bacteria that invade through the mucosal breaches into the intramural compartments or grow within microscopic cysts , and gas production related to defects in food digestion causing excessive fermentation . in our case , abdominal ct revealed the presence of a large amount of feces in the colon and rectum , and free air in the abdomen . the authors assumed that free air , which was released after a mucosal injury due to internal pressure caused by the presence of a large amount of feces in the colon and rectum , had penetrated the bowel wall through the bowel mucosa . there are no reports of sp occurring secondary to intestinal cystic pneumatosis caused by a large amount of feces . there are few reports of patients who were diagnosed with sp in the preoperative stage . chandler et al .   reported that 28% patients with misleading pneumoperitoneum findings were subjected to operations that , in retrospect , might not have been necessary . identified 196 case reports of sp patients , among which 45 underwent exploratory surgery without any evidence of perforated viscus . we therefore suggest that it is very difficult for surgeons to diagnose sp and indicate the correct course of treatment . in conclusion , a thorough medical history , appropriate laboratory tests , radiological techniques and physical examinations might be valuable tools for diagnosing sp and avoiding unnecessary laparotomy . we suggest that in uncertain cases , sp should be differentiated from free air resulting from gastrointestinal perforation and patients should be referred for emergency exploratory laparotomy . the published research is compliant with the guidelines for human studies and animal welfare regulations .
we report a rare case of spontaneous pneumoperitoneum . 
 an 82-year - old japanese male patient was referred to our hospital because of constipation and abdominal pain . 
 abdominal computed tomography revealed a large amount of feces in the colon and rectum , and free air in the abdomen . 
 based on these findings , the patient was diagnosed with gastrointestinal perforation . 
 emergency exploratory laparotomy was performed . 
 neither perforation nor ischemic changes were recognized in the digestive tract . 
 the patient 's defecation was managed postoperatively until discharge on the 13th postoperative day . 
 the authors assumed that free air , which was released after a mucosal injury due to the internal pressure caused by the presence of a large amount of feces in the colon and rectum , had penetrated the bowel wall through the bowel mucosa . 
 we herein report the present case while also reviewing the pertinent literature .