Postgrad Med J (1991) 67, 999 - 1003 © The Fellowship of Postgraduate Medicine, 1991

Pneumoperitoneum without peritonitis

Barry D. Daly,' J. Ashley Guthrie' and Neville F. Couse2

Departments of 'Radiology and 2Surgery, St James's University Hospital, Beckett Street,Leeds LS9 7TF, UK

Summary: We present our experience with 5 patients, all of whom were noted to have radiologicalsigns of pneumoperitoneum in the absence of clinical features of peritonitis. All 5 cases were eventuallyshown to be due to causes not requiring surgery. We review the numerous unusual causes ofpneumoperitoneum which do not require urgent surgical intervention and emphasize their importance incases where the absence of signs of peritonitis may cause diagnostic difficulty.

Introduction

Gastrointestinal perforation accounts for 90% ofcases of pneumoperitoneum when post-operativecauses are excluded.' There are, however, numer-ous other causes of pneumoperitoneum2-4 andwhen patients with these conditions present there isoften diagnostic difficulty. This group of patientswithout peritonitis must be differentiated fromthose with peritonitis in whom the clinical signs aremasked. We present the case histories and radio-logical findings in 5 patients with pneumoperi-toneum without signs of peritonitis and highlightthe causes of 'benign' pneumoperitoneum.

Case reports

Case I

A 34 year old woman presented complaining ofintermittent abdominal pain and diarrhoea over a 2week period. Physical examination revealed mildgeneralized abdominal tenderness but was other-wise normal. Chest and abdominal radiographsdemonstrated pneumoperitoneum (Figure 1). Aprovisional diagnosis of visceral perforation wasmade but as overt signs of peritonitis were absentthe patient was treated conservatively. The abdom-inal radiographs were subsequently interpreted astypical of pneumatosis cystoides coli. Bariumenema confirmed the diagnosis (Figure 2). Hersymptoms resolved on conservative treatment andthe pneumoperitoneum resolved within 10 days.

E~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ........ ..... ..'n'iFigure 1 Case 1: chest radiograph showing largepneumoperitoneum. Gas filled cysts in the wall of thesplenic flexure (arrows) were not recognized initially.

Case 2

A 60 year old woman with severe chronic obstruc-tive airways disease presented with a 2-day historyof lower abdominal pain. On examination therewas mild abdominal tenderness but no otherabnormality. Chest and abdominal radiographsdemonstrated a large amount of air under thediaphragm (Figure 3). Visceral perforation wassuspected but she was treated conservativelybecause of the absence of signs of peritonitis.Radiological and endoscopic examinations of the

Correspondence: J.A. Guthrie, M.R.C.P., Lincoln WingRadiology Department, St James's University Hospital,Beckett Street, Leeds LS9 7TF, UKAccepted: 20 May 1991

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Figure 2 Case 1 barum enema showing submucosaland subserosal gas-filled cysts typical of pneumatosiscystoides coli are seen in the descending colon (arrows).

Figure 3 Case 2: chest radiograph shows a large pneu-moperitoneum (arrows) and changes of chronic obstruc-tive airways disease.

oesophagus, stomach, duodenum and colon werenormal. Subsequently a small bowel barium exam-ination demonstrated gas filled cysts in the wall ofthe jejunum and ileum typical of pneumatosiscystoides intestinalis (Figure 4). These cysts wererecognized in retrospect on the initial plain abdom-

no:h: .....h i.......

Figure 4 Case 2: small bowel barium meal. Gas cysts(arrows) are interspersed between the valvulae coniventesof the jejunum.

inal films. Although the patient's symptoms resolv-ed spontaneously, free subdiaphragmatic gaspersisted for 14 months after the initial presenta-tion.

Case 3

A 46 year old man with acute myeloid leukaemiaunderwent autologous bone marrow transplanta-tion. Five weeks post-transplantation he developedintermittent diarrhoea, colicky lower abdominalpain and a pyrexia of 38TC. Abdominal examina-tion was normal. Cultures of faeces, urine, blood,sputum and swabs from his oral cavity werenormal. Radiographs of his chest and abdomendemonstrated pneumoperitoneum and features ofpneumatosis cystoides intestinalis and coli. Thiswas confirmed with contrast studies. The pneumo-peritoneum and pneumatosis resolved spontan-eously and he remains well 8 months later.

Case 4

A 13 year old boy was admitted with an extensivestaphylococcal pneumonia and required ventila-tion. While being ventilated, extensive pneumo-peritoneum was noted on chest radiographs. Therewere no clinical signs of perforation and thepresence of pneumomediastinum and retroperi-toneal gas on the same radiographs confirmed thatair was tracking into the peritoneal cavity via themediastinum and retroperitoneal spaces (Figure 5).There was no evidence of pneumatosis intestinalison the plain films. The pneumoperitoneum resolv-ed quickly when ventilation was discontinued.

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Figure 5 Case 4: chest radiograph showing pneumo-mediastinum (large arrow), pneumoperitoneum (smallarrows) and retroperitoneal air (curved arrows). Much ofthe free intraperitoneal gas lies in front of the liver on thissupine film. There is collapse ofthe right lung with abscessfonnation.

Case S

A 30 year old woman presented for elective investi-gation of right upper quadrant pain. She wasasymptomatic at presentation but an abdominalradiograph unexpectedly showed free intraperi-toneal gas. This was confirmed on an erect chestfilm. Physical examination was entirely normal.She was admitted for observation. A more detailedhistory subsequently revealed that she had hadorogenital intercourse 12 hours before the radio-graphs were taken. The pneumoperitoneum resolv-ed within 4 days. No cause was found for heroriginal symptoms.

Discussion

In surgical practice, pneumoperitoneum common-ly occurs following gastrointestinal perforation oras residual air following laparotomy. There is,however, an increasing number of causes of

pneumopetitoneum that do not require urgentsurgical intervention but which, nonetheless, maycause diagnostic confusion and possibly result inunnecessary laparotomy (Table I). All the patientsdescribed in this report caused initial diagnosticdifficulty and a surgical opinion was sought with aview to laparotomy. The absence of signs ofperitonitis led to appropriate conservative manage-ment in all cases.

Three of our patients developed pneumoperi-toneum secondary to pneumatosis cystoides ofsmall (intestinalis) or large (coli) bowel. This is awell recognized but curious condition in which gascysts form in the subserosa or submucosa of thebowel wall as either a primary idiopathic pheno-menon or secondary to a number ofcauses includ-ing chronic obstructive airways disease, asthma,proximal bowel distension (e.g. pyloric stenosis)and small bowel disease (e.g. scleroderma andWhipple's disease).8-'0The mechanisms giving rise to pneumatosis

cystoides are disputed. Raised intra-thoracic pres-sure, due to bouts ofcoughing, vomiting or ventila-tion in the presence of obstructive airways disease,has been purported to give rise to local intra-thoracic pulmonary interstitial emphysema withsubsequent spread of air to the mediastinum andretroperitoneum and, eventually, into the bowel

Table I Causes of pneumoperitoneum

A. Pneumoperitoneum with peritonitisPerforated viscusNecrotizing enterocolitisBowel infarctionPenetrating abdominal injuries

B. Pneumoperitoneum without peritonitisThoracic causes

Positive pressure ventilationPneumomediastinum/pneumothoraxChronic obstructive airways diseaseAsthma

Abdominal causesPost laparotomyPneumatosis cystoides coli/intestinalisJejunal diverticulosisEndoscopyParacentesis/peritoneal dialysis/laparoscopyBone marrow transplantation

Female pelvic causesInstrumentation (e.g. hysterosalpingography,

rubin's test)Pelvic examination (esp. post-partum)Post-partum knee-chest exercises5Oro-genital intercourse6Vaginal douching6CoitusWater-skiing7

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wall via the mesentery." This forms gas-filled cystswhich cause pneumoperitoneum without peritoni-tis, either by rupture or diffusion.2"12 More recently,Pieterse et al."3 have demonstrated colonic histo-pathological changes supporting a local low gradeinflammatory process which they propose as aninitiating factor.

Pneumatosis cystoides intestinalis or coli may beasymptomatic or present with intermittent colickyabdominal pain, diarrhoea and occasionally bloodper rectum.'3 4 The 3 cases with pneumatosis in ourseries are typical in this regard. The condition mostfrequently involves the left hemicolon and may bediagnosed by recognition of the submucosal cystson plain radiographs, in contrast studies or atsigmoidoscopy. The cysts are less frequently con-fined to the small bowel when they are moredifficult to identify on plain radiographs (case 2).The condition may resolve spontaneously, as in ourcases, although both encysted or free gas maypersist for some time. Treatment with hyperbaricoxygen and antibiotics has been successfulalthough the condition often recurs.'",6Pneumoperitoneum in association with pneuma-

tosis intestinalis occurring in immunosuppressedpatients presents a particular diagnostic problem.Day et al.'7 reported the development of pneuma-tosis intestinalis in 18 patients following bonemarrow transplantation. Four of these patientssubsequently developed pneumoperitoneum or ret-roperitoneal gas and one of the patients required alaparotomy for perforation. The other 3 weretreated conservatively and were alive at 6 monthsfollow up. The cause of pneumatosis is thought tobe due to atrophy oflymphoid follicles in the bowelwall after high dose steroid therapy.'8 Gas-filledcysts develop where the mucosa has become thin-ned. Mucosal atrophy secondary to systemicchemotherapy or irradiation prior to bone marrowtransplantation may also be contributing factors.A similar pattern of intramural bowel gas maydevelop in immunosuppressed patients with severeenteric infections and bowel infarction. Day et al."7noted 7 such patients in which pneumatosisdeveloped within the clinical context ofmultiorganfailure and shock, all of whom died. The clinical

signs of multiorgan failure and shock allow thedifferentiation between this group and the grouptypified by our patients with pneumatosis andbenign pneumoperitoneum. However, it must bestressed that the signs ofperitonitis may be minimalor absent in immunosuppressed patients and adiagnosis of 'benign' pneumoperitoneum should beaccepted with caution.The development of pneumoperitoneum in a

patient on a ventilator is always of great concern.Such patients are invariably ill with a greater risk ofgastrointestinal perforation. Tracking of air fromthe mediastinum into the retroperitoneum andperitoneal cavity is well recognized.'9 The detectionofpneumomediastinum and retroperitoneal air in apatient with pneumoperitoneum on a ventilatorallows recognition of positive pressure ventilationas the underlying cause. Ventilation associatedpneumoperitoneum has been most frequentlyreported in neonates with respiratory distress syn-drome20 but has also been reported as a cause ofunnecessary laparotomy in adults.2'The female genital tract provides a portal of

entry for air into the peritoneal cavity. This isparticularly likely to occur in the early post-partumperiod and numerous causes have been reported(Table I). Case 5 of our series emphasizes the valueof a detailed history when pneumoperitoneumdevelops in a female patient without obvious causeor evidence of peritonitis. Our patient was atypicalin that she was neither pregnant nor in the post-partum period at the time of presentation.

In summary, pneumoperitoneum is an impor-tant radiological finding and in each case perfora-tion of a viscus must be considered. If there are nosupporting clinical features of peritonitis, a carefulhistory and search for radiological evidence ofpneumatosis cystoides, pneumomediastinum, pneu-mothorax or retroperitoneal air may point to abenign cause and reduce the risk of unnecessarylaparotomy.

Acknowledgement

We thank Dr Frank Keeling for permission to report onhis work.

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