Abstract
Pneumoperitoneum is most commonly associated with hollow viscus perforation and represents a surgical emergency. However, a subset of cases, termed benign pneumoperitoneum, occur without visceral perforation and can often be managed conservatively. Idiopathic cases remain particularly rare, with few reports in the literature. We present a retrospective case series of three patients from three tertiary care hospitals with idiopathic benign pneumoperitoneum. All patients were hemodynamically stable at presentation, with imaging demonstrating intraperitoneal free air and no clinical signs of sepsis. Management strategies included laparotomy in one patient, laparoscopy in another, and observation in the third. This series adds to the limited reports on idiopathic benign pneumoperitoneum and supports conservative management in carefully selected patients, while acknowledging the difficulties with clinical decision making. Awareness of this rare entity may help avoid unnecessary operative intervention. Serial clinical assessment and close observation are important considerations in management of this unique patient population.
Introduction
Pneumoperitoneum, defined as the presence of free intraperitoneal gas, is most commonly caused by hollow viscus perforation which is a surgical emergency [1]. The majority of cases are caused by perforations of the sigmoid colon, duodenum, and appendix, requiring prompt operative management to control intra-abdominal sepsis [2]. Non-surgical, or ‘benign’ pneumoperitoneum represents a very rare entity, accounting for ˂1% of all pneumoperitoneum cases [2, 3]. Consequently, reported cases series of benign pneumoperitoneum are critical to advance understanding [3]. Improving recognition of this uncommon diagnosis is essential to avoid unnecessary surgical interventions, particularly in clinically stable patients [4, 5].
Benign pneumoperitoneum has been attributed to several mechanisms including thoracic sources (mechanical ventilation, barotrauma), gynecological causes (coitus, vaginal insufflation), iatrogenic events (endoscopic procedures, peritoneal dialysis, laparoscopic surgery), and idiopathic cases with no identifiable etiology [6–9]. Radiologically, free air alone is not pathognomonic for surgical hollow viscous perforation; clinical correlation remains paramount. Patients with benign pneumoperitoneum often remain hemodynamically stable, without peritonitis or sepsis. These patients can safely be managed conservatively with observation, supportive care, and serial examinations.
The diagnostic dilemma lies in differentiating benign pneumoperitoneum from surgical emergencies, as the clinical presentations can often overlap. Previous reports highlight the risks of unnecessary laparotomy when benign causes of pneumoperitoneum are misclassified in both adult and neonatal cases [7, 10, 11]. Despite its clinical importance, idiopathic benign pneumoperitoneum remains under-recognized, and underreported. Published evidence is limited to isolated case reports, leaving uncertainty around natural history, prognostic indicators, and optimal management. This case series contributes to the existing literature by describing three patients with idiopathic benign pneumoperitoneum, highlighting diagnostic considerations, management strategies, and the role of conservative treatment in appropriately selected patients.
Methods
This retrospective case series follows the PROCESS 2020 guideline for reporting case series [12]. Patients were identified from three tertiary care hospitals in Ottawa, Ontario, Canada. The study complied with the Declaration of Helsinki. As per the Tri-Council Policy Statement 2, Article 2.5, full review by the Ottawa Health Science Network Research Ethics Board was deemed exempt. Informed consent was obtained from all patients for publication of anonymized details. The authors declare no conflicts of interest and have not received any external funding.
Case series
Case 1
A 61-year-old male presented with a 1-month history of intermittent right-sided abdominal pain. His past medical history included coronary artery disease status post remote coronary artery bypass surgery, end-stage renal disease on hemodialysis, peripheral vascular disease, type 2 diabetes, peptic ulcer disease, below knee amputation, remote appendectomy, and cholecystectomy. Prior to initiation of hemodialysis, he had a peritoneal dialysis catheter in place for ∼1 year, but this was never used and later removed 18 months prior to his presentation to hospital.
On presentation, he was afebrile and hemodynamically stable. His abdominal exam was benign. Biochemical investigations were normal apart from hyperkalemia and mild acidosis. Computed tomography (CT) imaging demonstrated small volume pneumoperitoneum in the right upper quadrant with mild thickening of the duodenum (Fig. 1a). Given these imaging findings and the patient’s history of peptic ulcer disease, smoking, and type 2 diabetes, an exploratory laparotomy was performed for presumed perforated duodenal ulcer. No perforation was identified intraoperatively; instead, the right colon appeared mildly thickened but healthy with multiple serosal air locules without obvious perforation. Following discussion with a second surgeon, the decision was made to proceed with a right hemicolectomy with primary anastomosis. He had an uncomplicated postoperative course and was discharged on postoperative day four. Pathology confirmed pneumatosis intestinalis without evidence of ischemia.
(a and b) Small volume pneumoperitoneum predominantly in the right hemiabdomen (see lung window) with mild wall thickening of the second part of the duodenum (white arrow). Suspected duodenal perforation given wall thickening and distribution of free air though no definitive bowel wall defect identified. (c) Oral contrast passing through level of ileocolic anastomosis with no contrast leak identified. Stable pneumoperitoneum and pneumatosis intestinalis. (d) Moderate pneumoperitoneum with unclear source. Majority of free air in anterior abdomen though additional questionable nodular locules in the lesser sac medial to the second and third portion of duodenum.
He subsequently presented 15 months later with abdominal pain, nausea, vomiting, and large-volume pneumoperitoneum on CT. Given his hemodynamic stability and reassuring laboratory results and abdominal exam, repeat CT imaging with oral and rectal contrast was completed. Oral contrast was present at the ileocolonic anastomosis with no leak or other source of perforation identified (Fig. 1b). He was therefore managed conservatively with resolution of his symptoms.
Seventeen months later, he presented again with coffee-ground emesis and epigastric pain. He was hemodynamically stable. Upright X-ray showed free air, and subsequent CT with oral contrast showed moderate pneumoperitoneum without identifiable source (Fig. 1c). He remained stable throughout observation and was discharged the next day after full recovery.
Case 2
An 81-year-old male presented with confusion, weakness, subjective fevers, mild abdominal pain, and diarrhea. His medical history included bipolar disorder on valproic acid, diverticulosis, hypothyroidism, dyslipidemia, and remote cholecystectomy and appendectomy. He was mildly tachycardic and afebrile. Examination showed mild right-sided tenderness. Laboratory values were normal, without leukocytosis. CT showed free air predominantly in the upper abdomen without free fluid (Fig. 2a and b). Diagnostic laparoscopy was performed to rule out intra-abdominal sepsis given his new onset of confusion.
(a and b) Moderate volume pneumoperitoneum, with free air mostly distributed in the right upper quadrant and mid anterior abdomen, as well as around the duodenum. Suspected secondary to perforated duodenal ulcer given the distribution of free air, specifically in the region of the proximal duodenum. There is some mild inflammatory change of distal small bowel in the right lower quadrant (white arrow). No sigmoid diverticulitis. (c) There is a focal segment of colonic wall thickening and pericolic inflammatory change involving the sigmoid colon (white arrow), with reactive inflammatory changes to the bladder. There is trace pneumoperitoneum in the upper abdomen that has decreased from previous CT.
Adhesiolysis from prior cholecystectomy and appendectomy was performed. The stomach, duodenum, and entirety of his small bowel and colon were thoroughly examined without identifiable perforation or contamination. Multiple small bowel and sigmoid diverticula were present without inflammation. Intraoperative esophagogastroduodenoscopy confirmed no abnormalities with a negative air leak test. He recovered uneventfully and was discharged after seven days for deconditioning with home support.
One month later, he re-presented with abdominal pain and subjective fevers. He had moderate tenderness to the lower abdomen without peritonitis. Vitals and white cell count were normal. CT showed acute sigmoid diverticulitis with focal thickening and pericolonic inflammation (Fig. 2c). Residual free air was present but reduced. He was re-admitted for antibiotics and supportive care and discharged on oral antibiotics after 3 days. He has since been assessed virtually in follow-up 2 months after his laparoscopy, with normal gastrointestinal function and no recurrent abdominal pain.
Case 3
A 78-year-old male presented to the emergency room after chest radiography for pneumonia revealed moderate volume of subdiaphragmatic air. His past medical history included hypertension, mild chronic obstructive pulmonary disease (COPD), and prior prostate cancer treated with laparoscopic prostatectomy and radiotherapy.
His history of present illness included a cough and fatigue without any gastrointestinal symptoms. Examination showed stable vitals and mildly distended abdomen, without tenderness. He had a mildly elevated white cell count, but otherwise reassuring blood work. CT confirmed large-volume predominantly right-sided pneumoperitoneum without free fluid (Fig. 3a). Repeat CT with oral contrast revealed a distal esophageal diverticulum measuring 2.8 cm in diameter without leak and non-inflamed small bowel diverticula. The etiology of his presentation remained unclear but was presumed to be related to a micro-perforation of an esophageal or small bowel diverticulum which had since sealed off. Given his clinical stability, he was treated conservatively with bowel rest and antibiotics. He was discharged on day 5.
(a) Large right-sided pneumoperitoneum without associated free fluid or identifiable perforation site. (b and c) CT 8 months later showing extensive free intraperitoneal air, predominantly in the anterior upper abdomen. Lung windows provided for ease of visualization of intraperitoneal air distribution. (d and e) Persistent pneumoperitoneum on CT during third presentation for benign pneumoperitoneum, with corresponding lung window.
Subsequent outpatient upper endoscopy confirmed a large esophageal diverticulum. His colonoscopy was also normal. Eight months later, he sustained a mechanical fall, causing left chest wall pain. This again showed pneumoperitoneum on chest X-ray and oral-contrast CT (Fig. 3b). His 2.8 cm esophageal diverticulum was noted to have increased in size, measuring 4.9 cm, but without contrast leak. He was admitted briefly for observation and discharged the next day with no gastrointestinal symptoms.
Six weeks later, he presented again with a fall, and a third instance of incidental pneumoperitoneum was detected on CT (Fig. 3c). He remained asymptomatic and was conservatively managed. On discharge, he was referred to Geriatric Medicine for fall prevention.
Discussion
This case series describes three patients with idiopathic benign pneumoperitoneum managed via laparotomy, laparoscopy, or observation, reflecting persistent diagnostic uncertainty and therapeutic clinical equipoise of this rare condition. Importantly, none demonstrated convincing evidence of gastrointestinal perforation or intra-abdominal sepsis, and all had favorable outcomes. These findings reinforce that management should be individualized and guided by clinical physiology and examination rather than the radiographic presence of free air alone.
A key consideration in differentiating pathologic from benign pneumoperitoneum lies in the physiology of intraperitoneal gas dynamics [1, 10]. In cases of visceral perforation, intraperitoneal gas is typically accompanied by leakage of enteric contents, leading to chemical and bacterial peritonitis. This results in an inflammatory cascade with peritoneal irritation, third spacing, systemic inflammatory response, and potential hemodynamic instability [1]. In contrast, benign pneumoperitoneum involves the presence of free air without contamination. Gas may enter the peritoneal cavity through various potential mechanisms, including transdiaphragmatic migration (from thoracic sources), iatrogenic insufflation, or transient micro-perforations that seal spontaneously. In these cases, the peritoneum absorbs gas primarily via diffusion into the bloodstream, with carbon dioxide being rapidly resorbed and nitrogen more slowly. The absence of inflammatory response allows for physiological equilibration without progression to sepsis. This distinction underpins the clinical divergence between ‘surgical’ pneumoperitoneum associated with peritonitis and ‘non-surgical’ pneumoperitoneum characterized by physiological tolerance of free air.
Prior literature similarly characterizes benign pneumoperitoneum as uncommon, requiring clinically nuanced decision-making. Avoidance of laparotomy is appropriate in the majority of cases, despite the fact that most reported cases had identifiable iatrogenic causes, which could likely have a more predictable clinical trajectory [5, 7, 10]. Similarly, pediatric case series also emphasize selective laparotomy in stable patients [4, 11]. These findings align with the principle that physiology, rather than imaging alone, should dictate management.
Building on this, a structured clinical pathway can guide decision-making regarding operative versus non-operative management:
Initial assessment and resuscitation – Hemodynamic instability mandates immediate resuscitation and operative exploration.
Assessment for peritonitis – Diffuse peritoneal signs, including guarding, rigidity, and rebound tenderness, indicate peritoneal inflammation and necessitate surgery regardless of imaging findings.
Laboratory and physiologic markers – Leukocytosis, metabolic acidosis, or rising lactate support a systemic inflammatory process and favor operative management.
Radiographic evaluation – Features such as free fluid, luminal contrast extravasation, or focal inflammatory changes increase suspicion for perforation. In contrast, isolated free air without these findings may support conservative management.
Clinical trajectory – Stable, afebrile with benign abdominal exams and no physiological derangements may be managed non-operatively with close observation.
Adjunctive evaluation – When uncertainty persists, diagnostic laparoscopy provides a low-morbidity option to directly assess for perforation while avoiding non-therapeutic laparotomy.
Ongoing reassessment – A non-operative approach requires vigilant monitoring (serial exams and repeat imaging as indicated) are essential with a low threshold to escalate to operative intervention if deterioration occurs at any stage.
This framework emphasizes a physiology-driven approach that distinguishes between patients requiring immediate surgery and those suitable for observation. It operationalizes decision-making beyond listing indications for surgery, instead integrating dynamic clinical variables.
The recurrence of idiopathic benign pneumoperitoneum as observed in Cases 1 and 3 further illustrates its unpredictable natural history. Recurrence may understandably raise concern for occult or intermittent leak; however, in the absence of peritonitis or physiological compromise, it does not independently mandate surgical exploration. These cases highlight the importance of careful follow-up and clear documentation among treating clinicians to avoid unneeded repeat imaging or unnecessary surgery. Setting patient expectations and raising provider awareness are essential.
The primary implication is the avoidance of unnecessary surgery in patients without peritonitis, as routine laparotomy carries avoidable morbidity, especially to those who are elderly or harbor significant comorbidities. A physiology-based approach supports selective operative intervention while preserving patient safety. In equivocal cases, laparoscopy offers diagnostic clarity with lower morbidity, such as in Case 2. Radiographic features, including absence of free fluid, bowel wall thickening, or contrast leak, suggest lack of enteric contamination. When combined with clinical stability, these findings support conservative management with close observation.
Limitations of this case series include small sample size and lack of standardized follow-up, limiting generalizability. The absence of gold-standard diagnostic confirmation in conservatively managed cases restricts mechanistic conclusions. Finally, without a comparator group, the relative benefits of surgical versus conservative management cannot be formally assessed. Future research should focus on larger cohorts to identify predictors of benign versus surgical pneumoperitoneum and refine decision pathways, including need for follow-up or predictors of recurrence.
Conclusion
Idiopathic benign pneumoperitoneum, though rare, is an important diagnostic consideration when free air occurs without peritonitis. Conservative management is often safe when guided by clinical assessment, with laparoscopy as an adjunct if uncertainty persists. Decisions should prioritize physiology and clinical context over imaging to avoid unnecessary intervention.
Funding
None declared.
Conflicts of interest
None declared.
