Case Presentation: A 63-year-old man with lung adenocarcinoma with multiple rib metastases and lytic spinal lesions was receiving palliative radiation treatment when computed tomography (CT) incidentally revealed a fluid collection along the anterior cecum with pneumatosis. Cultures taken during CT-guided abscess drainage were positive for piperacillin-tazobactam-sensitive enterococcus, and the patient was started on antibiotics. His vitals were stable and he was in no acute distress. Serial abdominal exams showed a soft, non-distended abdomen mildly tender to palpation in the left lower quadrant without rebound or guarding, and an intact percutaneous drain present in the right mid-abdomen, which had been draining purulent liquid for several days. His leukocytosis was on a slight downtrend (13.84 to 13.54 K/mm3). However, follow-up CT scan of the abscess unexpectedly revealed diffuse pneumoperitoneum with near resolution of the original fluid collection. He immediately underwent exploratory laparotomy and was found to have a quarter-sized perforation of the cecum, large purulent necrotic abscess cavity with significant free air, and a small capsular liver tear near the gallbladder. A right colectomy, end ileostomy, and long Hartmann’s pouch were created without complications. The patient transitioned to a regular diet, bacteremia resolved, and he continued with his palliative radiation treatments.
Discussion: Classically, pneumoperitoneum secondary to bowel perforation presents with symptoms including fever, nausea, severe abdominal pain, and peritoneal signs. Uncommonly, pneumoperitoneum can present silently without clinical signs of illness, as described in this case report and various case studies. This patient is at increased risk for developing pneumoperitoneum based on a combination of physical, chemical and biological factors, including advanced age, corticosteroid use, abdominal infection, and radiation therapy contributing to tissue damage. Corticosteroid and high dose oxycodone may have helped to mask symptoms of pneumoperitoneum. Studies have described increased likelihood of silent bowel perforation during corticosteroid treatment possibly due to anti-inflammatory effects that disrupt the normal process of healing and obscure symptoms.
Conclusions: Pneumoperitoneum secondary to bowel perforation is a life-threatening emergency that requires prompt surgical intervention. In rare cases, immunosuppressive or anti-inflammatory agents may impair inflammatory response, and patients may have little or no pain and tenderness. A high index of suspicion should be maintained in the setting of bowel disease with risk factors for bowel perforation despite a benign physical exam.