Idiopathic spontaneous pneumoperitoneum

Abstract

Spontaneous pneumoperitoneum is the presence of free air in the peritoneum without evidence of any perforation of hollow viscera. The usual presentation includes acute abdominal pain with leukocytosis and elevated inflammatory markers. Here we present a case of spontaneous pneumoperitoneum occurring recurrently in a 58-year-old man with inclusion body myositis and hypertension who presented with cellulitis of both legs. Abdominal computed tomography demonstrated retroperitoneal free air; however, colonoscopy, esophagogastroduodenoscopy, and a prior laparoscopy did not demonstrate any perforation of hollow viscera. Conservative management with antibiotics and symptom control with antiemetics and pain medicines led to clinical improvement, and the patient was discharged home in stable condition.

Pneumoperitoneum is defined as the presence of free air inside the peritoneal cavity. Usually, it results from a rupture of intraperitoneal hollow viscera, which requires surgical intervention. However, a small proportion of cases of pneumoperitoneum present without any evidence of intraperitoneal perforation and are grouped as spontaneous pneumoperitoneum (SP). Most reported cases of SP have been incidental findings in patients with abdominal pain.^1–7 Here we report a case of SP identified incidentally on imaging of the abdomen in a patient presenting with sepsis associated with lower-extremity cellulitis without any identifiable cause for the pneumoperitoneum.

CASE DESCRIPTION

A 58-year-old man with inclusion body myopathy and hypertension presented with 2 days of worsening pain and swelling of both legs extending to the abdomen. He also had nausea, vomiting, fever, chills, and dyspnea at presentation. His past medical history included recurrent cellulitis resulting from immobilization due to him being wheelchair-bound. Two months earlier, he had been hospitalized for acute abdominal pain, and a computed tomography (CT) scan incidentally showed retroperitoneal free air. A diagnostic laparoscopy performed at that time demonstrated free air in the lesser sac without any evidence of bile staining or obvious perforation. He was symptom free in the intervening period, and a CT did not show any extravasation of contrast.

At the time of this presentation, his blood pressure was 140/80 mm Hg, heart rate was 126 beats/minute, and peripheral oxygen saturation was 95% on 2 L/minute of oxygen. Electrocardiogram showed atrial flutter. At presentation the white blood cell count was 20,000/µL and C-reactive protein was 22 mg/dL. The patient was resuscitated with intravenous fluids and started empirically on vancomycin, cefepime, and metronidazole. His home dose of prednisone (20 mg once daily) was resumed for inclusion body myositis. Atrial flutter resolved with one dose of metoprolol.

CT scan with contrast of the abdomen and pelvis showed retroperitoneal and posterior mediastinal air without any extravasation of contrast material (Figure 1). CT scan of both legs showed cellulitis without any fluid or air collection or abscess. Esophagogastroduodenoscopy showed acute gastritis with erosion, erythema, friability, and granularity of the gastric body mucosa, but no perforation. Colonoscopy showed internal hemorrhoids and few diverticula in the entire colon without any evidence of perforation. Upper gastrointestinal (GI) follow-through was attempted twice but the study could not be completed due to vomiting of the contrast material. The patient improved with intravenous antibiotics and supportive management, including pain control with opioid medicines, antiemetics, antipyretics, and intravenous furosemide for volume overload. His nausea and cellulitis resolved with expectant management, and he was able to tolerate oral food. He was transitioned to oral doxycycline on day 8, for a total 14 days of antibiotics for cellulitis, and was discharged home in stable condition on day 10.

Figure 1.

Abdominal CT scan showing free retroperitoneal air in the (a) sagittal and (b) coronal view.

DISCUSSION

Recurrence of SP is rarely reported.^8–10 Recurrent cases are associated with underlying comorbidities that predispose to pneumoperitoneum formation, such as diverticulosis,^11–13 pneumatosis intestinalis,^14,15 chronic cough,¹⁰ constipation,¹⁶ and rarely systemic sclerosis.^17–19 Recently, a few cases of SP have been reported in patients infected with SARS-CoV-2.^20–24 SP has sometimes been reported in patients on mechanical ventilation⁴; such cases are thought to originate from air leaks from the lungs, which then spread to contiguous anatomical spaces by the Macklin effect.²⁵ Although few diverticuli were seen on coloscopy in our patient, there was no evidence of perforation, thus making these a less likely source of origin of the pneumoperitoneum. Our patient also had inclusion body myositis, which has never been reported to be associated with pneumoperitoneum. Rare cases of smooth muscle involvement of the GI tract have been reported in inflammatory myopathies such as polymyositis, eosinophilic myositis, and dermatomyositis.²⁶ The mechanism of GI tract involvement in myopathies is poorly understood; a possible hypothesis is a non-inflammatory acute endarteropathy with ischemia, ulceration, and perforation of the GI tract resulting from vascular intimal hyperplasia and thrombi, as seen in juvenile dermatomyositis.²⁷

Chronic and high-dose corticosteroid therapy has been implicated in the increased incidence of colonic perforation in both diseased and nondiseased bowel. Corticosteroids inhibit the inflammatory process, leading to impairment of mucosal repair and decreased inflammatory signs. Also, corticosteroids cause degeneration of mucosal lymphoid tissue leading to thinning of the bowel wall, which thus increases the propensity of bowel wall perforation with decreased walling off of perforated lesions.^28,29 Chronic steroid treatment may increase the risk of microperforation of the bowel wall, presenting seemingly as SP, which may have been a contributing factor in our patient.

Our case shows that SP is an important differential, especially in patients with incidentally discovered pneumoperitoneum without any signs of acute abdomen. Chronic steroid use may predispose to SP formation.