Enterocutaneous Fistula and Pneumoretroperitoneum due to Ruptured Psoas Abscess

Psoas abscess is a rare condition that can present with vague clinical features. Its insidious onset can lead to a delay in diagnosis, resulting in high rates of complications and mortality. Here we describe a unique case of a patient presenting with enterocutaneous fistula and pneumoretroperitoneum due to ruptured psoas abscess.

right lower chest wall. It also extended into the subcutaneous plane and the overlying skin through a defect in the posterolateral aspect. These findings were consistent with enterocutaneous fistula (►Figs. 2 and 3).
Percutaneous drainage of the abscess was done. Vancomycin, metronidazole, and ceftriaxone were started empirically till the culture and sensitivity reports were obtained. Vancomycin was continued for the next 6 weeks owing to the culture reports suggestive of Staphylococcus aureus infection. Surgical management was done after 10 weeks by the closure of the superficial defect by debridement, local flap, and skin grafting. The management of the defect in ascending colon was done by resection of the affected part followed by end-to-end anastomosis. The patient was discharged postoperatively after 12 days. His recovery was good and the follow-up after 2 weeks, 1 month, and 6 months was uneventful. However, the patient did not consent for colonoscopy during the follow-ups.

Discussion
Psoas abscess is classified into primary and secondary types. In the primary type, the cause is believed to be hematogenous spread from a distant site. This occurs more frequently in children, intravenous drug abusers, and immunocompromised patients. 5 Staphylococcus aureus is the principal bacteria involved. 6 The secondary type is due to direct extension of an intra-abdominal source of infection, mainly caused by enteric bacteria. The most common cause is Crohn's disease. 7 Other causes include appendicitis, diverticulitis, colorectal carcinoma, pyelonephritis, vertebral osteomyelitis, infected abdominal aortic aneurysms, and other rarer causes. The published literature indicates there is a difference in epidemiology between the developed and developing worlds. In Asia and Africa, 99.5% of abscesses are primary. However, in Europe, only 17.7% are primary. 6 Computed tomography (CT) is the current gold standard radiological investigation in the diagnosis of psoas abscess, with a reported sensitivity of 100%, specificity of 77%, and an accuracy of 88%. 8,9 CT can precisely portray any pathological process in the iliopsoas muscle and can reveal the related retro or intraperitoneal changes that could describe the etiology. Features of psoas abscess on CT scan are a focal   Ruptured Psoas Abscess Patel, Patel e287 low-density area within an enlarged psoas muscle. Other possible features include an abscess edge that may enhance with intravenous contrast, free gas within the lesion, and infiltration of surrounding fat. 10 Fistula is a transmural communication between two epithelialized surfaces. Enterocutaneous fistula is a tract between skin and bowel. It is usually seen in the case of Crohn's disease, diverticulitis, colon cancer, or trauma. However, our patient had no history of Crohn's disease, diverticulitis, colon cancer, or trauma. Due to the fistula, contents of the ascending colon entered the retroperitoneum. This explains the greenishcolored collection with the feculent smell. The pneumoretroperitoneum can be explained by the defect in the abdominal wall as well as the perforation in the ascending colon.
Definitive repair of the enterocutaneous fistula should be performed if spontaneous closure fails to occur by 12 weeks after nutritional optimization, control of sepsis, and wound care. Timeline to definitive repair is not firmly established but may be delayed in cases where nutrition is maintained and multiple surgeries have been previously performed. 11 Prerequisites to definitive fistula operative intervention requires nutritional optimization, sepsis control, addressing psychological morbidity, and clinical signs of softening scars and abdominal wall on examination. Avoidance and adequate repair of any enterotomy are essential as 36% of recurrent fistulas are due to inadvertent injury to the bowel. 12 Operative success rate for definitive enterocutaneous fistula resolution is 80 to 95%. 11 Recurrence rates are reduced (18%) when the involved bowel is fully mobilized and resected. Rate of recurrence is as high as 33% in case of wedge resection/bowel repair or oversewing. 13 Similarly in our case, resection of the affected part of ascending colon followed by end-to-end anastomosis was done.

Conclusion
Psoas abscess can remain undiagnosed for a long time. It may present with significant complications like spinal nerve involvement, peritonitis, bowel perforation, abdominal aorta rupture, necrotizing fasciitis, enterocutaneous fistula, osteomyelitis, septic arthritis, and septic shock. Hence, early diagnosis and prompt treatment are necessary.
Enterocutaneous fistula following psoas abscess usually occurs secondary to underlying gastrointestinal diseases like Crohn's disease. However, it can also occur in absence of an underlying secondary pathology. It should be managed conservatively initially. Surgical management should be done only after controlling the underlying infection.

Note
This case has not been published/presented before. Informed consent was obtained from the patient for publication of case details.

Funding
None.

Conflict of Interest
None declared.