[A woman with fever and a painful hip].

An immunocompromised 78-year-old woman had a painful hip and subacute fever. An abdominal CT scan revealed a diverticular sigmoid stenosis fistulating to the presacral space, with free gas in the paravertebral musculature and spinal canal. Because a deep necrotising infection was suspected, she underwent surgery and was treated with antibiotics. She recovered completely.