Back pain from a burger

Abstract

In August, 2006, a 26-year-old man presented to the emergency department at our hospital, with lower-back pain of acute onset. He was sent home with painkillers. He returned 3 days later, with gradually worsening pain in the right buttock, radiating to the thigh. He also had mild shortness of breath on exertion. 2 weeks before the pain started, the patient had travelled to Spain with his girlfriend, where they had enjoyed an unremarkable week’s holiday. On examination, the patient’s temperature was 39°C, and the arterial oxygen saturation only 88%. Blood pressure and heart rate were normal; chest radiography showed nothing of note. Blood tests revealed a leucocytosis (11×109 cells per L), and increased concentrations of C-reactive protein (350 mg/L) and liver enzymes (nearly three times the upper limit of the normal range); the albumin concentration was only 25 g/L, but the total-protein concentration was 65 g/L (normal range 60–80 g/L). There was no evidence of renal or thyroid dysfunction. CT of the pelvis showed an abscess, measuring 15×18 mm, in the right iliac and psoas muscles, close to the sacroiliac joint (fi gure). The joint itself had features of sacroiliitis: a fl uid collection, and a peripherally enhancing capsule. We used CT guidance to take a sample from the abscess—which was found, on microscopy, to contain gram-negative rods: we therefore prescribed ceftriaxone. We cultured eight blood samples, and a sample of abscess fl uid—all of which, by the next day, were found to contain Salmonella enteritidis, sensitive to ceftriaxone and ciprofl oxacin. Meanwhile, the patient had become increasingly short of breath. CT showed bilateral pulmonary infi ltrates and pleural eff usions, confi rming the provisional diagnosis of pneumonia. A pleural tap showed a transudate (protein concen tration 17 g/L). Echocardiography and abdominal CT showed nothing of note; and specifi cally, no evidence of endocarditis or mycotic aneurysm. Further exploration of the history revealed only one additional detail—the patient had eaten a badly cooked hamburger in Spain, although without any subsequent gastrointestinal symptoms. We found no evidence of immunodefi ciency: an HIV test was negative; lymphocyte subpopulations and immuno globulin concentrations were normal. We treated the patient for 3 weeks with intravenous ceftriaxone, and for another 3 weeks with ciprofl oxacin. His pain slowly subsided. After treatment, CT showed complete resolution of the pulmonary infi ltrates and the abscess, but extensive erosions of the sacroiliac joint. 3 months after discharge, the patient still had mild back pain, radiating to the right thigh, on exercise. However, when last seen, in July, 2007, he was well. Non-typhoidal species of salmonella typically cause gastroenteritis. However, up to 5% of patients also develop bacteraemia, which can lead to secondary focal infections, of which pneumonia is the commonest. By contrast, infection of muscles or large joints is rare— although the muscle most often aff ected is the psoas muscle. People with bacteraemia do not necessarily have symptoms of gastroenteritis, especially if they are immunocompromised; notably, salmonella can be transported from the gut to the bloodstream by CD18-expressing phagocytes, without triggering an immune response from the gut mucosa. Non-typhoidal salmonella infections are an increasing public-health problem in many countries—probably because of changes in food preparation and consumption, and the rapid growth of international trade in food products. Nosocomial outbreaks have been reported: in April 2007, more than 250 patients and staff were infected by a hospital kitchen in Germany.