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Pyogenic sacroiliitis is a rare condition with often vague symptoms mimicking common conditions such as protruded disk, muscular strain, or visceral pain. Therefore the diagnosis is often missed or delayed. In 1986, Cohn and Schoetz reviewed patients with pyogenic sacroiliitis.1 In 12.6% of these cases sacroiliitis mimicked the acute abdomen. In 40–60% fever and a raised erythrocyte sedimentation rate were present. Blood cultures were positive in 60%. Magnetic resonance imaging and computer tomography can be helpful, but especially when blood cultures are negative, joint aspiration can be crucial for establishing the diagnosis. We present two cases of infectious sacroiliitis.
CASE REPORTS
Patient 1
A 19 year old woman was admitted to hospital with a 4 day history of pain in the right hip and buttock, and fever. Walking was difficult and transfers were impossible to make. Recently she had scratched the skin of her head causing some wounds. Monthly she used plugs during her menstruation. There were no abdominal complaints. She neither smoked nor used alcohol. Her medical history was unremarkable.
Examination showed a sick woman, with a temperature of 40.8°C and normal blood pressure. A general internal examination was normal. The right sacroiliac joint showed tenderness on pelvic compression without further limitations. The erythrocyte sedimentation rate was 40 mm/1st h, C reactive protein 240 mg/l, white blood cell count 8.4×109/l. Plain x ray examinations of chest, hip, and pelvis and ultrasonography of the hip were normal. Bone scan showed an increased uptake in the right sacroiliac joint. Magnetic resonance imaging demonstrated sacroiliitis of that joint. Four blood cultures disclosed Staphylococcus aureus. Treatment was started with 2 weeks’ intravenous flucloxacillin 12 g daily, followed by an oral 2 week course 2 g daily. Mobility improved and she was discharged after 3 weeks. Follow up radiography showed sclerosis of the right sacroiliac joint. A year later she was still free of complaints.
Patient 2
A previously healthy 14 year old girl presented with acute, severe pain in the buttock radiating to the right leg and a temperature of 38°C. Three weeks before admission her whole family was on holiday in Kenya, where they all experienced a short period of diarrhoea. It resolved completely in a few days. In Kenya she had used both milk and yoghurt, but no eggs. On holiday she had used plugs. There were no injuries or infections. Examination disclosed tenderness of the right sacroiliac joint and buttock.
A stress test of that joint was positive. Further physical examination was normal. Bearing weight on the right leg was impossible. The erythrocyte sedimentation rate was 77 mm/1st h, C reactive protein 131 mg/l, white blood cell count 12.4×109/l. Plain x ray examinations of chest, pelvis, and lumbar spine and ultrasonography of the hips were normal. Magnetic resonance imaging showed right sided sacroiliitis (fig 1⇓). Blood cultures were negative, but cultures of stool and synovial fluid (after computed tomography guided punction) disclosed Salmonella group D.
T2 sequence magnetic resonance imaging showing sacroiliitis of the right sacroiliac joint.
Treatment was started intravenously with ciprofloxacin 200 mg twice a day for 10 days. Pain decreased and mobility improved. She was discharged after 10 days and continued oral ciprofloxacin 500 mg twice a day for 3 weeks. Three months after presentation she was mobile without pain. A follow up pelvic x ray examination showed erosive changes and sclerosis of the right sacroiliac joint.
DISCUSSION
Pyogenic sacroiliitis is rare, especially if caused by Salmonella. A review pointed to Staphylococcus aureus as the leading causative organism. Only 16 of the 200 cases were due to Salmonella.2 In brucellosis the sacroiliac joint was the most commonly affected osteoarticular site.3Pseudomonas species were often found in intravenous drug abusers.4 Tuberculosis has usually been an indolent cause.5 Sacroiliitis due to Streptococcus pneumoniae is uncommon.6 High suspicion of a pyogenic sacroiliitis requires joint aspiration in order to establish the causative organism even if blood cultures and conventional radiography are normal.