Postpartum Septic Sacroiliitis Misdiagnosed as Sciatic Neuropathy

Early diagnosis of septic sacroiliitis is difficult because symptoms are nonspecific, especially during pregnancy and the postpartum period. We describe a female patient with left buttock pain radiating down the thigh after an uncomplicated induction delivery. She was afebrile and had no apparent abnormality on pelvic x-ray or computed tomography scan. A sensory deficit in the lateral portion of her left lower limb was found, and electromyography showed neurogenic abnormalities in the left lower limb. She was initially misdiagnosed as sciatic neuropathy. As her symptoms worsened, septic sacroiliitis is considered. Bone scintigraphy showed increased 99mTc-methylene diphosphonate uptake in the left sacroiliac joint, and magnetic resonance imaging scan showed a signal abnormality in the left sacroiliac joint. The diagnosis of septic sacroiliitis was then confirmed by the rapid efficacy of antibiotic therapy. This report suggests that irritation and injury of spinal nerves can be the presenting signs in septic sacroiliitis.