Case Report

Spontaneous septic diskitis: a common complaint with a serious pathologic cause that should

not been overlooked

Abstract

Many people who have low back pain are likely to be out of work and taking medication and probably make demands on both primary and secondary health care as well as the private sector. Septic diskitis is a rare cause of back pain, accounting for less than 0.01% of cases in the primary care setting (Carragee EJ. Pyogenic vertebral osteomyelitis. J Bone Joint Surg Am. 1997;79:874-80). It has been associated with a high morbidity and mortality in the past. Although it is an unusual complication in a postoperative patient, it is even more rare in a nonoperative patient. It accounts for 2% of all osteomyelitis (Maiuri F, Iaconetta G, Gallicchio B, Manto A, Briganti F. Spondylodiscitis. Clinical and magnetic resonance diagnosis. Spine. 1997;22:1741-6) and may occur spontaneously, after surgery (especially after Epidural anesthesia), in the immunosuppressed, and Systemic Infections. It has the potential to be an orthopedic pitfall in the emergency department because it can be presented with nonspecific symptoms, nonspecific laboratory abnormalities, and nondiagnostic radiographic studies. We present a case of low back pain in a previously healthy individual as a result of spontaneous septic diskitis, which had been initially misdiagnosed in the private sector as herniation of an intervertebral disk.

A previously healthy 46-year-old woman presented to the emergency department (ED) with a complaint of acute, atraumatic onset of severe low back pain for 3 days. She was first treated in the private sector with nonsteroidal antiin- flammatories and bed rest for herniation of an intervertebral disk. Her back symptom was partially resolved with the treatment, but she developed fever and chills 2 days after. There was no significant medical history. On examination, she was febrile, with no knocking tenderness of the bilateral costovertebral angle. She had full range of spinal movements with some low back pain and no localized spinal tenderness. Straight leg raising was between 25? and 30? on both sides. There was no neurologic deficit. Examination results were otherwise unremarkable.

Investigations showed leukocytosis with polymorpho- nuclear leukocytes predominant, normal C-reactive protein, and normal urinalysis result. Blood cultures yielded a growth of Staphylococcus aureus. Plain lumbar radiographs were unremarkable. Magnetic resonance imaging demonstrates an increased signal intensity and marked reduced height with annular bulging of L5 through S1. Increased signal intensity of bony structures of the lower L5 and upper S1 vertebral bodies, more extensive on left side, were found on fast recovery fast spin echo (FRFSE) (Fig. 1). The findings were consistent with septic diskitis. The patient responded well to intravenous oxacillin and gentamycin and did not require any surgical intervention.

At least 70% of adults will have low back pain during their lifetime [1]. Up to 85% of patients with low back pain cannot be given a definitive diagnosis because of the poor

Fig. 1 Magnetic resonance imaging demonstrates an increased signal intensity and marked reduced height with annular bulging of L5 through S1. Intervertebral disk with anterior bulging and increased signal intensity of bony structures of lower L5 and upper S1 vertebral bodies, more extensive on the left side, are found on FRFSE.

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associations between symptoms, signs, Imaging results, and Pathologic findings [2]. In most cases, back pain is related to nonserious musculoskeletal causes that resolve sponta- neously, but it can be a manifestation of serious spinal disease, as the present case illustrates. Thus, it is important to develop a systematic approach to the diagnosis and treatment of back pain to avoid unnecessary testing and so as not to miss potential serious pathologic causes.

Diagnosis of septic diskitis is difficult and often delayed because of a lack of localizing signs and symptoms and because it is an uncommon condition. The onset may be acute or insidious, and radicular or spinal compressive symptoms and signs may be present. It should be considered in any patient with back pain, fever, and bacteremia. Diskitis usually arises from hematogenous spread, unless infection is directly introduced-for exam- ple, by instrumentation. The microbiologic yield from a disk biopsy reportedly varies between 47% and 90%, and

S. aureus was the most common bacterium in disk biopsy [3]. Purulent infection may spread to surrounding Soft tissues, and Epidural abscess formation is recognized. Long- term neurologic sequela may result, and mortality of between 7% and 18% has been reported [4]. When abnormalities are suspected, and there are no clinical changes or radiologic signs of local abnormality, a bone scan may be helpful. Magnetic resonance imaging will confirm abnormalities, and computed tomography may facilitate biopsy under radiologic guidance [5].

This case illustrates that the diagnosis of diskitis in the ED can be extremely challenging given the lack of specific diagnostic laboratory tests, with the frequency of a normal plain radiograph, and there may be no abnormal signs on

examination of the spine. Especially when a previously healthy patient presents with a common complaint as back pain and fever, septic diskitis should always be included in the differential diagnosis.

Henry Chih-Hung Tai MD Wei-Lung Chen MD, MS Chien-Cheng Huang MD Jiann-Hwa Chen MD Yung-Lung Wu MD

Department of Emergency Medicine

Cathay General Hospital

Taipei, Taiwan Fu Jen Catholic University School of Medicine

Taipei, Taiwan E-mail address: [email protected]

doi:10.1016/j.ajem.2007.08.007

References

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3. Chew FS, Kline MJ. diagnostic yield of CT-guided percutaneous aspiration procedures in suspected spontaneous infectious diskitis. Radiology 2001;218:211-4.
4. Del Curling Jr O, Gower DJ, McWhorter JM. Changing concepts in Spinal epidural abscess: a report of 29 cases. Neurosurgery 1990;27: 185-92.
5. Frank A. Low back pain. BMJ 1993;307:323-4.