The prospect of incidental detection of unsuspected skeletal tuberculosis by bone scintigraphy should not be overlooked

Background: The potential roles of bone scintigraphy in the evaluation of tuberculosis are not well-defined. It is commonly considered that skeletal tuberculosis occurs only after pulmonary tuberculosis. Bone scintigraphy was not known to be an effective imaging modality in the evaluation of skeletal tuberculosis, especially in those without known systemic tuberculosis. Purpose: To assess the prospect of bone scintigraphy in the detection of skeletal tuberculosis in patients who came to the department of nuclear medicine to evaluate back pain. Methods: Patient records and the images of 1817 cases of consecutive bone scintigraphy performed for the evaluation of unknown causes of back pain were retrospectively reviewed. The imaging findings were compared with the status of tuberculosis before and after scintigraphy. Results: Sixteen patients had skeletal tuberculosis confirmed by histopathological examination. Six patients had solitary while 10 had multifocal skeletal lesions. Before bone scintigraphy, 2 patients were suspected but not confirmed to have pulmonary tuberculosis, 4 were suspected to have skeletal tuberculosis by other modalities while the remaining 10 patients were not suspected to have tuberculosis in any part of the body. Following bone scintigraphy, among those 10 patients who were unsuspected of having tuberculosis, further tests demonstrated that 3 had pulmonary tuberculosis in addition to skeletal tuberculosis and 1 had cervical tuberculous lymphadenitis. In total, among those 16 patients with confirmed skeletal tuberculosis, only 6 had concurrent extraskeletal tuberculosis while 10 patients had their tuberculosis limited to the skeletal system. Conclusions: Our results indicate that pulmonary or systemic tuberculosis is not a prerequisite for skeletal tuberculosis. Skeletal tuberculosis should be among the differential diagnoses when there is a positive bone scan in patients without a malignancy in an endemic region.