Tc-99m DMSA SPECT imaging in patients with acute symptoms or history of UTI. Comparison with ultrasonography.

Although planar cortical scintigraphy has been demonstrated to be a sensitive test for the detection of renal infection and scarring, one criticism has been radiation dose to the renal cortex. Recent studies of cortical SPECT suggest a sensitivity for detection of lesions equal to, or greater than, that of planar scans. The authors prospectively performed SPECT scans on 36 patients referred for recurrent urinary tract infection (UTI) (11 of 36), or recent onset of symptoms of UTI (25/36) after 30-40% of the standard 130 MBq (3.5 mCi) adult dose of Tc-99m DMSA was administered. Comparison was made with ultrasonography (US) performed at, or near, the same time. Of 67 kidneys evaluated, 34 (51%) demonstrated focal cortical loss on Tc-99m DMSA scintigraphy, 1 kidney was small in size, and 32 kidneys were normal. Abnormalities were noticed in only 13 (19%) of kidneys on US. Previously, US has been the primary imaging modality in the evaluation of the young patient with UTI. Triple-headed Tc-99m DMSA SPECT scintigraphy is a more sensitive, low-dose (12 mGy, 1.2 r) method of detecting renal cortical abnormalities. As such, it is a more appropriate test for identifying sites of cortical infection and scarring and for following patients on prophylactic therapy for evidence of asymptomatic break-through infections.