Technetium-99m dimercaptosuccinic acid scan in evaluation of renal cortical scarring: Is it mandatory to do single photon emission computerized tomography?

OBJECTIVES: Renal cortical scintigraphy with technetium-99m (Tc-99m) dimercaptosuccinic acid (DMSA) is the method of choice to detect acute pyelonephritis and cortical scarring. Different acquisition methods have been used: Planar parallel-hole or pinhole collimation and single photon emission tomography (SPECT). This study compared planar parallel-hole cortical scintigraphy and dual-head SPECT for detection of cortical defects. PATIENTS AND METHODS: We retrospectively reviewed 190 consecutive patients with 380 kidneys and 200 DMSA scans referred to rule out renal cortical scarring. The diagnoses were 52 vesicoureteric reflux, 61 recurrent urinary tract infection, 39 hydronephrosis, 20 renal impairment, and 18 hypertension. All patients were imaged 3 h after injection of Tc-99m DMSA with SPECT and planar imaging (posterior, anterior, left, and right posterior oblique views). For each patient, planar and SPECT images were evaluated at different sittings, in random order. Each kidney was divided into three cortical segments (upper, middle and lower) and was scored as normal or reduced uptake. The linear correlation coefficient for the number of abnormal segments detected between planner and SPECT techniques was calculated. RESULTS: From 200 DMSA scans, 100 scans were positive for scar in SPECT images, from which only 95 scans were positive for scar in planner imaging. Out of the five mismatched scans, three scans were for patients with renal impairment and high background activity and two scans were for very small scars. No significant difference was seen in the average number of abnormal segments detected by planar versus SPECT imaging (P = 0.31). The average correlation coefficient between was high (r = 0.91 – 0.92). CONCLUSIONS: Tc-99m DMSA renal cortical scanning using SPECT offers no statistically significant diagnostic advantage over multiple views planar imaging for detection of cortical defect.