TECHNETIUM-99M-DMSA RENAL CORTICAL SCINTIGRAPHY TO DETECT EXPERIMENTAL ACUTE PYELONEPHRITIS IN PIGLETS - COMPARISON OF PLANAR (PINHOLE) ANDSPECT IMAGING

The purpose of this study was to directly compare the sensitivity and specificity of SPECT and pinhole imaging for the detection of acute py elonephritis using histology as the standard of reference. Methods: Bi lateral vesicoureteral reflux of infected urine was induced in 16 pigl ets (32 kidneys) by unroofing the intravesical ureter and subsequently instilling a broth culture of E. coli into the bladder, DMSA scans we re obtained by both pinhole and SPECT techniques at 24 hr (4 piglets), 48 hr (5 piglets), 72 hr (4 piglets) and 10 days (3 piglets) after in stillation of bacteria into the bladder. Kidneys were harvested immedi ately after scintigraphy for histopathologic examination. Results of t he SPECT images, pinhole images and histologic findings were interpret ed independently in a blinded fashion. The images of each kidney were classified as positive or negative for pyelonephritis regardless of th e severity and number of lesions. To evaluate accuracy of SPECT and pi nhole imaging for the detection of individual lesions, each kidney was arbitrarily divided into three zones (upper, middle and lower). Image findings were then compared with the pathology results for the presen ce or absence of pyelonephritis in each zone. Results: Histopathology revealed pyelonephritis in 24 of 32 kidneys (58 of 96 zones). The sens itivity of the DMSA scan for detection of affected kidneys was 92% for SPECT and 83% for pinhole; overall accuracy was 88% for both. The sen sitivity of SPECT for the detection of affected renal zones was slight ly better than pinhole imaging (91% compared with 86%), but its specif icity was lower (82% compared with 95%) resulting in a similar accurac y. Excluding four piglets where scans were obtained within 24 hr after instillation of bacteria into the bladder, the sensitivity of SPECT a nd pinhole for the detection of affected kidneys were 95% and 90%, res pectively. Their overall accuracy were 96% and 92%. In this subgroup, the sensitivity, specificity and accuracy of SPECT for the detection o f involved zones were 96%, 95% and 96%, respectively. The correspondin g values for pinhole imaging were 90%, 95% and 92%, respectively. Conc lusion: Although the sensitivity of SPECT for the detection of acute p yelonephritis is slightly better than pinhole DMSA scan, the overall a ccuracy of these two imaging techniques is essentially the same.