To evaluate the usefulness of the posterior 180 degrees acquisition technique for renal defects in acute pyelonephritis (APN), a prospective study was conducted using planar imaging, 360 degrees and posterior 180 degrees renal single photon emission computed tomography (SPECT) with 99Tcm-dimercaptosuccinic acid. Sixty subjects with the suspicion of APN were included. The kidneys were divided into three zones: each was graded as positive, equivocal or negative for renal defects. To evaluate inter-observer variation, each study was read in a double-blind fashion by two nuclear physicians. Renal defects were found in 24 patients (31 kidneys and 47 zones) with posterior 180 degrees SPECT, 23 patients (29 kidneys and 44 zones) with 360 degrees SPECT (McNemar's test, P = 0.375 for zones) and 15 patients (16 kidneys and 24 zones) with planar image (P = 0.001 for zones, vs 180 degrees and 360 degrees SPECT). The proportion of positive agreement for posterior 180 degrees and 360 degrees SPECT between readers for the presence of renal defects was 0.81 and 0.62, respectively, whereas the proportion of negative agreement was 0.92 and 0.87, respectively. Both posterior 180 degrees and 360 degrees SPECTs significantly detected more renal defects than planar imaging. The detectability of renal defects in APN by posterior 180 degrees renal SPECT was equal to 360 degrees SPECT but inter-observer agreement was better.