Subtraction nephrotomography during urography of transplanted kidneys.

Hypocycloid tomography with photographic subtraction was applied during the early nephrographic phase of urography in 48 transplanted kidneys. The quality of demarcation between cortex and medulla in the subtracted nephrotomogram was evaluated and categorized into 4 groups: Excellent, good, poor, and absent demarcation. The renal function determined by 24-h endogenous creatinine clearance did not correlate with the quality of demarcation. Among 30 cases with excellent or good demarcation only one patient experienced rejection within 8 days after the urography. In 18 cases with poor or absent demarcation 9 had an episode of rejection. Absence of demarcation was only observed in this group of patients. Segmental renal infarcts were demonstrated occasionally on the subtracted early nephrotomogram. Thus, tomographic demonstration of the initial distribution of contrast medium in a transplanted kidney may prove to be of value in the diagnosis both of rejection of transplanted kidneys and renal infarcts.