The sensitivity and specificity of Hippuran renography as a diagnostic investigation of renal transplant rejection.

Renography is a valuable investigation of a graft, as it can alert suspicions of rejection before it is clinically discernible. Renographic signs of rejection are delayed excretory phase and decreased Hippuran uptake in phase 1 and 2. A prospective trial was performed including 319 necrokidney transplanted patients. In 139 patients, acute rejection was diagnosed on clinical parameters. The material was divided into two groups: 1. Transplant patients suffering from acute tubulointerstitial nephropathy and having unmeasurably low creatinine clearance and an initial renogram showing an accumulation curve. 2. Patients with functioning grafts exposing a renogram with an excretion phase. The prevalence of rejection was 0.19 and 0.33, respectively, in the two groups. The sensitivity and specificity of renography as a parameter for diagnosing rejection was for group 1: Sensitivity 0.77 and specificity 0.95. Group 2: Sensitivity 0.68 and specificity 0.84. Efficiency of renography as a predictive test for the whole material was 74 percent. In group 1: 92 percent and in group 2: 79 percent. Acute rejection was diagnosed with renography in group 1 in 30/39 episodes before it was clinically evident. In group 2, with functioning grafts, rejection was diagnosed in 67 percent of the cases one to two days before it was clinically manifest. On the day of clinically manifest rejection, 92 percent of the renograms showed positive signs of rejection. False positive renographic signs of rejection were mainly caused by urinary tract obstruction, infection, and medication.