With a double isotope technique, simultaneous tracing of 131-I-hippuran renogrm and 197-Hg-chlormerodrin uptake curve are routinely carried out. This procedure not only saved the time required for each tracing, but served to quantitatively evaluate renograms in patients with urinary tract abnormalities. The dose of 197-Hg used was over 5 times larger than that of 131-I, since the rate of 131-I counts in the 197-Hg window was experimentally confirmed to be under 10 per cent at these doses.
1) The changes of urine flow from the pelvis to the bladder caused by acute ureteral obstruction, voiding in the presence of vesicoureteral reflux, and bladder filling, altered the hippuran renogram pattern. The alterations were characterized by a delay in excretory phase, a sudden elevation of slow down curve, and a prolongation of renal transit time. However, the chlormerodrin uptake curves were not affected by these urine flow changes.
2) Bladder emptying by catheterization in patients with large amount of residual urine produced the renogram pattern with shortened transit time, and revealed that T 1/2 value of the slow component of blood disappearance curve was also decreased. However, changes of the chlormerodrin uptake curve and its blood disappearance curve after bladder emptying were negligible.
The problems in computer assessment of 131-I-hippuran renograms in patients with urinary tract abnormalities were investigated, and the advantages of simultaneous tracing of 197-Hg-chlormerodrin uptake curve were emphasized.