Nephrography with radioactive hippuran in transplanted kidneys: interpretation, limitations, and usefulness.

A total of 485 nephrographies (NGs) performed on 95 patients in 1982 were analyzed statistically. The different modes of orthoiodine-hippuran (OIH) handling by the transplanted kidneys are summarized by six different basic curve patterns. The formation of these patterns is an effect of the prolongation of the time to the curve maximum, the time to 75% of the maximum, and the time until the intersection of the bladder and kidney curves. Also, intraparenchymal retention of activity leads to changes in the OIH curves. The basic curve patterns were correlated with the increase of serum creatinine levels, and thus, OIH-NG has to be interpreted as a differentiated marker of renal function. Renal-transplant rejection does not produce a specific pattern of OIH curve, as seen from comparison of the curve-type distribution in rejection and non rejection periods (chi 2 = 0.0866). The diagnostic values of the OIH is limited to purely functional statements, allowing only an indirect diagnosis of renal-transplant rejections without permitting the differential diagnosis of other causes of renal disturbance. OIH-NG is useful for monitoring renal function because it resolves different function levels very sensitively even at identical creatinine values. Furthermore, it makes it possible to estimate the prognosis of renal functional improvement when creatinine levels are elevated.