The effects of renal pelvic pressure elevation on isotope nephrography and renal transit time, an experimental study

Radionuclide procedures are clinically used for assessing obstruction in dilated urinary tracts. The precise correlation of the isotope retention function with the level of the renal pelvic pressure is not known as yet. It was measured experimentally using 20 minipigs. By means of ureterostomies in situ reaching into the pyelon the 40 kidneys were subjected to varying pressures (seven to 62 cm. H2O) while the renal processing of 123-I-orthoiodine-hippuric-acid was recorded. The correlation of five radionuclide parameters with the pelvic pressure was computed: the time to the peak value of the isotope nephrography (t-max) and renal transit time correlated very well with high grade pelvic pressure (greater than 37 cm. H2O): r = 0.91 and 0.86 respectively, but much less well with low grade pelvic pressure (less than 37 cm. H2O): r = 0.73 and 0.62 respectively. The slope of the third phase of the isotope nephrography (tan-turn) and the time to the turning point of its tangent (t-turn) correlated only weakly with elevated renal pelvic pressure: r = 0.62 and 0.59 respectively. In conclusion, radionuclide procedures give excellent qualitative information on the level of pelvic pressure. They cannot, however, be used even as an indirect means for quantitatively assessing elevated renal pelvic pressure, which in urinary obstruction is thought to be one of the factors jeopardizing renal function.