[Radioisotopes in the exploration of upper urinary tract obstruction]

The authors describe the various possibilities offered by isotope studies in cases of obstruction of the upper urinary tract. This examination allows: -- exploration of the dilatation itself, -- and isotope study of renal function. The dilatation can be explored either by means of the nephrogram with hyperdiuresis or by measurement of the renal transit time. The nephrogram with hyperdiuresis will give a precise answer: definite obstruction or no obstruction. Intermediate forms are possible, in which a mathematical interpretation of the curves of decay of the renal radioactivity will help distinguish between hypotonia without obstruction and true obstruction with dilatation. A marked decrease in renal function or severe vesico-renal reflux can interfere with the interpretation of these curves. Measurement of the renal transit time with the mathematical calculation of deconvolution is a valuable application of isotopes, but it is less practical than the nephrogram with hyperdiuresis. The isotope study of renal function is a promising technique, as it is able to study the global clearance without the need for blood tests (this is true for both the glomerular filtration rate and for the measurement of renal blood flow). Furthermore, this technique should allow each kidney to be studied separately. Separate measurements do not provide an absolute value for each kidney, but evaluate the part played by each kidney in the global renal function, which can be measured simply by means of the isotope study.(ABSTRACT TRUNCATED AT 250 WORDS)