The detailed characteristics of a nephrogram are more meaningful if studied in relation to the corresponding arteriogram. The appearance of a nephrogram in several forms of acute renal failure, including the second-set kidney transplant reaction, can be explained by a diversity of function among the nephrons. Those nephrons derived from outer cortical glomeruli are considered to be mainly geared to excretion and reabsorption whereas those nephrons derived from inner cortical glomeruli, are mainly geared to reabsorption and concentration. A nephrogram appearing in a severely oliguric or anuric kidney can be explained on the basis that outer cortical filtration has been seriously reduced or has ceased while inner cortical filtration continues but the filtrate is concentrated and reabsorbed. A kidney involved in this haemodynamic upset would more precisely be diagnosed as being in a state of acute excretory renal failure. The severe interference with excretory function is compatible with a total renal blood flow reduced by only 20-40 per cent.After several hours involvement in the severe haemodynamic upset evoked by a second-set kidney transplant reaction, inner cortical perfusion fails and at this stage no nephrogram is observed. A similar lack of a nephrogram associated with inadequate cortical perfusion was observed at 24 hr after subjecting a kidney to 2 hr total warm ischaemia which causes cortical necrosis.These principles permit a review of intravenous pyelographic techniques to be made with the recommendation of using small physiological doses of anti-diuretic substances, about half the currently recommended dose of contrast and free but not excessive access to water because the above injected doses of anti-diuretic hormone act maximally during an established water diuresis.
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