The radiology of obstructive atrophy of the kidney

The authors describe a radiological investigation of the changes in the kidney produced by extra-renal urinary obstruction. Fifty consecutive patients were investigated, all of whom showed the characteristic appearances of obstructive, or ‘back pressure’, atrophy of the kidney, the diagnostic features of which are a generalised and uniform degree of papillary atrophy and decrease of renal substance thickness. Functional and other associated changes are described, with the factors influencing their development. In 34 patients there was evidence of present or past urinary tract obstruction. An argument is put forward to support the thesis that the other 16 cases were also due to the effects of obstruction, which has been ‘silent’. The differential diagnosis from chronic pyelonephritis, papillary necrosis, and renal tuberculosis is discussed, and atypical findings following prolonged obstruction are described. A classification of obstructive and post-obstructive effects on the kidney is suggested. These changes are often complicated by secondary events such as arteriolarsclerosis, hypertension or infection. The value of radiology in defining the essential basic process of renal back pressure atrophy is stressed, and some mention made of its clinical significance.