The urographic appearances of ureteric obstruction secondary to bladder carcinoma.

It is usually assumed as a result of experiments that post-obstructive and hydronephrotic atrophy are due to raised intrapelvic pressure. In acute ureteric obstruction raised intrapelvic pressure is associated with renal colic; the absence of pain in chronic obstruction has been a stumbling block to acceptance of the back pressure theory. In ureteric obstruction due to bladder carcinoma the complete spectrum of nephrographic appearances ranging from those of high pressure obstruction to low pressure obstruction is seen in the absence of pain. This shows that acute ureteric obstruction may be painless and therefore post-obstructive and hydronephrotic atrophy may be preceded in man by a raised intrapelvic pressure. This removes the stumbling block.