What is the role of imaging studies in the workup of adults with hydronephrosis and hydroureter?

Updated: Dec 16, 2020
  • Author: Dennis G Lusaya, MD; Chief Editor: Bradley Fields Schwartz, DO, FACS  more...
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Early diagnosis of urinary tract obstruction is important because most cases can be corrected and a delay in therapy can lead to irreversible renal injury.

Bladder catheterization should be performed initially if there is reason to suspect that bladder neck obstruction leading to acute or chronic urinary retention may be present. Possible clues to this diagnosis include suprapubic pain, a palpable bladder, or unexplained renal failure in an older man.

Radiologic tests are generally used to exclude obstruction at the level of the ureters or above by detecting dilatation of the collecting system. It is important to remember, therefore, that obstruction can occur without dilatation in the following three settings:

  • Within the first 1-3 days, when the collecting system is relatively noncompliant and less likely to dilate: In this setting, unilateral obstruction can usually be diagnosed by duplex Doppler ultrasonography, which detects an increased resistive index (a reflection of increased renal vascular resistance) in the affected compared with the contralateral kidney. [10] This test is of no value with bilateral involvement because it cannot distinguish obstruction from intrinsic renal disease.

  • When the collecting systems are encased by retroperitoneal tumor or fibrosis: In this setting, hydronephrosis may be present in the absence of ureteral dilatation. Retroperitoneal fibrosis can occur in a number of settings, including retroperitoneal fibrosis (most commonly idiopathic or associated with beta-blocker or methysergide use, malignancy, or a connective-tissue disorder) and with the fibrotic reaction that surrounds a renal transplant. [11] Thus, the diagnosis of renal insufficiency due to asymptomatic obstruction in a transplanted kidney may be made based on renal biopsy findings, which show diffuse tubular dilatation, rather than the signs of rejection or cyclosporine nephrotoxicity.

  • When the obstruction is mild, a setting in which renal function is not usually impaired

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