Posterior urethral valve

Clinical History

A two-year-old boy with difficulty in urination, dribbling and abnormal growth was referred for voiding cystourethrography.

Imaging Findings

During the voiding phase of the cystourethrogram, a linear lucency was noted in the posterior urethra, with proximal dilatation. The urinary bladder demonstrated irregular outlines with formation of diverticula (Fig. 1).

No vesico-ureteric reflux was detected during procedure. However, ultrasound demonstrated bilateral hydronephrosis and hydroureter down to the level of distal ureters as well as urinary bladder wall thickening and irregularity (Figs. 2, 3, 4). This could be due to vesico-ureteric reflux which was not detectable by voiding cystourethrography.

Discussion

Posterior urethral valve (PUV) is the most common cause of urinary tract obstructive anomaly in male children. The prevalence of PUV is 1 in 8000 newborns. [1, 2]

The exact anatomy and embryology of the PUV is not clear. [3] However, numerous theories have been suggested. Tolmatschew indicated that PUV might represent an overdevelopment of the normally placed folds and ridges of the urethral wall; and thus with progressive distention of these folds, obstruction may occur. [4]

The presence of this abnormal valve results in anatomical narrowing and blockage of the urethra which in turn causes secondary pathologies to develop. [4]
The renal damage could occur through the presence of VUR, infection, or impaired ureteric drainage caused by either obstruction, reflux or impaired motility. It may manifest in the form of hydronephrosis with cortical loss and cortical scarring. [4] In our case the patient had bilateral moderate hydronephrosis and hydroureter, however, adequate cortices were present.
The severity of the damage could be mild, treatable with conservative treatment, to severe, resulting in renal failure and pulmonary hypoplasia during intra-uterine life due to oligohydramnios. [5]

The diagnosis of PUV can be made during antenatal life with ultrasound. However, ultrasound findings for diagnosis of PUV are bladder wall thickening and urinary bladder dilatation which is not specific enough (43%). [6]
Voiding cystourethrogram remains the gold standard test for the diagnosis of the posterior urethral valve. However, ultrasound is a valuable screening test in suspected children before performing an invasive test. [7]

Valve ablation therapy provides excellent outcome for those being treated early, and abnormal bladder changes disappears within 1 year after treatment. Vesicostomy with delayed valve ablation therapy is proved to be less effective than primary valve ablation therapy. [8]

Differential Diagnosis List

Final Diagnosis

Posterior urethral valve

URL:	https://www.eurorad.org/case/13976
DOI:	10.1594/EURORAD/CASE.13976
ISSN:	1563-4086