Urethral Valves vs. Urethral Polyp
Left picture: The cause of the voiding disorders with chronic urinary retention are posterior urethral valves. The small filling defect between the posterior and the distal urethra, which in the picture runs from bottom left to top right, corresponds to the sail-like valves; this pathognomonic sign of valves is often not depicted. Right picture: Here, the cause of the voiding disorder is a urethral polyp which ranges from the lower end of the seminal colliculus to the distal urethra. The filling defect which is caused by the polyp is partially washed round by contrast. Analogous to the picture of the contralateral case, shape and calibre of the different segments of the urethra are determined by the cause and the location of the urethral obstruction, and, in addition, by the degree of the micturation disorder.
Left picture: Voiding cystourethrography (= VCUG) in a newborn with a palpable bladder and a dripping micturation, which occurs sporadically with a weak stream. The posterior urethra is dilated and elongated. Distally from it, the urethra, which is distinctly recognizable at the beginning, ends in a minute structure. Right picture: VCUG in a male toddler with weak and thin urinary stream. A dilatation and ballooning of the posterior urethra is visible. Distally from it the urethra remains dilated, but with a decreasing calibre.