King Edward Memorial Hospital - Departments: Radiology

Radiology

Case of the Month

Case No. :	07
Month :	July
Year :	1999
Contributor :	Dr. Jigna Rathod

Other Cases

Clinical History | Radiological Findings | Discussion | Clinical Presentation | Differential Diagnosis

Radiological findings

Clinical Presentation

Clinical History :

A five year old boy presented with incontinence of urine and dribbling micturition since 6months. Blood and urine studies were normal.

Ultrasonography showed left hydronephrosis and hydroureter. The urinary bladder was distended and the walls were irregular and trabeculated. A micturating cystourethrogram was obtained :-

Figure 1

Radiological Findings :

The urinary catheter could be passed easily into the bladder to obtain a cystourethrogram.

The urinary bladder is distended and grossly trabeculated. There is a triangular dilatation of the posterior urethra with the apex of the triangle pointing inferiorly. There is crescentic filling defect along the length of the dilated posterior urethra.

No vesico-ureteric (VU) reflux was evident.

These findings are classical of posterior urethral valves.

Discussion :

Posterior urethral (PU) valves are most common cause of severe urethral obstruction in male infants and make up 80% of intrinsic urethral obstruction in children.

Usually, they are congenital and are produced by mucosal folds in post urethra possibly due to a malformation of the urethral crest ). Urethral valves may rarely occur in girls and are believed to be due to the persistence of the cloacal membrane. Rarely too, valves may occur in the anterior urethra..

PU valves occur in about 1 in 7000 male children and account for 10% of all urinary tract obstructions.

Clinical presentation can be from minimal disability to end stage renal failure. Nearly half the cases are diagnosed before the second month of life.

Morphology :

PU valves are obstructing urethral folds and are classified into three types.

Type I : Most common, two folds at the level of the verumontanum with a central, vertical slit-like orifice. The folds are derived from the plicae colliculi.

Type II : They are believed to be mucosal folds extending anterosuperiorly from the verumontanum towards the bladder neck. Most of urologists believe these folds are merely changes in urethra secondary to out flow obstruction and do not represent true valves.

Type III : An iris type diaphragm or membrane attaching to the entire circumference of urethra, distal to the verumontanum. There is pinpoint, eccentric orifice which results in forward ballooning of valve and is referred to as "sail in wind" appearance.

Incomplete type III valves are crescentic or semilunar in shape and may be soft and redundant enough to prolapse in to bulbous urethra with voiding.

Type III valves are oriented transversely and are associated with renal dysplasias and minimal upper tract dilatation.

Based on findings in some patients with the Prune Belly syndrome, a fourth type of urethral valve consisting of an anterior infolding of urethra below the verumontanum has been described.

Pathophysiology :

The pathological consequences of PU Valves are determined by the location and severity of obstruction. Increased resistance to urine outflow causes bladder muscle hypertrophy with trabeculation and saccules.

Vesical diverticuli are found in about 40% of patients. The bladder neck participates in muscle hypertrophy and often thickness at its posterior lip, sometimes creating an appearance of bladder neck obstruction on MCU. On the other hand, secondary bladder neck stricture may be an important obstructive phenomenon when valves have been undiagnosed for many years.

Proximal to the valves, the post urethra widens and elongates - the dilatation often including the prostatic utricle, ejaculatory ducts and the prostatic duct.

Reflux :

VUR is seen in 30-70 % of boys with PU valves. Unilateral reflux is twice as common as bilateral reflux. In some boys, reflux appears to be primary - that is. the result of a congenitally short intramural ureter and ectopic lateral orifice ; in others, it develops because of paraureteral diverticulum. Valves with bilateral reflux carry worse prognosis compared to those with unilateral or no reflux.

In 15-20% fetuses, there is an associated renal dysplasia. Unilateral reflux, dysplasia, large congenital bladder diverticula and urinary extravasation are three "pop-off " mechanisms that may lead to better preservation of renal function in boys with post. valves.

Clinical Presentation :

Results from obstruction, infection or both.
Signs of obstructions usually seen in utero and neonates.
Infections or voiding disturbances in older children.
Depending on severity of obstruction, presence or absence of dysplasia, renal failure may be present at birth or later.

50% of fetuses do not survive ; associated lung hypoplasia with oligohydramnios and renal dysplasia accounting for death in most cases.

Infant present with weak urinary system; in older children with less severe obstruction, there may be repeated urinary tract infections. Hydronephrosis, reflux and renal failure is less common.

Pre-natal Ultrasonography :

90% fetuses have distended, thick-walled bladder.

Dilated post urethra and/or moderate to severe dilatation of upper urinary tract in half the cases.

Less commonly, there may be urinoma, fetal urinary ascites, dystrophic bladder wall and peritoneal calcifications.

Oligohydromnios, pulmonary hypoplasia is poor prognostic indicator.

In adults, hydronephrosis may be the presenting pattern.

Differential Diagnosis:

In Utero :

Bilateral UPJ obstruction.
Bilateral multicystic or autosomal dominant polycystic kidneys.
Severe reflux and Prune Belly syndrome.
Post urethral polyp and urethral valve.

Post Natal Imaging :

Ultrasonography shows hydronephrosis, perinephric urine collection, dilated tortuous ureters up to bladder. The bladder wall is thickened. When the bladder is full a dilated post urethra and prominent bladder neck may be seen.

IVU : Best for assessing the improvement in upper tract dilatation after valve ablation.

MCU : The verumontanum is an important landmark for diagnosing lesions of the post urethra and often enlarged with type I valves.

In the lateral projection, a typical type I valve causes a crescentic radiolucent defect that bulges in to contrast column below the verumontanum giving rise to the spinning top or bullet nose appearance.

A wind-sock appearance seen with type III valves when they prolapse in to bulbous urethra.

The posterior urethra above the valves is dilated and elongated. The bladder neck impression is a prominent. Bladder trabeculation, saccules, small diverticulum are common.

Unilateral or bilateral reflux.

Prominent bladder neck with detrusor hypertrophy.

Bilateral hydronephrosis

Transurethral resection or fulguration.

Percutaneous antegrade ablation via a cystostomy tract or retrograde balloon catheter ablation.