19.5 Clinical Features

•In 1919, H. H. Young was the first to classify posterior urethral valves into three types as follows:

–Type I:

•This is the most common type.

•This type of obstruction is believed to result from abnormal insertion and absorption of the most distal aspects of the Wolffian ducts during bladder development.

•In the healthy male, the remnants of these ducts are observed as the plicae colliculi.

•The reported incidence is 1 per 8,000–1 per 25,000 live births.

•PUVs are the cause of renal insufficiency in approximately 10–15 % of children undergoing renal transplant.

•Approximately one third of patients born with PUV progress to end stage renal disease (ESRD).

•PUVs are usually diagnosed before birth or at birth when a boy is evaluated for antenatal hydronephrosis.

•Before the era of prenatal ultrasonography,

sal fins extending from the bottom of the verumontanum distally along the prostatic and membranous urethra.

–Type II:

•This is the least common variant.

•It is characterized by vertical or longitudinal folds between the verumontanum and proximal prostatic urethra and bladder neck.

–Type III:

•This is the second common variant.

•It is due to a disc of tissue distal to verumontanum.

•These valves are observed as a membrane in the posterior urethra

•These are believed to originate from incomplete canalization between the anterior and posterior urethra.

•It is also theorized to be a developmental anomaly of congenital urogenital remnants in the bulbar urethra.

•It has been suggested that obstructions in the posterior urethra are more appropriately termed congenital obstructions of the posterior urethral membrane (COPUMs).

•The congenital urothelial remnants of type III posterior urethral valves have been eponymously referred to as Cobb’s collar or Moorman’s ring.

19.5Clinical Features

•PUV is the most common cause of lower urinary tract obstruction in male neonates.

tion, or renal failure.

•In the pre-antenatal ultrasonography era, a late presentation of PUV was considered a good prognostic indicator suggestive of a lesser degree of obstruction.

•Prenatal diagnosis

–The widespread use of antenatal ultrasonography has made it possible to diagnose more cases of posterior urethral valves antenatally.

–Currently, the diagnosis of PUV is usually made early at birth when a boy is evaluated for antenatally diagnosed hydronephrosis.

–It was estimated that 10 % of boys diagnosed with prenatal hydronephrosis had PUVs.

–Patients who are not diagnosed by antenatal ultrasound may present shortly after birth with distended bladder and difficulty to pass urine.

–Despite widespread use of antenatal ultrasonography, some patients with PUVs do present later in life.

•Delayed presentation

–PUVs manifest as a spectrum of disease severity.

–The delayed clinical presentation of PUVs include:

• Urinary tract infection

• Diurnal enuresis in boys older than

5 years

•Secondary diurnal enuresis

•Voiding pain or dysfunction

•An abnormal urinary stream

–PUVs are sometimes discovered during evaluation of abdominal mass or renal failure.

–Hydronephrosis or proteinuria found on examination for unrelated conditions may be the first sign of PUVs.

•Neonates born with severe posterior urethral valve may present with severe pulmonary distress secondary to pulmonary hypoplasia due to oligohydramnios. Physical findings can include the followings:

–Poor fetal breathing movements

–Small chest cavity

–Abdominal mass (ascites)

–Potter facies

–Limb deformities (skin dimpling)

–Indentation of the knees and elbows due to compression within the uterus

•In older children, physical findings can include:

–Poor growth

–Hypertension

–Lethargy

–A large lower abdominal mass representing a markedly distended urinary bladder

•A smaller number of patients with PUV will present late and their clinical presentation include:

–Diurnal enuresis

–Dribbling or poor urine stream

–Urinary tract infection

–Hematuria

19.6Investigations and Diagnosis

•With routine use of obstetric ultrasonography the prenatal diagnosis of posterior urethral valve is becoming increasingly common.

•The antenatal ultrasound demonstrates significant hydronephrosis with possible renal cortical thinning. The kidney is larger than expected for the patient’s gestational age. The hydronephrosis may be bilateral and both kidneys may be affected.

•As a result of the routine use of antenatal ultrasound, the number of cases of PUV diagnosed prenatally has increased.

•Currently, approximately 50–75 % of boys with PUV will be suspected on prenatal ultrasound.

•The prenatal ultrasound findings suggestive of PUV include:

–A thick walled bladder

–The ‘keyhole’ sign with a dilated bladder and posterior urethra

–Unilateral or bilateral hydroureteronephrosis

–Echo bright kidneys

–Oligohydramnios

•Postnatally, the patient must be stabilized prior to any investigation.

•Complete blood count

•Serum electrolytes, BUN and creatinine.

–To be accurate and to avoid maternal placental effect, these should be checked at least 24 h after birth.

–The newborn is unable to concentrate urine because of renal immaturity at birth.

–This defect is exacerbated by renal dysplasia such as that found with posterior urethral valves and if the renal dysplasia is significant, the serum creatinine fails to reach a normal level during the first year of life.

–Serum creatinine levels >0.8 mg/dL during the first year of life have been demonstrated to be associated with poor long-term renal function.

–This is considered a negative prognostic indicator.

•Plain abdominal radiographs do not add to the actual diagnosis of posterior urethral valves but may show the ground-glass appearance seen in those with urinary ascites.

•Chest radiographs may be useful in the evaluation of pulmonary hypoplasia.

•Renal and bladder ultrasonography

–Postnatal renal ultrasonography is the initial investigation to be done in those with suspected posterior urethral valve.

–This is important as an initial noninvasive and devoid of radiation investigation.

–Ultrasonography is helpful but not diagnostic (Figs. 19.2, 19.3, and 19.4).

–Features suggestive of posterior urethral valves are:

•Unilateral or bilateral hydronephrosis

•Enlarged kidneys with thinning of the renal cortex

•In those with renal dysplasia, the renal parenchyma is typically hyperechogenic with visible small cysts (<10 mm), but in the most mildly affected cases, renal ultrasonographic findings may be normal.

•A thickened bladder wall with trabeculations, and bladder diverticula

•The bladder may be of large or small volume, but it is invariably thick-walled.

•A dilated posterior urethra

•Echogenic lines that are the actual valve leaflets might be seen.

•The combination of the dilated, thickwalled bladder and dilated posterior

urethra has been described as having a keyhole appearance.

•Urinary ascites or perinephric collections due to urinomas may also be seen, most commonly soon after birth, and are caused by rupture of the urinary tract, typically at the level of the calyces.

•Voiding cystourethrogram (VCUG) (Figs. 19.5, 19.6, 19.7, 19.8, 19.9, 19.10, and 19.11):

–This is more specific for the diagnosis of posterior urethral valve.

–This should be performed under fluoroscopy, with imaging of the posterior urethra, especially during the voiding phase.

–PUV on voiding cystourethrogram is characterized by an abrupt tapering of urethral caliber near the verumontanum, with the specific level depending on the developmental variant.

Fig. 19.7 A micturating cystourethrogram showing posterior urethral valve. Note the dilated posterior urethra and the small anterior urethra. Note also the dilated thickened urinary bladder

SMALL ANTERIOR

URETHRA

DILATED THICKENED

URINARY BLADDE

DILATED POSTERIOR

URETHRA

–The diagnosis of PUV is indicated by the following features:

•A thickened trabeculated bladder

•A dilated or elongated posterior urethra

•The bladder neck is typically hypertrophic, leading to a lucent ring or collar

•Visualization of the valve leaflets

•The posterior urethral valve is seen as a nonopacified line that separates the dilated posterior urethra from the nor- mal-caliber distal urethra

•The findings of bladder diverticula

Fig. 19.8 A micturating cystourethrogram showing posterior urethral valve. Note the dilated posterior urethra and the small anterior urethra. Note also the dilated thickened urinary bladder and severe unilateral vesicoureteric reflux

Fig. 19.9 A micturating cystourethrogram showing posterior urethral valve. Note the dilated posterior urethra and the dilated thickened urinary bladder. Note also the absence of vesicoureteric reflux

HYDRONEPHROSIS

SEVERE

VESICOURETERIC

REFLUX

DILATED THICKENED

URINARY BLADDER

HYPERTROPHIC

BLADDER NECK

DILATED POSTERIOR

URETHRA

SMALL ANTERIOR

URETHRA

DILATED THICKENED

URINARY BLADDE

DILATED POSTERIOR

URETHRA

•Hydroureteronephrosis may be seen.

•Delayed images may show bladder or urethral pathology, but the lower urinary tract is better visualized with VCUG.

•Computed Tomography:

–This is rarely necessary for the diagnosis of posterior urethral valves.

–Elevated serum creatinine levels generally preclude use of IV contrast material.

–CT scans with IV contrast enhancement may reveal:

•Dysplastic and/or dilated kidneys

•Delayed renal function and excretion

•Hydroureter

•Dilated bladder with wall thickening, trabeculation, and diverticula

•A dilated posterior urethra might be seen

•Magnetic Resonance Imaging:

–Magnetic resonance imaging (MRI) is rarely used to diagnose posterior urethral valve

–The findings are similar to those of CT scanning

–Gadolinium-based contrast agents used in MRI have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD).

–The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans.

–NSF/NFD is characterized by:

•Red or dark patches on the skin

•Burning, itching, swelling, hardening, and tightening of the skin

•Yellow spots on the whites of the eyes

•Joint stiffness with trouble moving or straightening the arms, hands, legs, or feet

•Pain deep in the hip bones or ribs

•Muscle weakness

•Sometimes it is fatal

•Nuclear Imaging:

–Nuclear cystography is useful to define the presence of vesicoureteral reflux but it is not useful to define the extent or degree of reflux.

–Renal scintigraphy can determine the relative renal function.

–The bladder should be drained prior to the study to eliminate the effect of a distended, high-pressure bladder on renal function and drainage.

–The presence of a much thickened hypertrophied bladder wall may lead to secondary ureterovesical junction obstruction.