Posterior urethral valve: A case report in an older Nigerian child

Abstract

Posterior urethral valve (PUV) is an anomaly of the urinary tract in male children and is the leading cause of urinary tract obstruction in the pediatric population. PUV is diagnosed radiologically by ultrasonography, both pre- and postnatally, and using micturating cystourethrography. Its prevalence and age of diagnosis may vary by demographic and ethnic background. This case highlights an older Nigerian child that presented with recurrent urinary tract symptoms and was subsequently diagnosed with PUV. The study further explores the key radiographic findings and analyzes the radiographic imaging features of PUV in various populations.

Introduction

Posterior urethral valve (PUV) is a rare congenital abnormality that is characterized by membranous folds found in the lumen of the posterior urethra and lead to bladder outlet obstruction. As the most common cause of urinary tract obstruction in the pediatric population, PUV occurs exclusively in male patients and can result in a variety of consequences that affect structures found both inside and outside the genitourinary system [1,2]. PUV can lead to a plethora of debilitating conditions including chronic kidney disease, acute urinary retention, and in extreme cases, pulmonary hypoplasia, cardiovascular defects, and craniofacial abnormalities secondary to low amniotic fluid levels [3]. As a valve defect that often develops early in the gestational period before the male urethra complete develops at 14 weeks, the bladder and upper urinary tract are exposed to elevated pressure throughout development. Consequently, this causes detrimental physiological changes to the urinary bladder and kidneys and produces a substantial level of obstruction for the remainder of fetal development [1].

PUV is a rare disorder, affecting between 2.2-4 per 10,000 (0.02%-0.04%) births in Nigeria [4,5] and between 0.4-1 per 10,000 (0.004%-0.0125%) births in the United States [6,3], yet it is the most common cause of urinary outflow obstruction in pediatric patients and the most common cause of renal failure (17%) from obstructive uropathy in childhood [1,4]. PUV is found to have a higher incidence in Blacks and in children with Down's syndrome. However, incidence and reporting rates vary based on region, especially between regions in Nigeria [3].

The most typical presentation for PUV is noted by the detection of hydronephrosis during routine prenatal ultrasound (US), as early 14 gestational weeks, with subsequent definitive diagnosis following birth [1,7,8]. The presentation of PUV in the first year of life can mostly manifest by the presentation of urinary tract infections and urinary sepsis. Other signs can include abdominal distension, palpable bladder or kidneys, poor urinary stream, urinary dribbling, failure to thrive, or poor feeding. Roughly half of all males presenting with PUV over 5 years of age present with urinary incontinence or enuresis [1,7].

Accurate and timely imaging is essential in the management of PUV as it aids in the diagnosis and detection of the antecedent complications of the disorder. The imaging modalities employed include micturating cystourethrography (MCUG) and ultrasonography [1,4,9]. Blood urea nitrogen and creatinine is an indelible serum biomarker that is also pertinent in these patients to monitor renal function [4]. However, assessment of renal function can also be performed utilizing a technetium 99m (^99mTc) dimethylsuccinic acid (DMSA) renal scan. DMSA is a renal cortical agent and DMSA renal scans provide information about both the appearance and function of the kidneys [10].

Here, we report a case of a 9-year old male who had been having difficulty in passing urine since infancy with imaging findings of PUV and chronic bladder outlet obstruction on US and MCUG. This case highlights the role of imaging in the diagnosis and management of PUV in an older male of an ethnicity with known high prevalence for the condition.

Case report

A 9-year-old Nigerian male presented with a history of urinary retention and recurrent fevers since infancy. The patient was febrile and normotensive on initial examination. Physical examination further revealed mild abdominal distension and suprapubic tenderness. However, the kidneys were not ballotable. The urogenital system examination revealed a normal urethral orifice and intact external genitalia.

Complete blood count revealed a hematocrit of 34%, mild leukocytosis (11,500/μL) and neutrophilia (78%). Biochemical examination revealed normal blood urea nitrogen, creatinine, and serum electrolytes. Urinalysis revealed pyuria and urine bacterial culture yielded no growth. A clinical diagnosis of chronic obstructive uropathy secondary to PUVs with urinary tract infection was subsequently made.

Abdominopelvic US revealed enlarged kidneys (Fig. 1). The right kidney measured 9.8 cm × 4.4 cm in length and antero-posterior depth, respectively. The left kidney measured 10.2 cm × 4.7 cm in length and antero-posterior depth, respectively. The length measurements were larger than that of the normal expected length for the patient's given height (127 cm) at 6.87 cm. Bilateral severe dilatation of the pelvicalyceal system was also present as evidenced by multiple communicating anechoic structures with an associated complete thinning of the renal parenchyma (Fig. 1). Additionally, a pelvic US revealed complete bilateral dilatation of the ureters between the renal pelvis and its insertion site at the urinary bladder (Fig. 2). The urinary bladder was distended and contained low level echoes. Thickening of the bladder wall (12.3 mm) with irregularity of its outline (trabeculations) were also noted (Figs. 2 and 3). The post void residual volume was significantly elevated as well, measuring 291.39 mL (Fig. 4).

Fig. 1.

Sagittal B- mode ultrasound scan of the abdomen showing enlarged kidneys with multiple communicating anechoic structures within them (calyces-star) and both renal pelvis (cross). There is also associated complete thinning of the renal parenchyma bilaterally.

Fig. 2.

Transverse scan of the pelvis showing the urinary bladder (cross) with thickened walls and irregular outline (trabeculation) as well as dilated distal ureters (star).

Fig. 3.

Sagittal and transverse B- mode ultrasound scan of the pelvis showing the urinary bladder (star) with low level echoes within it. It also shows thickening of its wall with irregularity of its outline (trabeculations- block arrows).

Fig. 4.

Sagittal and transverse B- mode ultrasound scan of the pelvis showing the urinary bladder – post void (star). The urinary bladder contained significant post void residual volume (291 mL) with low level echoes within it.

MCUG showed a well distended oval shaped urinary bladder with irregularity of its outline, indicating the presence of trabeculations (Fig. 5). Multiple tiny outpouchings were consistent with diverticular formation (Fig. 5). The posterior urethra was dilated and elongated giving a spinning top appearance (Fig. 6) with a transverse filling defect detected, thereby revealing PUVs (Fig. 6). The anterior urethra appeared to be of normal caliber with a smooth outline (Fig. 6). No vesicoureteral reflux was seen. A radiologic diagnosis of PUV with chronic bladder outlet obstruction was subsequently confirmed. The patient underwent a valvotomy shortly thereafter but neglected to follow up after being discharged.

Fig. 5.

Bladder view of a micturating cystourethrogram (MCUG) showing a well distended urinary bladder, with irregularity of its outline indicative of trabeculations (block arrow). It also shows multiple tiny outpouchings consistent with diverticular formation with the largest seen on the right lateral wall (bent arrow).

Fig. 6.

Micturating cystourethrography (MCUG) showing a dilated and elongated posterior (prostatic) urethra giving the “spinning top” appearance (block arrow), with a transverse filling defect seen within it consistent with a posterior urethral valve (bent arrow). The anterior urethra (curved arrow) shows a normal caliber and smooth outline.

Discussion

PUV is the most common cause of bladder outlet obstruction in male pediatric patients. The embryological defect leading to the development of PUV is not known. Many authors believe the anomaly is caused by abnormal integration of the Wolffian ducts into the urethra, while others say it is a result of persistence of the cloacal membrane [3]. According to the Young classification, there are 3 types of PUV, with type I being by far the most commonly encountered [[1], [2]]. Type I (95%) represents sail-like folds from the verumontanum distally along the urethra. Type II valves likely have only historical significance and are not considered to be a clinical entity, but rather hypertrophied urethral folds extending from the verumontanum to the bladder neck. Type III (5%) valves represent a septum thought to represent an incomplete dissolution of the urogenital membrane [1,2]. Recently, type I and II valves have been said to represent the same entity, and are actually considered a COPUM (congenitally obstructing posterior urethral membrane) [1], which this patient had.

The clinical manifestations of PUV are highly variable and depend on the patient's age and degree of obstruction. It may range from minimal obstruction to severe obstruction with bilateral severe hydroureteronephrosis, end-stage renal disease, and even bladder rupture [1]. This patient had severe hydroureteronephrosis as at the time of presentation.

Along with the imaging modalities previously mentioned, the second trimester US (anomaly scan) is now routine in obstetrical care. However, in cases of PUV, US commonly demonstrates bilateral hydroureteronephrosis with a thick walled bladder and “keyhole sign” in the bladder neck [1]. In this case, the keyhole sign could not be demonstrated in the patient. In both the prenatal and postnatal periods, PUV is suspected in the presence of bilateral hydronephrosis with ureteral dilatation associated with increased thickness of the bladder wall, as well as hyperechoic renal parenchyma and increased post void residuals greater than 50 mL in older males, the latter of which was observed in this patient. All males with suspected PUV are advocated to have a MCUG at birth as it is the gold standard for the diagnosis of PUV [1,[8], [9], [10]].

The posterior urethra is always dilated and elongated giving a “spinning top” appearance, one which was seen in this patient. In addition, the urinary bladder wall is commonly thickened with different degrees of trabeculation and pseudodiverticula, a finding which was also seen in this patient. Imaging can sometimes reveal severe obstruction and reflux of contrast into the ejaculatory ducts and spermatic vesicles; however, this was not seen in our patient. About 27%-55% of patients with PUV also have vesico-ureteric reflux, a finding that would otherwise suggest a unilateral valve defect, and some may express reflux into the prostate; however, this was not seen in our patient [7,10,11].

A patient presenting to their provider with signs and symptoms of PUV at an older age is not uncommon in Nigeria. One study pointed out a mean age of presentation of 3.95 years [12]. There are a few reasons elucidated in the literature that may point to the discrepancy regarding the age of PUV diagnosis. There still remain significant barriers to women receiving prenatal USs to detect PUV such as high travel time to practitioners, financial constraints, long wait times and negative perspectives. Socio-demographic variables such as the education of the patient also significantly impact many Nigerians' perception of the critical role of prenatal USs [13]. Additionally, many Nigerian patients who present with PUV are lost to follow-up, such as this patient. This is most likely due to parental ignorance after viewing the return of normal urine stream and also due to difficulties in compliance as parents have difficulties in visiting their healthcare provider for prenatal visits [14]. Without proper follow-up, patients may experience bladder dysfunction in the future [15]. More must be done to alleviate these barriers to healthcare and ensure mothers in Nigeria can understand the long term risks of deferring prenatal USs.

Interestingly, the patient described in the case, whose demographics and ethnicity would otherwise reveal a higher likelihood of being diagnosed with PUV, was not diagnosed until he was an older age. PUVs are usually detected during infancy by prenatal sonography; rarely they may be diagnosed during later childhood, adolescence or even adulthood, especially amongst African populations [16].

It is important to note that the timing of PUV diagnosis affects clinical outcome. In a retrospective study of 52 for patients with PUV treated in 1994-2008, Gestational age at diagnosis was an important predictor of postnatal renal outcome [17]. It was found that a diagnosis PUV after 1 year of age is associated with a lower risk of developing renal insufficiency on long-term follow up [17]. Cystoscopic valve ablation is the current initial treatment of choice for PUVs: this will usually alleviate the obstruction, but vesicoureteral reflux will occur in a third of patients [18]. For patients with vesicoureteral reflux following cystoscopic valve ablation or bladder neck incision, treatment with prophylactic antibiotics resolved this issue in a majority of cases. A common complication is a urethral stricture due to trauma associated with instrumentation [18].

Conclusion

PUV is an anomaly of the urinary tract of male children which in the older child presents with recurrent urinary tract symptoms. PUV is diagnosed radiologically by ultrasonography (both pre- and postnatally) and also by the use of MCUG.

Patient consent

Written informed consent for publication was obtained from the patient described in the PUVs case.