Multiple urethral anomalies: anterior urethral diverticulum, posterior urethral valves, and distal hypospadias

Contrast-enhanced voiding urosonography part 2: urethral imaging

Ultrasound (US) has been increasingly used as an important imaging tool to assess the urethra in children. The earliest reports of pediatric urethral sonography involved imaging the urethra in a non-voiding state, during physiological voiding of urine, and after instillation of saline. The introduction of US contrast agents has continued to improve visualization of urethral anatomy. Contrast-enhanced US of the urethra can be performed during the voiding phase of a standard contrast-enhanced voiding urosonography (ceVUS) exam or with retrograde instillation of a contrast agent, depending on the exam indication. Both techniques are well tolerated by children and provide accurate information about urethral pathology and periurethral soft tissues. This article reviews the technical aspects and imaging findings of urethral pathologies in children using contrast-enhanced US, both by the voiding and retrograde instillation techniques.

PUVs are more common in boys with hypospadias

INTRODUCTION

The association between posterior urethral valves (PUVs) and hypospadias has previously been reported in case reports. After the identification of this twin pathology in a number of patients, a national retrospective review of all patients with this dual diagnosis was performed.

PATIENTS AND METHODS

All patients were identified in each centre from surgical databases of prospectively collated information on all surgical procedures. The medical notes were reviewed to ascertain demographics, the type of hypospadias, the mode of presentation of the valves and the outcome.

RESULTS

Twenty-eight patients who had the dual diagnosis of hypospadias and PUV between 2002 and 2017 in the four tertiary paediatric centres where specialist paediatric urology is undertaken in our country were identified. Most patients (n = 24) had the valves diagnosed after hypospadias surgery. The median age at the time of hypospadias surgery was 1.4 years (range 1-4 years). There were 12 proximal and 16 mid or distal hypospadias. The commonest presentation was with problems voiding after surgery in 14 cases with a further seven boys who had urinary tract infections. Four patients had a urethro-cutaneous fistula after repair that initiated further assessment. Two boys had distal dehiscence of their repair. There was one boy presented with new onset daytime incontinence. The median time of follow-up after valve incision surgery was 4.9 years (range 0.1-12.3 years). Twenty-two patients (three pre toilet training) had no ongoing urinary symptoms. Twenty-one boys have normal renal function with one patient in stage 3b chronic kidney disease. The incidence of this dual diagnosis in Scotland is estimated at one in 100 cases of hypospadias in the paediatric population.

CONCLUSION

The incidence of PUV in boys with hypospadias is estimated at 1% patients.

Rare copy number variants implicated in posterior urethral valves

The cause of posterior urethral valves (PUV) is unknown, but genetic factors are suspected given their familial occurrence. We examined cases of isolated PUV to identify novel copy number variants (CNVs). We identified 56 cases of isolated PUV from all live-births in New York State (1998-2005). Samples were genotyped using Illumina HumanOmni2.5 microarrays. Autosomal and sex-linked CNVs were identified using PennCNV and cnvPartition software. CNVs were prioritized for follow-up if they were absent from in-house controls, contained ≥ 10 consecutive probes, were ≥ 20 Kb in size, had ≤ 20% overlap with variants detected in other birth defect phenotypes screened in our lab, and were rare in population reference controls. We identified 47 rare candidate PUV-associated CNVs in 32 cases; one case had a 3.9 Mb deletion encompassing BMP7. Mutations in BMP7 have been associated with severe anomalies in the mouse urethra. Other interesting CNVs, each detected in a single PUV case included: a deletion of PIK3R3 and TSPAN1, duplication/triplication in FGF12, duplication of FAT1--a gene essential for normal growth and development, a large deletion (>2 Mb) on chromosome 17q that involves TBX2 and TBX4, and large duplications (>1 Mb) on chromosomes 3q and 6q. Our finding of previously unreported novel CNVs in PUV suggests that genetic factors may play a larger role than previously understood. Our data show a potential role of CNVs in up to 57% of cases examined. Investigation of genes in these CNVs may provide further insights into genetic variants that contribute to PUV.

Congenital anterior urethral diverticulum: antenatal diagnosis with subsequent neonatal endoscopic management

Congenital anterior urethral diverticulum is a rare cause of urethral obstruction in boys. We report on the antenatal diagnosis of this rare phenomenon, making this the sixth prenatally diagnosed case in the English literature (to the best of our knowledge). Our initial prenatal assessment, postnatal endoscopic management, along with the eventual clinical course is outlined. The embryologic theories, differential diagnosis, literature review, imaging, and treatment modalities of this entity are discussed.