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Anterior Urethral Valves-An Unusual Cause of Hydrops Fetalis

Anterior Urethral Valves (AUV) are a less common cause of lower urinary tract obstruction than Posterior Urethral Valves (PUV). AUV may present with symptoms of mild to severe obstruction and renal impairment at any age. Here we report possibly the first case of AUV presenting as hydrops fetalis. This late preterm infant presented with postnatal presentation of hydrops leading to respiratory failure. There was marked ascites, a left-sided inguinal hernia and hypospadias. Immune and most non-immune causes of hydrops were ruled out. Mild hydronephrosis with poor renal function and dependency on bladder catheterization for urinary output remained. While the ascites gradually improved, the bladder outlet obstruction persisted without evidence for PUV. Voiding cystourethrogram (VCUG) led to suspicion of AUV which was confirmed and managed with cystoscopic valve ablation. We review the physiology, clinical presentations, treatment and outcomes of AUV in the context of a differential diagnosis based on neonatal ascites values.

.    AUV has been reported to lead to end stage renal disease requiring dialysis in up to 4% of cases [5].

Discussion
Antenatal suspicion for fetal LUTO may be raised in 2.2 per 10,000 births [6]. Routine ultrasonography findings in pregnancy consistent with LUTO are genitourinary abnormalities, hydronephrosis, megacystis, altered renal morphology, size, and echogenicity, as well as secondary oligo-or anhydramnios [6]. The most common reason for fetal LUTO is PUV in 64% of cases. About a third to 45% of AUV had fetal hydronephrosis, and infectious presentations dominate in the neonatal age [2,4]. Prognosis is better when AUV is diagnosed prenatally and intervened on early [2].
Fetal and neonatal ascites may develop in a variety of conditions and is usually accompanied by hydrops, i.e. fluid accumulation in 2 or more fetal serous cavities, such as skin, ascites, pleural and pericardial effusions [7]. Portal hypertension in liver disease is contrasted with non-cirrhotic ascites with a wide spectrum of infectious, cardiac, gastrointestinal, malignant and renal etiologies, among others [8]. Serum ascites albumin gradient (SAAG) has replaced the transudative/ exudative approach in adults, with a value ≤ 1.1g/L preferentially indicating non-cirrhotic causes [8,9]. Table 1 gives an overview of common fetal and neonatal ascites biochemical analysis values which may aide in differential diagnosis [10]. Our patient's values in the context of his other diagnostic findings were most consistent with overflow and capillary leak syndrome seen in chronic renal conditions [11]. Some urinary output must have been preserved in-utero in keeping with a more dynamic obstruction with AUV compared to PUV, as the mother had not been measuring small due to potential fetal anuria, there was no clinical evidence of pulmonary hypoplasia, and there was no bladder hypertrophy or rupture. The latter makes urinary ascites also unlikely. Unfortunately, we did not obtain creatinine values from the peritoneal fluid.
High index of suspicion is required in considering AUV as it often leads to less severe and more dynamic urethral obstruction [12]. A VCUG may be helpful to rule out PUV. The obstruction in AUV in contrast may appear as dilation of the anterior urethra proximal to the valve or diverticulum with abrupt distal narrowing ( Figure 2) [2,3,13]. Urethro-cystoscopy may also be considered in the diagnosis, and cystoscopic transurethral ablation of the valve or diverticulum is the treatment of choice in cases of isolated AUV and associated with a good outcome [3,14]. AUV associated with anterior urethral diverticula may require urethroplasty [3,14]. Up to 80% of children with AUV will develop bladder dysfunction or instability, hyperreflexia, and diminished compliance and capacity may be seen on urodynamic studies [12,14]. As with PUVs, long-term renal function is contingent on preoperative renal damage and preserved degree of glomerular filtration rate [15].

Conclusion
Anterior urethral valves (AUV) is an important but

Acknowlegements
Department of Radiology, Alberta Children's Hospital (for providing us with the radiographic images).

Statement of Ethics
No Research Ethics Board was involved due to case report nature of manuscript. The subject's parents and legal guardians have given their written informed consent to publish their case (including publication of images).

Disclosure Statement
None of the authors have a conflict of interest to disclose.

Funding
None.