What is a posterior urethral valve?
Have you ever considered the possibility of the urethra not being able to perform its function properly?
And what are the consequences of such a condition?
Here we are going to answer all of these questions by shedding some light on posterior urethral valves, their nature and their impact on the child as well as on his later adult life.
Abbreviation
Posterior urethral valve: PUV
The urinary system
Structure
The urinary system also known as the (Renal Tract) is simply the filter of the body to remove all kinds of wastes from our blood in the form of urine. Its main parts are:
The kidneys
They are two bean-like structures on both sides of the body just below the diaphragm that separate the chest from the abdomen and close to the back, they are the most important part of the renal system and their functions include:
- Wastes removal from the body
- Regulation of the fluids and electrolytes
- Release of Erythropoietin: a hormone responsible for the production of red blood cells
- Control of the blood pressure
The ureters
Two long tubes of about 30 cm in length projecting from the middle of both kidneys and extending down below until reaching the bladder, continuously propel down urine droplets to be collected in the bladder, and also they prevent backflow.
The urinary bladder
Both ureters empty into one bladder which acts as a reservoir for urine where it is stored until a urination stimulus comes. Its capacity is about 500ml but fortunately, it can hold up to 1500ml. the emptying end of the bladder; the bladder neck is surrounded by tight muscles forming a sphincter to prevent the outflow of urine.
In males, the neck of the bladder is encircled by the Prostate gland which drains into the urethra.
The urethra
The last and outermost part of the urinary system is the urethra, urine passes through it from the bladder to the outside of the body. Its external opening is also surrounded by a urethral sphincter.
It is length differs between males and females, in females it is 4 cm while in adult males it is around 15-25 cm and is composed of three parts:
- Prostatic
- Membranous
- Penile1
Posterior urethral valves
- 1 in every 8000 baby boys has a PUV, making it the most common congenital anomaly in male newborns and one of the leading causes of end-stage renal disease in children2
- PUV is a congenital malformation in which a valve-like fold or flap of tissue is abnormally found within the early part of the urethra close to the bladder; they appear from birth and are found almost exclusively in males
- It causes an obstruction to the normal flow of urine and this in turn leads urine to build up and cause complications depending on the degree of obstruction, the more severe the obstruction the earlier it will present as most of the time it can present during pregnancy follow-up visits before birth
- This obstruction leads to changes in the bladder with time, which affects its capacity to hold urine and pressure starts to build up within it, then this pressure transmits to the ureters and causes further complications. This condition is called vesicoureteric reflux and it is associated with urinary tract infections, urine incontinence and progressive worsening of kidney functions which - if severe in the neonate - can present with reduced liquor or amniotic fluid due to the reduced urine production by the fetus3
Higher risk is found in
- Babies with family members with congenital anomalies in the urinary system
- Babies of mothers of younger ages during pregnancy
- Maternal pre-existing hypertension before pregnancy4
Presentation
Antenatal (during pregnancy)
Most of the cases are diagnosed on antenatal ultrasound when it shows findings consistent with PUV.
Postnatal (after birth)
In the less severe cases, symptoms appear after the baby is born or even at an older age such as:
- Difficulty and delay in passing urine
- Increased frequency of urination due to the incomplete voiding
- A weak stream of urine
- Dripping of urine
- Enlarged bladder that can be felt at the lower part of the tummy
- Frequent urinary tract infections can lead to sepsis3,5
How PUVs are diagnosed
The diagnosis of PUVs is reached with a combination of the characteristic symptoms mentioned above aided by imaging findings.
Ultrasound
Ultrasound scan uses sound waves to visualise the internal organs of the body.
The ultrasound signs of PUVs that appear on pregnancy scans and after-birth baby scans are:
- Distended bladder
- Enlargement of the ureters and the prostatic part of the urethra
- Kidney changes
- Oligohydramnios: reduced amniotic fluid of the foetus
An ultrasound scan needs to be repeated to confirm the diagnosis.
Voiding/micturating cystourethrogram (MCUG)
It is the most accurate method to diagnose PUVs.
It involves catheterizing the baby which means inserting a tube into the urethra and then injecting a dye through it into the bladder to observe urine voiding and show bladder and urethral structure and patency.
Cystoscopy
Like MCUG but instead of the dye a camera is inserted through the urethra to view the bladder and the inside of the urethra.
Other forms of imaging
To test for excretion function of the kidney like:
- DTPA (Diethylenetriamine Pentaacetic Acid renal scan)
- MAG3 (mercaptoacetyltriglycine)
- Function and structure defects like DMSA (Dimercaptosuccinic acid scan)3,5
What are the available options to manage PUVs?
Before birth
Fortunately, it is now possible to perform surgeries on foetuses before birth to correct urethral malformations and to prevent complications; examples of such surgeries are:
- Vesicoamniotic shunting: Inserting a tube through the mother’s abdomen and uterus and into the foetus's skin to create an opening between the bladder and the amniotic fluid to drain urine and bypass the urethra
- Fetoscopic valve ablation: insertion of an instrument with a camera to destroy the valve
However, they have their limitations and carry a significant risk.
After birth
Surgical treatment
In the emergency situation of urine retention or if the neonate is unwell, the baby needs to be stabilised and correction of the fluid status and electrolytes should be performed. The urethra is then catheterized with a small feeding tube to drain the urine-filled distended bladder then more definitive options are considered.
PUV ablation
It is the standard treatment for PVU, it uses many techniques to have access through the urethra to destroy the tissue of the valve such as knife cold ablation, balloon ablation and laser.
Diversion methods
The most commonly used one is called vesicostomy which literally means creating an opening into the bladder, to drain the urine through the skin, it is used in the more severe cases of low birth weight neonates whose urethral cannot accommodate valve ablation.
Possible related complications after surgical treatment
Vesicoureteric reflux
- Urethral stricture: narrowing within the urethra caused by trauma by the instruments during the operation
- Bladder neck obstruction6
Medical treatment
Is used mainly to control the symptoms and to prevent complications and it is used in only chosen conditions, they include:
- Antibiotic prophylaxis: especially in the cases of vesicoureteric reflux to prevent urinary tract infections
- Anticholinergic treatment (oxybutynin): decreases the risk of bladder dysfunction
- Angiotensin-converting enzyme inhibitors (ACEIs): to preserve kidney function
- Alpha-blocker treatment: reduces the effect of the obstruction
Others
In cases of reduced bladder sensation and function.
- Encouraging bladder emptying at night
- Pelvic floor exercise
- Intermittent catheterization6,3
Complications of PUVs
- Vesicoureteral reflux: Unilateral or bilateral Vesicoureteral reflux is found in three to half of child males with PUVs and resolves in at least one-third of them. It is associated with urinary tract infections and if not managed properly it can lead to kidney dysfunction.
- Bladder dysfunction: Appears in one-third of the cases even with ablation treatment.
- Kidney disease and end-stage renal failure: Urine retention and recurrent infections predispose patients with PUVs to kidney tissue changes and scarring which lead to dysfunction that progresses to renal failure with time.
- Fertility problems: Therefore regular follow-up is essential for controlling these complications; the protocols vary between centres and countries and even between individual cases. However, the goal is universal.
Follow-up checks include:
- Taking blood and urine samples to test for kidney function.
- MCUG
- Renal scans: DMSA-MAG37
Factors that predict poor outcomes are
- Early age at detection (less than 24 weeks of pregnancy)
- Urinary sepsis
- High serum creatinine
- Bilateral vesicoureteric reflux7
Impact of PUVs on life
It is greatly dependent on the degree of kidney damage; with the advancement of treatment options, they are experiencing complications at a later age like in adolescence and adulthood.8
Having a child with PUVs has a significant impact on family life both financially and socially therefore it is always advised to seek support and counselling to address these issues to be able to manage them effectively9
Summary
PUVs are congenital malformations of the urethra that present prenatally or postnatally, it affects newborn male babies and causes urine flow obstruction. Follow-up is necessary to prevent complications like vesicoureteric reflux, bladder dysfunction and kidney disease to improve their quality of life.
References
- Faris M, Al-Mukhtar S, Ibrahim RH. Anatomy of the urinary system physiology. Stanford Child Heal [Internet]. 2020;(May):2023. Available from: https://www.stanfordchildrens.org/es/topic/default?id=anatomyoftheurinarysystem-85-P04568
- Uthup S, Binitha R, Geetha S, Hema R, Kailas L. A follow-up study of children with posterior urethral valve. Indian J Nephrol. 2010;20(2):72–5.
- Chapters B, Papers O, Bingham G, Rentea RM. SHARE @ Children's Mercy Posterior Urethral Valve. 2021;
- van der Zanden LFM, Groen in ‘t Woud S, van Rooij IALM, Quaedackers JSLT, Steffens M, de Wall LLL, et al. Maternal risk factors for posterior urethral valves. Front Pediatr. 2023;11(April):1–8.
- Elder JS, Shapiro E. Posterior Urethral Valves. Ashcraft’s Pediatr Surgery, Fifth Ed. 2009;744–54.
- Abdelhalim A, Hafez AT. Antenatal and postnatal management of posterior urethral valves: where do we stand? African J Urol [Internet]. 2021;27(1). Available from: https://doi.org/10.1186/s12301-021-00238-7
- Sharma S, Joshi M, Gupta DK, Abraham M, Mathur P, Mahajan JK, et al. Consensus on the Management of Posterior Urethral Valves from Antenatal Period to Puberty. J Indian Assoc Pediatr Surg. 2019;24(1):4–14.
- Lopez Pereira P, Martinez Urrutia MJ, Espinosa L, Jaureguizar E. Long-term consequences of posterior urethral valves. J Pediatr Urol [Internet]. 2013;9(5):590–6. Available from: http://dx.doi.org/10.1016/j.jpurol.2013.06.007
- Harper L, Botto N, Peycelon M, Michel JL, Leclair MD, Garnier S, et al. Financial and relational impact of having a boy with posterior urethral valves. Front Pediatr. 2023;11(August):1–5.
