POSTERIOR URETHRAL VALVES
Dr. Vivek M. Rege
Pediatric Surgeon & Pediatric Urologist
B J Wadia Hospital For Children, Hurkisondas Hospital, Wockhardt Hospital, Mumbai
This is one of the major common urological anomalies found in boys. This may present with very non specific symptoms or may present with acute kidney failure. The cause of this anomaly is abnormal embryology and persistence of a fold. This remains and forms flaps or valves in the urethral passage of the male child. These valves are like one way doors that open inwards towards the bladder. When the boy attempts to pass urine, they come together, close or narrow the lumen of the urethra, this causes an obstruction to the passage of urine, and the boy strains to do so. The formation of these abnormal valves occurs around 4th month of gestation and depending on the severity of the obstruction, damage to the entire urinary system may be minimal or devastating and irreversible leading to renal failure with infection(sepsis) and death in newborns.
The effect of these valves occurs in a sequential back pressure effect on the urinary system. All this begins to occur even before the birth of the child as, the child normally passes urine in the amniotic fluid around it from before birth. The valves cause obstruction in the urethra. In the male urethra which is longer than the female urethra, there are 3 parts called the prostatic urethra that is surrounded by the prostate gland – also called posterior urethra; there is a small membranous urethra that passes thru the sphincter and then the pendular urethra within the penis. The valves are usually in the posterior urethra and hence are commonly called Posterior Urethral Valves(PUV). If the valves cause a severe obstruction, urine needs to be forced into the urethra distal to the valves, this gives rise to dilatation or ballooning of the urethra proximal to the valves. With passage of time, the bladder which is not being completely emptied, begins retaining urine and hence starts growing in size by stretching and expanding to accommodate the excess unpassed urine within. Each time the boy attempts to pass urine, the bladder contracts to empty totally, but is unable to do so due to the obstruction. This results in thickening of the musculature of the bladder – hypertrophy. With time, the continuously distended and hypertrophic bladder begins to transmit the pressure backwards, up the ureters and to the pelvis of the kidney. There is now a gradual build up of urine in the ureter that cannot empty into the bladder because –firstly, the bladder itself is at high pressure, and secondly, the thick bladder muscle acts like an obstruction where the ureter is joining the bladder and hence does not allow the urine to flow into the bladder. Meanwhile, the kidney continues to excrete urine as usual and there is more urine than can be accommodated in the ureter, which begins to balloon and dilate. This is then transmitted one step further to the pelvis of the kidney which also balloons and dilates till the elasticity allows. Once the capacity of the pelvis to stretch and dilate is reached, the pressure now falls on the kidney substance or parenchyma which is the main area that is responsible for making of urine. The pressure restricts the ability of the kidney to work normally and if there is no let up in pressure, the function of the kidney begins to deteriorate and if left uncorrected even after birth, or if the stagnant urine in the pelvis and ureter gets infected – that kidney starts failing. The same mechanism is also occurring on the other side kidney too. Thus, it is easy to understand why a severe uncorrected obstruction of the lower urinary tract can cause both the kidneys to loose function over a period of time; infection will only accelerate the process. This also illustrates that early diagnosis, early therapy may reverse this process and preserve the renal function.
Presentation of the boy will depend on the severity of obstruction. The boy may present at birth or as late as 3 – 4 years. The symptoms are the same – difficulty in passing urine, straining to pass urine, dribbling of urine, poor stream of urine. There may be distension of the lower abdomen caused by a stretched out filled up bladder. The common mistake that can be made is to diagnose this condition as phimosis as described elsewhere and then get a circumcision done. The symptoms may persist after this and then a suspicion of internal obstruction is thought of. Newborns may also be brought with few urinary symptoms and more non specific ones like abdominal distension, failure to thrive, signs of infection (sepsis) somewhere in the body, recurrent urinary infections with fever. Older children may also come with nonspecific complaints like not growing well, recurrent urinary infections, frequency of urine, burning during urination, pain in the flank etc. An examination may show an easily felt bladder that remains palpable even after the boy has passed urine. Observing the stream of urine while the child is micturiting will reveal a poor stream, falling close to the body, child straining while passing urine. When posterior urethral valves are suspected, investigations are a must to arrive at the diagnosis, the severity of the damage already caused, planning of the mode of treatment. Once again it cannot be emphasized enough that the reversibility of the damage to the function of the kidney cannot be judged at the time of diagnosis. Only, a regular follow up with the relevant investigations will tell the amount and presence of improvement even after the ideal and best therapy. This is the most frustrating part of this condition that often I have struggled hard, done multiple tests, procedures, surgeries to successfully relieve the obstruction, treated the infection aggressively only to see the child slide into renal failure at a later age and require renal transplant to save his life. This shows the importance of a long follow up of the child till he reaches adulthood.
Investigations are required to diagnose and know the severity of damage to the entire urinary system and must be carried out regularly and completely. The main radiological investigations are an Ultrasonography(USG) for kidneys ureters and bladder and a Voiding Cysto Urethrogram (VCU).
USG will show a large dilated bladder, thickening of the walls will suggest long standing and severe obstruction, there may be outpouchings called diverticuli that are diagnostic of severe obstruction. With bad obstruction, the ureters will also be dilated, elongated and tortuous filled with urine. The kidney pelvis will also be hugely dilated with a thinning of the parenchyma of the kidney, all this on one or both sides. This investigation does not give any idea of function only the dimensions and appearance of the organs being looked at. Bilateral dilated upper tracts prove an obstruction distal to the bladder and in boys the commonest is PUV.
Sonography of 2 patients with Valves
VCU - is the next investigation wherein a small tube is passed into the urethra of the child upto the bladder and the bladder is filled with a contrast liquid that is seen as white on a x ray picture. When the bladder is full one x ray is taken to look for the shape, size of the bladder. The distorted shape of the bladder with multiple outpouchings may be seen, there may or may not be a secondary reflux of urine from the bladder into the ureter(s) as described in Urinary Reflux chapter. Next the tube is removed from the bladder and the child is asked to pass urine and a second x ray is taken as the child is passing urine. This is the most important picture – this will show a dilated posterior urethra proximal to the valves, described as pear shaped; the valves are seen as negative shadows in the center of the urethra beyond which the urethral caliber is narrow. Reflux not previously seen may be now visualized on one or both sides. A third picture is taken after the child has passed urine and may show incomplete evacuation of the urine and residual contrast in the bladder.
Voiding Cystourethrogram of patients, left shows reflux in both ureters, right shows no reflux. Both show dilated urethra (yellow arrow) and small irregular bladder(white arrow)
Besides the radiological investigations routine blood tests including those to check the function of the kidneys are done to know the state of the kidneys at the time of diagnosis – but this will give only an overall picture of normal function of both kidneys together not individual ones. For this another radiological study –Radio Nuclear DTPA Scan of the kidneys is done. Here radioactive contrast is injected in the vein of the boy and pictures of the kidney are taken at intervals. This investigation will give exact individual percentile function of the kidneys, it will also show the obstruction in the bladder as well as a secondary one at the junction of the ureter and bladder if present. This can be used as a baseline study for serial scans after therapy to show an improvement of the percentile function of the kidneys. Other investigations are done t look for the complications associated with this entity – like electrolyte imbalances and infection of urine and also in the blood stream by sending both blood and urine for Culture studies and treating the infection first before specific therapy for the PUV.
Treatment of this condition will depend on severity of the obstruction, and, other complications at the time the condition is diagnosed. In those fortunate boys who are not in electrolyte imbalance, nor renal failure, nor gross infection the valves can be tackled immediately. The use of a Cystoscope a type of an endoscope that can be inserted into the urethra of the child is used to look at the urethra and bladder from inside. There are various sizes of the Cystoscopes including a very tiny one that can go inside the urethra of a newborn too. Using the Cystoscope-Resectoscope - I am able to visualize the valves from inside and with the resectoscope loop and cut them with a coagulating current and relieve the obstruction at one go. After the procedure a catheter is kept to drain the bladder of urine and keep the area cut dry. The catheter is removed after 3 days and the child passes urine on his own with a good stream. The child is sent home on that day, but, will need to come regularly for a follow up investigations. The USG will now show no residual urine, the upper tract dilatation should decrease over the years, the DTPA Scan should show a gradual increase in the percentile function of the kidneys.
Tiny Cysto –resectoscopes that can enter the newborns urethra
However, not all boys are so lucky to get away with such good results, some may be detected late or are born with very severe obstruction and bad complications. In such boys just a Cystoscopic resection of the valves will not be adequate to treat them. In these boys, the complications like the electrolyte imbalances, the infection needs to be controlled first, and then go for a cystosopic resection of the valves. At times to get over the renal failure and to decompress the back pressure on the upper tracts, there is a need to divert the urine proximal to the site of the obstruction. This is done by opening the bladder to the skin to allow the urine to drain out directly, or at times the ureter has to be taken to the skin to allow urine to flow freely and the pressure to come down, let the child grow, the renal function return to a good level and then do a Cystoscopic resection of the valves and then close the diverted urinary tract. Again the importance of the follow up for a long period has to be emphasized to look for improvement in the function. At times, despite all the best efforts, I have been unable to get the function above what it was when I began the treatment. Gradually some of these children will go into renal failure and the only final treatment available for these children is a Renal Transplant to save them. Treatment of complicated cases of PUV is very exacting, intricate and complicated with a day to day monitoring of these boys in an Intensive Care Unit with higher antibiotics, elctrolyte corrections, charting of the urine output on an hourly basis and so on. Suffice it to say this condition can be very simple or extremely complicated to manage depending on various factors already discussed.
Last Updated: 27th January 2009