At least 1 % of fetuses demonstrale dilatations of urinary tract on ultrasound during pregnancy. The best for comparisions is an anter-posterior dimension od renal pelvis. The thickness of renal parenchyma and dilatation of renal calyces is also important, but the more detailed the description, the more subjective and examiner dependant. It is also influenced by many factors – fetal posture, degree of hydration of the fetus and mother and how much the bladder is filled during examination. The AP renal pelvis dimension is more practical. In third trimester 7-9mm is mild dilation, 9-15 mm moderate and more then 15mm we consider severe. Important for general assesement of the situation is if the deformation is uni- or bilateral and if we notice the expty bladder or if it is always full. Overdistended bladder presenting “keyhole” sign is typical for posterior urethral valves (which is really uncommon condition).
All these patients require thorough follow-up in the first months of life, but rarely they require prenatal interventions. My experience with this subject is modest, but I’d met a few patients treated prenatally. I’d even attended labour of a patient with multiple stents. One of them peforated a leg of a baby, othe was inserted almost in the spine, one flew freely in amniotic fluid and one seemed to be in renal region – but it did not drain any urine….After months of just observation it turned out the the treated kiney did not require any concern or treatment. Sometimes even quite big prenatal dilatations resolve spontaneously. Unfortunately we lack diagnostic tools to precisely predict which patients will deteriorate renal function and would benefit from early treatment. Generally, I would only exceptionally treat one-sided disease, when sure that the other kidney has normal parenchyma. Patients with bilateral damage, with signs on posterior urethral valve may benefit from early stenting, which may let them develop more useful kidneys. There is still no consensus between pediatric urologists, nephrologists and neonatologists as far as prenatal interventions are concerned.
The basic tool here is ultrasonography. It should be performed in neonatal department after birth and repeated in 7th day , when urine production reaches higher levels. When comparing ultrasonogram one should always remember that a degree of widening of upper urinary tract depends on bladder. “Flaccid” kidneys and ureters will look dilated, when bladder is full. If the bladder is always full we can suspect the problem, from the other hand if we see it empty we can almost exclude posterior urethral valve. Another key factor in neonatal assesment are serum levels of urea, creatinine and cystatin C.
If the bladder is always full and the serum urea and creatinine elevated bladder decmpression should be considered. For short time it can be bladder catheter introduced throug urethra or puncture cystostomy. Any of this is an invasive action because it can promote the first urinary infection which is really no good for newborn. Often they are recurrent and require more and more sophisticated antibiotics. For longer bladder decompression only Blocksom cystostomy is accpetable, bacause it does not require permantent catheter presence.
Generally observation and examinations from first weeks of life classify a child into one of the following groups:
– non-obturative dilatation of upper urinary tract – uni- or bilateral slight widening of upper urinary tract, less then 10mm renal AP diameter, without visible ureters. Prognosis is very good, it requires just ultrasonography follow-ip, initially monthly. If renal pelvis is wider diuretic scintygraphy may be considered, depending on the shape of deformation and condition of renel parenchyma. These neonates comprise the greates group of patients consulted in the first age of age, and more then 90% will resolve. We can imagine, that these patients transient obstruction in their prenatal life that made upper urinary tract dilated of flaccid. The obstructio spontaneously subsided or is just subsiding. Such “hydronephrosis” is usually more prominent when the bladder is full. One should also remember that newborn and neonatal bladder tends to magazine urine under higher pressures, whereas ureters and kidneys are compliant. Horizoltal position and lack of physical activity also impair upper urinary tract dreinage. All these factors disappear with time.
– hydronephrosis caused by pelviureteric junction obstruction – usually unilateral, though there are exceptions sometimes. Typical ultrasonographic apperance of true obstruction is “Miki Mouse” sign on transverse section and persistent obstruction with empty bladder. The neccesity of surgical intervention increases when AP diameter of renal pelvis is higher then 20mm. Direct indication for surgery are “Miki Mouse” sign and obstruction on diuretic scintygraphy and renal parenchyma loss in subsequent studies and urinary tract infections. One should asses diuretic scintygraphy with reserve, especially in neonates.
– one-sided dilation of pelvi-calyceal system and ureter (primary hydronephrosis and megaureter) – here also medical actions should depend on degree of dilatation, if it is one sided or bilateral, if it affects just a ureter or ureter and kidney and frequency of of urinary tract infections. Many of these children, depending on ultrasonographic apperance should have cystographic examination performed in first months of life. It is needed to exclude vesico-ureteral reflux. It is an invasive examination, which may introduce the first infection with some dose of bad luck. Vesico-ureteral reflux of higher grade, if confirmed, requires treatment. If the reflux is ruled out we call it primary hydronephrosis et megaureter and generally do nothing, just follow-up. If the pathology is bilateral we should know biochemical renal function parameters. Sometimes we should consider cystourethroscopy ( direct visual examination of lower urinary tract in general anesthesia), but there is no hurry if dilatations are mild and kidneys look well on ultrasonography. Before 4 moth of age cystourethroscopy may be traumatic and requires fine pediatric equipment. Forceful manipulations of neonatal urethra may have casastrophic consequences (urethral stricture, laceration). Generally it is belived that 80% of patients with of primary megaureter and hydronephrosis will not require surgical treatment. Ureteric diameter bigger then 10mm and the same AP dimension the the kidney with calyceal dilation require serious follow up and dynamic renoscintygraphy. Isolated dilation of distal ureter, even 20mm in diameter, is usually benign and will resolve in years. Some children with promient dilatation of kidney and ureter may show tendency to urinary tract infections, sometimes difficult to treat. Staged surgical treatment – uretero-cutaneous fistula, later ureteral reimplantationa and then fistula closure – is reserved for most severe cases and should be considered individually.
– Vesico-ureteral reflux confirmed by cystourethrography – is real surgical issue in neonatal age. In this period the kidney is vulnerable to destruction caused by infections and even the preassure of refluxing urine. We belive after 5 year of life the kidney is resistant to sterile urine preassure, though probably it depends on individual. In boys we should always consider posterior urethral valve, but the condition is really rare, much less frequent then “just” bilateral relux. Mainly girls may have reflux into the lower moiety of duplex kidney. In almost all cases the treatment of choice is urethrocystoscopy, valve ablation if present and Dflux or Vantris subureteral injection. In massive bilateral reflux secondary to posterior urethral valve or duplex kidneys destroyed by upper pole hydronephrosis and lower pole reflux one should consider for first years of life vesico-cutaneous fistula or uretero-custaneous anastomoses. Simple loop in one sided leasions and Sober type when both sides are affected (some urine is expected to pass into bladder, to let it work). The idea is to secure upper urinary tract in the period of particular vulnerability.
In duplex kidney big ureterocoele may contribute to lower pole reflux. In this cases we can incise ureterocoele during cystoscopy, which is minimally invasive intervention. It may be joined with Deflux or Vantris injection.
– upper urinary tract duplications and associated pathologies – so called duplex kidney is a singe oragan with duplicated renal pelvis and ureter. The ureters may join together on their way to baladder or drain there separately. In this case ureter of the upper kidney moiety drains lower then normally and tends to be obstructed. It may open in bladder triangle forming “ureterocoele”, in posterior urethra, seminal vesicle or even on female vulva, next to urethral orifice. Upper moiety ureter drain to the bladder higher then normally, which makes it’s intramular part less oblique and promotes vesico-ureteral reflux. It must be stressed that in most cases duplication causes no harm, ureters drain side-by-side and pathology develops. But in less lucky situation we can encounter, solo or in combinations:
– dysgenesia and hydronephrosis of upper moiety of various degree
– vesico-ureteral reflux into lower moiety, rarely into upper or both
– hydronephrosis of lower moiety caused by pelvi-ureteric stricture
In prominent bilateral anomaly, which is more often encountered in girls, the destruction of renal parenchyma is comparable with this seen in posterior urethral valve in boys. Basic diagnostis is made with ultrasonography. Upper pole “cyst” or dilatation brings into mind possibility of duplication with upper moiety obstruction. Widening of lower pole pelvis requires cystographic verification with vesico-ureteral reflux suspected. The most detailed anatomy can be obtained with spiral tomography with intravenous contrast meterial, though it is invasive – radiation dose is quite big and general anesthesia required in small children.
Surgical management is very individual, depending on particular combination of pathologies. We should always remember that our goal is to save renal parenchyma, prevent infections and first of all save the patient as many dyscomforts of treatment as possible. There is no place for reckless decisions, staged treatment with ureterocutaneous fistula, heminephrectomies of totally atrophic and asymptomatic upper pole and so on.
– posterior urethral valve is the most uncommon cause ot upper urinary tract dilatation encountered in newborns and neonates. It can be observed in 1:4000-8000 live births. Most of this children present with biochemical features of renal disease. The bladder almost always full, maybe with exeption of oligurica phase …