Year : 2006 | Volume
: 22 | Issue : 1 | Page : 10--14
Antenatal hydronephrosis current evaluation and management
Pediatric Urology, The Johns Hopkins School of Medicine, Baltimore, MD, USA
Pediatric Urology, Marburg 1, 600 North Wolfe St., Baltimore, MD 21287-2101
Use of antenatal ultrasound for evaluation of congenital anomalies in early pregnancy has become a common practice. Hydronephrosis is the most common anomaly observed. Urologists are being referred such cases more frequently. Prenatal intervention is experimental and being done in advanced centers. Though there are defined criteria of intervention, it is still not clear as to who will benefit. Majority of patients develop urinary insufficiency postnatally. This review was undertaken to discuss the issues in evaluation, diagnosis and management of neonates born with hydronephrosis diagnosed on prenatal ultrasound. Most patients will have relatively benign course, however identification of those who will have potentially serious postnatal problems, permits early intervention.
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Mathews R. Antenatal hydronephrosis current evaluation and management.Indian J Urol 2006;22:10-14
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Mathews R. Antenatal hydronephrosis current evaluation and management. Indian J Urol [serial online] 2006 [cited 2021 Jan 20 ];22:10-14
Available from: https://www.indianjurol.com/text.asp?2006/22/1/10/24646
Universal utilization of antenatal evaluation with ultrasound has made the prenatal identification of hydronephrosis commonplace. Determination of the etiology for the hydronephrosis and definitive management is usually performed post-natally. This review will encompass the identification of antenatal hydronephrosis as well as go over the current postnatal evaluation and management of the most frequently noted anomalies that are associated with antenatal hydronephrosis.
Incidence of antenatal hydronephrosis
Hydronephrosis is the most common congenital anomaly observed with antenatal ultrasonography. Although hydronephrosis is typically an isolated anomaly, it can be associated with the presence of ureteral or bladder dilation and other associated urinary anomalies (i.e. posterior urethral valves, ureteroceles, etc.) Early detection of hydronephrosis was recognized as being able to help with postnatal management in the 1970s., Soon after the initial identification of ultrasonographic abnormalities, it was recognized the presumed diagnosis could not be always confirmed with certainty prior to delivery. The identification of hydronephrosis does however permit early parental counseling and in some instances allows antenatal interventions to be considered.
Diagnosis and classification of antenatal hydronephrosis
Antenatal diagnosis of hydronephrosis can be made as early as the 12th week of gestation. Kidneys should be definitely visualized by 20 weeks of gestation. Fetal urine is the primary source of amniotic fluid after the 16th week of gestation. Only 9% of uropathies are identified at 17 weeks of gestation, however 90% should be identifiable by 33 weeks of gestation.
Fetal hydronephrosis is identified if the pelvic diameter is > 4 mm on antenatal ultrasound. Multiple systems of classification have been used for fetal hydronephrosis. The Society of Fetal Urology Classification utilizes five grades of classification based on renal pelvic dilation, number of calyces visualized and degree of parenchymal atrophy [Figure 1]. Other systems of classification have utilized the antero-posterior pelvic diameter associated with morphology of the calyces. Currently most practitioners use the SFU Classification for description of antenatal hydronephrosis.
The causative factors for antenatal hydronephrosis can be broadly categorized into those leading to obstruction, those leading to reflux and the largest group comprising of non-obstructive and non-refluxing "idiopathic" hydronephrosis. Prenatal hydronephrosis is secondary to primary ureteropelvic junction obstruction in 65.6%, multicystic kidney in 9.4%, vesicoureteral reflux in 7.0%, duplex system in 5.4%, ureterovesical junction obstruction in 4.0% and posterior urethral valves in 3.0%. Although many of these entities may be presumptively diagnosed prenatally, confirmation of the diagnosis is made postnatally.
Antenatal intervention for the management of hydronephrosis has been performed in an attempt to improve the postnatal outcome of significant urinary tract obstruction. Intervention for upper tract anomalies continues to be controversial. At present temporary drainage of the upper tracts has been performed for patients with massive hydronephrosis that would preclude delivery. Puncture and drainage of the hydronephrotic kidney just prior to delivery has been performed for this indication, although this is not without potential risk. At this time, findings of significant upper tract obstruction are used to council parents about the potential post-natal management and prognosis.
Prenatal management for lower urinary tract obstruction however has been performed in selected cases. Most commonly, these obstructions are secondary to urethral atresia or posterior urethral valves in males. Fetal lower urinary tract obstructions in females are usually associated with syndromes or cloacal obstructions and prenatal intervention has not been shown to be of benefit in these patients. Infants that present with oligo or anhydramnios secondary to obstruction are at risk for postnatal pulmonary complications secondary to hypoplasia. Prenatal intervention in males that fit criteria for intervention has been in the form of urinary diversion with vesicoamniotic shunting or primary endoscopic ablation of the obstruction.
An algorithm for management has been suggested for patients that are potential candidates for antenatal intervention [Figure 2]. Selection of patients for these approaches are based on specific criteria. Amnioinfusion is utilized to permit complete visualization of the fetus. Complete anatomical survey is performed to rule out other severe anomalies. Karyotyping is performed to determine sex and normal chromosomal patterns. Patients with distal urinary obstruction (i.e. posterior urethral valves, urethral atresia) identified by bilateral hydroureteronephrosis and bladder dilation with decrease in the amniotic fluid volumes and normal urinary parameters on repeated bladder tap, are candidates for intervention. Three urinary taps are performed 48-72 hours apart and urinary electrolytes are evaluated [Figure 3].
Urinary diversion is performed with the use of fetal paralysis and ultrasound guided placement of a double pigtail catheter between the fetal bladder and the amniotic cavity. It is important to place the catheter into the lowest point possible in the bladder to prevent extrusion from the bladder once it has drained. Immediate problems associated with placement of the shunt were noted in 45% of patients. Typically these are mechnical problems associated with displacement of the shunt. Overall survival was 47% although if amniotic fluid volume was not restored, mortality was 100%. Even if bladder drainage can be achieved, long-term improvement of renal function is hard to achieve. With poor urinary function prior to intervention, 87% of patients developed urinary insufficiency postnatally. Institutions that have considerable experience with the techniques of antenatal intervention continue to report poor long-term rates of renal preservation, with lack of predictability of successful outcomes. The most recent study from an institution with a large experience with this technique indicates that 45% of those infants undergoing prenatal shunting had acceptable renal function.
Fetal cystoscopic evaluation was initially introduced in 1995 as an adjunct to diagnosis in infants that were being considered for vesicoamniotic shunting. Since then it has been used for intervention in selected institutions for the fulguration of posterior urethral valves. This technology has been limited to very few centers at this time. Data is being compiled in a National Data base to determine the long-term prognosis of children that are having or have had antenatal intervention for fetal uropathy.
At birth infants should undergo complete physical examination to evaluate for other potential congenital anomalies. If they are medically unstable (eg. Infants with posterior urethral valves) they should be started on antibiotic therapy and catheter drainage should be instituted. Patients should then have repeat evaluation with ultrasound to confirm the presence of hydronephrosis and additionally voiding cystourethrogram (VCU) should be performed to determine the presence of vesicoureteral reflux (VUR) and exclude the presence of posterior urethral valves. Antibiotic prophylaxis is instituted until the voiding cystourethrogram has determined that vesicoureteral reflux is absent.
VCU is recommended in all patients that have antenatal hydronephrosis including those patients that are noted to have resolution of hydronephrosis at birth as 14% of infants will still have VUR and 45% in one study were noted to have a urinary tract abnormality.
Patients that are noted to have hydronephrosis at birth should also have follow-up diuretic renal scanning performed to determine if significant obstruction is present. Renal scanning is typically performed at 4 weeks of age. Although initial renal scan may indicate lack of obstruction, serial ultrasound follow-up is indicated as some patients may present later in life with obstruction., Aksu et al have suggested that if the antenatal pelvic diameter is > or = to 5 mm postnatal follow-up would be recommended. The grade of hydronephrosis has been correlated to need for later surgical intervention and the potential for development of urinary tract infections. Higher grades of hydronephrosis appear to correlate with greater potential for both need for surgery and urinary tract infections.
Management of antenatal hydronephrosis
The most important aspect of management of antenatal hydronephrosis is determination of the underlying cause of the hydronephrosis. Once identified, management in most instances can be instituted rapidly. This review will only detail the management of the most frequent entities (ureteropelvic junction obstruction and vesicoureteral reflux) identified by antenatal hydronephrosis and confirmed at birth.
Ureteropelvic junction obstruction
Obstruction of the ureteropelvic junction is one of the most frequent causes for hydronephrosis detected on prenatal evaluation. The etiology of the ureteropelvic junction obstruction can be due to muscular abnormalities of the ureter, ureteral polyps, ureteral folds (i.e. intrinsic abnormalities), crossing vessels (extrinsic abnormalities), or secondary to vesicoureteral reflux. Most patients presenting with prenatally diagnosed ureteropelvic junction obstruction are asymptomatic. It has been suggested that patients presenting with symptoms in the current age of routine prenatal ultrasound evaluation have a higher incidence of crossing vessels as the etiology of their UPJO as compared to historical controls.
Diagnosis as noted above is made postnatally with the use of diuretic renal scintigraphy. Typically this is performed at 4 weeks following birth. Determination of significant obstruction uses two parameters - differential renal function and drainage times. These parameters are followed to determine success of intervention or conservative management strategies. Reduction in differential renal function (10 minutes) may be candidates for observational management.
Recently use of dynamic magnetic resonance imaging has been utilized to identify patients that may have intermediate degrees of obstruction and may be candidates for surgical correction. This technique will require sedation or perhaps general anesthesia to accomplish in small infants and has so far been utilized in investigational protocols at institutions that have an interest in this technology. Excellent anatomic definition can be achieved using this modality.
Once diagnosis of high grade obstruction is established management is with surgical reconstruction. Population based studies have indicated that although the rate of repair of UPJO has remained relatively stable, repair in now being performed at an earlier age, reflecting the earlier diagnosis of significant UPJO following prenatal evaluation. This view has however been challenged in a more recent examination of nationwide operative trends in the United States. The most frequently utilized reconstruction technique is dismembered pyeloplasty that can be performed using an extraperitoneal approach anterior to the 12th rib, a posterior approach via a dorsal lumbotomy or using laparoscopic techniques. Success rates in providing drainage are high using any of the approaches, however this does not translate to improvement in function. Studies looking at the outcome of pyeloplasty have indicated that improvement in function was only seen in patients that had crossing vessels as the etiology for the UPJO.
The lack of improvement in renal function noted following pyeloplasty has led many to consider a conservative approach to management. This approach needs to be combined with close follow-up and early surgical intervention if functional deterioration is noted. A recent review of patients that were followed for 16 years on a conservative protocol indicated that as many as 50% eventually needed surgical repair. The major indicators of a need for eventual surgical correction were the presence of renal function Vesicoureteral reflux
Retrograde flow of urine from the bladder to the kidneys will also lead to antenatal hydronephrosis. This is the next most common cause of hydronephrosis in most series. Seventeen percent of infants diagnosed with antenatal hydronephrosis will have a diagnosis of vesicoureteral reflux. Low-grade reflux (grades I - III) may be missed on antenatal evaluation as there may not be dilation of the renal pelvis. VCU is the only certain way to determine absence of VUR in infants, and is recommended even in those infants in whom postnatal ultrasound indicates resolution of hydronpehrosis. Grades IV and V may be noted as prenatal hydronephrosis. VUR may also be noted in infants that have distal obstruction (i.e. posterior urethral valves, urethral atresia, etc.). There is a male predominance in infants diagnosed with reflux at birth (M:F = 3:1) and a greater percentage of patients with grade IV and greater reflux (62.5%). There has been a consideration that racial differences may exist in the incidence of reflux between black and non-black populations. This difference remains controversial. Many patients will have global dysplasia with loss of function noted at birth even prior to development of a urinary tract infection. Circumcision is recommended in infancy in boys with VUR detected at birth.
Once diagnosis of reflux has been made on VCU, determination of renal dysplasia is performed with the use of dimercaptosuccinnic acid (DMSA) scan. Potential for spontaneous resolution seems to be higher in patients with antenatally diagnosed reflux, and therefore initial management should be conservative. Even patients with higher grades of reflux (IV-V) have 37-40% potential for resolution with follow-up.,, Long-term follow-up of children with antenatally diagnosed reflux indicates that incidence of urinary tract infections was low, renal growth was normal and hypertension was unusual. Prophylactic antibiotic therapy continues to be recommended for management although there is no definitive data indicating benefit in preventing urinary tract infections and renal scarring.,
Indications for surgical intervention remain similar to that in the older patient population. Recently endoscopic injection with detranomer/hyaluronidanse copolymer (Deflux™) for resolution of reflux has been suggested as a primary modality for infants with reflux., As this is a minimally invasive treatment regimen, it has been suggested that the potential risks of antibiotic therapy can be avoided with use of this agent. Since there is a higher potential for spontaneous resolution even in higher grades of reflux, surgical intervention should be limited to those infants with recurrent urinary tract infections or those failing conservative management strategies.
The routine use of antenatal ultrasonography has led to early diagnosis of urologic conditions that have postnatal consequences. In many instances earlier diagnosis has been able to lead to intervention with improved outcomes (i.e. UPJO, posterior urethral valves, VUR etc.). Additionally, the ability to counsel parents and make preparations for delivery of children at institutions that are capable of managing newborns with life threatening illness has changed management strategies. Most children with antenatal hydronephrosis will have relatively benign courses, however identification of those that will have potential serious postnatal problems permits early intervention. The role of prenatal intervention continues to be defined and long-term follow-up of infants that have been managed in this way is crucial to understand where these modalities fit into our management armamentarium.
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