Management of prenatally detected fetal hydronephrosis

Severe antenatally diagnosed renal disorders: background, prognosis and practical approach

Nowadays most renal disorders, especially urinary tract malformations and renal cystic disease, are diagnosed antenatally. In cases of severe bilateral disease, intrauterine renal dysfunction may lead to renal oligohydramnios (ROH), resulting in pulmonary hypoplasia which affects perinatal mortality and morbidity as well as the long-term outcome. However, some infants may only have mild pulmonary and renal disease, and advances in postnatal and dialysis treatment have resulted in improved short- and long-term outcome even in those infants with severe ROH. Here, we review the current state of knowledge and clinical experience of patients presenting antenatally with severe bilateral renal disorders and ROH. By addressing underlying mechanisms, intrauterine tools of diagnosis and treatment as well as published outcome data, we hope to improve antenatal counselling and postnatal care. KEY SUMMARY POINTS: 1. Nowadays most renal disorders are diagnosed antenatally, especially urinary tract malformations and renal cystic disease. 2. Severe kidney dysfunction may lead to renal oligohydramnios, which can cause pulmonary hypoplasia and is a risk factor of perinatal mortality and postnatal renal outcome. However, as considerable clinical heterogeneity is present, outcome predictions need to be treated with caution. 3. Advances in postnatal and dialysis treatment have resulted in improved short- and long-term outcomes even in infants with severe renal oligohydramnios. 4. A multidisciplinary approach with specialist input is required when counselling a family with an ROH-affected fetus as the decision-making process is very challenging.

Current management of antenatal hydronephrosis

The strategy for the management of children with urinary tract anomalies has changed considerably as a result of the development of ultrasound equipment and techniques that allow for detailed fetal evaluation. Hydronephrosis is the most common urogenital anomaly detected, suggesting that an obstructive process may be potentially present. The goal of postnatal management is to identify and treat those patients whose renal function is at risk, while leaving alone the high percentage of patients who are at no risk of renal damage. This management involves a spectrum of radiological, medical, and surgical interventions for diagnosis, surveillance, and treatment. In this article, we review our current understanding of the natural history of antenatal hydronephrosis and its management.

Fetal hydronephrosis as a predictor of neonatal urologic outcomes

OBJECTIVES

The ability to predict surgically relevant fetal renal hydronephrosis is limited. We sought to determine the most efficacious second- and third-trimester fetal renal pelvis anteroposterior diameter cutoffs to predict the need for postnatal surgery.

METHODS

We retrospectively reviewed the medical records of mothers and neonates who had a prenatal sonographic examination in our Perinatal-Pediatric Urology Clinic and received follow-up care. Hydronephrosis was defined as a renal pelvis anteroposterior diameter of 5 mm or greater in the second trimester and 7 mm or greater in the third trimester. Hydronephrosis was subdivided into mild, moderate, and severe.

RESULTS

Of 8453 fetuses, 96 met the criteria and were referred to our clinic. Isolated hydronephrosis was diagnosed in 74 fetuses, of which 53 received postnatal follow-up evaluations. The areas under the receiver operating characteristic curves for predicting postnatal surgery in the second and third trimesters were 0.770 and 0.899, respectively. The second-trimester renal anteroposterior diameter threshold that best predicted post-natal surgery was 9.5 mm (sensitivity, 71.4%; specificity, 81.1%). The third-trimester threshold that best predicted postnatal surgery was 15.0 mm (sensitivity, 85.7%; specificity, 94.6%).

CONCLUSIONS

The fetal renal anteroposterior diameter on second- and third-trimester sonography is predictive of an increased risk for neonatal urologic surgery. Surgical risk is best predicted by a third-trimester renal anteroposterior diameter threshold of 15 mm.

[Postnatal follow-up of children having antenatal hydronephrosis]

The application of antenatal ultrasound for the evaluation of congenital anomalies in early pregnancy has become a common practice. Hydronephrosis is the most common anomaly observed. Antenatal interventions are experimental and done in advanced centers. Though there are defined criteria of intervention, it is still not clear as to who will benefit. Most patients will have relatively benign course, however identification of those who will have potentially serious postnatal problems permits early intervention. This study gives recommendations for the postnatal examination and follow-up of the newborns having hydronephrosis diagnosed on antenatal ultrasound.

Congenital urinary tract obstruction

Congenital urinary tract obstruction is a heterogenous condition with a varying natural history. Accurate diagnosis within the late-first and second trimesters allows for counselling of the parents and planning of multi-disciplinary care for the pregnancy and newborn. Antenatal investigations to predict postnatal renal function are of varying accuracy. However, some factors have been shown to be predictive of poor outcome in terms of renal function at birth and infancy. There is the possibility of in-utero intervention in these fetuses.

Incidence Based Fetal Urological Counseling Using the Virtual Pediatric Urology Registry: Importance of Insignificant Fetal Pyelectasis (Sonographically Evident Renal Pelvis)

PURPOSE

Since 1985, counseling for fetal renal pelvic dilatation has been done to determine whether there is need for newborn urological evaluation. This is likely if the anteroposterior width of the renal pelvis exceeds categorical cutoffs, ie 4 mm or greater before gestational age 33 weeks, or 7 mm or greater after 33 weeks. Cases below these categorical cutoffs are deemed not to merit newborn testing. We examined our fetal registry to determine the incidence of urological pathology in cases deemed not to merit newborn testing.

MATERIALS AND METHODS

Since 1980, we have prospectively input fetal ultrasound and postnatal followup data into customized Virtual Pediatric Urology Registry software. The Virtual Pediatric Urology Registry compares index case findings against those archived in the registry and then outputs the incidence of newborn diagnoses. Diagnoses are grouped as having limited or extensive urological care.

RESULTS

The Virtual Pediatric Urology Registry has 1,128 cases registered and data on 2,292 fetal ultrasound studies that were done between gestational ages 12 and 43 weeks (average +/- SD 29.3 +/- 7). There are measurements of anteroposterior pelvic width for 1,712 cases. Pediatric data include ultrasound for 2,596 cases, diuretic renal scan for 449 and voiding cystourethrogram for 574. Surgery was done for renal/bladder obstruction or vesicoureteral reflux in 358 cases (32%). Mean followup was 9.8 months old (range 1 day to 14 years). Of the total of 1,128 fetal cases 148 (13%) showed anteroposterior pelvic width below categorical cutoffs, so that they were deemed not to merit newborn testing. However, the Virtual Pediatric Urology Registry incidence based method identified that extensive urological care extended to 30 of these 148 cases (20%). There were 31 cases identified at less than gestational age 33 weeks, which showed newborn urological pathology in 11 (35%), including hydronephrosis in 4, surgery in 3, vesicoureteral reflux in 2, solitary kidney in 1 and death in 1. There were 117 cases identified at gestational age 33 weeks or greater, which showed newborn urological pathology in 19 (16%), including vesicoureteral reflux in 8, hydronephrosis in 7 and surgery in 4.

CONCLUSIONS

We found that about 13% of cases of fetal renal pelvic dilatation were insignificant because the measurement was below currently accepted cutoffs that merit postnatal followup. However, 20% of these cases in fact showed extensive urological care needs. The Virtual Pediatric Urology Registry provides an array of likely newborn diagnoses in neonates. Counseling by the incidence based method is more effective than by the current cutoff method.

Prenatal hydronephrosis

Hydronephrosis is the most common genitourinary tract anomaly identified on prenatal ultrasound studies. Ureteropelvic junction obstruction accounts for approximately 50% of the cases of prenatally detected hydronephrosis. Postnatal evaluation allows for the identification of the cause and further management. Rarely, in utero intervention may be performed for severe oligohydramnios associated with hydronephrosis. Prenatal consultation with a pediatric urologist is useful in decreasing parental anxiety and facilitating postnatal management.

Outcome of fetal renal pelvic dilatation diagnosed during the third trimester

OBJECTIVES

The aim of this study was to evaluate renal function and the need for postnatal treatment--antibiotic therapy and/or surgery--in relation to the grade of fetal renal pelvic dilatation (RPD) found on third-trimester ultrasound examination.

METHODS

The retrospective study included 78 children, born between 1995 and 2000, with 115 dilated fetal renal pelvic units. The children were allocated to three groups based on pelvic anteroposterior diameter (APD) detected on third-trimester ultrasound: APDs of 7-9.9 mm, 10-14.9 mm and > or = 15 mm were classified as mild dilatation, moderate hydronephrosis and severe hydronephrosis, respectively. Renal function was assessed by scintigraphy.

RESULTS

None of the 20 children with mild dilatation experienced a urinary tract infection (UTI) or underwent surgery; two had associated renal or urinary tract abnormalities. In contrast, five out of 22 (23%) children with moderate hydronephrosis and 23 out of 36 (64%) with severe hydronephrosis had either a UTI or required surgery (P < 0.001); associated abnormalities were also more common (6 out of 22 and 15 out of 36, respectively). There was no significant correlation between the grade of antenatal RPD and postnatal ipsilateral renal function.

CONCLUSIONS

The need for postnatal treatment increased significantly with the grade of antenatal RPD. Children with antenatal mild dilatation were discharged early from follow-up whereas those with moderate and severe fetal hydronephrosis needed close follow-up by a multidisciplinary team.

Genitourinary imaging in children

Genitourinary imaging in children has gone through a metamorphosis in the past 30 years, paralleling technical advances in sonography, CT scanning, and MR imaging. The imaging sequences for hydronephrosis and UTI are still controversial and require outcomes analysis to determine which studies are most beneficial and efficacious.

In utero therapy for lower urinary tract obstruction

Lower urinary tract obstruction has a significant impact on neonatal and child health. Pulmonary hyperplasia and renal impairment could be direct or indirect consequences of this condition leading to significant morbidity and mortality. Evaluation of fetuses with suspected lower urinary tract obstruction is performed not only to confirm the diagnosis but also to assess renal prognosis. Ultrasound examination and urinary analysis aid in the evaluation of these fetuses. The decision to perform fetal intervention in these cases is a difficult one. Vesico-amniotic fetal shunting, open fetal surgery and more recently endoscopic fetal surgery for this condition are available as possible modalities of fetal intervention. Case selection for fetal intervention is extremely important in order to both avoid unnecessary intervention in those unlikely to survive, and also to avoid procedure related complications in fetuses likely to do well without intervention. Vesico-amniotic shunting has the advantage of bypassing the obstruction, however it is often associated with complications. Open fetal surgery is not usually recommended because of the complications and high fetal loss rate. Endoscopic surgery to visualise and treat the cause of lower urinary tract obstruction has been tried. Fetal endoscopic surgery is in its infancy and endoscopic procedures are limited to a few groups. This current review addresses evaluation, case selection and therapeutic options for lower urinary tract obstruction in utero. It also discusses the limited data against which the efficacy of the various options can be assessed. The current state of fetal intervention is detailed in the present review.

Consensus on the prenatal management of antenatally detected urological abnormalities

PURPOSE

The incidence of an antenatally detected genitourinary abnormality is 0.5% of all pregnancies assessed, and rarely is antenatal intervention indicated. A survey of pediatric urologists was undertaken to evaluate current practice patterns and recommendations regarding the need to intervene in the antenatal period.

MATERIALS AND METHODS

A survey instrument was mailed to all members of the Society for Fetal Urology. There were 7 case scenarios that addressed critical decision points in patients with antenatally detected genitourinary abnormalities.

RESULTS

A total of 112 of 188 Society for Fetal Urology members (60%) completed the survey. Observation with serial ultrasound was recommended for a 32-week fetus with ureteropelvic junction obstruction. For a 36-week fetus with suspected posterior urethral valves without oligohydramnios most respondents elected no intervention with a minority favoring early delivery. For a 23-week fetus with suspected posterior urethral valves and oligohydramnios with normal bladder electrolytes most respondents agreed with a vesicoamniotic shunt. There was no clear consensus for a 20-week fetus with suspected posterior urethral valves, oligohydramnios and a nonfunctioning right kidney. Most respondents recommended serial ultrasound to follow an 18-week fetus with suspected posterior urethral valves and normal amniotic fluid. Antenatal intervention was not recommended for a 20-week fetus with bilateral renal cystic disease, and most respondents elected no intervention for a 28-week fetus with a solitary kidney with suspected ureteropelvic junction obstruction and normal amniotic fluid.

CONCLUSIONS

Situations that warrant antenatal intervention for a genitourinary abnormality are exceedingly low and may include cases of oligohydramnios, suspected favorable renal function and the absence of life threatening congenital abnormalities. In cases with normal amniotic fluid antenatal intervention is not recommended regardless of the detected abnormality. There is an emerging trend toward early delivery of fetuses with severe genitourinary abnormalities, normal amniotic fluid and confirmed lung maturity.

Consensus on the prenatal management of antenatally detected urological abnormalities

PURPOSE

The incidence of an antenatally detected genitourinary abnormality is 0.5% of all pregnancies assessed, and rarely is antenatal intervention indicated. A survey of pediatric urologists was undertaken to evaluate current practice patterns and recommendations regarding the need to intervene in the antenatal period.

MATERIALS AND METHODS

A survey instrument was mailed to all members of the Society for Fetal Urology. There were 7 case scenarios that addressed critical decision points in patients with antenatally detected genitourinary abnormalities.

RESULTS

A total of 112 of 188 Society for Fetal Urology members (60%) completed the survey. Observation with serial ultrasound was recommended for a 32-week fetus with ureteropelvic junction obstruction. For a 36-week fetus with suspected posterior urethral valves without oligohydramnios most respondents elected no intervention with a minority favoring early delivery. For a 23-week fetus with suspected posterior urethral valves and oligohydramnios with normal bladder electrolytes most respondents agreed with a vesicoamniotic shunt. There was no clear consensus for a 20-week fetus with suspected posterior urethral valves, oligohydramnios and a nonfunctioning right kidney. Most respondents recommended serial ultrasound to follow an 18-week fetus with suspected posterior urethral valves and normal amniotic fluid. Antenatal intervention was not recommended for a 20-week fetus with bilateral renal cystic disease, and most respondents elected no intervention for a 28-week fetus with a solitary kidney with suspected ureteropelvic junction obstruction and normal amniotic fluid.

CONCLUSIONS

Situations that warrant antenatal intervention for a genitourinary abnormality are exceedingly low and may include cases of oligohydramnios, suspected favorable renal function and the absence of life threatening congenital abnormalities. In cases with normal amniotic fluid antenatal intervention is not recommended regardless of the detected abnormality. There is an emerging trend toward early delivery of fetuses with severe genitourinary abnormalities, normal amniotic fluid and confirmed lung maturity.

Perinatal differential diagnosis of cystic kidney disease and urinary tract obstruction: anatomic pathologic, ultrasonographic and genetic findings

According to the classification of Osathanondh and Potter of cystic kidney diseases an antenatal differential diagnosis is presented, which is based on the anatomic pathologic, ultrasonographic and genetic findings. Since the ultrasound evaluation influences the obstetric and neonatal management, each second and third trimester sonography should consider the most common malformations in pediatric autopsies. The autosomal recessive polycystic kidney disease (ARPK), autosomal dominant polycystic kidney disease (ADPK), multicystic renal dysplasia, obstructive multicystic kidneys and cystic renal malformations found in other syndromes with genetic linkage are discussed in this review.

Sonography of the neonatal genitourinary tract

Ultrasound has become the modality of choice for the evaluation of the neonatal genitourinary tract. High frequency linear, vector, and curved array transducers (7 MHz, 5 MHz, 12 MHz) and portability of the equipment make a rapid bedside evaluation with exquisite anatomic detail possible. A major advantage of sonography over other modalities is real time observation and circumvention of sedation.

Fetal urinary tract abnormalities. Natural history, pathophysiology, and treatment

Urologic abnormalities are commonly detected on routine obstetric sonographic examinations. The progressive nature and potential reversibility of obstructive urologic anomalies have led to interest in in utero treatment of these lesions. Over 90% of obstructive urologic lesions do not need treatment until after birth. For a select group of patients, antenatal treatment may improve postnatal renal and pulmonary function. When indicated, minimally invasive nephroamniotic or vesicoamniotic stenting is the preferred method of treatment.

Postnatal management of hydronephrosis diagnosed in utero

In this review we identify the causes of antenatal hydronephrosis and detail management options. A large majority of these patients can be treated safely and effectively after birth.