Antenatal Hydronephrosis (Urinary Tract Dilation) Treatment & Management

Updated: Jul 27, 2021
  • Author: Dennis B Liu, MD; Chief Editor: Marc Cendron, MD  more...
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Medical Care

At present, no medical interventions are indicated for the treatment of antenatal hydronephrosis (urinary tract dilation). However, medical therapy is indicated in fetuses with oligohydramnios and the resultant pulmonary hypoplasia.

Pulmonary hypoplasia is the precursor for bronchopulmonary dysplasia that develops in the neonate and is the major cause of mortality in this patient population. Surfactant is needed to decrease surface tension at the air-liquid interface of the alveoli, and glucocorticoids administered to the mother in the antepartum period have been shown to stimulate production of surfactant-associated proteins and enhance lung maturation. [43]

A number of randomized trials concluded that antenatal corticosteroids, given between 48 hours and 7 days before preterm delivery, decrease the incidence of respiratory distress syndrome and death. [44, 45] However, short-term adverse effects were noted, including hypertension, hyperglycemia, infections, intestinal perforations, gastrointestinal (GI) bleeding, inhibition of somatic growth, and hypertrophic cardiomyopathy. [46, 47, 48]  Potential long-term adverse effects included impaired somatic, lung, and brain growth. [43] Risks and benefits must be carefully weighed in each patient.


Surgical Care

Intervention for a fetus with antenatal hydronephrosis (dilatation of the upper urinary tract) is controversial for the following reasons:

  • Obtaining an accurate diagnosis with current technology is difficult
  • The natural history of each disease process causing antenatal hydronephrosis is variable and has not been fully elucidated
  • The lack of data regarding the success and complications of intervention has impeded progress in defining specific indications for treatment

The main considerations in evaluating a fetus with antenatal hydronephrosis are gestational age, laterality of the lesion, the presence of unfavorable prognostic factors, volume of amniotic fluid, and overall fetal well-being.

Lesions detected early in fetal development may have a significant impact on renal and pulmonary development. Laterality of the lesion is significant, with bilateral lesions being more predictive of poor outcome. The presence of unfavorable prognostic factors, such as renal cortical cysts and echogenic parenchyma on antenatal ultrasonography (US), elevated levels of urinary electrolytes on vesicocentesis, and reduced lung volume or thoracic circumference, should also be considered. [49]

The presence of oligohydramnios is the most significant indicator of poor fetal outcome, and intervention should not be considered in its absence. In the presence of multiple fetal anomalies or chromosomal anomalies predictive of poor outcome, parents may elect to terminate the pregnancy.

A management strategy has been developed on the basis of findings from initial and serial antenatal US. [28] Significant unilateral hydronephrosis does not necessitate antenatal intervention; however, it should be evaluated in the postnatal period with follow-up renal US (if needed), voiding cystourethrography (VCUG), and diuretic renography. [50, 51]

Bilateral hydronephrosis without bladder distention is more significant and should be monitored ante partum with serial US examinations to look for bladder distention and development of oligohydramnios. Postnatal evaluation should be performed as above. A fetus that presents with bilateral hydronephrosis and a distended bladder should raise serious concern for an obstructive process, such as urethral atresia or urethral valves.

If oligohydramnios is not present, serial examinations are adequate with definite postnatal evaluation as described above. In the presence of oligohydramnios, evaluation for the presence of unfavorable prognostic factors with karyotype analysis and vesicocentesis is warranted. Referral to a tertiary care center should also be a consideration. Fetuses with findings consistent with a poor outcome generally are not good candidates for antenatal intervention. Personnel and technology should be available to perform the necessary workup and offer intervention if this course of action is deemed appropriate.

Fetuses whose antenatal hydronephrosis is milder (but still suggestive of a significant underlying pathologic cause) require immediate neonatal consultation with a pediatric urologist. This consultation can direct further inpatient workup or provide an outlet for outpatient monitoring.

Treating a potentially obstructive process in the presence of oligohydramnios by diversion of urine into the amniotic space would seemingly allow normal renal and lung development. Relief of the obstructed flow of urine should optimize eventual renal function, and restoration of normal levels of amniotic fluid should prevent the development of pulmonary hypoplasia. However, both experimentally and in clinical situations, this is not entirely true.

Sufficient evidence indicates that restoring amniotic fluid volume is beneficial for lung development and preventing pulmonary hypoplasia; however, little evidence indicates that renal function is improved with this intervention. Experimental models and autopsy evaluations have demonstrated that irreversible dysplasia is often present by the time hydronephrosis is detected. [28] Intervention should only be considered in fetuses with oligohydramnios and a significant chance of recovery of renal function on the basis of renal prognostic factors.

Antenatal intervention is limited by technical considerations and lack of adequate comparison between the varying modalities with regard to patient selection and outcome measures, especially whether fetal intervention improves postnatal outcomes. Numerous advances have been made in refining current modalities; however, no prospective randomized trials are currently under way that compare the outcomes of the various interventions.

The first successful in-utero decompression was achieved with open fetal surgery by creating bilateral cutaneous ureterostomies in a 21-week fetus. [52] Although the intervention was successful, the neonate did not survive, because of pulmonary complications.

Open vesicostomies have also been attempted; however, these open interventions have been abandoned in favor of percutaneous shunt procedures.

Such approaches were eloquently described in a review by Freedman et al, who discussed several technical advances that allowed more success than was achieved in initial attempts (eg, use of amnioinfusion to enhance fetal visualization, use of fetal paralysis, routine use of antibiotics, and increased focus on proper catheter placement), as well as specific outcome measures needed for appropriate evaluation of the effects of fetal intervention (eg, gross survival, postnatal survival, shunted survival, and nadir creatinine at 1 year). [4]

Laparoscopic approaches have also been described [53, 54]  but have been associated with high rates of complications.

Fetal cystoscopic ablation of posterior urethral valves has been described; success rates have varied. [55] The fetoscope is passed percutaneously through a cannula into the fetal bladder, and ablation of the valves is achieved with laser coagulation.

Other less invasive techniques have been developed to help prevent oligohydramnios-induced pulmonary hypoplasia. As previously mentioned, serial transabdominal amnioinfusion is helpful in placement of percutaneous shunts. It may also have a therapeutic role in the reduction of pulmonary hypoplasia. [56] This intervention could be useful in fetuses with oligohydramnios associated with antenatal hydronephrosis.



Consultations are indicated as directed by the initial evaluation but may include the following:

  • Neonatologist
  • Pediatrician
  • Pediatric urologist
  • Pediatric nephrologist
  • Pediatric cardiologist
  • Pediatric cardiac surgeon
  • Pediatric surgeon
  • Pediatric orthopedic surgeon
  • Pediatric neurosurgeon

Long-Term Monitoring

Most neonates with antenatal hydronephrosis (dilatation of the upper urinary tract) can be discharged home, provided that inpatient evaluation does not preclude further evaluation or intervention in a hospital setting. Djahangirian et al suggested that whereas patients with an initial postnatal APD of 10 mm or greater and a SFU grade of 3-4 should be followed, all patients with an APD of less than 10 mm, especially with an SFU grade of 1-2, can be safely discharged, in that they are unlikely to experience complications. [57]

Outpatient follow-up with the pediatric urologist depends on the diagnosis (see DDx). Evaluation and management of the neonate or infant in the outpatient setting is directed by the underlying cause of antenatal and postnatal hydronephrosis. Appropriate follow-up with other subspecialties may also be necessary if antenatal and postnatal evaluation warrants such management.

Typically, neonates with antenatal hydronephrosis are evaluated with postnatal US. The optimal timing of the initial postnatal US examination is not important, provided that repeat serial imaging is done so as to ensure that the degree of hydronephrosis in a relatively dehydrated neonate is not underestimated. [58]  Postnatal US 1-4 weeks after birth is recommended.

The most common inpatient and/or outpatient medication prescribed in the setting of antenatally detected hydronephrosis persisting in the postnatal period is a prophylactic antibiotic against urinary tract infection (UTI). This medication is given with the aim of preventing UTIs and possible renal damage that may result from pyelonephritis. It is not prescribed to all patients with hydronephrosis and is administered to patients according to the underlying cause of their hydronephrosis. Generally, a penicillin-based antibiotic is appropriate in this age group.

Herz et al studied 405 children with asymptomatic antenatal hydronephrosis, of whom 278 received continuous antibiotic prophylaxis (CAP) and 178 did not. [59]  They concluded that CAP may have a significant role to play in reducing the risk of febrile UTI for children with identifiable risk factors (eg, ureteral dilatation, high-grade vesicoureteral reflux, and ureterovesical junction obstruction) but appears to be unnecessary otherwise.

The European Association of Urology/European Society for Paediatric Urology Guidelines Panel carried out a systematic review aimed at determining whether CAP is effective for antenatal hydronephrosis and, if so, what the most and least beneficial antibiotic regimens are. [60] ​ Outcomes included reduced UTIs, decreased drug-related adverse events (AEs), and improved kidney function. The Panel was unable to establish whether CAP is superior to observation in decreasing UTIs, nor could it reach any conclusions about drug-related AEs or kidney function, because of lack of data. There was some evidence that CAP can reduce febrile UTI in particular subgroups.