Fetal Hydronephrosis
- Management Summary
- Introduction
- Definition
- Differential Diagnosis
- Postnatal Investigation
- Management
- Areas of Uncertainty in Clinical Practice
Management Summary
Introduction
Ultrasonographic examination of the fetus has become a routine examination of pregnancy. Victorian Perinatal Data confirms that 97% of pregnant women undergo antenatal ultrasound. In 1% of pregnancies a significant structural anomaly is detected. Urological anomalies comprise 30-50% of all fetal abnormalities.
An Australian study published by Tam and colleagues in 1994 established an incidence of fetal hydronephrosis of 5.1 per 1000 live births. More recently a prospective UK study identified fetal hydronephrosis in 2.3% of women. The extent to which postnatal investigation of stable minimal hydronephrosis is required remains a debated issue.
Definition
No agreed international classification exists.
The Australian Society for Ultrasound in Medicine defines hydronephrosis according to gestation by antero-posterior renal pelvic diameter.
| 18 - 20 weeks | ﾳ 4mm |
| 32 weeks | ﾳ 6mm |
| any gestation | ﾳ 10mm (regarded as severe hydronephrosis) |
80% of fetal hydronephrosis is mild with 20% classified as moderate/severe.
The Society for Fetal Urology considers the appearance of the calyces, renal pelvis and parenchyma to grade the degree of hydronephrosis from I - V (minimal to severe).
|
Calyceal dilatation |
Size of Pelvis |
|
|
Grade 1 |
Physiological |
1 cm |
|
Grade 2 |
Normal calyces |
1 - 1.5 cm |
|
Grade 3 |
Slight dilatation | > 1.5 cm |
|
Grade 4 |
Moderate dilatation |
> 1.5 cm |
|
Grade 5 |
Severe dilatation, atrophic cortex |
> 1.5 cm |
Differential Diagnosis
Mild fetal hydronephrosis appears to be associated with an excellent prognosis, most likely representing the spectrum of physiological renal pelvic dilatation.
Persistant moderate or progressive fetal hydronephrosis may be due to
Pelviureteric junction obstruction (PUJ)
Vesico-ureteric reflux (VUR).
Severe bilateral hydronephrosis is associated with structural or chromosomal anomaly in 55% of cases.
Posterior urethral valves in the male fetus- may be suggested antenatally by observation of bladder trabeculation post voiding
Multicystic, dysplastic kidney may appear as marked hydronephrosis although echogenic foci can usually be seen within the renal margins
Renal duplications
Megaureters
Postnatal Investigation
- perform a physical exam to exclude other problems
- imaging studies
Severe hydronephrosis requires immediate imaging. Investigation of mild/moderate hydronephrosis is better delayed until good urine flow is established (at least 5 - 7 days post delivery).
- renal ultrasound is required for all infants
- micturating cystourethrogram is required to exclude VUR
- isotope renography is required to exclude PUJ obstruction. MAG3 study can be done within 3-5 days of birth whereas DTPA is best delayed to 6 weeks of age when GFR is maximal
Management
Severe Hydronephrosis
In severe prenatal hydronephrosis joint antenatal consultation with the paediatrician and paediatric urologist may be beneficial in informing parents of likely diagnoses and postnatal course. The possibility of transfer to a tertiary paediatric facility soon after birth to decompress the urological system may need discussion. Oligohydroamnios is an independent predictor of poor outcome because of the association with pulmonary hypoplasia.
After birth severe hydronephrosis ﾱ palpable mass should be referred promptly to a paediatric urologist.
Mild
When the fetal hydronephrosis is mild or moderate and the infant is to be discharged home prior to confirmatory imaging antibiotic prophylaxis against urosepsis is considered prudent.
Eg: Trimethoprim 2mg/kg/day once daily as prophylaxis
Once imaging excludes VUR antibiotic prophylaxis can be ceased.
If VUR is excluded and the degree of hydronephrosis is moderate, isotope renography is required to exclude PUJ obstruction.
If PUJ obstruction is found referral to a paediatric urologist is appropriate.
All remaining uncomplicated hydronephrosis can be serially monitored with ultrasonography at 6 - 12 monthly intervals until resolution is documented.
Areas of Uncertainty in Clinical Practice
As mild fetal hydronephrosis is associated with an excellent prognosis the extent of postnatal investigation is controversial. Some authors suggest that ultrasonography combined with careful clinical review is all that is required.
The place of antibiotic prophylaxis prior to postnatal ultrasound is also questioned. If the infant remains in hospital until the time of ultrasound and/or micturating cystourethrogram some authors suggest that antibiotic therapy is unnecessary in the absence of proven infection.
Where prenatal pelvicalyceal dilatation is marked outcome is difficult to predict. The presence of a thin crescent of echogenicity over a distended calyx (the egg-shell sign) may indicate raised intrarenal pressure justifying aggressive management.
References:
Yates J, Lumley J, Bell R. The prevalence and timing of obstetric ultrasound scans. Final report to all Victorian hospitals. Centre for the Study of Mother's and Children's Health, Monash University. 1993.
Anderson N, Boswell O, Duff G. Prenatal Sonography for the detection of fetal anomalies: Results of a prospective study and comparison with prior series. Am J Roentgenol 1995;165:943-950.
Thomas DFM. Fetal Uropathy. Br J Urol 1990;66:225-31.
Tam JC, Hodson EM, Choong KC et al. Postnatal diagnosis and outcome of urinary tract abnormalities detected by antenatal ultrasound. Med J Aust 1994;160:633-37.
Sairam S, Al-Habib A, Sasson S and Thilaganathan B. Natural history of fetal hydronephrosis diagnosed on mid-trimester ultrasound. Ultrasound Obstet Gynaecol 2001;17:191-6.
Dudley JA, Haworth JM, McGraw ME, Frank JD, Tizard EJ. Clinical relevance and implications of antenatal hydronephrosis. Arch Dis Child 1997;76:F31-34.
Grignon et al. Urinary tract dilatation in utero: classification and clinical applications. Radiology 1986; 60:645-7
Elder JS. Antenatal Hydronephrosis. Fetal and neonatal management. Pediatr Clin North Am 1997;44:1299-1321.
Oliveira EA et al. Prognostic factors in fetal hydronephrosis:a multivariate analysis. Pediatr Nephrol 1999;13:859-64.
Harding LJ, Malone PS, Wellesley DG. Antenatal minimal hydronephrosis: is its follow-up an unnecessary cause for concern? Prenat Diagn 1999;19:701-5.
Yerkes EB, Adams PC, Pope JC 4th, Brock JW 3rd. Does every patient with prenatal hydronephrosis need voiding cystourethrography? J Urol 1999;162:1218-20.
Jones CL, Walker RG, Powell HR. Recent Advances in the management of vesico-ureteric reflux. J Paediatr Child Health 1993;29:325-7.
Dewan PA, Anderson K. The egg-shell sign: a possible indicator of raised intrarenal pressure. Pediatr Surg Int 2000;16:527-8.
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