What Postnatal Tests Should be Performed for Prenatal Hydronephrosis?

Patient Presentation
A 29-year-old pregnant mother comes to clinic because she is upset and confused about recommended evaluations for her unborn son.
A 32-week gestation ultrasound showed mild bilateral hydronephrosis. It had been performed for discrepant uterine measurements and estimated date of confinement over the past two prenatal visits.
No other fetal abnormalities were found on the ultrasound.
The mother had been sent to see a pediatric nephrologist who recommended performing a renal ultrasound and a voiding cystourethrogram (VCUG) prior to discharge from the hospital after birth.
The mother is not concerned about the renal ultrasound but is visibly upset about the VCUG.
The past medical history reveals the mother to be 36 weeks gestation. She has had no problems with the pregnancy other than discrepent measurements. Uterine measurements since the ultrasound correlated appropriately at 34 and 36 weeks gestation.
This is her second pregnancy and she had no problems with the first pregnancy and her child is healthy.
The family history reveals no renal, genitourinary problems, nor congenital abnormalities in the family.
The diagnosis of antenatally-diagnosed bilateral mild hydronephrosis was made. The mother was told by the general pediatrician that he understood that usually the baby has a renal ultrasound at 1-2 weeks after birth and again at 6 weeks to see if the hydronephrosis remains and to determine if there are other anatomical problems.
If the ultrasound continues to be abnormal the second time then a VCUG is performed. The VCUG results would then determine what other followup and treatment are necessary.
The mother was also told that if other anatomical problems were shown on the first ultrasound, then other tests might be needed and done before the second ultrasound at 6 weeks. The physician explained that he generally recommended prophylactic antibiotics until the first ultrasound was shown to be normal, but that using antibiotics was controversial.
The physician also told the mother that he would re-check the results of the ultrasound and the recommendations of the pediatric nephrologist to make sure there were not other reasons why the nephrologist had recommended the renal ultrasound and VCUG so early after the baby was born.

Genitourinary abnormalities are commonly found on antenatal ultrasounds (2-9/1000 births) with male fetuses more commonly affected than females (2:1).
There are different classifications of antenatal hydronephrosis. Generally, hydronephrosis is diagnosed if the renal pelvis is > 4 mm in a fetus < 24 weeks gestation, and >10 mm in a fetus > 24 weeks gestation.
Antenatal hydronephrosis is the most common abnormality found.
When compared to the postnatal diagnoses of hydronephrosis, antenatal ultrasound has a false-positive result rate of 9-22%.
The high false-positive rate may be the result of different criteria for diagnosing hydronephrosis and in utero resolution of the hydronephrosis.
Most prenatal hydronephrosis (80%) resolves spontaneously in utero or in the first year of life.

The most common causes of antenatal hydronephrosis in one study were:
Transient hydronephrosis – 48%
Physiological hydronephrosis – 15%
Ureteropelvic junction obstruction – 11%
Vesicoureteral reflux – 9%
Megaureter – 4%
Multicystic dysplastic kidney – 2%
Ureterocoele – 2%
Renal cysts – 2%
Posterior urethral valves – 1%
Others – 6%

Learning Point
The recommendations for who to evaluate with antenatal hydronephrosis, what type of evaluation to do and when to do the evaluation are conflicted.
Two recent review articles recommend an early ultrasound (at 2 days in one study and 1 week in the other) and a later ultrasound (at 1 month in one study and 6 weeks in the other).
Both recommended a VCUG if the hydronephrosis persisted on the postnatal ultrasounds with further evaluation and treatment as is appropriate.
One review article stated that several other studies have pointed out the poor predictive value of ultrasound for vesicoureteral refux and therefore some authors insist on the need for a VCUG in all cases.

Prophylactic antibiotics are also controversial with one review study beginning antibiotics after the diagnosis of postnatal hydronephrosis is made and another one recommending antibiotics be begun at birth and continued until after the second ultrasound is normal.

Another review article drew these practical conclusions from the literature:
1. The likelihood of postnatal significant pathology is proportional to the antenatal hydronephrosis severity.
2. The differential diagnosis of the pathology varies according to the antenatal hydronephrosis severity.
3. Spontaneous resolution of antenatal hydronephrosis in utero or in the first year of life is common.
4. Spontaneous resolution of vesiculoureteral refux (even severe grades) is common in the first two years of life.
5. Surgical treatment is often not necessary early on in the patient’s life and appropriate monitoring is necessary.
6. Prenatal screening has decreased infant urinary tract infections, but some will still occur.

A search of the websites for the American Academy of Pediatrics, American Academy of Family Physician, American Society of Pediatric Nephrologists, and the American College of Radiology did not find any policy statements or clinical practice guidelines regarding evaluation of antenatal hydronephrosis.

Questions for Further Discussion
1. What evaluation and treatment are recommended for an infant diagnosed with vesicoureteral refux?
2. What evaluation and treatment are recommended for siblings of patients with vesicoureteral reflux?
3. When is the best time to perform an antenatal ultrasound for possible hydronephrosis?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Information prescriptions for patients can be found at MEDLINEplus for this topic: Kidney Diseases

To view current news articles on this topic check Google News.

Shokeir AA, Nijman RJM. Antenatal hydronephrosis: changing concepts in diagnosis and subsequent management. BJU International. 2000:85;987-994.

Woodward M, Frank D. Postnatal management of antenatal hydronephrosis. BJU International. 2002:89;149-156.

Toiviainen-Salo S, Garel L, Grignon A. et. al. Fetal hydronephrosis: is there hope for consensus? Pediatr Radiol. 2004:34;519-529.

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effecively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    5. Patients and their families are counseled and educated.
    8. Health care services aimed at preventing health problems or maintaining health are provided.
    9. Patient-focused care is provided by working with health care professionals, including those from other disciplines.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Practice Based Learning and Improvement
    12. Evidence from scientific studies related to the patients’ health problems is located, appraised and assimilated.

  • Interpersonal and Communication Skills
    17. A therapeutic and ethically sound relationship with patients is created and sustained.
    19. The health professional works effectively with others as a member or leader of a health care team or other professional group.

  • Systems Based Practice
    24. Cost-effective health care and resource allocation that does not compromise quality of care is practiced.
    25. Quality patient care and assisting patients in dealing with system complexities is advocated.
    26. Partnering with health care managers and health care providers to assess, coordinate, and improve health care and how these activities can affect system performance are known.

    Donna M. D’Alessandro, MD
    Associate Professor of Pediatrics, Children’s Hospital of Iowa

    March 20, 2006