This document discusses perinatal hydronephrosis (ANH), which refers to dilation of the renal pelvis detected on prenatal ultrasound in 1-3% of pregnancies. ANH is most commonly used to define this condition but measurements and definitions vary. Ultrasound remains the main imaging modality used, while MRI can provide additional detail. Factors like gestational age, bladder filling, and grading systems impact ANH assessment and prediction of postnatal outcomes. Counseling involves discussing differential diagnoses, natural histories, and management plans. Fetal intervention is rarely needed but may be considered to improve pulmonary and renal development in cases of late oligohydramnios or poor fetal urine markers.

1. PERINATAL
HYDRONEP
HROSIS
Dr G Praveen Chandra

2. Fetal Imaging
• The increased use of maternal-fetal ultrasound
has led to the development of the field of
perinatal urology.

3. ANH
• Antenatal hydronephrosis (ANH)
• identified in 1% to 3% of all pregnancies
• one of the most common birth defects
detected.

4. • Ultrasonography continues to be the mainstay
of fetal imaging.
• With experience, this modality provides
intricate detail and diagnostic capability that is
similar to that of ultrasonography in the
neonate.

5. • Fetal magnetic resonance imaging (MRI)
• a valuable adjunct
• when further delineation of anatomic detail is
believed to be necessary to optimize diagnosis
and/or management strategy

6. • Use of complementary computed tomography
is controversial
• the additive information may not outweigh the
added risk of fetal and maternal radiation
exposure.

7. FETAL DIAGNOSIS

8. • ANH:
• Defined as an anteroposterior diameter (APD)
of the renal pelvis greater than 5 mm.
• But the consensus on the definition of ANH is
lacking.
• With the rapid improvement of ultrasound
technology, the incidence of detection of renal
anomalies may be changing.

9. • In a single institutional study,
Study Period
Incidence of
Urinary tract
abnormlaities
1989-1993 0.3%
1999-2003 0.76%

10. • A large prospective study of 11,986 Swedish
women conducted between 1978 and 1983
identified renal anomalies in 0.28% of fetuses.
• Over two thirds of the anomalies were
hydronephrosis (0.18%)

11. • A British prospective screening study of 6292
pregnant women at 28 weeks’ gestation
demonstrated
• hydronephrosis in 1.40% of patients,
• with postnatal confirmation in 0.65%

12. Elements of Prenatal
Urologic USG Diagnosis

14. Hydronephrosis

15. • Hydronephrosis, or dilation of the renal pelvis,
is the most common urologic abnormality
found on ultrasound evaluation.

16. • Numerous grading systems have been developed
• however, there is no consensus on the best and most
consistent method of reporting ANH.
• Measurement of the APD has been used widely
• but there have been no formal studies to determine the
interobserver and intraobserver reproducibility of ANH
measurement.

18. Disadvantages of
use of APD
• APD fails to describe
• pelvic configuration,
• calyceal dilation &
• laterality of findings,
which should be
included.
• APD can be affected by
• gestational age,
• hydration status of the
mother
• bladder hypertonicity &
• degree of bladder distention

19. • Because the dimensions of the renal pelvis
may normally increase with gestational age,
most investigators have adjusted threshold
APD values for early and later gestational age.

20. • Unfortunately, a simple threshold APD value
that separates normal from abnormal does not
exist
• even severe cases of ANH have the potential to
resolve without incident
• whereas mild degrees of ANH have the
potential to progress

21. • Varying the minimal APD threshold can
significantly alter the specificity and sensitivity
of APD as a measure of ANH and postnatal
pathology.
• To date there is no consensus on the optimal
APD threshold for determining the need for
postnatal follow-up.

22. • An APD cutoff of 15 mm for determining
obstruction yielded a postnatal sensitivity of
73% and specificity of 82%.
Late Gestational age APD
cutoff
Abnormality detection
10mm 23%
7mm 68%

23. ANH categories by APD
• There is near-total agreement that APD greater
than 15 mm represents severe or significant
hydronephrosis.
• A lower threshold of 4 to 5 mm is an
appropriate value for considering APD to be
abnormal

25. Alternative
Measurements
• 3D volume measurements of the renal pelvis.
• Hydronephrosis index to correct for bladder
distention for a more precise evaluation.
• Society for Fetal Urology (SFU) ultrasound
grading system of ANH.

26. SFU
USG
grading

27. • MRI may also prove useful in prenatal
evaluation
• Advantage: high anatomic detail without
ionizing radiation exposure.
• High cost and limited data currently confound
the optimal use of this modality in the context of
ANH.

28. Diagnostic Accuracy
• The ability to determine definitive postnatal
pathology based on antenatal findings is
difficult.

29. • In a systematic review of the ANH literature, Lee and
colleagues in 2006 attempted to determine the risk of
a pathologic diagnosis for patients with varying
severity of ANH .
• The review included 1308 patients who were identified
with ANH and sufficient postnatal radiographic follow-
up.

30. Other category includes
prune-belly syndrome,
VATER (vertebral, anal, tracheo-esophageal and renal anomalies) syndrome,
solitary kidney,
renal mass, and
Unclassified causes.

31. • The degree of ANH was defined by APD
identified in a particular trimester.
• Approximately 36% of the patients had a
postnatal pathologic diagnosis.
• The overall risk for any pathologic process
increased with increasing degree of ANH.

32. • However, the risk of vesicoureteral reflux
(VUR) remained consistent regardless of the
degree of ANH
• ANH is not an appropriate indicator for VUR.

33. • Earlier literature suggests that obstruction
location can be determined prenatally in 88%
of cases.
• but many researchers have reported a high
false-positive rate (9% to 22%) .

34. • The majority of false-positive findings in these
studies involved nonobstructive causes of
hydronephrosis, such as
• high-grade reflux,
• large nonobstructed extrarenal pelves, or
• transient hydronephrosis.

35. • Early and accurate diagnosis of posterior urethral
valves is critical but difficult.
• The hallmark signs of an in utero diagnosis of posterior
urethral valves have been described
• Oligohydramnios,
• dilated posterior urethra,
• thickened bladder
• hydroureteronephrosis
• increased renal echogenicity.

36. • Regardless, there are very few studies that have
prospectively examined the clinical urologic
implications of these findings alone or in combination.
• In one series of 22 fetuses, the false positive rate was
as high as 58% .
• In a population-based series the sensitivity in
detecting valves was as low as 23%.

37. • Regardless of the degree or severity of the
finding, after any antenatal detection of a
urinary tract anomaly a thorough fetal survey
must be conducted.

38. • Amniocentesis and karyotype should be
considered if intervention or a major anomaly
is suspected,
• because the incidence of concurrent
chromosomal anomalies is relatively high in
fetuses with concomitant urologic anomalies.

39. ANTENATAL
MANAGEMENT OF
FETAL UROPATHIES

40. • Up to 3% of all pregnancies involve fetal urinary
tract anomalies.
• vast majority associated with hydronephrosis.
• Less than 5% of all detected anomalies have
severe enough obstruction that might warrant
antenatal intervention.

41. • The primary role for the perinatal urologist is
to provide education and counseling for
prospective parents in an objective manner.

42. • The counseling urologist should
(1) provide reassurance and dispel misconceptions,
(2) provide a reasonable differential diagnosis
(3) supply information regarding the natural history of the
disease,
(4) give antenatal recommendations &
(5) provide a postnatal management plan.

43. • The need for continued antenatal evaluation is
debatable and unclear
• particularly with mid- and late-trimester mild and
moderate hydronephrosis.
• More regular follow-up is reasonable
• In severe unilateral or bilateral hydronephrosis,.
• If there is a suspicion of bladder outlet obstruction.

44. • Normal fetal growth parameters,
• amniotic fluid volume,
• renal appearance (echogenicity, degree of
hydronephrosis, cystic changes) &
• extrarenal fluid collections
should be monitored closely.

45. Rationale & Indications
for Fetal Intervention

46. • Overall, the need to consider in utero intervention for
obstruction is uncommon.
• However, in the specific cases in which it should be
considered, the rationale for antenatal treatment of
hydronephrosis is to maximize development of
• pulmonary and
• renal function.

47. • These two aspects of fetal development are
closely linked because
• urine comprises more than 90% of amniotic fluid
volume by the 16th week of gestation and
• oligohydramnios during the 2nd trimester is
often associated with a lethal postnatal
outcome secondary to pulmonary hypoplasia

48. • Before prenatal surgical intervention for
obstructive uropathy, it is critical to assess the
risk-benefit ratio.
• The time of onset of oligohydramnios has been
shown to be an important determinant of
outcome.

49. • In fetuses in which adequate amniotic fluid was
documented at up to 30 weeks’ gestation in
association with a urologic abnormality,
• pulmonary outcomes were satisfactory and
• postnatal clinical problems were related to renal disease.
• Therefore, in the setting of late-onset oligohydramnios
there appears to be limited usefulness of urinary tract
decompression or early delivery for pulmonary
reasons.

50. • It is also unclear whether early delivery to
permit earlier postnatal urinary decompression
is beneficial.
• If early delivery is considered, maternal
corticosteroid administration for pulmonary
development should be considered.

51. • The most widely accepted indicator of
salvageable renal function is analysis of fetal
urine.

52. Indications and Conditions for
in-Utero Urinary Decompression

53. Use of fetal urine β2 microglobulin
• An indicator of tubular damage.
• In normal postnatal kidneys, >99.9% of β2 microglobulin
is reabsorbed and metabolized in the proximal tubules.
• In postnatal renal disease with damage to this area, β2
microglobulin is excreted in the urine.
• Including this parameter, poor renal outcome has been
predicted with a specificity of 83% and sensitivity of 80%

54. • Findings on antenatal ultrasound have also
been examined with regard to prediction of
long-term postnatal renal function.

55. • In a systematic review of 13 articles encompassing 251
women,
• oligohydramnios and
• appearance of the renal cortex (increased echogenicity
or cystic changes) at the diagnosis of lower urinary tract
obstruction
were the best factors to predict poor renal function
(defined as creatinine >1.2 mg/dL).
• In this particular study, gestational age at diagnosis
(<24 weeks) was not predictive of renal function.

56. Clinical Experience

57. • The ability to diagnose severe prenatal hydronephrosis
and advances in fetal intervention have helped
develop prenatal surgery for obstructive uropathy.
• Harrison and colleagues (1982) described the initial
report of fetal surgery in a 21-week-old fetus with
bilateral hydroureteronephrosis secondary to
posterior urethral valves.

58. • More recently, with improved technology
• the initial method of decompression with open surgery
has largely been replaced by in utero shunt placement.
• The shunt is placed under ultrasound guidance using a
Seldinger technique through a trocar.
• Current practice uses the Rodeck shunt, which lies flat
against the abdomen to minimize shunt dislodgment

60. Complications of Shunting
1. Shunt dislodgment
2. Bowel herniation.
3. Amnioinfusion may be needed to improve visualization for
shunt placement
• this may lead to excessive fetal movement.
4. Occasionally the fetus needs to be paralyzed for accurate
placement.
5. Very large bladders may cause the shunt to be placed too
high in the abdomen, resulting in dislodgment from the
bladder after it decompresses.

61. 6. Induction of premature labor,
7. Perforation of fetal bowel and bladder,
8. fetal loss,
9. fetal and/or maternal hemorrhage and
infection.

62. Fetal Cystoscopy
• Fetoscopic methods for direct intervention to provide
prolonged bladder drainage have also been explored.
Advantage over vesicoamniotic shunting:
improved drainage and
restoring normal cycling of the bladder.

63. Drawbacks of Fetal Cystoscopy
• There are no studies to determine if this method of
decompression is adequate in the face of significant
prenatal bladder dysfunction.
• Furthermore, fetoscopic intervention also introduces
the additional potential for iatrogenic injury to the
urethra, bladder neck, or external urethral sphincter.

64. Clinical Outcomes

65. • To date, the reported long-term outcomes of
antenatal intervention for severe obstructive
uropathy (e.g., posterior urethral valves,
prune-belly syndrome, urethral atresia) are
mixed

66. Long-term outcomes of
in-utero vesicoamniotic shunting
Acceptable renal
function
45%
Mild impairment
22%
Renal failure
33%

67. Best Renal Outcome
with shunting
0
20
40
60
prune-belly syndrome
PUV
Urethral atresia
57%
43%
25%

68. PLUTO trial
• European-based multicenter randomized clinical trial
• PLUTO (Percutaneous Shunting for Lower Urinary
Tract Obstruction)
• Aim:
To evaluate the safety and effectiveness of vesicoamniotic
shunting as compared with conservative management in
singleton pregnancies with ultrasound evidence of lower
urinary tract obstruction

69. Results of PLUTO trial
CATEGORY NUMBER
Vesicoamniotic shunt patients 16
Controls 15
Total 31 cases

70. Live births Postnatal
deaths
12
4
Shunted cases, n=16
Live births Postnatal
deaths
12
8
Controls, n=15

71. • All postnatal deaths were from pulmonary hypoplasia.
• Although underpowered, the study demonstrated a
nonsignificant increase in survival in the vesicoamniotic
shunt group.
• Consistent with the results of the systematic review of
existing prenatal intervention data, there was minimal
likelihood of surviving with longterm normal renal
function.

72. • Overall, it appears that select in utero intervention for
the appropriate patient may reduce the risk of
neonatal mortality.
• Without doubt, more sensitive and specific markers to
better identify which fetus will benefit from in utero
shunting need to be defined.

73. Postnatal management
of
Antenatally detected
Hydronephrosis

74. • A child with a prenatal diagnosis of a urologic renal
abnormality such as ANH should be carefully evaluated
and followed by a pediatric urologist from birth.
• The vast majority of these children appear entirely
healthy and in the absence of prenatal ultrasound
findings would not have any indications for regular
urologic follow-up.
• Parental anxiety is common and should be addressed
directly with prenatal counseling and education.

75. Unilateral
Hydronephrosis

76. • The presence of prenatally detected unilateral dilation
of the kidney warrants postnatal ultrasound evaluation
in a timely but nonurgent fashion (3 to 8 weeks of life).
• The most common diagnoses associated with this
finding are
1. UPJ obstruction,
2. VUR,
3. UVJ obstruction &
4. Megaureter.

77. • Normal postnatal ultrasound examination
findings indicate that obstructive uropathy is
not present;
• however, normal findings do not indicate
whether the child has VUR.

78. • It is important to keep in mind that a postnatal
ultrasound evaluation performed within the
first 48 hours of life may not yet demonstrate
hydronephrosis or may underestimate the
degree of hydronephrosis secondary to
physiologic oliguria in the newborn.

79. VCUG &
Prophylactic Antibiotics
• The current trend in management of ANH minimizes
postnatal prophylactic antibiotics and testing for VUR
• in cases of resolved ANH or
• in mild to moderate cases of persistent postnatal ANH
owing to a lack of evidence for a benefit to
screening.

80. • Severe ANH
• may be associated with an increased risk of febrile
urinary tract infection and
• possibly may indicate a higher grade of VUR.
• Infants with severe ANH should be placed on a
prophylactic antibiotic (amoxicillin, 10 to 25 mg/kg/day)
and undergo VCUG.

81. • Diuretic renography…
• with technetium-99m mercaptoacetyltriglycine
• reserved for those with persistent moderate or
severe postnatal hydronephrosis not related to
VUR.

82. • Perhaps the most challenging aspect of managing ANH
is determining if and when postnatal surgical correction
for obstruction is appropriate.
• regardless of the degree of ANH, moderate or severe
postnatal hydronephrosis with evidence of decreased
renal function should be an indication for surgical
intervention.

84. Bilateral Hydronephrosis

85. • Infants with bilateral hydroureteronephrosis
may have
1. posterior urethral valves,
2. bilateral VUR,
3. bilateral UPJ or UVJ obstruction, or a
combination of these findings.

86. • For the child with bilateral
hydroureteronephrosis suggestive of bladder
outlet obstruction,
• ultrasound evaluation and
• VCUG
should be performed promptly.

87. • In boys, the presence of posterior urethral valves is the
most important diagnosis to be ruled out.
• In girls, an obstructing ectopic ureterocele would be
the most likely cause of bladder outlet obstruction.
• In the event that an obstructive lesion is discovered, it
should be corrected promptly.

88. • For children with suspected lower urinary tract
obstruction (e.g., posterior urethral valves),
• prompt bladder decompression and
• antibiotic prophylaxis (amoxicillin 10 to 25
mg/kg/day)
should be initiated before radiographic
intervention.

89. Thank You