Background: Specific findings on prenatal US have been found to be predictive of the final postnatal diagnosis. Unfortunately, in clinical practice, we are often asked to evaluate patients with prenatal hydronephrosis but do not have any information with regard to their prenatal US. We are then forced to base clinical decisions on the postnatal US findings. The purpose of this study is to evaluate the predictive value of the postnatal US parameters using our database of 1441 children with prenatal hydronephrosis.
Methods: Since 1998, we maintained an IRB-approved database of all children with prenatal hydronephrosis referred to our institution. Only children who had their radiological evaluation (US, VCUG, MAG-3 and DMSA) at our instution were included in the study. Children with MCDK, chromosomal anomalies, spinal dysraphism, or had their first postnatal US done after 60 days were excluded from the study. A univariate and multivariate analysis of the postnatal US parameters and patient demographics were performed in 1441 children with 2804 affected renal units.
Results: The results are presented here as tables.

Renal Units Characteristics	Any Pathology	VUR	UPJ	Ureteral Obstruction	Others
Hydronephrosis grade	n (%)	n (%)	n (%)	n (%)	n (%)
	95% CI	95% CI	95% CI	95% CI	95% CI
Normal	179 (19.4%)	135 (14.6%)	8 (0.9%)	31 (3.4%)	7 (0.8%)
	(16.9%, 22.2%)	(12.4%, 17.2%)	(0.4%, 1.7%)	(2.4%, 4.7%)	(0.4%, 1.6%)
Mild	290 (29.6%)	185 (18.9%)	76 (7.7%)	41 (4.2%)	7 (0.7%)
	(26.4%, 33.0%)	(16.1%, 21.9%)	(6.1%, 9.8%)	(3.0%, 5.7%)	(0.3%, 1.5%)
Mild-Moderate	105 (44.3%)	57 (24.1%)	39 (16.5%)	14 (5.9%)	4 (1.7%)
	(37.4%, 51.5%)	(18.3%, 30.9%)	(12.1%, 22.1%)	(3.2%, 10.7%)	(0.5%, 5.4%)
Moderate	259 (62.1%)	107 (25.7%)	96 (23.0%)	74 (17.7%)	9 (2.2%)
	(56.8%, 67.1%)	(21.3%, 30.6%)	(19.0%, 27.6%)	(14.1%, 22.1%)	(1.0%, 4.6%)
Moderate-Severe	102 (91.9%)	28 (25.2%)	59 (53.2%)	24 (21.6%)	1 (0.9%)
	(83.4%, 96.2%)	(17.8%, 34.5%)	(43.4%, 62.7%)	(14.5%, 30.9%)	(0.1%, 6.1%)
Severe	131 (96.3%)*	34 (25.0%)*	83 (61.0%)*	34 (25.0%)*	3 (2.2%)*
	(91.5%, 98.5%)	(18.4%, 33.0%)	(52.3%, 69.1%)	(18.3%, 33.2%)	(0.5%, 8.9%)
Ureter Dilatation
Absent	723 (31.8%)	397 (17.5%)	322 (14.2%)	33 (1.5%)	19 (0.8%)
	(29.5%, 34.2%)	(15.6%, 19.6%)	(12.6%, 15.9%)	(1.0%, 2.1%)	(0.5%, 1.5%)
Present	343 (64.4%)*	149 (28.0%)*	39 (7.3%)*	185 (34.7%)*	12 (2.3%)*
	(59.3%, 69.1%)	(23.3%, 33.1%)	(4.9%, 10.7%)	(30.0%, 39.8%)	(1.1%, 4.4%)
Kidney Echogenicity
Absent	1031 (37.6%)	529 (19.3%)	352 (12.9%)	210 (7.7%)	27 (1.0%)
	(35.4%, 39.9%)	(17.5%, 21.3%)	(11.5%, 14.4%)	(6.5%, 9.0%)	(0.6%, 1.6%)
Present	35 (53.8%)*	17 (26.2%)**	9 (13.8%)**	8 (12.3%)**	4 (6.2%)*
	(40.2%, 67.0%)	(15.3%, 41.1%)	(6.3%, 27.9%)	(5.4%, 25.5%)	(2.4%, 14.9%)
Parenchymal Thinning
Absent	1037 (37.4%)	531 (19.1%)	346 (12.5%)	214 (7.7%)	30 (1.1%)
	(35.2%, 39.7%)	(17.3%, 21.1%)	(11.1%, 14.0%)	(6.6%, 9.1%)	(0.7%, 1.7%)
Present	29 (93.5%)*	15 (48.4%)*	15 (48.4%)*	4 (12.9%)**	1 (3.2%)**
	(77.5%, 98.4%)	(31.2%, 66.0%)	(31.2%, 65.9%)	(4.9%, 29.8%)	(0.5%, 19.7%)
Duplicity
Absent	959 (36.1%)	487 (18.3%)	350 (13.2%)	159 (6.0%)	30 (1.1%)
	(33.8%, 38.3%)	(16.5%, 20.3%)	(11.7%, 14.7%)	(4.9%, 7.2%)	(0.7%, 1.8%)
Present	107 (74.3%)*	59 (41.0%)*	11 (7.6%)**	59 (41.0%)*	1 (0.7%)**
	(65.2%, 81.7%)	(32.3%, 50.2%)	(4.1%, 13.9%)	(32.4%, 50.1%)	(0.1%, 4.8%)
Thickened Bladder
Absent	1057 (38.0%)	544 (19.6%)	358 (12.9%)	216 (7.8%)	27 (1.0%)
	(35.8%, 40.3%)	(17.7%, 21.6%)	(11.5%, 14.4%)	(6.6%, 9.1%)	(0.6%, 1.5%)
Present	9 (37.5%)**	2 (8.3%)**	3 (12.5%)**	2 (8.3%)**	4 (16.7%)*
	(16.6%, 64.3%)	(1.2%, 41.2%)	(3.0%, 39.8%)	(1.2%, 41.2%)	(4.2%, 47.6%)
* p<0.05; **p>0.05

Renal Units	Any Pathology	VUR	UPJ	Ureteral Obstruction	Other
Hydronephrosis grade	Odds Ratio (OR)
Normal	1	1	1	1	1
Mild	1.77	1.33	9.75	1.2	0.83
Mild-Moderate	3.22	1.77	24.92	1.37	1.92
Moderate	5.79	1.67	45.59	3.6	2.75
Moderate-Severe	41.46	1.52	208.3	5.12	1.2
Severe	90.07	1.33	386.1	4.81	2.99
Ureter Dilatation	3.1	1.52	0.21	27.6	NS
Kidney Echogenicity	1.82	NS	NS	NS	7.58
Parenchymal Thinning	4.43	2.94	NS	NS	NS
Duplicity	2.56	2.42	0.22	4.54	NS
Thickened Bladder	NS	NS	NS	NS	24.88

Conclusion: In a metanalysis review of literature done previously, we found that the quality of the data available was poor and consequently, no statistically significant conclusions can be made regarding the predictive value of the first postnatal US. The findings in this study allow for specific risk assessment based upon the first postnatal US parameters such as the hydronpehrosis grade, ureteral dilation and duplex system. This information is essential for counseling and for determining which radiological tests will be necessary to evaluate for the etiology of prenatal hydronephrosis.