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Saudi Journal of Kidney Diseases and Transplantation
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ORIGINAL ARTICLE Table of Contents   
Year : 2009  |  Volume : 20  |  Issue : 2  |  Page : 246-250
Causes and outcome of prenatally diagnosed hydronephrosis

1 Pediatric Nephrology Unit, Abuzar Children’s Hospital, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
2 Radiology Department, Golestan Medical Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran

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Hydronephrosis is the most common abnormal finding in the urinary tract on prenatal screening with ultrasonography (U/S). Hydronephrosis may be obstructive or non­obstructive; obstructive lesions are more harmful to the developing kidneys. The aim of the study was to evaluate the causes of renal pelvic dilatation and the outcome of postnatal treatment in infants with hydronephrosis diagnosed prenatally with U/S. We prospectively studied 67 (60 males) newborns with hydronephrosis diagnosed prenatally and confirmed postnatally with U/S from Sept. 2005 to Oct. 2007. The patients were allocated to three groups based on the mea­surement of the anteroposterior renal pelvic diameter (APRPD) in transverse plane: mild (6-9.9 mm), moderate (10-14.9 mm) and severe (> 15 mm) hydronephrosis. Voiding cystourethrography (VCUG) was obtained in all of the patients to rule out vesicoureteral reflux (VUR). In cases with negative VUR, Diethylenetriamine-pentaacetic acid (DTPA) scan with diuretic renography was performed to detect ureteropelvic joint obstruction (UPJO). Twenty two cases (32.8%) had mild, 20 (29.9%) had moderate, and 25 (37.3%) had severe hydronephrosis. The causes of hydroneph­rosis were VUR (40.2%), UPJO (32.8%), posterior urethral valves (PUVs) (13.4 %), and transient hydronephrosis (13.4 %). The lesion was obstructive in 37 (55.2%) infants. Totally, 33 (49.2%) patients with hydronephrosis (9 mild, 9 moderate, and 15 severe) subsequently developed com­plications such as UTI and renal insufficiency, or required surgery. Associated abnormalities were observed in 15 (22.4%) patients. We conclude that every newborn with any degree of hydro­nephrosis should be assessed postnatally for specific diagnosis and treatment.

Keywords: Urinary tract anomaly, Vesicoureteral reflux, Posterior urethral valves

How to cite this article:
Ahmadzadeh A, Tahmasebi M, Gharibvand MM. Causes and outcome of prenatally diagnosed hydronephrosis. Saudi J Kidney Dis Transpl 2009;20:246-50

How to cite this URL:
Ahmadzadeh A, Tahmasebi M, Gharibvand MM. Causes and outcome of prenatally diagnosed hydronephrosis. Saudi J Kidney Dis Transpl [serial online] 2009 [cited 2021 Dec 9];20:246-50. Available from: https://www.sjkdt.org/text.asp?2009/20/2/246/45572

   Introduction Top

The introduction of fetal ultrasonography (US) has allowed for the detection of many intra­uterine anomalies. Indeed, most anomalies are detected during routine fetal US done from 18-20 weeks of gestation.

Urinary tract anomalies are readily identified, and hydronephrosis is the most common ano­maly comprising 50% of congenital malfor­mations. [1] Intuitively, hydronephrosis is found in 0.59% [2] to 1.4% of fetuses, [3] and is consi­dered obstructive in nature. However, ante­natal hydronephrosis can be the result of non­obstructive processes such as vesicoureteral reflux (VUR), non-refluxing non-obstructed megaureter, and prune belly syndrome.

Bilateral obstructive lesions are more harmful to the developing kidneys than unilateral ones since urine is a major component of amniotic fluid and necessary for normal lung develop­ment and prevention of compression defor­mities. However, many cases of congenital hydronephrosis improve or resolve sponta­neously without surgical intervention. [2] There­fore, differentiation of obstructive lesions and non-obstructive lesions is extremely important in determining the outcome of the fetuses. [4],[5]

We aim in this study to evaluate causes of renal pelvic dilatation (RPD), renal function, and need for postnatal (medical and or surgi­cal) treatment in infants with hydronephrosis diagnosed with US.

   Methods and Subjects Top

We prospectively studied 70 newborns with congenital hydronephrosis from Sept. 2005 to Oct. 2007.

Inclusion criteria included unilateral or bilateral anterio-posterior renal pelvis diameter (APRPD) diagnosed prenatally (6 mm in the third trimester) and confirmed postnatally with US, which was performed in all of the patients at least one time on the day between 5-10 of postnatal life.

Exclusion criteria included perinatal death, incomplete data and no written informed con­sent obtained from the parents. All of the ultra­sound examinations were done by the two expert ultrasonographists in the radiology de­partments of Imam Khominee and Golestan hospitals.

We used Hitachi 525 ultrasound machine, prenatally with probe 3.5 MHZ and postnatally with 5-10 MHZ. Postnatally, the patients were allocated to three groups based on APRPD measured in transverse plane: mild (6-9.9 mm), moderate (10-14.9 mm), and severe (> 15 mm) hydronephrosis.

Voiding cystourethrography (VCUG) was performed in all of the patients to rule out VUR. In cases with negative VUR, Diethyl­enetriamine-pentaacetic acid (DTPA) scan with diuretic renography was performed to detect ureteropelvic joint obstruction (UPJO).

Renal function was assessed with both serum creatinine level corrected to age and DTPA scan. Prior to diuretic renography, serum crea­tinine was measured to confirm the absence of renal dysfunction. Patients should be at least 1 month of age during this assessment because newborns have a low glomerular filtration rate (GRF), and the dilatation can be mistaken for occlusive type due to immature excretory function. Also, newborns could respond poorly to diuretics. [6]

Statistical Analysis

Statistical analysis of data was performed by using the SPSS (version 14) program. P values < 0.05 were considered significant.

   Results Top

There were 96 dilated kidneys in 70 new­borns (60 males); three patients (6 dilated kid­neys) with incomplete data and no written informed consent by parents were excluded.

Based on the prenatal APRPD, 90 kidneys were dilated: mild dilation in 54 (60%), moderate in 19 (21.1%), and severe in 17 (18.9%). However, postnatally 88 kidneys remained dilated: mild dilation in 24 (27.2%), moderate 32 (36.4%) and severe in 32 (36.4%), [Table 1]. Bilateral renal pelvis dilation was observed in 21 newborns.

Out of the 67 infants, 22 (32.8%) had mild, 20 (29.9%) had moderate, and 25 (37.3%) had severe hydronephrosis. The most common causes of hydronephrosis were VUR (40.2%), UPJO (32.8%), PUVs (13.4%) and transient hydronephrosis (13.4 %), [Table 2].

Out of 22 infants with mild hydronephrosis 9 (41%) had transient hydronephrosis, 3 had UPJO, 9 had VUR (including 3 boys with posterior urethral valves (PUVs)), and one had non-obstructive hydronephrosis.

Among 20 infants with moderate hydronephrosis, 10 (50%) had VUR (3 PUVs), 4 UPJO, 3 duplication, 2 non-obstructive hydronephrosis and one non-refluxing non-obstructed mega­ureter, [Table 3].

Out 25 infants with severe hydronephrosis, 15 (60%) had UPJO, 6 (24%) had VUR (5 primary VUR, one PUV), 3 had UVJO and one had multicystic dysplastic kidney. Eventually, 9/22 (41%) with mild hydronephrosis, 9/20 (45%) infants with moderate hydronephrosis, and 15/25 (60%) with severe hydronephrosis had UTI, renal insufficiency or required sur­gery. Associated abnormalities were observed in 15 (22.4%) patients; 4/22, 8/20, and 3/25 in the three groups, respectively. Finally, 12 (18%) infants had no underlying abnormality, 9 with a transient hydronephrosis and 3 with a non-obstructive hydronephrosis.

   Discussion Top

In the appearance of intrauterine hydroneph­rosis was first described by Garrett et al. in 1975. [7] Since then, others authors have docu­mented the ability of US to detect this condi­tion in utero. [8],[9] In our series, out of 67 new­borns, 55 (82%) had an underlying pathology, which was close in incidence to the study conducted by Aksu et al who reported an underlying pathology in 75.1% of newborns with congenital hydronephrosis. [10]

In our study, 60% of the infants were males. Essentially, obstructive lesions were more common in males and PUVs were only seen in boys. In our series, 9 (13.4%) had PUVs, but the other lesions were also more common in the gender.

In the present study, the most common causes of dilation of renal pelvis were VUR (40.2%) and UPJO (%32.8), which were not consistent with the study of Aksu who found UPJO in 62.7% and VUR in 16.6% of cases. However, Woodward and Frank [11] recently reported 11% UPJO and 9% VUR.

Multicystic dysplastic kidney is a separate anomaly potentially confused with the hydro­nephrosis prenatally. Our findings were not comparable with the study of Woodward parti­cularly in the rate of transient hydronephrosis (13.4% vs 48%). However, in our study, 37 (55.2%) infants had obstructive lesions 22 UPJO, 5 UVJO, 9 PUVs, and one idiopathic megaureter representing the role of US in detection and early relief of the obstructive process.

Obstructive uropathy occurs in 1 in 1000 live births and accounts for 23% of chronic renal insufficiency in children. Nearly 7% of neo­natal deaths occur in infants with major renal and urinary tract anomalies. [5],[6] Obstruction in­duces the renin-angiotensin-aldosterone sys­tem, causing vasoconstriction, interstitial fib­rosis, and ischemic atrophy as well as induc­tion of apoptosis in the obstructed kidney.

While early correction of the obstructive pro­cess is followed by a significant hemodynamic recovery. [12],[13] In the present study, hydronephrosis was confirmed postnatally in all the 67 fetuses with suspected hydronephrosis i.e. there was a good correlation between the pre­natal and postnatal US findings. The diagnosis was mainly on the basis of measurement of the APRPD with US. Our findings showed that APRPD was a simple and sensitive technique for prerenal diagnosis of congenital hydro­nephrosis, allowing identification of 100% of cases. Therefore, postnatal follow-up studies are warranted if an APRPD is greater than or equal 6 mm in the third trimester.

The rate of mildly dilated kidneys diagnosed prenatally decreased from 60% to 27.2% post­natally. While, the rate increased in both the moderate and severely dilated groups from 21.1% and 18.9% to 36.4% in each. This indi­cates that mildly dilated kidneys should also be carefully followed up as the more severe groups.

We conclude that our study demonstrates the most common causes of hydronephrosis in fetuses. These include VUR, UPJO, PUVs and transient hydronephrosis. Postnatal assessment of infants with hydronephrosis facilitates the correct determination of the nature and site of the lesion, and allows an appropriate manage­ment. We believe that every newborn with any degree of hydronephrosis should be assessed postnatally.

   Acknowledgments Top

The authors would like to thank Dr. Dawoodi for assisting in U/S examinations at Imam, s Khomimee hospital and Mr. Cheraghian for statistical analysis of the results.


MGM participated in data collection. TM helped in US examinations, analysis and inter­pretation of the data. AA participated in data collection analysis, interpretation of the data and also draft of the manuscript.


This study was supported by the vice- chancellor for research affairs, Ahvaz Jundi­shapur University of Medical Sciences.

   References Top

1.Liang CC, Cheng PJ, Lin CJ, Chen HW, Chao AS, Chang SD. Outcome of prenatally diag­nosed fetal hydronephrosis. J Reprod Med 2002;(47):27-32.  Back to cited text no. 1    
2.Woodward M, Frank D. Postnatal management of antenatal hydronephrosis. BJU Int 2002; (89):149-56.  Back to cited text no. 2    
3.DiSandro MJ, Kogan BA. Neonatal manage­ment: Role for early intervention. Urol Clin North Am 1998;25(2):187-97.  Back to cited text no. 3    
4.Diamond DA, Peters CA. Perinatal urology, In: Avener ED, Harmon WE, Niaudet P (eds). Pediatric Nephrology, 5th edn, Philadelphia, Lippincott William &Wilkins 2004:73-80.  Back to cited text no. 4    
5.Chevalier R. Obstructive uropathy. In: Kher KK, Schnaper HW, Makker SP (eds). Clinical Pediatric Nephrology 2nd edn, Informa healthcare, 2006:507-16.  Back to cited text no. 5    
6.Shimada K, Kakizaki H, Kubota M, et al. Standard method for diagnosing dilatation of the renal pelvis and ureter discovered in the fetus, neonate or infant. Int J Urol 2004;11 (3):129-36.  Back to cited text no. 6    
7.Garrett WJ, Kossoff G, Osborn Ra. The diagnosis of fetal hydronephrosis, megaureter and urethral obstruction by ultrasounic echo­graphy. Br J Obstet Gynecol 1975;82:115-20.  Back to cited text no. 7    
8.Sanders R, Graham D. Twelve cases of hydro­nephrosis in utero diagnosed by ultrosono­graphy. J Ultrasound 1982;1:341-8.  Back to cited text no. 8    
9.Blane Ce, Koff SA, Bowerman RA, Barr M. Nonobstructive fetal hydronephrosis: Sono­graphic recognition and therapeutic implica­tions. Radiology 1983;147:95-9.  Back to cited text no. 9    
10.Aksu N, Yavascan O, Kanqin M, et al. Post­natal management of infants with antenatally detected hydronephrosis. J Pediatr Nephrol 2005; 20:1253-2.  Back to cited text no. 10    
11.Woodward M, Frank D. Postnatal management of antenatal hydronephrosis. BJU Int 2002;89 (2):149-56.  Back to cited text no. 11    
12.Chevalier RL, Chung KH, Smith CD, et al. Renal apoptosis and clusterin following ure­teral obstruction: The role of maturation. J Urol 1996;156(4):1474-9.  Back to cited text no. 12    
13.Chevalier RL, Gomez RA, Jones CE. Developmental determinants of recovery after relief of partial ureteral obstruction. Kidney Int 1988;33(4):775-81.  Back to cited text no. 13    

Correspondence Address:
Ali Ahmadzadeh
Pediatric Nephrology Unit, Abuzar Children’s Hospital, Jundishapur University of Medical Sciences, Ahvaz
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