Etiology of Hydronephrosis in Neonates

Fetal hydronephrosis as one of the most common abnormalities that has occurred in fetals, affecting 0.17 to 2.3% of pregnancies, is found in the prenatal ultrasound examination (1, 2). It occurs as kidney swelling due to failure of normal drainage of the urine from the kidney to the bladder (3, 4). This condition commonly affects only 1 kidney, however, it may involve both kidneys (5, 6). Hydronephrosis is not a primary condition and results from other underlying diseases that result from a blockage or obstruction in the urinary tract (7-9). Acute unilateral obstructive uropathy is one of the most common causes of hydronephrosis, other causes include a torsion of ureteropelvic junction, tumors in or near the ureter, and narrowing of the ureter from congenital defect or injury (2, 10, 11). Clinical manifestations are based on the duration of obstruction; mild symptoms include frequently urinating and increase in urge to urinate (12-14). Other potential symptoms include abdominal or flank sharp pain, nausea, vomiting, incomplete voiding, urinating, pain, and fever (15, 16). This has been diagnosed by an ultrasonography, and since treatment focuses on getting rid of blocking flow of urine based on the obstruction reasons, it represents a transient condition that resolves maturation of tubular function, increasing ability of reabsorption, and maturation of ureteropelvic junction in the kidney (3, 17, 18). Based on this content, hydronephrosis has a high prevalence in children and its etiology varies in different studies. Therefore, the aim of this was an etiology evaluation in neonates with hydronephrosis.

In total, 314 children (Table 1) with hydronephrosis were included (175 males (55.7%) and 139 females (44.3%)), familial history was seen in 6 children (1.8%), the average gestational age in 250 children (79.6) was term and preterm. As shown in Table 2, since 132 children (42%) are idiopathic and do not have a clear etiology in our examination, most common etiology of hydronephrosis in this study was VUR, which was seen in 100 children (31.8%). The lowest prevalence was ureterocele. The mean birth weight was 3430 ± 44.2 (g). In regards to disease severity, 19 children have severe hydronephrosis, in regards to the amniotic volume, 26 children were polyhydramnius and 22 children were oligohydramnios, and 253 children were normal in the DTPA scan. As shown in Table 3, in the hydronephrosis severity section, severe and moderate severity in VUR etiology, and mild severity in idiopathic etiology, was most common, which was a statistically significant difference in the 2 groups (P = 0.0001). In addition, as shown in Table 4, gender and gestational age in different groups of hydronephrosis etiology were significantly different (P = 0.0001).

Our results showed etiology prevalence in hydronephrosis and its correlation with different factors such as gender, gestational age amniotic fluid volume, hydronephrosis severity, birth weight, familial history, and severity of hydronephrosis. The following, in the most relevant studies, have been discussed.

Lee et al. in a large metaanalysis, demonstrated that the risk of any postnatal pathology in mild hydronephrosis was 11.9% and the risk of vesicoureteral reflux was not significantly different among all severity (19). Ali et al. in a descriptive retrospective study, evaluated hydronephrosis etiology and their treatment at 2 teaching hospitals of Khyber Pukhtoon Khawa. They have concluded that since obstructive etiology requires surgical correction, physiological hydronephrosis and VUR can be treated by medical treatment. Vemulakonda et al. conducted a study regarding prenatal hydronephrosis. In this study, they evaluated surgical intervention prognosis in this type of hydronephrosis and concluded that it has good prognosis in neonates (20). Niu et al. in a study regarding ureteral polyps as an etiological factor, evaluated 15 cases with hydronephrosis. They have examined UPJ with 3D images and concluded that although it is a important etiology in hydronephrosis, its diagnosis is difficult (21). Yiee et al. in a study regarding management of hydronephrosis, concluded that ultrasounds, voiding cystourethrograms, and nuclear renograms for diagnosis and surveillance are the best management approach in children (22). Kaya et al. in a study regarding hydronephrosis etiology, evaluated 65 children with hydronephrosis in the department of pediatrics nephrology. They have concluded that the problem in terms of diagnosis, monitoring, and treatment of antenatal hydronephrosis was not constituted (23). Sudhakar et al report procidentia uteri as an etiology of hydronephrosis. In this they have concluded that use of vaginal pessary to prolapse reduction, reversed the obstructive uropathy (24). Drake et al. considered ureteropelvic obstruction as a possible etiology of hydronephrosis in children. In this, they have been reported and reviewed 88 children and infants affected with hydronephrosis secondary to ureteropelvic obstruction (25).

However, due to the very few clinical studies that have been carried out regarding etiology of hydronephrosis, further studies will be needed. It is suggested to evaluate the impact on the gestational age on accuracy of the ultrasonography in diagnosing and grading of hydronephrosis, maternal and fetal factors, and UTI effects on prognosis of hydronephrosis.