Postnatal evaluation of intrauterine hydronephrosis due to ureteropelvic junction obstruction 1 Avaliação pós-natal de hidronefrose intra-uterina por estenose da junção ureteropiélica

PURPOSE: Fetal hydronephrosis is a frequent finding due to advances in prenatal ultrasonography. The definition of fetal and neonatal urinary tract obstruction is a very difficult task requiring confirmation of reduced renal function and hydronephrosis. In this study we followed a series of consecutive patients with intrauterine hydronephrosis that persisted during post-natal life. METHODS: 116 newborns with antenatal hydronephrosis diagnosed by ultrasound and submitted to a specific post-natal evaluative protocol with a follow-up period of 6 years. RESULTS: In 45 (38.8%) of 116 patients, ureteropelvic junction (UPJ) obstruction was confirmed and surgical correction of the UPJ obstruction was done in 19 patients. From 26 children who were initially submitted to non-surgical treatment, only 6 (23%) needed a surgical approach during follow up. Overall analysis showed that surgery was performed in 25 patients with UPJ obstruction, and the others 20 patients were kept under clinical observation, since normal renal function was confirmed by scintigraphy scans. CONCLUSION: Fetal hydronephrosis due to UPJ obstruction deserves careful postnatal evaluation. UPJ obstruction is the most frequent anomaly and its surgical treatment has very precise indications. The evaluative protocol was useful in identify patients that could be followed-up with a non-surgical approach.


Introduction
Hydronephrosis detected during fetal life represents a major challenge to the attending physician.Until the mid-80's, and based on the concept that hydronephrosis was synonymous of obstruction, the surgical treatment was routine 1 .From this decade several studies had shown that the dilation of the urinary tract was not necessarily indicative of obstruction, registering cases of spontaneous regression of hydronephrosis 2,3 .Currently, the diagnose of urinary tract obstruction in children is made by demonstration of hydronephrosis associated with progressive reduction of renal function assessed by radioisotopes 4,5 .The analysis of sequential images obtained by ultrasound associated with scintigraphic assessment of renal function provides objective tools that helps in the decision make to opt for clinical observation or surgery in those children whose hydronephrosis persists in the post-natal life 6 .
Among the anomalies of the urinary tract detected by ultrasound during fetal life and coursing with hydronephrosis, ureteropelvic junction obstruction (UPJ) stands out by its frequency.The surgical benefits and successful outcome are well defined, providing high cure rates.
The aim of this study was to evaluate a series of consecutive patients with intrauterine hydronephrosis secondary to UPJ stenosis, which persisted during post-natal period, and submitted to a specific evaluative protocol.

Results
The diagnosis of UPJ stenosis was performed in 45 (38.8%) of 116 patients with intrauterine hydronephrosis.Of these patients, 33 (73%) were male and 12 (27%) female.The involvement was unilateral in 33 and bilateral in 12 (Figure 1).
In the remaining 71 children (61.2%) the etiological factors of hydronephrosis were vesicoureteral reflux, primary megaureter, multicystic renal dysplasia, ureterocele and anterior or posterior urethral valves.These patients were not included in the current presentation.

Postnatal evaluation of intrauterine hydronephrosis due to ureteropelvic junction obstruction
Acta Cirúrgica Brasileira -Vol.28

Discussion
Fetal hydronephrosis (FH) is a common anomaly, affecting 1-5% of pregnancies 8 .With the increasing use of ultrasound in the prenatal evaluation from the mid 80's, hydronephrosis began to be diagnosed in intrauterine life [9][10][11] .
Hydronephrosis secondary to ureteropelvic junction stenosis is the more often renal anomaly diagnosed, and occurs in about half of the cases of antenatal hydronephrosis without ureteral dilatation 12 .
Today, postnatal ultrasound findings as hydronephrosis grade, parenchymal thickness, ureteral dilation and duplex system may suggest hydronephrosis etiology and may help in predicting outcome 13 .
In most cases neonatal hydronephrosis is a benign condition that may even present spontaneous resolution, but it is known that children with antenatal hydronephrosis are at greater risk of postnatal pathology 14 .Therefore, a follow-up protocol that can differentiate patients that will require a surgical approach is an useful tool 15 .
Up to 80's a classic solution to hydronephrosis was the surgical approach 16 and some authors advocated that hydronephrosis would compromise the renal function in the absence of treatment 17 .Many discussions started to clarify which intrauterine ureteropelvic dilation would be considered physiological or pathological.A study of Grignon et al 18 defined that all fetal renal pelvis with an anteroposterior diameter bigger than 10 mm on ultrasound deserves investigation on postnatal period.However, additional studies had shown that in many infants with severe hydronephrosis the kidneys were not obstructed, with no evidence of contralateral compensatory renal hypertrophy 19 .
In the 70s and 80s, the diuretic renogram was described and recognized for the clinical evaluation of hydronephrosis, as simple, safe and minimally invasive, providing information related to the differential renal function, and presence or absence of urinary obstruction 20,21 .Today, diuretic renogram and scintigraphy are currently used to confirm an obstructive pattern and assess differential renal function 22 .
Urinary tract obstruction is now defined by the presence of hydronephrosis plus a decrease of renal function 2,4,5,23 .Thus, in the last years, the indication of a pyeloplasty was made through evaluation of renal function: decrease more than 10% from initial renal function or initial renal function less than 40% on scintigraphy 24,25 .Another important factor to be considered is the rise of hydronephrosis showed by sequential ultrasound, always analyzed with functional data 26 .
Pyeloplasty in children is a procedure that has proven efficacy and safety 27 but not without risks.Recurrence of ureteropelvic junction obstruction, urinary fistula, urinoma and surgical infection are some of the complications of surgery, and relevant complications due to anesthesia should not be forgotten 28,29 .So, pyeloplasty should be indicated as precise as possible.
A prospective study with a large numbers of patients followed with conservative treatment showed the need for conversion to surgical treatment in 22% of patients during a followup period of 10 years 6 .By adopting similar approach, our study showed that in only 6 from 26 patients (23%) it was necessary the conversion from clinical observation to surgery procedure during a follow-up period of 6 years.
Committee and was conducted by analysis of medical records of 116 consecutive children with congenital hydronephrosis diagnosed by prenatal ultrasound and submitted to an investigative protocol.Only patients with hydronephrosis secondary to UPJ obstruction, presenting normal serum levels of urea and creatinine, were included in this study.Clinical follow-up was performed with ultrasound examination during the first week of life to confirm hydronephrosis.Prophylactic antibiotic was introduced until VCUG, performed after the first month of life, confirmed absence of vesico-urethral reflux.At the end of the first month of life the patients were re-evaluated with a new renal ultrasound and the renal function assessed by a diuretic renogram (DTPA) and renal scintigraphy (DMSA).The presence or absence of urinary tract obstruction was defined by values of T1/2 ≥ 20 minutes or T1/2 ≤ 10 minutes, respectively.The indication of surgical treatment of UPJ obstruction was based on the presence of hydronephrosis, obstructive pattern at renogram values and relative renal function inferior than 40%, as defined by scintigraphy.During the clinical follow up of those patients, the surgical approach to correct UPJ stenosis was indicated only when the scintigraphy showed a reduction of the relative renal function (equal or greater than 10%), or in those patients with increasing hydronephrosis documented by ultrasound (reduced thickness of renal parenchyma and an increased anteroposterior diameter of the renal pelvis, associated with obstructive renogram pattern).Patients returned to the hospital every three months during the first year, and every six months during the second year and thereafter annually.Dismembered pyeloplasty technique as described by Anderson and Hynes 7 was performed in all patients who underwent a surgical treatment.

6 FIGURE 1 -
FIGURE 1 -Clinical and anatomic characteristics of 45 new-born with neonatal hydronephrosis due to uretopelvic junction obstruction.