Postnatal follow-up of patients with antenatal hydronephrosis

Introduction: Hydronephrosis is defined as the expansion of the renal pelvicalyceal system and is the most frequently detected genitourinary system anomaly in the antenatal period. HN, which can be detected early in prenatal follow-up thanks to advanced diagnostic imaging methods, may regress over time or progression in the degree of HN may be seen in follow-up. Studies have not reached a consensus regarding the postnatal evaluation and follow-up plan for infants with antenatal HN. Babies diagnosed with HN during prenatal follow-up are at risk of recurrent urinary tract infections, damage to the renal parenchyma, growth and development retardation, impaired renal function and renal failure if they are not followed up regularly. İntention: In our study, we aimed to retrospectively evaluate the demographic data, etiologic reasons, prognosis of the patients who were followed up according to the algorithm and to formulate recommendations for the follow-up of the patients. Materials- Methods: Between March 2016 and March 2021, 150 patients who were followed up with a prenatal diagnosis of HN in the Division of Pediatrics, Department of Pediatrics, Division of Pediatric Nephrology, Akdeniz University Faculty of Medicine Hospital between March 2016 and March 2021 and who were not additionally followed up antenatally but were found to have HN in the first 6 months postnatally were included in the study. The study was conducted retrospectively, no investigations were requested from the patients and the data were screened to record antenatal, demographic, biochemical, complete urinalysis, USG, advanced imaging, surgical intervention and follow-up findings at the first 5 years of age. Results: In our study, 117 (78%) of the 150 patients evaluated with a diagnosis of antenatal HN were male and 33 (22%) were female, with a male to female ratio of 3.54; the median age at first presentation was 1 month (IQR 0-2 months). Hydronephrosis was detected in 116 (77.3%) patients in the antenatal period and in 34 (22.7%) patients in the first 6 months postnatally. Among 116 patients diagnosed with HN in the antenatal period, 65 (56%) were diagnosed by fetal USG performed in the 2nd trimester and 51 (44%) in the 3rd trimester. At the time of admission (month 0), 144 of 150 patients underwent USG and it was found that 75 (52%) patients had unilateral HN, 61 (42.3%) had bilateral HN, and 8 (5.7%) patients did not have HN detected in the antenatal period on USG performed at admission. The rate of left renal hydronephrosis in patients with unilateral HN was 73.3%. It was observed that 76 (50.7%) of the patients had no history of UTI during follow-up, 56 (37.3%) had a history of UTI with fever and 18 (12.0%) had a history of UTI without fever. The incidence of UTI in patients with severe HN was higher than in patients with mild HN (73%/36%). In our study, physiologic/transient HN was the most common diagnosis with a rate of 48.7%, followed by UPBD with 14.7%, VUR with 8.7%, UVBD with 6.7%, double collecting system with 6%, MKDPB with 6%, PUV with 4%, renal agenesis with 3.3% and other diagnoses with 2% in postnatal follow-up. In the USG performed at admission, it was observed that the frequency of obstructive pathologies increased as the severity of HN increased according to both the measurement of the PACS and the SFU classification system, and the predictive power of ultrasonography findings in predicting the diagnosis of VUR was inadequate. It was determined that 90.6% of the patients with HN whose HN findings completely resolved within the first year had mild grade HN and 3.1% had severe grade HN on the USG performed at admission, and 63.2% of the patients whose HN findings completely resolved within the second year had mild grade HN and 5.3% had severe grade HN on the USG performed at admission. In our study, 59 patients underwent VCUG and reflux was detected in 23 of them. Among the patients in whom reflux was detected, 19 had a history of DMSA scintigraphy and 11 of these patients had scarring. Of the 11 patients with reflux detected on VCUG, 9 had high-grade VUR and 2 had low-grade VUR, and the risk of scar development in high-grade VUR was 2.72 times higher than in low-grade VUR (grade <3), and this was associated with scar development in the kidney and consequent loss of function in high-grade VUR. In our study, 46 of 150 patients required surgery. Patients diagnosed with UPBD were the most common group requiring surgery with a rate of 41.3%. The need for surgical treatment was significantly increased in patients with severe grade and SFU stage 3-4 HN on admission USG. Conclusions: Although non-pathologic (physiologic/transient HN) HN is detected in the majority of patients with antenatal HN, it is important to detect pathologic HN. It was concluded that patients with severe HN on postnatal USG should be followed up meticulously in terms of urinary tract infection, obstructive pathologies, and renal parenchymal damage; in patients with mild HN, the rate of invasive examinations, repeated and frequent follow-up should be reduced and the Akdeniz University algorithm can be used safely in patients with unilateral HN. Keywords: Hydronephrosis, USG, Postnatal follow-up, Obstructive pathologies