Early Predictors of Surgical Intervention in Antenatally

Abstract

Background:

Antenatally detected hydronephrosis (ANH) remains one of the most common fetal anomalies identified on ultrasonography. Determining which infants will require surgical intervention remains clinically challenging. This study aimed to identify early postnatal predictors of surgery among infants with ANH managed at a tertiary pediatric urology centre.

Methods:

We conducted a prospective cohort study between January 2019 and December 2023, enrolling 212 neonates with ANH confirmed postnatally. Serial ultrasonography, diuretic renography, and voiding cystourethrogram (VCUG) were performed as indicated. Key predictors—anteroposterior pelvic diameter (APD), Society for Fetal Urology (SFU) grade, differential renal function (DRF), and drainage half-time (T½)—were correlated with eventual need for pyeloplasty.

Results:

Of 212 infants (male:female ratio 3.2:1), 54 (25.5%) required surgery within the first two years. Mean initial APD was significantly higher in the surgical group (23.4 ± 5.8 mm) vs. conservative group (12.9 ± 4.7 mm; p < 0.001). SFU Grade III–IV and DRF < 40% were independent predictors of surgery on multivariate analysis (OR 5.2 and 4.3 respectively). A combined APD > 18 mm with T½ > 20 min predicted intervention with 88% sensitivity and 82% specificity.

Conclusions:

Early postnatal APD, SFU grade, and drainage curve parameters reliably predict need for surgical correction in ANH. Integrating these predictors into follow-up algorithms can optimize timing of pyeloplasty and reduce unnecessary imaging.

Keywords: antenatal hydronephrosis, pyeloplasty, predictors, ultrasound, paediatric urology, renal function

Introduction

Antenatally detected hydronephrosis is identified in approximately 1–5% of all pregnancies. While many cases resolve spontaneously, a subset progress to significant obstruction requiring surgical correction, typically pyeloplasty.¹

The central dilemma in paediatric urology lies in discriminating observation-worthy hydronephrosis from those needing timely intervention—before function declines yet avoiding overtreatment.²

Despite the use of SFU grading, APD thresholds, and nuclear imaging, predictive precision remains inconsistent across populations.³,⁴ This prospective cohort study was designed to derive clinically usable early predictors of surgical requirement in ANH within an Indian tertiary paediatric setting.

Methods

Study Design and Participants

• Design: Prospective cohort study

• Setting: Department of Paediatric Urology, [Institution Name Redacted], from Jan 2019 to Dec 2023

• Inclusion: Neonates with antenatally diagnosed unilateral or bilateral hydronephrosis confirmed postnatally (APD ≥ 7 mm).

• Exclusion: Multicystic dysplastic kidneys, posterior urethral valves, associated syndromes, or incomplete follow-up.

  
  

Evaluation Protocol

• Ultrasound: Performed at day 5–7, 6 weeks, and at 3-month intervals.

• Grading: SFU system (Grade I–IV).

• Nuclear Renography: Diuretic (Tc-99m MAG3) scans at 6 weeks and thereafter as indicated.¹

• VCUG: Selectively in bilateral cases or suspected reflux.

• Outcome: Need for surgical intervention (Anderson–Hynes pyeloplasty) determined by functional deterioration (DRF drop > 10%), worsening hydronephrosis, or symptomatic presentation.

  
  

Statistical Analysis

Data were analyzed using SPSS v26. Continuous variables were compared using t-test; categorical data via Chi-square. Multivariate logistic regression identified independent predictors of surgery. ROC curve established optimal cutoff for APD and T½. P < 0.05 was considered significant.

Results

Demographics

Out of 212 infants, 162 (76.4%) were male. Mean gestational age was 38.1 weeks; mean birth weight 2.9 kg. Hydronephrosis was unilateral in 174 (82%) and bilateral in 38 (18%).

Baseline Characteristics

Figure 1: ROC Curve

Predictive Modeling

On multivariate regression, three parameters remained significant:

Figure 2: Patient Flowchart

Discussion

Our data reaffirm that initial postnatal APD, SFU grade, and drainage curve parameters serve as strong predictors for surgical need.¹,² While prior studies have proposed variable APD cutoffs (10–20 mm), our ROC-derived value of 18 mm achieved robust predictive accuracy in an Indian cohort—aligning with findings from Nguyen et al. (2010) and Song et al. (2018).¹,⁴,⁶

Clinical Implications

• Streamlined surveillance: Infants with APD < 10 mm and SFU I–II can safely undergo extended ultrasound follow-up without renography.¹

• Timely surgery: Those with combined predictors (APD > 18 mm, DRF < 40%, T½ > 20 min) should be considered early for pyeloplasty before function declines.

• Parental reassurance: Quantitative risk estimation helps mitigate anxiety and improve compliance with follow-up.

Limitations

Single-centre design and limited long-term renal outcome data are acknowledged. Multi-institutional collaboration could validate these thresholds further.

Conclusion

Among neonates with antenatally detected hydronephrosis, initial postnatal APD > 18 mm, SFU III–IV, and DRF < 40% independently predict surgical requirement.²,³ A composite algorithm based on these parameters can safely guide individualized follow-up and surgical timing in paediatric urology practice.

References

• Nguyen HT, Herndon CD, Cooper C, Gatti J, Kirsch AJ, Kokorowski P, et al. The Society for Fetal Urology consensus statement on the evaluation and management of antenatal hydronephrosis. J Pediatr Urol. 2010;6(3):212–31. doi:10.1016/j.jpurol.2010.02.205.

  
  

• Arora S, Gupta DK, Srinivas M, et al. Predictors for the need of surgery in antenatally detected ureteropelvic junction obstruction: a prospective study. Pediatr Surg Int. 2015;31(12):1103–1110. PubMed ID: 25986208.

  
  

• Onen A. Grading of hydronephrosis: an ongoing challenge. Front Pediatr. 2020;8:458. doi:10.3389/fped.2020.00458.

  
  

• Zhang L, et al. Diagnostic value of anteroposterior diameter of renal pelvis to predict significant uropathy: a systematic analysis. J Pediatr Urol. 2018;14(3):230–237. (Relevant review — APD cutoffs vary 18–27 mm).

  
  

• Sidhu G, Beyene J, Rosenblum ND. Outcome of isolated antenatal hydronephrosis: a systematic review and meta-analysis. Pediatrics. 2006;118(2):586–593. doi:10.1542/peds.2005-2009.

  
  

• Sen S, et al. Outcome of patients with antenatally diagnosed renal pelvic dilatation: APD cut-offs and predictive performance. J Pediatr Surg. 2022;57(5):985–992.