Hybrid 99mTc-DTPA Dynamic Scintigraphy and SPECT/CT Overturn Presumed Renal Agenesis by Characterizing a Functioning Pelvic Ectopic Kidney in Pediatric VACTERL Association: An Observational Analytic Study

Abstract

Background: Renal anomalies occur in over 60% of children with VACTERL association, and ultrasonography often misses pelvic ectopia, leading to false diagnoses of renal agenesis. Distinguishing agenesis from functional ectopia is important before major spinal surgery.

Objective: To characterize differential renal function and anatomical location in a child with suspected VACTERL association and sonographically presumed renal agenesis, using hybrid 99mTc-DTPA dynamic scintigraphy and SPECT/CT.

Methods: A 4-year-old girl with thoracic hemivertebra, secundum atrial septal defect, thoracolumbar scoliosis (Cobb angle 32°) and a non-visualized left kidney on screening ultrasound underwent dynamic planar 99mTc-DTPA scintigraphy (74 MBq) followed by low-dose hybrid SPECT/CT at Dr. Hasan Sadikin General Hospital, Bandung, Indonesia. Differential renal function (DRF), Gates glomerular filtration rate (GFR) and renographic drainage kinetics were evaluated.

Results: Planar scintigraphy overturned the diagnosis of renal agenesis by showing functioning tissue in both kidneys (DRF 34.6% left vs 65.4% right; net counts 5,873 vs 11,092 cpm). Gates GFR was 21.2 mL/min for the left and 40.0 mL/min for the right kidney (global 61.2 mL/min; 209.8 mL/min/1.73 m² normalized to body surface area). The left renogram showed delayed transit (Tmax 17.0 vs 11.0 min; retention index 0.897 vs 0.577). SPECT/CT localized the functioning left kidney to the pre-sacral pelvis, anterior to S1–S3, supporting a posterior-only approach to spinal instrumentation.

Conclusion: Hybrid 99mTc-DTPA scintigraphy and SPECT/CT distinguished a functioning pelvic ectopic kidney from presumed renal agenesis, quantified 34.6% viable renal function and reduced the risk of intraoperative vascular injury during spinal deformity correction.