Diagnostic Utility of Radionuclide Shunt Flow Studies in Pediatric Ventriculoperitoneal Shunt Malfunction with Negative CT and X-ray Findings

Background Ventriculoperitoneal (VP) shunt malfunction is a common complication in pediatric patients with hydrocephalus. Conventional imaging modalities such as computed tomography (CT), magnetic resonance imaging (MRI), and shunt series radiographs often miss certain malfunctions, especially when imaging results are unclear. Radionuclide shunt flow studies (SFS) may provide added diagnostic insight in these cases. Objective To assess the diagnostic contribution of radionuclide SFS in detecting VP shunt malfunctions in pediatric patients with inconclusive conventional imaging results. Materials and Methods This retrospective study included all radionuclide SFS performed between January 2018 and December 2023 at a Children’s Hospital. Imaging results from CT or limited MR, X-ray shunt series, and radionuclide SFS were categorized as positive or negative. Cases identified as positive on radionuclide SFS but negative on conventional imaging ('NM-only positive') were reviewed considering surgical outcomes. Results A total of 109 radionuclide shunt flow studies (SFS) were performed. Among 102 patients with same-day or near-day CT/MR, 25 (22.9%) demonstrated abnormal SFS findings despite negative CT/MR and X-ray shunt series (“NM-only positive”). Thirty-five patients underwent surgery, and shunt malfunction was confirmed in 21; notably, 10 of these (47.6%) were detected solely by SFS. Upright delayed imaging, performed in 38 patients, demonstrated a high negative predictive value (95.8%) with improved discriminatory ability compared with supine imaging alone. Overall SFS sensitivity and specificity were 80% and 33.3%, respectively, with a PPV of 83.3%. Conclusion Radionuclide shunt flow studies provide clinically meaningful diagnostic information in pediatric patients with suspected VP shunt malfunction, particularly when CT and X-ray studies are non-diagnostic. Nearly half of surgically confirmed malfunctions in this cohort were identified exclusively by radionuclide imaging. The addition of upright positional imaging substantially improved negative predictive value and enhanced functional assessment. Standardization of acquisition parameters including gravity-assisted imaging may further optimize the role of SFS in evaluating shunt dysfunction.