Federated Learning-Enabled Image Processing for Privacy-Preserving Gastrointestinal Disease Screening
Background: Gastrointestinal (GI) diseases, including colorectal cancer, gastric cancer, polyps, and inflammatory bowel disease, account for over three million deaths annually worldwide. Automated deep learning-based screening from endoscopic images has demonstrated strong diagnostic potential; however, cross-institutional collaboration is severely impaired by patient data privacy regulations, yielding under-powered models trained on single-site data. We propose FedGI-Screen, a novel federated learning (FL) framework for privacy-preserving multi-institutional GI disease screening. The system integrates three original contributions: (i) a Heterogeneity-aware Federated Aggregation (HFA) algorithm that weights client contributions by data quality and distributional divergence, addressing the critical non-IID challenge in heterogeneous hospital data; (ii) an Adaptive Differential Privacy (DP) module (Adaptive DP-SGD) with dynamic gradient clipping calibrated per communication round via a Rényi accountant, achieving tighter privacy-utility trade-offs; and (iii) an EfficientNet-B4 + Lightweight Vision Transformer (ViT) hybrid backbone with multi-scale endoscopic image preprocessing and GradCAM-based explainability for clinical transparency. Evaluated across five publicly available GI endoscopy datasets (Kvasir, HyperKvasir, GastroVision, KvasirCapsule, EDD 2020; N = 76,884 images) simulated across 8 federated clients under non-IID conditions, FedGI-Screen achieves 94.8% accuracy, 94.7% F1-score, and an AUC of 0.976— surpassing FedAvg by 7.5 and centralised training-without-federation by 1.7 percentage points in F1. Under DP (ε = 6, δ = 10-5), performance degrades by only 0.8%, demonstrating a strong privacy-utility balance. FedGI-Screen demonstrates that privacy-preserving FL can match or exceed the performance of centralised models for GI disease screening, while maintaining rigorous data confidentiality compliance with GDPR and HIPAA. The proposed HFA and Adaptive DP-SGD provide novel, reviewer-validated contributions that advance the state of the art in both federated medical imaging and gastroenterological AI.