Correlation between Diabetic Retinopathy and the Stage of Peripheral Arterial Disease among Patients with Diabetes Mellitus: A Cross-Sectional Study

Abstract

Background: Diabetes mellitus is associated with both microvascular and macrovascular complications. Diabetic retinopathy (DR) reflects systemic microvascular injury, whereas peripheral arterial disease (PAD) represents a major macrovascular complication. Whether the severity of DR is associated with the clinical severity of lower-extremity PAD is clinically relevant, particularly in resource-limited settings. Objective: To assess the association between the severity of diabetic retinopathy and the clinical stage of lower-extremity peripheral arterial disease among patients with diabetes mellitus. Methods: A hospital-based cross-sectional observational study was conducted in the Department of Vascular Surgery in collaboration with the Department of Ophthalmology at Dhaka Medical College Hospital, Bangladesh, from January 2023 to June 2026. A total of 120 patients aged ≥40 years with type 2 diabetes mellitus and clinically established lower-extremity PAD were included. PAD severity was classified according to the Rutherford classification (stages 2–6), while diabetic retinopathy was graded as no DR, mild non-proliferative DR (NPDR), moderate NPDR, severe NPDR, or proliferative DR (PDR). Clinical and laboratory variables, including duration of diabetes, HbA1c, and serum creatinine, were also assessed. Associations between ordinal variables were evaluated using Spearman's rank correlation coefficient. Results: The mean age of the participants was 59.8 ± 9.6 years, and 94 (78.3%) were male. Diabetic retinopathy was present in 77 (64.2%) patients, including 22 (18.3%) with mild NPDR, 26 (21.7%) with moderate NPDR, 15 (12.5%) with severe NPDR, and 14 (11.7%) with PDR. Rutherford stages 2, 3, 4, 5, and 6 were present in 19 (15.8%), 27 (22.5%), 24 (20.0%), 33 (27.5%), and 17 (14.2%) patients, respectively. The distribution of diabetic retinopathy severity differed significantly across Rutherford stages (Pearson χ²=37.70, df=16, p=0.002). Vision-threatening diabetic retinopathy, defined as severe NPDR or PDR, was present in 29 (24.2%) patients. It was more frequent among patients with chronic limb-threatening ischaemia (Rutherford stages 4–6) than among those with intermittent claudication (Rutherford stages 2–3), occurring in 27/74 (36.5%) and 2/46 (4.3%) patients, respectively. Diabetic retinopathy severity also showed positive correlations with Rutherford stage (ρ=0.49, p<0.001), duration of diabetes (ρ=0.54, p<0.001), HbA1c (ρ=0.48, p<0.001), and serum creatinine (ρ=0.39, p=0.002). Conclusion: Greater severity of diabetic retinopathy was significantly associated with more advanced clinical stages of lower-extremity peripheral arterial disease. The strong ordinal association between retinopathy severity and Rutherford stage suggests that diabetic retinopathy may serve as a clinically relevant marker of systemic vascular disease burden. Larger prospective studies are warranted to determine the temporal relationship and clinical utility of this association.