Interrelationship of diabetic neuropathy, retinopathy and nephropathy in type 2 diabetes mellitus: a cross-sectional analysis

To investigate the interrelationships between peripheral neuropathy, diabetic retinopathy (DR), and nephropathy in patients with type 2 diabetes mellitus (T2DM), with a specific focus on how DR severity correlates with the presence and severity of diabetic neuropathy and nephropathy. In this cross-sectional study, adult patients with at least five years’ duration of T2DM and preserved renal function (eGFR ≥ 60 mL/min/1.73 m²) were evaluated. DR was graded using the International Clinical Diabetic Retinopathy Severity Scale, and DME was assessed by spectral-domain optical coherence tomography. Peripheral neuropathy was quantified via nerve conduction studies (NCS), specifically sural sensory nerve action potential (SNAP) amplitude, while nephropathy was evaluated by urinary albumin-to-creatinine ratio (UACR) and eGFR. A total of 155, 138, and 94 patients completed neuropathy, retinopathy, and nephropathy assessments, respectively. Among the 138 participants who underwent fundus examination, 60% had proliferative diabetic retinopathy (PDR) and 32% had diabetic macular edema (DME). A significant inverse correlation was found between SNAP amplitude and both DR severity (p = 0.001) and DME presence (p = 0.001), indicating worse nerve conduction in advanced retinal disease. Patients with DME had a fourfold higher likelihood of impaired SNAP values (OR = 4.0; 95% CI: 1.849–8.653). Additionally, DME presence was associated with significantly higher UACR (p = 0.011), and nephropathy severity showed a mild but significant association with DR stage (p = 0.047). The severity of DR and the presence of DME correlate strongly with peripheral neuropathy and increased albuminuria in T2DM patients, reflecting shared microvascular pathology. Retinal findings, particularly DME, may serve as accessible clinical markers for identifying individuals at elevated risk of systemic microvascular complications.