Association between venular tortuosity and impaired renal function in an ageing population.

Introduction Microvascular damage is a common feature of eye and kidney disease. Renal microvascular damage is not easily identified, so advancements in imaging the retinal microvasculature may offer opportunistic, non-invasive evaluation of similar microangiopathic changes in the kidney. Renal decline increases with age and can lead to chronic kidney disease (CKD) and early detection is beneficial. We assessed retinal microvascular parameters against renal function measures in the NICoLA. Methods Retinal microvascular parameters (central retinal arteriolar/ venular equivalents (CRAE/CRVE) arteriolar to venular ratio (AVR), fractal dimension and tortuosity) were measured from optic disc centered fundus images and analysed using semi-automated software. Linear and logistic regression models were used to assess associations between microvascular parameters and the continuous variables of renal function (eGFR Creatinine (SeCr) and Cystatin C (Scys)) and the binary trait of CKD status, respectively. Minimally adjusted models included age and gender with fully adjusted models also including diabetes, smoking, alcohol, education, body mass index, antihypertensive medication, mean arterial blood pressure, triglycerides, high and low-density lipoproteins. Results Retinal and renal measures were available for 1,860 of the 3,518 NICoLA participants. In unadjusted, minimally adjusted and fully adjusted linear regression models, no significant associations were detected between CRAE, CRVE, AVR, fractal dimension or tortuosity and eGFRSeCr or eGFRScys. CKD status, defined by eGFRSeCr < 60 mL/min per 1.73 m2, was significantly associated with venular tortuosity in all models (β=0.8; 95%CI: 1.3, 4.1; P=0.004). There was no significant associations detected between CKD status and any of the other retinal parameters assessed. Conclusion Our findings support previous reports that variation in retinal venular geometry may be indicative of renal dysfunction. These non-invasive retinal measures may help identify early mechanistic pathways for microvascular complications in individuals at high risk of renal disease early in the course of diabetes.