Overview

• Nephropathy may already be established at presentation in type 2 patients and is a common long-term complication for those with type 1 diabetes

• An increasing proportion of patients are living long enough to develop end stage renal failure, requiring expansion of renal replacement services

• Progression of renal impairment is reduced through control of blood pressure, glycaemia and lipids, and angiotensin converting enzyme inhibition

• Angiotensin converting enzyme inhibitors should be offered to all patients with any degree of albuminuria unless contraindicated

• Monitoring of renal function is an important task for primary care, and thresholds for referral to secondary care should be locally agreed and widely understood

• Renal impairment affects other aspects of diabetes management including choice of drugs and dosages

Introduction

Despite improvements in early detection, prevention, and treatment, diabetic nephropathy is still a major cause of mortality and morbidity. At 25 years from diagnosis of diabetes, around one-third of type 1 patients and a fifth of those with type 2 have end stage renal failure, although these figures are improving. The development of proteinuria is usually the first indication. Worsening renal function makes associated hypertension more difficult to control, leading to more generalised vascular disease and further renal damage. Untreated, renal function may deteriorate to the point of dialysis dependence typically over a period of years.

Looking on the brighter side, urinalysis detects at an early stage a problem whose natural history can now be modified, and where this is not possible or unsuccessful, adequate quality of life can usually be maintained through dialysis or transplantation. Mortality rates in dialysis and transplant patients are falling. Urinary albumin can now be detected at concentrations lower than that possible through conventional urinalysis. As discussed below, this 'microalbumin' signals the need for active measures to control risk factors and prevent further progression.

Epidemiology

Diabetic nephropathy is the most common specific primary renal diagnosis in patients entering UK programmes for renal replacement therapy (RRT), accounting for around 22% of new cases in 2006. The ratio of men to women is 1.6, due to accompanying renovascular disease which is commoner in men. The prevalence in the population is increasing, reflecting the rising prevalence of diabetes, improved survival and treatment, and a rise in referral rates for RRT particularly in the type 2 population, with better access to dialysis units.

Van Dijk and colleagues describe the variation across different European centres (Van Dijk et al. 2005). Their figures show a steady rise in incidence of RRT throughout the 1990s, particularly among type 2 patients, where an increase of nearly 12% per year was observed (Figure 12.1). In the older age groups the ratio of men to women increased during this decade. Improved mortality rates from cardiovascular disease may partly explain this trend. Whilst survival rates for dialysis patients are generally improving, mortality among those with diabetic nephropathy is still higher than in those with other causes of renal disease, partly due to co-morbidity including cardiovascular disease.

The cyclical nature of causation in diabetic nephropathy (Boxes 12.1 and 12.2) makes it extremely worthwhile as a preventive endeavour, because the benefits (e.g. of blood pressure control) feed back on themselves in the long run.

Box 12.1 Breaking the cycle

Hypertension and vascular disease

Hypertension and vascular disease

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