Diabetic Nephropathy

What is Diabetic Nephropathy?

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Diabetic Nephropathy is a common complication of diabetes mellitus in which there is long term damage to the kidneys as a result of long-term poorly controlled diabetes. The renal vessels and the glomerulus (filtering part of the kidney) are the main areas affected. Diabetic nephropathy is characterised by the presence of a protein called albumin in the urine, hypertension (high blood pressure), oedema (swelling), and progressive renal insufficiency.

Statistics on Diabetic Nephropathy?

The incidence of Diabetes Mellitus (DM) in the Western World has increased dramatically over the past two decades. The prevalence of DM in the US rose from 8.9% in 1976 to 12.3% in 1994. This rate of increase is greater for type II than type I diabetes mellitus. Diabetic nephropathy affects 25-45% of patients diagnosed with DM under age of 30 years. It also less commonly occurs in those diagnosed at an older age.

Risk Factors for Diabetic Nephropathy

1. Diabetes Mellitus - Type I and type II 2. Uncontrolled diabetes - Increased rate of progression 3. Hypertension- Increased rate of progression 4. Smoking- Accelerates the deterioration in renal function

Progression of Diabetic Nephropathy

The natural history of this condition is quite predictable, more so in the case of type I diabetes mellitus. The first change is an increase in glomerular perfusion and renal hypertrophy that occur in the first two years of illness. Over this time glomerular filtration increases. Over the next three years, GBM thickening, glomerular hypertrophy and expansion of the mesangium will return this increase to normal. After 5-10 years of type I DM (more variable in type II) patients will begin to pass small amounts of protein (microalbuminuria) in the urine. Blood pressure may begin to rise at this point. Without intervention, the microalbuminuria will progress to gross amounts of protein in the urine (proteinuria). The natural history of type II DM differs from type I in three important ways: 1. Microalbuminuria (small but abnormal amounts of albumin ) or overt nephropathy (nerve breakdoown) may be present at diagnosis of type II DM reflected the long asymptomatic period common to patients with type II diabetes. 2. Hypertension more often co-exists with proteinuria in patients with type II DM. 3. Microalbuminuria is less predictive of deterioration to ESRD in type II diabetics.

How is Diabetic Nephropathy Diagnosed?

Patients may need to undergo the following tests to assess the possible progression towards diabetic nephropathy. These include: 1. Blood tests to assess urea, electrolytes and creatinine to assess for any obvious renal impairment. 2. Glycated Hb to assess diabetes control.

Prognosis of Diabetic Nephropathy

Diabetic nephropathy is a serious complication of diabetes mellitus. It occurs at an earlier stage and most frequently in those with poor control of their diabetes. With appropriate therapy, the deterioration of kidney function can be slowed, but will lead to renal failure over a number of years. Judicious management of blood pressure, glucose stability and overall health will slow the progression of this condition.

How is Diabetic Nephropathy Treated?

The ultimate treatment is prevention. The following measures should be undertaken in all patients with diabetes with or without diabetic nephropathy:

Stabilisation of blood glucose concentration
Strict blood pressure control (preferably <130/85 in diabetics without proteinuria)
Administration of ACE inhibitors

Once microalbuminuria is present, the above measures are still recommended but their impact on disease progression is somewhat reduced. The recommended target blood pressure in those with proven microalbuminuria is <120/80 to adequately slow the disease process. The dose of ACE inhibitors should be titrated against urinary protein such that proteinuria is eliminated or minimised without overt side-effects. If the side-effects of ACE inhibitors becomes intolerable, other agents such as angiotensin II receptor blockers or calcium channel blockers can be used.

Diabetic Nephropathy References

Braunwald, Fauci, Kasper, Hauser, Longo, Jameson. Harrison's Principles of Internal Medicine. 15th Edition. McGraw-Hill, 2001
Cotran, Kumar, Collins 6th edition. Robbins Pathologic Basis of Disease. WB Saunders Company. 1999.
Kumar P, Clark M. Clinical Medicine, 5th Ed, WB Saunders, 2002.
Longmore M, Wilkinson I, Torok E. Oxford Handbook of Clinical Medicine, 6th Ed, Oxford University Press, 2004.