Diabetic Nephropathy

The term “Diabetes” was first coined by Araetus of Cappadocia and the term “Mellitus” by Thomas Willis is one of the leading causes of end-stage renal disease in developed countries. If the diabetes is not under control, it will produce renal changes known as diabetic nephropathy (diabetic kidney disease). 

Who Is Likely To Develop This Condition?

1. Poor glycaemic control
2. Long duration of diabetes
3. Pre-existing hypertension
4. Family history of diabetic nephropathy
5. History of smoking
6. Obese people

Changes In The Kidney

Diabetes mellitus produces stepwise changes in the kidney. First, there will be vasoconstriction in the efferent arteriole due to the activation of the renin-angiotensin-aldosterone system resulting in hyperfiltration. So, the glomerular filtration rate will be more in the initial stage. As this stage progresses there will be mesangial expansion and nodular lesions occur which is known as Kimmelstiel – Wilson nodule (Nodular glomerulosclerosis). After this condition, there will be a loss of sialoproteins in the glomerulus leading to the passage of albumin resulting in microalbuminuria and macroalbuminuria. In the end, it will lead to end-stage renal disease. All these changes start to occur after 10 to 15 years of diabetes mellitus.

Clinical features

Usually in the early stage, diabetic nephropathy the patient will be asymptomatic. In the late stage presenting complaints are:

• Passing foamy urine due to proteinuria
• Edema of the leg, ankle, face
• Elevated blood pressure
• Increased frequency of urination
• Loss of concentration

Screening For Diabetic Nephropathy

Screening helps to diagnose the condition at an early stage.

1. A test for the presence of microalbuminuria to be performed annually.
2. At diagnosis in patients with type 2 diabetes (type 2 diabetes usually remains asymptomatic for a longer period).After 5 years of diagnosis with type 1 diabetes.
3. Early morning urine measured for albumin: creatinine ratio(ACR). 
4. If the microalbuminuria is positive in 2 out of 3 tests and ACR > 30mg/mmol creatinine, it confirms the diagnosis of nephropathy.   

Conditions producing microalbuminuria to be ruled out:

• Urinary tract infection
• Congestive heart failure 
• Febrile illness
• Vigorous exercise

Management

1. Angiotensin-converting enzyme inhibitors seem to reduce the risk of the development of the end-stage renal disease. It is to be started at the diagnosis of microalbuminuria.
2. Angiotensin II  receptor blockers seem to be beneficial.
3. If these drugs are not tolerated, calcium channel blockers such as Diltiazem and Verapamil can be used.
4. Hyporeninemic hypoaldosteronism occurs in diabetic nephropathy due to injury to the juxtaglomerular apparatus. So there will be associated renal tubular acidosis.
5. In the above condition, alkalinizing agents such as Shohl’s solution may be used.
6. Hyperkalemia occurs due to renal disease and drug usage should be monitored.
7. A low dose of insulin is given if there is a development of nephropathy.
8. Low protein diet.
9. If it is in the end-stage, dialysis or renal transplantation helps to survive the patients.

Prevention

• Good glycaemic control.
• Maintaining blood pressure.
• Regular physical exercise.
• Low salt diet.
• Weight reduction. 
• Avoid smoking.

References

1. Harrison’s Principles Of Internal Medicine, 20th ed.
2. Davidson Principle and Practices of Medicine 20th ed
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3749019/

Author’s Footnote

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