Introduction
Minimal change nephropathy is called so as the changes are not detectable in the light microscope. It can be detected only using an electron microscope. It is proposed to be caused by altered T-cell response, resulting in damage to the filtering unit of the kidneys. It can affect both children and the adult population. The main symptom is proteinuria which leads to further complications of the nephrotic syndrome. Diagnosis and treatment at the right time would provide a better prognosis.
What Is Minimal Change Nephropathy?
Minimal change nephropathy is also known as minimal change disease. Minimal change nephropathy is a condition affecting the kidneys' glomeruli. It is characterized by the excessive loss of protein in the urine. It is reported to be one of the common causes of nephrotic syndrome.
What Are the Other Terminologies Used Earlier for Minimal Change Nephropathy?
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It was initially called lipid nephrosis due to the presence of lipid-laden macrophages in the proximal tubular cells of the kidney.
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Nil disease, as there is no or little evidence of inflammatory changes in the glomerulus.
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Idiopathic nephrotic syndrome as it shows no association with other conditions such as glomerulonephritis or systemic diseases.
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Other names include:
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Steroid-sensitive nephrotic syndrome.
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Steroid-responsive nephrotic syndrome.
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What Are Glomeruli?
The glomerulus, the Greek word, means “to filter.” Glomeruli are the cluster of small looping blood vessels lined by endothelial cells; podocytes line the outer surface of the glomerular capillaries. The function of the glomeruli is filtration. Any disease affecting the glomerulus would affect the filtration capacity of the kidney leading to nephrotic syndrome.
What Is Nephrotic Syndrome?
Nephrotic syndrome is a disease of the kidney which is characterized by excessive proteinuria (loss of protein in the urine). It is caused due to any injury or alteration in the glomeruli of the kidneys.
What Is the Epidemiology of Minimal Change Nephropathy?
It is reported to be more prevalent in the Asian population, followed by European and North American populations. It is more common in children around the age of two to six years. It is also common in men and older women with a long-term history of non-steroidal anti-inflammatory drugs (NSAID). About 10 % to 25 % of the cases of nephrotic syndrome in adults result from minimal change disease.
What Is the Etiology of Minimal Change Nephropathy?
The exact etiology of this condition is unclear. It is reported to be an idiopathic condition, but few studies have shown some evidence that it could develop about;
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Allergic reactions (reactions to a bee sting).
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Post upper respiratory tract infections.
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In people under NSAIDs for a prolonged period.
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Following ingestion of gold, penicillamine, mercury, ampicillin, etc.,
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May develop as a consequence of cancer conditions (Hodgkin's lymphoma, leukemia, etc.,)
What Is the Pathogenesis of Minimal Change Nephropathy?
Studies have shown that the T lymphocytes play a major role in the development of the disease. T-cells were found to release a certain factor called glomerular permeability factor (GPF) and cytokines; these factors would mediate the abnormal glomerular permeability. Thereby causing injury to the glomeruli resulting in excessive loss of protein in the urine (proteinuria) and impaired kidney function.
What Are the Signs and Symptoms of Minimal Change Nephropathy?
The symptoms include,
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Heavy Proteinuria - Abnormal and excessive excretion of plasma proteins in the urine, more specifically albumin.
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Generalized Edema - It is the collection of fluid in the interstitial spaces leading to swelling of the soft tissues of the body. The edema is generalized, primarily affecting the hands and feet.
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Hypoalbuminemia - Decreased serum albumin levels occur as a result of excessive loss of albumin in the urine.
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Weight Gain - This happens due to water retention in the body as a consequence of impaired kidney function.
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Sodium Retention - Sodium retention in patients with minimal change disease occurs due to two reasons:
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One is due to hypoalbuminemia; there will be reduced plasma oncotic pressure causing the fluid from the blood vessels to move to the interstitial space causing hypovolemia. To compensate for this renin-aldosterone mechanism is stimulated in the kidneys leading to more sodium retention.
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The other possible reason could be the inability of the damaged glomeruli and the diseased kidney to eliminate sodium.
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Hyperlipidemia - Increased serum lipid levels occur due to hypoalbuminemia; more lipoproteins will be secreted in the body, causing hyperlipidemia.
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Risk of Infection - These patients show a high risk for infection due to increased loss of antibodies in the urine, decreased ability to synthesize antibodies, and generalized edema resulting from water retention would serve as an ideal environment for the growth of bacteria.
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Thyroid Dysfunction - Few studies report that in patients with minimal change disease, there is a loss of T3, T4, and thyroid binding globulin in the urine. Hence reduced serum T3 and T4 levels.
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Risk of Hemostatic Disorders -These patients exhibit a high risk for thromboembolic events due to increased platelet aggregation, increased production of factors V and VIII, and increased procoagulant activity.
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Hypertension - It may occur as a result of impaired kidney function and altered compensatory mechanisms.
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Acute Kidney Failure - This is the sudden failure of the kidneys to perform their physiological activities. Though it is rare in patients with minimal change disease, it can affect around 10 to 25 % of adults. It has been proposed that pre-existing conditions, hypovolemia, chronic use of NSAIDs, and high blood pressure could be the risk factors.
How Is Minimal Change Nephropathy Diagnosed?
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History: Asking for medical history from the patient to understand the symptoms and the history of medications will help in planning further investigations.
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Clinical Examination: Examination of the patient for the presence of edema in the lower half of the body (in mild cases), periorbital edema, and generalized edema in severe cases.
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Urine Test:
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Proteinuria - Presence of protein in the urine.
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Hyperalbuminuria - Presence of increased albumin in the urine.
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Blood Test:
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Hypoalbuminemia - Decreased serum albumin in the blood.
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Hyperlipidemia - Increased lipid levels in the serum.
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Hypercholesterolemia - Increased serum cholesterol levels.
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Microscopic Examination: Under light microscopy, the tissue does not elicit any change. The changes can be seen only under the electron microscope. The loss of epithelial foot processes along with the obliteration of the slit-pore membrane, can be appreciated under the electron microscope.
How Is Minimal Change Nephropathy Managed?
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Immunosuppressant Drugs - The first line of treatment in children and adults with minimal change in nephropathy is corticosteroids such as Prednisolone are given to suppress the T-cell activity. Other immunosuppressants like Mofetil, Rituximab, and Calcineurin inhibitors can be tried in children developing intolerance to steroids.
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Diuretics - Can be given to eliminate the retained water and to relieve edema.
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Albumin - Albumin can be administered intravenously to compensate for the excessive loss of urine.
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Antihypertensives - Antihypertensive medications such as ACE (angiotensin-converting enzyme) inhibitors and ARBs (angiotensin-receptor blockers) can be given to control blood pressure.
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Statins - Can be given to control the increased cholesterol profile in the blood.
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Diet Restriction - Low salt diet is indicated to help control the disease.
What Is the Prognosis of Minimal Change Nephropathy?
It shows a good prognosis with prompt treatment in both children and adults. Studies state that children show a much better prognosis than adults and older people as children respond relatively faster to the steroids than the older population, who are often associated with other health complications that affect the prognosis. However, if left untreated, it may progress to renal failure.
Conclusion
Minimal change in nephropathy results in nephrotic syndrome with increased loss of protein in the urine. It is called the histopathological lesion of the kidney, as the changes are detectable only under the electron microscope. Though it produces multiple symptoms in a shorter duration, the prognosis is good with early diagnosis and timely management.
