Kidneys shrink, a condition known as kidney atrophy, primarily due to a reduced blood supply to the kidneys and/or the loss of nephrons, the functional units responsible for filtering waste.
Here's a more detailed breakdown:
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Reduced Blood Supply (Ischemia): When the kidneys don't receive enough blood, they can't function properly, leading to cell death and shrinkage. This can be caused by:
- Atherosclerosis: Hardening and narrowing of the arteries supplying the kidneys.
- Renal Artery Stenosis: A narrowing of one or both renal arteries.
- Blood Clots: Obstructions in the renal arteries.
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Loss of Nephrons: Nephrons are the tiny filtering units within the kidneys. Their destruction or loss leads to a decrease in overall kidney size. Causes include:
- Chronic Kidney Disease (CKD): A gradual loss of kidney function over time. Many conditions can cause CKD, including diabetes, high blood pressure, and glomerulonephritis (inflammation of the kidney's filtering units).
- Chronic Infections: Persistent kidney infections can damage nephrons.
- Obstruction: Blockage of the urinary tract (e.g., by kidney stones or an enlarged prostate) can lead to backpressure and nephron damage.
- Renal Hypoplasia: A congenital condition where a person is born with a smaller kidney.
Other Contributing Factors:
- Age: Kidneys naturally tend to shrink with age in some individuals.
- Certain Medications: Some medications can be toxic to the kidneys.
In summary, kidney shrinkage usually indicates an underlying problem affecting blood supply or causing direct damage to the kidney's functional units (nephrons). Identifying the cause is essential for managing and potentially slowing down the progression of kidney disease.
