Kidney Atrophy: Causes, Risks, and Diagnosis Explained

Renal atrophy

I experienced lower back pain six months ago, and upon examining my kidneys, it was found that my left kidney measures 9 cm while my right kidney measures 12.2 cm.
Both blood and urine tests were normal.
The doctor was uncertain whether the left kidney atrophy was congenital or acquired.
After another six months, a follow-up examination showed that the left kidney is now 8.2 cm, while the right kidney remains over 12 cm.
Blood and urine tests are still normal.
If the atrophy is acquired, is it likely to cause atrophy in the other kidney as well? If it is congenital, would it not affect the other kidney? Is further testing necessary to determine whether the atrophy is congenital or acquired? How can one ascertain whether the atrophy is congenital or acquired?

jet, 20~29 year old female. Ask Date: 2008/10/08

Dr. Wang Weijie reply Internal Medicine

Hello, the normal size of a kidney is approximately 10-12 centimeters, and its shape resembles that of a fava bean.
Your left kidney is indeed smaller in size.
Distinguishing whether this is due to congenital atrophy or acquired atrophy is quite challenging.
It may be caused by chronic inflammation leading to kidney atrophy or vascular changes affecting the kidneys.
The formation of kidney lesions can be inferred from changes in urine, such as the presence of proteinuria or hematuria.
However, your blood tests show normal kidney function, and urine screening is normal.
It may be advisable to continue monitoring and follow-up, with regular (approximately every six months) kidney function tests and urine examinations.
Additionally, it is important to avoid actions and behaviors that could harm the kidneys, such as using unverified remedies, unknown herbal medicines, pain relievers, and being mindful of dietary adjustments.
Wishing you health and safety.

Reply Date: 2008/10/08

More Info

Understanding kidney atrophy, particularly in the context of your situation, involves recognizing the potential causes, risks, and diagnostic approaches to differentiate between congenital (or developmental) and acquired (or secondary) causes of renal atrophy.

Kidney Atrophy Overview:
Kidney atrophy refers to the reduction in size of one or both kidneys, which can occur due to various factors. In your case, the left kidney has decreased in size from 9 cm to 8.2 cm over six months, while the right kidney remains stable at 12.2 cm. Normal blood and urine tests are reassuring, but the size discrepancy raises questions about the underlying cause.

Causes of Kidney Atrophy:
1. Congenital Causes: Some individuals are born with one kidney that is smaller than the other (renal hypoplasia). This condition is often asymptomatic and may not lead to any functional impairment of the larger kidney.

2. Acquired Causes: Kidney atrophy can also result from various acquired conditions, including:
- Chronic Kidney Disease (CKD): Long-standing conditions such as hypertension or diabetes can lead to kidney damage over time.

- Obstruction: Conditions that block urine flow (like kidney stones or tumors) can cause damage to the affected kidney.

- Ischemia: Reduced blood flow to the kidney due to vascular diseases can lead to atrophy.

- Infections or Inflammatory Diseases: Conditions like pyelonephritis can cause scarring and shrinkage of the kidney.

Risks Associated with Kidney Atrophy:
If the atrophy is acquired, there is a risk that the other kidney may also be affected, especially if the underlying cause is systemic (like hypertension or diabetes). Conversely, if the atrophy is congenital, the other kidney is typically unaffected in terms of size and function, although it may still be at risk if there are systemic health issues.

Diagnosis and Further Evaluation:
To determine whether the atrophy is congenital or acquired, further evaluation may be necessary. Here are some steps that can be taken:
- Imaging Studies: A renal ultrasound or CT scan can provide more detailed information about the kidneys' structure and any potential obstructions or abnormalities.

- Functional Tests: A nuclear medicine scan can assess the function of each kidney, helping to determine if the smaller kidney is functioning adequately.

- Family History and Symptoms: Discussing any family history of kidney disease or related symptoms can provide clues about the congenital nature of the atrophy.

Conclusion:
In your case, since the left kidney has shown a decrease in size and the right kidney remains stable, it is essential to monitor the situation closely. Given that your blood and urine tests are normal, this suggests that the remaining kidney is compensating well. However, it would be prudent to consult with a nephrologist for further evaluation, especially if there are any changes in symptoms or kidney function. They may recommend additional imaging or functional tests to clarify the cause of the atrophy and to ensure that both kidneys remain healthy. Regular follow-up is crucial to monitor kidney health and to address any potential issues early on.

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