Sarcoidosis can also affect the kidneys. When sarcoidosis affects the kidneys, it is called renal sarcoidosis.
How Can Sarcoidosis Affect the Kidneys?
Renal sarcoidosis can manifest in various ways, ranging from subtle abnormalities to severe kidney dysfunction.
Here are some of the key ways sarcoidosis can impact the kidneys:
* Granulomatous Interstitial Nephritis:
This is the most common kidney manifestation of sarcoidosis. It involves the formation of non-caseating granulomas (small clumps of inflammatory cells) within the kidney's interstitium (the tissue surrounding the tubules and blood vessels). These granulomas can disrupt normal kidney function, leading to inflammation and scarring.
* Hypercalcemia and Hypercalciuria:
Sarcoidosis can lead to elevated levels of calcium in the blood (hypercalcemia) and urine (hypercalciuria).
This occurs because the granulomas in sarcoidosis can produce an active form of vitamin D, which increases calcium absorption from the gut and bone resorption.
High calcium levels can directly damage the kidneys, leading to nephrocalcinosis (calcium deposits in the kidney tissue) or kidney stones. Both of these can impair kidney function over time.
* Kidney Stones (Nephrolithiasis):
As mentioned above, hypercalciuria due to sarcoidosis significantly increases the risk of developing kidney stones.
These stones can cause pain, block urine flow, and lead to recurrent infections, all of which can damage the kidneys.
* Glomerulonephritis:
Less commonly, sarcoidosis can directly affect the glomeruli, which are the tiny filtering units of the kidneys.
This condition, known as glomerulonephritis, can lead to protein and blood in the urine, and if left untreated, can progress to kidney failure.
* Renal Vascular Involvement:
In rare instances, sarcoidosis can affect the blood vessels supplying the kidneys, potentially leading to reduced blood flow and kidney damage.
Symptoms of Renal Sarcoidosis
The symptoms of renal sarcoidosis can be non-specific and may include:
* Fatigue
* Weakness
* Nausea and vomiting
* Loss of appetite
* Increased thirst and frequent urination (due to hypercalcemia)
* Back or flank pain (due to kidney stones)
* Swelling in the legs, ankles, or feet (edema)
* High blood pressure
In some cases, people with renal sarcoidosis may not experience any symptoms until the kidney damage is advanced.
Diagnosis and Treatment
Diagnosing renal sarcoidosis often involves a combination of blood tests (to check kidney function and calcium levels), urine tests, imaging studies (such as ultrasound or CT scan of the kidneys), and sometimes a kidney biopsy to confirm the presence of granulomas.
Treatment for renal sarcoidosis typically focuses on suppressing the inflammation and managing the complications.
This often involves:
* Corticosteroids: These medications are the mainstay of treatment for sarcoidosis and can help reduce inflammation in the kidneys.
* Immunosuppressants: In some cases, other immunosuppressant medications may be used to help control the disease and reduce the need for high doses of corticosteroids.
* Managing Hypercalcemia: Strategies to lower calcium levels may include increased fluid intake, dietary modifications, and medications that inhibit vitamin D production or calcium absorption.
* Kidney Stone Management: Treatment for kidney stones may involve increased fluid intake, medications to prevent stone formation, or procedures to remove existing stones.
* Supportive Care: This includes managing blood pressure, addressing fluid retention, and maintaining a healthy lifestyle.
Living with Renal Sarcoidosis
If you have sarcoidosis, it's important to be aware of the potential for kidney involvement and to discuss any concerns with your doctor.
Regular monitoring of kidney function is crucial, even if you don't have symptoms. Early diagnosis and appropriate treatment can help preserve kidney function and improve overall outcomes for individuals with renal sarcoidosis.