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Niere und Sarkoidose: Was müssen Sie darüber wissen?

Sarcoidosis is an autoimmune multi-systemic inflammatory disease of unknown etiology. The hallmark of this disease is the presence of non-caseating granulomasthat look like grains of sand affecting multiple organs. The presence of manygranulomas then affects the normal functioning of the organs in which they are present. It can affect almost all organs of the body, but more often it affects the lungs, mesotheliomaadrenal glands, lymph nodes, eyes and skin.

How common is it?
Sarcoidosis occurs more often in young adults of both sexes, it is more common in women with a peak incidence at the ages of 25-35. A second peak is observed in women over 50 years of age and is rare in children. Sarcoidosis occurs throughout the world in all tribes. Its average frequency is 16.5 per 100,000 men and 19 per 100,000 female population.

What are the main clinical indications?
When granulomas grow or accumulate in one or more organs of the body then they can cause various symptoms, depending on which organs are affected. Symptoms usually appear gradually. The lungs are the most common organ affecting 90% of the cases. When they are affected, symptoms such as cough, fever, weight loss and fatigue may occur.  Also, 25% of patients with sarcoidosis will develop several skin lesions during the disease. "Nodular erythematous " is a characteristic lesion, usually seen in the acute onset of the disease and disappears within a few weeks or a few months of its occurrence. in about 1/3 of the patients the eyes are affected with iridocyclitis being more common.

How often can sarcoidosis affect the kidney?
This is uncertain. Studies give very different numbers because of the heterogeneity of the renal involvement and because renal involvement is often asymptomatic. Renal involvement in sarcoidosis patients is estimated at approximately 35 to 50% of patients.

How does the kidney affect in this case?
Common manifestations to a sarcoidosis patient resulting from the kidney are:
1. hypercalciuria (large amounts of calcium in the urine)
2. nephrocalcinosis (a generalized calcium deposition in the kidneys)
3. nephrolithiasis
Often these manifestationsoccur due to the disorder in calcium metabolism due to sarcoidosis.
4. the kidney can also participate directly with the occurrence of granulomatous interstitial nephritis (which occurs in 7 to 20% of sarcoidosis patients)
5. the appearance of some form of vasculitis in the kidney due to sarcoidosis
6. rarely with glomerulonephritis (inflammation in the glomerulus). Common manifestations of the kidney are also albuminuria (proteinuria), microscopic hematuria, glucosuria (sugar in the urine).

How does sarcoidosis cause neovascularization?
In the granulomas of sarcoidosis, activated vitamin D is produced. This increases the absorption of calcium from the intestine and kidneys, resulting in an increase in the amount of calcium in the blood that sometimes leads to an increase in its blood concentration (hypercalcemia). The above calcium is excreted by the kidneys, while its high concentration produces nephrolithiasis with more frequent calcium oxalate or calcium phosphate (14% of patients with sarcoidosis), neovascularization and polyuria.

I have sarcoidosis. What is the prognosis with regard to my kidney?
The chance of developing chronic end-stage renal disease is very low. If it occurs, it will be due to nephropathy due to hypercalcemia and even prolonged and untreated hypercalcemia, a chronic condition that can be predicted.

I have sarcoidosis. What should I look out with regard to my kidney?
Your treating physician is aware that a patient with sarcoidosis should be examined. Blood calcium testing, 24-hour urine calcium levels, renal function control with urea creatinine and urinalysis as well as kidney ultrasound are the proper tests to monitor the potential renal involvementin sarcoidosis.

By the Scientific Director Aristides Paraskevopoulos

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