Kidney involvement in sarcoid
| Classification according to ICD-10 | |
|---|---|
| D86 + | Sarcoid |
| N16.2 * | Renal tubulo-interstitial disease in blood disorders and disorders involving the immune system - Renal tubulo-interstitial disease in sarcoid |
| ICD-10 online (WHO version 2019) | |
The Sarcoidosis is a multisystem disease of unknown cause that with microscopic nodules ( granulomas accompanied) and can affect all organ systems. In contrast to tuberculosis, there are no dead cells ( non-casing granulomas ) in the granulomas . The incidence peak of the disease is around 40 years of age. The disease is chronic with phases of changing activity and may require long-term treatment with cortisone . The diagnosis can also be made as a chance finding during a lung x-ray examination.
Kidney involvement in sarcoid is rare. Depending on the definition of kidney involvement ( hematuria , nephrocalcinosis or renal insufficiency ), 0.7–9.7% of patients are affected. The frequency of an increased calcium level in the blood ( hypercalcemia ) is given as 10–20%, the frequency of increased calcium excretion in the urine ( hypercalcuria ) is around 50%. Kidney involvement can also be the first and even the only manifestation of sarcoid.
The most common cause of kidney damage in sarcoid is calcification of the kidneys ( nephrocalcinosis ). Less common causes are nodular inflammation of the connective tissue of the kidneys ( granulomatous interstitial nephritis ), inflammation of the kidney corpuscles ( glomerulonephritis ) and damage to kidney vessels , kidney tubules or urinary tract .
Hypercalcemia and hypercalciuria
Disturbances of calcium metabolism in sarcoid have been known since around 1930. Normally, 25-hydroxy-vitamin D is hydroxylated to 1,25-dihydroxy-vitamin D in the kidney by 1α- hydroxylase. This hydroxylation is inhibited by increased calcium levels. In patients with sarcoid, macrophages (cells that make up granulomas) are also able to produce 1α-hydroxylase. This 1α-hydroxylase is not inhibited by increased calcium levels. The lack of negative feedback leads to an increased calcium absorption via the intestine and an increased calcium release from the bones . The calcium level in the blood rises (hypercalciemia), there is an increased excretion of calcium via the kidneys into the urine (hypercalciuria). The parathyroid hormone drops. Hypercalcemia leads to a reduction in blood flow to the kidneys and calcification of the kidneys ( nephrocalcinosis ). Hypercalciuria promotes the formation of kidney stones.
Kidney stones occur in about 10% of patients with sarcoid, and nephrocalcinosis occurs in less than 5% of patients. Nephrocalcinosis is the leading cause of chronic kidney failure in sarcoid. The diagnosis of nephrocalcinosis is made by ultrasound or computed tomography . General measures of treatment include drinking copious amounts of fluids, reducing the intake of calcium and vitamin D with food, and avoiding ultraviolet radiation . Corticosteroids inhibit 1α-hydroxylase. Calcium levels in the blood and urine can return to normal within a week of starting cortisone treatment .
Granulomatous interstitial nephritis
In rare cases there is a nodular inflammation of the connective tissue in the renal cortex ( granulomatous interstitial nephritis ). This can manifest itself in the appearance of red and white blood cells or protein in the urine as well as kidney failure . In half of the cases, increased levels of the angiotensin converting enzyme can be detected in the blood . The diagnosis is made by kidney puncture ( kidney biopsy ) and tissue examination of the kidney tissue obtained. The condition generally responds to treatment with corticosteroids within a few days . The kidney function is usually but not completely normalized by the treatment, so that chronic kidney damage often remains.
Other manifestations of renal sarcoid
Disturbances of the tubular function: Hypercalcemia can disturb the function of the kidney tubules. This leads to a reduced ability of the kidneys to concentrate with increased urine excretion ( diabetes insipidus renalis ) and to the loss of glucose , amino acids and phosphate in the urine ( Fanconi syndrome ). A lack of volume due to fluid loss can lead to an excessively high pH value in the blood ( contraction alkalosis ), but over-acidification of the blood is also possible as part of Fanconi syndrome.
Glomerular Diseases: Diseases of the kidney corpuscles are rare in sarcoid. The membranous glomerulonephritis has been described most frequently .
In rare cases, granulomatous inflammation can narrow the renal arteries and the urinary tract .
Web links
- "Sarcoidosis" in the Atlas of Renal Pathology (pdf, English)
Individual evidence
- ↑ Adam R Berliner, Mark Haas, Michael J Choi: Sarcoidosis: the nephrologist's perspective . In: American Journal of Kidney Diseases . 48, No. 5, November 2006, ISSN 1523-6838 , pp. 856-870. doi : 10.1053 / j.ajkd.2006.07.022 . PMID 17060009 .
