What is Sarcoidosis and the Kidney

Sarcoidosis is a multisystem granulomatous disorder which may involve the kidneys to a variable degree. Sarcoidosis results in renal disease in a number of different ways:

1. Abnormal calcium metabolism.
2. Interstitial nephritis.
3. Membranous glomerulopathy and other glomerular disorders.
4. Hypertension.
5. Obstructive uropathy with urolithiasis.

Statistics on Sarcoidosis and the Kidney

Sarcoidosis is a rare condition with an incidence of 19 per 100,000 population in the United Kingdom. It is more common in the USA but less common in Japan. The course of the disease is more severe in African-Americans than caucasians. Most patients develop symptoms between the ages of 20 and 40 years, with a known medical history of sarcoidosis. Only rarely is kidney disease the cause of the first clinical symptom.

Although most remain without symptoms of renal disease, it is estimated that 15-40% of patient with sarcoidosis have some involvement of the kidneys in this disease process.

Risk Factors for Sarcoidosis and the Kidney

The cause of sarcoidosis is unknown, but the condition is associated with the following predisposing factors:

1. Family history: Although no genetic link has been found, the disease tends to occur in family clusters.

2. Rural living: The condition occurs more commonly in the rural setting suggesting that exposure to certain chemicals or fungi may have a role in the development of disease.

3. Living in close proximity to people with sarcoidosis: The condition tends to also occur in clusters of unrelated people who live in close proximity.

Progression of Sarcoidosis and the Kidney

The natural history of sarcoidosis in the kidney is variable, depending on the extent of disease and resulting fibrosis that occurs throughout the disease process. The extent of kidney involvement can be reduced by using steroid treatment in the early stages of disease. The patient may also experience the development of kidney stones on a number of occasions throughout their lives, which may be acutely painful and require surgery or medications to hasten recovery. Deterioration of the condition to renal failure may occur in patients with severe kidney involvement in the disease process.

How is Sarcoidosis and the Kidney Diagnosed?

To investigate sarcoidosis renal disease, a number of blood and urine tests may be required to determine the overall function of the kidneys. This will allow assessment of how much damage has been done by the sarcoidosis. If the condition of sarcoidosis has not been previously diagnosed, blood tests and x-rays can be taken to confirm or deny the existence of sarcoidosis.

Prognosis of Sarcoidosis and the Kidney

The prognosis of this condition, like the natural history, is variable. The presence of scarring within the kidney carries a less favourable prognosis. Certain patterns of sarcoidosis affecting the glomerulus may also carry a poor prognosis, however, these are rarely encountered. With appropriate therapy, the majority of patients will maintain adequate renal function provided they follow medical advice carefully.

How is Sarcoidosis and the Kidney Treated?

The mainstay of treatment for sarcoidosis renal disease is steroid therapy. Although many have poor renal function on presentation, patients may respond dramatically to steroid therapy. The steroids are taken for 1-2 months at a high dose, which is then reduced for the remainder of the course, which should be no shorter than one year.

Supportive measures may also be required for patients with chronic renal failure. These patients must be closely observed and may require dialysis if kidney function is inadequate. Specific problems such as urinary stones will need medical and/or surgical intervention.

Sarcoidosis and the Kidney References

[1] Braunwald, Fauci, Kasper, Hauser, Longo, Jameson. Harrison’s Principles of Internal Medicine. 15th Edition. McGraw-Hill. 2001.
[2] Cotran, Kumar, Collins 6th edition. Robbin’s Pathologic Basis of Disease. WB Saunders Company. 1999.
[3] Kumar P, Clark M. Clinical medicine. WB Saunders 2002 Pg 545-549.
[4] Longmore M, Wilkinson I, Torok E. OXFORD HANDBOOK OF CLINICAL MEDICINE. Oxford University Press. 2001.

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