[Subclinical renal involvement in rheumatoid arthritis].
No evidence of renal involvement was found in 104 patients with rheumatoid arthritis in routine laboratory tests, including serum creatinine, urea, uric acid, sodium, potassium, calcium, phosphorus, and urinalysis. In view of recent publications (1-9) which report renal involvement in rheumatoid arthritis, we studied 16 patients of our group (nonrandomized, 3 men and 16 women, average age 55.4 years, average duration of disease 11.9 years). We examined creatinine clearance, urinary excretion of alpha-2 microalbumin, beta-2 microglobulin, cystine, and urine concentration and acidity after a 10-hour fast. 10 patients had disturbances in 1 or more of the functions examined, in 9 of whom tubular functions were involved. In 6 there was no evidence of renal involvement. There was no correlation between renal involvement and past or present therapy, but there were direct correlations between renal involvement, duration of disease and age. Thus we found evidence for subclinical renal damage not revealed by routine laboratory tests in patients with rheumatoid arthritis. This damage should be taken into consideration when operation, examination with contrast material, or treatment with other nephrotoxic agents are being considered in these patients.