Renal proximal dysfunction in patients with rheumatic diseases

Biochemical markers of renal disease in primary Sjögren's syndrome

Primary Sjögren's syndrome (SS) is characterized by an inflammatory process in the salivary and lacrimal glands, but the kidneys may also be involved. Renal tubular functions were studied in 27 patients with SS, all females, age 37-78. Both SS-patients with and without known distal renal tubular acidosis (dRTA) were included, dRTA was found in 18/27 (67%), impaired urine concentrating ability in 13/27 (48%). Hypocitraturia was identified in 20/27 (74%) and reduced tubular reabsorption of phosphate (TRP%) in 18/27 (67%). Tubular proteinuria (alpha 1-mikroglobulin) was present in 11/24 (46%), and tubular enzymuria (NAG) in 7/24 (29%). Hypocitraturia and/or dRTA were found in all patients with any kind of abnormal renal tubular function test. All except one of the patients with dRTA not treated with sodium bicarbonate had hypocitraturia. We conclude that distal tubular dysfunction was common in our SS-patients, but a concommitant proximal dysfunction was also seen. Determination of urinary citrate represents a valuable test for detection of renal disease in SS.

Microalbuminuria in patients with rheumatoid arthritis

OBJECTIVES

To assess (a) the prevalence of microalbuminuria in patients with rheumatoid arthritis, (b) the association between urinary albumin excretion and disease activity as estimated by the erythrocyte sedimentation rate and C reactive protein (CRP), and (c) the association between urinary albumin excretion and treatment with antirheumatic drugs.

METHODS

Sixty five patients with rheumatoid arthritis attending two rheumatology clinics were compared with 51 control subjects matched by age and sex. The controls consisted of 20 healthy subjects, 16 patients with osteoarthritis and 15 with non-articular rheumatism. Patients with hypertension, diabetes mellitus, or evidence of previous renal disease were not included. Urinary albumin was assayed by immunoturbidimetry in random urine samples on two occasions within seven months. The results were expressed as the ratio of urinary albumin to urinary creatinine ratio. Disease activity was assessed by the erythrocyte sedimentation rate and CRP. A drug history for the year before entry to the study was obtained for each patient.

RESULTS

Urinary albumin to creatinine ratio in patients with rheumatoid arthritis was significantly greater than in controls (p < 0.01). Microalbuminuria (urinary albumin to creatinine ratio 3-30 mg/mmol in either or both urine samples) was present in 27.7% of patients with rheumatoid arthritis and 7.8% of the control subjects. A significant relation was noted between urinary albumin to creatinine ratio and CRP, and the duration of disease. The number of patients treated with either gold or penicillamine was significantly greater in patients with microalbuminuria than in patients with normoalbuminuria.

CONCLUSIONS

Microalbuminuria is frequently present in patients with rheumatoid arthritis. Treatment with gold and penicillamine seems to increase the risk of developing microalbuminuria. Urinary albumin measured by immunochemical methods is a simple and sensitive test to detect early subclinical renal dysfunction and drug induced renal damage in rheumatoid arthritis. Urinary albumin excretion was found to be significantly correlated with CRP and may be a sensitive indicator of disease activity in patients with rheumatoid arthritis.

Changes of mineral metabolism in juvenile chronic arthritis

Thirty five children with ambulant JCA were studied to assess the biochemical parameters of bone metabolism. The mean age of the study group was 8.8 +/- 4.1 years and the mean duration of active disease 3.8 +/- 1.3 years. According to the onset of the disease the children belonged to the systemic (7), polyarticular (12) and pauciarticular type (16). All the patients were treated with NSAIDs. In addition the polyarticular group received either gold injections or D-penicillamine and the systemic group, steroids for at least 3 months. Two groups of controls were studied. The first one included fifteen children without chronic arthritis or bone disease and the second, four children who were treated with corticosteroids for a variety of reasons. In the group with systemic JCA Se Pi (1.28 +/- 0.29 mmol/l) and renal phosphate reabsorption (TmP/GFR = 1.07 +/- 0.18) were significantly lower than in the control groups (1.50 +/- 0.19; 1.54 +/- 0.25 mmol/l, p < 0.01 and 1.35 +/- 0.18; 1.29 +/- 0.23 mmol/l GF, p < 0.05). Also lower were serum alkaline phosphatase (58 +/- 16.4 versus 83 /- 24.2 and 80 +/- 15.6 IU/l, p < 0.05), osteocalcin (5.5 +/- 4.7 versus 11.0 +/- 4.5 and 10.0 +/- 5.7 ng/ml, p < 0.05), 25OHD (15.6 +/- 4.9 versus 27.3 +/- 6.2 and 20.6 +/- 9.8 ng/ml, p < 0.001) and 1,25(OH)2D (12.1 +/- 6.0 versus 20.9 +/- 11.0 and 27.6 +/- 3.2 pg/ml, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

A pharmacokinetic and tolerance study of romazarit in patients with rheumatoid arthritis

Romazarit is a new drug for which animal pharmacology suggests a disease-modifying action in rheumatoid arthritis (RA). These animal studies predict that plasma romazarit concentrations within the range 50-100 mg l-1 may be required for efficacy in the clinic. Therefore, a pharmacokinetic study was designed to estimate the dosage required to achieve these concentrations in man. Twenty-four patients with RA entered a double-blind controlled assessment receiving either placebo, 100 mg t.i.d., 350 mg b.i.d., or 350 mg t.i.d., for 6 days. Pharmacokinetic profiles were measured after single doses and after the last of the multiple doses. Adverse events were mainly trival and were distributed almost equally between all three treatment and the placebo groups. Plasma romazarit concentrations were not dose-proportional after the single doses. Mean peak plasma drug concentrations were 11.8, 66.7, and 159 mg l-1 at steady state after 100 mg t.i.d., 350 mg b.i.d., and 350 mg t.i.d. The mean urinary recovery of drug-related material (mostly ester glucuronides) was 71 per cent of the dose during the dosage interval. The renal clearance of romazarit glucuronides correlated with creatinine clearance (p less than 0.01). Saturable tubular secretion of glucuronides coupled with reversible glucuronidation would explain these findings. It is predicted that oral doses of 450 mg romazarit given 12-hourly will result in plasma concentrations within the target range of 50-100 mg l-1.

Drug interactions in arthritic patients

The drug treatment of 100 consecutive new patients admitted to a regional rheumatology centre was reviewed. Potential drug interactions actions were sought according to appendix one of the British National Formulary (September 1989) and identified in 55 of 100 patients. The clinical and laboratory features of these patients were then reviewed, showing that only 11 displayed clinical manifestations of a drug interaction. Five patients had drug induced drowsiness, which was easily corrected, five a raised serum creatinine, which was less easily corrected, and one both. Although there is considerable potential for drug interaction in patients with severe arthritis, the proportion of patients who display clinical manifestations of this is small.

Renal disorders in rheumatoid arthritis

Renal disorders are a frequent cause of death in patients with rheumatoid arthritis (RA), but are less apparent in living RA patients. In part, this may be because of insensitive screening methods. In this review, some of the relations among renal pathology, renal function, and antirheumatic therapy are clarified. A classification of renal disorders according to etiology is proposed. Two categories of disorders are distinguished: those related to RA and its complications, and those related to drug therapy. The disorders belonging to these categories are reviewed. Finally, a case is made for the existence of a third category, "RA nephropathy." It is hypothesized that this mild and nonspecific nephropathy is the result of cumulative minor insults caused by the disease and its therapy. The presence of such a "subclinical" nephropathy would explain the greater sensitivity of RA patients to other renal insults, and the high prevalence of renal failure at death.

An assessment of tenoxicam, a nonsteroidal anti-inflammatory drug of long half-life, in patients with impaired renal function suffering from osteoarthritis or rheumatoid arthritis

Fifty-eight patients, aged 48-87 years, with impaired renal function and mean initial creatinine clearance of 52.1 mls/min were recruited to a 12-week open study of tenoxicam 20 mg/day for osteoarthrosis or rheumatoid arthritis. Renal function was measured before and after a brief run-in period when patients discontinued all nonsteroidal anti-inflammatory drugs, taking paracetamol alone, prior to monthly monitoring thereafter. Fifty-four % of patients completed the study, the others being withdrawn from lack of efficacy (17%), adverse events (24%) or both (5%). During the run-in period the mean creatinine clearance of 28 patients completing the trial improved to 64.7 mls/min and then dropped to 57.9 mls/min during the course of 12 weeks treatment with tenoxicam. Serial analysis of haematological and biochemical safety parameters showed no drug-induced change of significance. Twenty-three% of patients felt worse and 45% better at the end of treatment. Seventeen patients withdrew because of adverse events. These were normally gastrointestinal and always unrelated to further deterioration in renal function. Tenoxicam, 20 mg/day, can be given safely for a period of at least three months in patients with mild or moderate renal impairment.

Urine- and serum beta 2-microglobulin in patients with rheumatoid arthritis: a study of 101 patients without signs of kidney disease

Serum levels and 24-hour urinary excretion of beta 2-Microglobulin (beta 2-M) was investigated in a group of 101 patients with rheumatoid arthritis (RA), without any other signs of renal disease in past or present, and in a comparable control group. Elevated 24-hour urinary beta 2-M excretion, due to renal proximal tubules dysfunction, was observed in 19% of the patients and not in the control group. There was a significant correlation with clinical signs of extra-articular RA. It is postulated that the observed increase may be an early symptom of renal involvement in RA. Elevated serum beta 2 levels, corrected for glomerular filtration rate, were observed in 44% of the RA patients and only in 3% of the control group and correlated with clinical signs of a more severe RA, as well as with increased 24-hour urinary beta 2-M excretion.

Renal biochemistry in rheumatic disease

In patients with osteo-arthritis, renal disease will almost invariably be the consequence of unrelated coincidental renal pathology. In polyarthritic rheumatoid arthritis and ankylosing spondylitis, renal disease can arise as part of the pathology of a systemic disease, or more likely its treatment. As a rule amyloidosis is the most important complication in terms of progressive irreversible loss of renal function. By contrast, SLE, polyarteritis and Sjögren's disease carry a much higher risk of renal involvement. The regular evaluation of renal function in such patients can enable the kidney damage to be assessed at an early stage and allow treatment to be instituted early.

Side effects of cyclosporin A treatment in patients with rheumatoid arthritis

Cyclosporin A (CyA) and azathioprine (Aza) were compared with respect to renal side effects in an open controlled, randomized study of patients with rheumatoid arthritis. Twelve patients were treated with CyA (mean dose 7.8 +/- 1.2 mg/kg/day) and 12 with azathioprine for 26 weeks. All patients also received prednisolone 5 mg/day. The patients had normal serum creatinine (less than 120 mumoles/liter) and protein-free urine before the trial. CyA increased serum creatinine in nine out of the 11 patients followed for 26 weeks, the mean increase was approximately 50%. Creatinine clearance was reduced by 31%. Mean arterial pressure (MAP) and serum potassium were significantly increased by CyA. Urinary beta 2-microglobulin excretion was significantly increased by CyA, in five of the patients more than ten times. Urinary kallikrein excretion was reduced by more than 50% and urinary albumin excretion was doubled. All these parameters remained normal and unchanged in the azathioprine group. CyA was withdrawn in seven patients after 26 weeks. Urinary beta 2-microglobulin was still increased by 85% nine months after CyA treatment. The other parameters were gradually normalized after three to nine months except for one patient who developed renal failure. Urinary beta 2-microglobulin excretion was a very sensitive parameter for renal tubular damage in this study.

Hypercalciuria in children with juvenile rheumatoid arthritis: association with hematuria

After discovering juvenile rheumatoid arthritis (JRA), hematuria, and urolithiasis associated with hypercalciuria in two children, urinary calcium excretion was examined in 38 patients with JRA. Fasting urine calcium/creatinine (mg/mg) (UCa/UCr) ratios were increased (greater than 0.21) in 12 patients, who had a mean UCa/UCr ratio of 0.34 +/- 0.14, compared with 0.09 +/- 0.06 in 26 normocalciuric patients with JRA. Increased UCa/UCr ratios were found more frequently in patients with systemic JRA (P less than 0.05); however, no relationship between UCa/UCr ratios and either functional classification or drug therapy was observed. Four children with increased urine calcium to creatinine ratios were examined more extensively. Twenty-four-hour urine calcium excretion ranged from 4.0 to 7.2 mg/kg/24 hours. An orally administered calcium loading test demonstrated fasting hypercalciuria after dietary calcium restriction in these four patients. Serum calcium, bicarbonate, phosphorus, and parathyroid hormone values were normal. Hematuria was found in six of 12 hypercalciuric patients with JRA but in only three of 26 normocalciuric patients (P less than 0.016). We conclude that urinary calcium excretion is frequently increased in patients with JRA and that hypercalciuria may be related to the pathogenesis of hematuria in some of them.