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[Urate nephrolithiasis. Cause of consequence?].

After World War II the incidence of urolithiasis increased consistently among the general population in this country. Nearly 25% of all examined renal calculi contain uric acid, sodium acid urate or ammonium acid urate as constituents. There are two peaks in lifespan of occurring urate stones: in the adolescence and in the age between 40 and 60 years. The following conditions are due to the formation of uric acid-containing stones: 1. Gout and primary hyperuricemia; 2. secondary hyperuricemia; 3. idiopathic cases with normal renal excretion of uric acid and normouricemia, but with a higher degree of acidity of the urine than normal considering the total renal excretion of acid products; 4. iatrogenic hyperuricemia during insufficient uricosuric therapy. Up to more than 30% of all the patients with recurrent formation of oxalate stones show a clear association with hyperuricemia, hyperuricosuria and increased renal excretion of calcium. In the presence of sodium urate a considerable promotion of precipitation of crystals consisting of calcium oxalate from a meta-stable solution may occur (so-called epitaxy). Frequently the existence of uric acid stones is without any symptoms. Modern views with regard to prophylactic procedures, diet, general and specific medical management including surgical intervention are presented.

Calcium↗

Hyperoxaluria in patients with idiopathic calcium nephrolithiasis.

We studied 476 patients with idiopathic renal calcium stone disease (286 M, 190 F) while they ate their customary diets. Each subject collected a 24-hour urine sample and completed a dietary diary for a 3-day period. Daily urinary oxalate excretion (M 0.24 +/- 0.15 mg/dl, F 0.23 +/- 0.15 mg/dl) and nutrient intake values were calculated and multiple regression analyses were performed. Daily urinary oxalate excretion was significantly (p < 0.001) related to urinary volume (R = 0.24), vitamin C intake (R = 0.33) and body mass index (R = 0.37) and inversely related to calcium intake (R = -0.35). We conclude that urinary oxalate reflects endogenous oxalate production, presumably related to body size, but also intestinal absorption of oxalate, related to dietary intake and to the effect of dietary calcium intake which reduces intestinal oxalate absorption.

Adult↗

[The immunological aspects of systemic enzyme therapy in the combined treatment of recurrent nephrolithiasis].

Results are submitted of treatment of 50 patients of different years of age, who were presenting with urolithiasis and concomitant chronic pyelonephritis, using methods of surgical treatment alone and in combination with a drug preparation of systemic enzymotherapy (SE) phlogenzyme. Based on the analysis of the findings obtained a conclusion has been drawn that the SE drug phlogenzyme is an effective medication for correction of disorders of the immune homeostasis in patients with urolithiasis and for prevention of recurrent lithogenesis after surgical interventions in kidneys and ureters.

Adjuvants, Immunologic↗

Low calcium diet in hypercalciuric calcium nephrolithiasis: first do no harm.

Many studies indicate that up-regulated production of 1,25(OH)2-vitamin D3 (calcitriol) with increased intestinal absorption of calcium is the primary event causing idiopathic hypercalciuria. Thus, a low calcium diet appears to be a straightforward strategy in calcium stone formers with hypercalciuria (HCSF). However, the efficacy of such a regimen has never been established, and lowering calcium intake from 1000 to 400 mg/day further enhances calcitriol production. On a diet chronically restricted in calcium, many stone formers increase their intake of animal flesh protein. The latter is known to increase renal mass, and calcitriol levels indeed are positively correlated with renal mass in animals as well as in HCSF. Thus, low calcium and high animal flesh protein consumption are independent stimuli for further up-regulation of calcitriol production. The rise in calcitriol suppresses parathyroid hormone synthesis thereby diminishing renal tubular calcium reabsorption, and increasing urinary calcium losses. Since calcitriol up-regulation also increases bone resorption, the combination of low calcium and high protein intake is particularly likely to induce negative calcium balance and thus osteopenia. Finally, low calcium intake carries the risk of insufficient intestinal binding of oxalate with subsequent increases in intestinal absorption and urinary excretion of oxalate. Indeed, most recent studies suggest that high amounts of calcium, when ingested simultaneously with oxalate-containing meals, are able to prevent hyperoxaluria during severe oral oxalate loading.

Calcitriol↗

Lectin-cytochemistry of experimental rat nephrolithiasis.

Lectin reactivity in epithelial apical cell coats of normal rat kidneys was compared to that from animals subjected to crystal inducing diets (CID). The aim was to see whether the absence of lectin reactivity in cell coats is related to intratubular calcium oxalate crystal retention. In normal rat kidneys, after a pre-embedding procedure, it was observed that at the ultrastructural level, reactivity was present but that the lectin specificity for the various parts of the nephron might have to be reconsidered. There was heterogeneity between the epithelial cells with respect to the presence of coat material in the tubular cell apices. Tubular epithelial cell apices from CID rats showed no obvious changes in lectin reactivity pattern. Lectin reactivity was present at the periphery of intratubular crystals but undetectable at true crystal attachment sites or reduced at cell apices in the vicinity of recently attached crystals or agglomerates. After a post-embedding reaction procedure, wheat-germ agglutinin (WGA)-lectin reactivity confirmed the presence of coat material in the cleft between cell apex and retained crystal at crystal-attachment sites. The WGA/Au-10 nm reaction products were also seen inside epithelial cells. WGA/Au-10 nm reaction products mark a crystal matrix component inside intratubular and retained crystals. A similar matrix was also marked by an alpha-osteopontin (alpha OPN/Au-10 nm) reaction product.

Animals↗

Pathological and immunocytochemical changes in chronic calcium oxalate nephrolithiasis in the rat.

In the present study, we exposed rats to a crystal-inducing diet (CID) consisting of vitamin D3 and 0.5% ethylene glycol (EG), and we investigated histologically the kidney damage induced by the deposition of calcium oxalate (CaOx) crystals. After 28 days, 50% of the animals had renal CaOx crystals, of which 60% also had small papillary stones. Most crystals were present in the cortex. The occurrence of these crystals coincided with morphological and cytochemical changes: glomerular damage, tubular dilatation and necrosis, and an enlargement of the interstitium. The number of epithelial and interstitial cells positive for the proliferating cell nuclear antigen (PCNA) was increased. Tamm-Horsfall protein (THP) was not only demonstrable in the thick ascending limb of the loop of Henle (TAL), but also frequently in glomeruli, in the proximal tubular epithelium, and in the papilla. In the lumen of the tubular system, it was associated with urinary casts. Reflection contrast microscopy (RCM) showed that the crystals were coated with a thin layer of THP. In spite of the high urinary oxalate concentrations, the above described cellular changes were not observed in CID-fed rats without renal crystals. We conclude, therefore, that in the kidney, the retained CaOx crystals rather than the urinary oxalate ions are responsible for the observed morphological and immunocytochemical changes.

Animals↗