Uninephrectomy enhances urolithiasis in ethylene glycol treated rats

Variation in the incidence of and risk factors for the development of nephrolithiasis after radical or partial nephrectomy

OBJECTIVE

to examine incidence of and risk factors for the development of nephrolithiasis in patients treated with radical nephrectomy (RN) or partial nephrectomy (nephron-sparing surgery, NSS).

PATIENTS AND METHODS

the study comprised a single-centre review of 749 patients treated with RN or NSS from August 1987 to June 2006. Demographics, medical and stone history, metabolic variables and postoperative stone events were recorded. Data were analysed within subgroups based on treatment (RN vs NSS). Multivariate analysis was used to identify risk factors for postoperative stone formation.

RESULTS

in all, 499 patients had RN and 250 had NSS (mean age 57.9 years; mean follow-up 6.3 years). There were no significant differences in their demographic factors, but tumours were significantly larger in RN (P < 0.001). There was no significant difference in preoperative urinary pH < 6.0 or stone history. Significantly fewer patients after NSS than RN formed calculi (NSS 1.6% vs RN 8.4%, P < 0.001), developed hypobicarbonataemia (NSS 7.2% vs RN 12.8%, P= 0.020), and a urinary pH of <6.0 (NSS 11.2% vs RN 19.4%, P= 0.004). Multivariate analysis showed that RN (odds ratio 18.18), postoperative urinary pH < 6 (15.63), previous stone disease (13.7), age <60 years (7.33, all P < 0.001), body mass index ≥ 30 kg/m(2) (3.26, P= 0.033), male gender (2.67, P= 0.039), and hypobicarbonataemia (2.46, P= 0.034) were significantly associated with the development of postoperative calculi.

CONCLUSIONS

patients undergoing RN have a significantly higher incidence of postoperative nephrolithiasis than a well-matched cohort undergoing NSS. In addition to RN, male sex, urinary pH < 6.0, hypobicarbonataemia, history of stone disease, obesity, and age <60 years were significantly associated with postoperative stone formation.

Effects of angiotensin II subtype 1 receptor blockade by losartan on tubulointerstitial lesions caused by hyperoxaluria

PURPOSE

Hyperoxaluria is a recognized cause of tubulointerstitial lesions and this circumstance could contribute to cause chronic renal disease. The renin-angiotensin system has a critical role in the development of interstitial fibrosis, mostly by angiotensin II type 1 receptor stimulation of pro-fibrotic mechanisms. We evaluated whether angiotensin II type 1 receptor blockade prevents oxalate renal lesions.

MATERIALS AND METHODS

We divided 2-month-old male Sprague-Dawley rats into 4 groups, namely group 1-control, group 2-hyperoxaluria, group 3-hyperoxaluria plus losartan and group 4-losartan. For 4 weeks groups 2 and 3 received 1% ethylene glycol (precursor for oxalates) in drinking water. Losartan (40 mg./kg. body weight) was administered in groups 3 and 4 daily. At the end of the study renal lesions were evaluated using anti-alpha-smooth muscle actin, anti-collagen type III, anti-monocytes/macrophages and anti-transforming growth factor-beta1 antibodies. To evaluate oxidative stress in renal tissue total glutathione and thiobarbituric acid reactive substances in kidney homogenates were determined. Regarding renal functional parameters, creatinine clearance and urinary albumin excretion were also studied.

RESULTS

Despite similar urinary oxalate levels compared with group 2 group 3 rats showed fewer tubulointerstitial lesions, consisting of significant lower scores for tubular atrophy, unspecific inflammatory cell infiltrate, ED1 mouse anti-rat monoclonal antibody (Serotec, Ltd., Oxford, United Kingdom) (monocytes/macrophages), crystal deposits, interstitial fibrosis, alpha-smooth muscle actin, collagen type III and tubulointerstitial transforming growth factor-beta1. Moreover, urinary albumin excretion and creatinine clearance were significantly improved in group 3 (p <0.01). Higher total glutathione and lower thiobarbituric acid reactive substances were also observed in this group (p <0.01). Thiobarbituric acid reactive substances were the most important and significant independent variable correlating with interstitial fibrosis (t ratio 4.867, p <0.04).

CONCLUSIONS

We believe that the renal-angiotensin system interaction by losartan produces a beneficial effect against renal lesions caused by hyperoxaluria through a number of actions, including a reduction in crystal formation in the tubular fluid, inflammatory reaction control and interaction with oxidative stress. These factors lead concurrently to preserve tubular epithelial cell and renal interstitium integrity. In addition, these results suggest that the principal mechanism of action should be mediated by angiotensin II type 1 receptors.

Testosterone enhances whereas estrogen inhibits calcium oxalate stone formation in ethylene glycol treated rats

PURPOSE

The present study was conducted to extend our earlier study on the role of testosterone in the pathogenesis of urolithiasis and to further investigate the influence of sex hormone on the pathogenesis of calcium oxalate stone.

MATERIALS AND METHODS

Adult Sprague-Dawley rats were divided into 9 groups, each containing 10 rats. Two groups of rats were left untreated and served as male and female controls. Another 7 groups of rats were fed a 0.5% ethylene glycol (EG) lithogenic diet for 4 weeks. Among them, 2 groups were male and female rats, 2 groups were castrated, 2 groups were castrated and then were subcutaneously implanted with testosterone, and 1 group of intact female rats was also subcutaneously implanted with testosterone. The stone and crystal deposits were examined by infrared spectrometer and polarizing and scanning electron microscope, respectively. Serum testosterone, creatinine and electrolytes and the renal excretion of, oxalate, citrate and creatinine were determined.

RESULTS

Subcutaneous implantation of exogenous testosterone restored calcium oxalate stone formation in castrated, EG-treated male rats (80%) and enhanced urolithiasis in castrated female rats receiving EG (40%). However, the testosterone effect was less striking in intact female rats fed EG (10%).

CONCLUSIONS

These data suggest that testosterone can promote and estrogen may inhibit calcium oxalate stone formation in EG-treated rats.

Nephrotoxicity of xenobiotics

Nephrotoxicity can be grouped by the xenobiotics place of action, by the clinical presentation or by the generic toxic effect. The latter can be dose related, indirect, idiosyncratic or allergic. Nephrotoxicity of lithium, demeclocycline, aminoglycosides, cyclosporine, mercuric ion, nonsteroidal anti-inflammatory drugs, methoxyflurane, ethylene glycol, D-penicillamine and methicillin is reviewed in light of all these three viewpoints, but emphasis is on toxic mechanisms.

The long-term stone recurrence rate and renal function change in unilateral nephrectomy urolithiasis patients

We evaluated the stone recurrence rate and long-term renal function in 50 patients with a solitary kidney 60 to 84 months (mean 70.6) after unilateral nephrectomy for urinary tract stone disease. Followup evaluation included a detailed history, physical examination, blood and urine biochemistry studies, urinalysis, urine culture, excretory urography, ultrasonography of the kidney and 131iodine-ortho-iodohippurate renography. The overall stone recurrence rate in unilateral nephrectomy urolithiasis patients was 30% (15 of 50). The mean interval until stone recurrence was 31.1 months (range 6 to 74) and the mean episodes of recurrence were 2.1 times per patient (range 1 to 5). Function of the remnant kidney in most patients was unchanged during followup. However, 2 of the 15 patients with recurrent stones had anuria during the acute attack of renal colic and, thus, required percutaneous nephrostomy urinary diversion, while 1 had proteinuria (3 gm. per day) and progressive renal failure 47 months after nephrectomy. The metabolic stone patients seemed to experience recurrence more easily than metabolic stone patients seemed to experience recurrence more easily than infection stone patients (37% versus 13%) but no statistically significant difference was noted (p = 0.198).