Giampaolo Zanetti

Increase in the Prevalence of Symptomatic Upper Urinary Tract Stones during the Last Ten Years

Purpose: In industrialized countries the prevalence of upper urinary tract stones has continually increased during the 20th century, but there are considerable differences between countries and also within the same country. To study whether there is still an increase in the frequency of renal stones, an investigation was undertaken to determine the prevalence of stone formers in a village near Milan, Italy, during two time periods, with an interval of 12 years.Materials and Methods: Questionnaires were administered in 1986 and 1998 to all adult (age >25 years) occupants of two random samples of households in the village. Participants were asked whether they had experienced a kidney stone during their lifetime.Results: The overall prevalence of stone formers among males was 6.8% in 1986 and 10.1% in 1998; that among females was 4.9% in 1986 and 5.8% in 1998. In all age classes, the respondents in the 1998 survey more frequently reported a history of stones than in 1986, but the prevalence of renal stones was significantly higher in 1998 than in 1986 only among males aged 31–40 and 51–60 years. The yearly incidence was estimated at 0.4%, with 0.6 and 0.18% in men and women, respectively.Conclusions: This marked increase in renal stones could be the result of environmental factors such as dietary habits and lifestyle, in particular the influence of an increased consumption of animal protein should be considered.

Calcium stone disease: a multiform reality

In calcium renal stones, calcium oxalate and calcium phosphate in various crystal forms and states of hydration can be identified. Calcium oxalate monohydrate (COM) or whewellite and calcium oxalate dihydrate (COD) or weddellite are the commonest constituents of calcium stones. Calcium oxalate stones may be pure or mixed, usually with calcium phosphate or sometimes with uric acid or ammonium urate. The aim of this study was to compare the clinical and urinary patterns of patients forming calcium stones of different composition according to infrared spectroscopic analysis in order to obtain an insight into their etiology. The stones of 84 consecutive calcium renal stone formers were examined by infrared spectroscopy. In each patient, a blood sample was drawn and analysed for serum biochemistry and a 24-h urine sample was collected and analysed for calcium, phosphate, oxalate, citrate and other electrolytes. We classified 49 patients as calcium oxalate monohydrate (COM) stone formers, 32 as calcium oxalate dihydrate (COD) stone formers and three as apatite stone formers according to the main component of their stones. Patients with COM stones were significantly older than patients with COD stones (P<0.002). Mean daily urinary calcium and urinary saturation with respect to calcium oxalate were significantly lower in patients with COM than in those with COD stones (P<0.000). Patients with calcium oxalate stones containing a urate component (≤10%) presented with higher saturation (P<0.012) with respect to uric acid in their urine (and lower with respect to calcium oxalate and calcium phosphate, respectively P<0.024 and P<0.003) in comparison with patients without a urate component in the stone. Patients with calcium oxalate stones with a calcium phosphate component (≥15%) showed higher (P<0.0016) urinary saturation levels with respect to calcium phosphate (and lower with respect to uric acid (P<0.009), compared with patients forming stones without calcium phosphate or with a low calcium phosphate component. Patients with calcium stones mixed with urate had a significantly lower urinary pH (P<0.002) and urinary calcium (P<0.000), and patients with calcium phosphate >15%, higher urinary pH (P<0.004) and urinary calcium (P<0.000). In conclusion, in the evaluation of the individual stone patient, an accurate analysis of the stone showing its exact composition and the eventual presence of minor components of the stone is mandatory in order to plan the correct prophylactic treatment. Patients with “calcium stones” could require various approaches dependent on the form and hydration of the calcium crystals in their stones, and on the presence of “minor” crystalline components that could have acted as epitaxial factors.

Effect of potential renal acid load of foods on urinary citrate excretion in calcium renal stone formers

The aim of this study was to investigate the influence of the potential renal acid load (PRAL) of the diet on the urinary risk factors for renal stone formation. The present series comprises 187 consecutive renal calcium stone patients (114 males, 73 females) who were studied in our stone clinic. Each patient was subjected to an investigation including a 24-h dietary record and 24-h urine sample taken over the same period. Nutrients and calories were calculated by means of food composition tables using a computerized procedure. Daily PRAL was calculated considering the mineral and protein composition of foods, the mean intestinal absorption rate for each nutrient and the metabolism of sulfur-containing amino acids. Sodium, potassium, calcium, magnesium, phosphate, oxalate, urate, citrate, and creatinine levels were measured in the urine. The mean daily PRAL was higher in male than in female patients (24.1±24.0 vs 16.1±20.1xa0mEq/day, P=0.000). A significantly (P=0.01) negative correlation (R=−0.18) was found between daily PRAL and daily urinary citrate, but no correlation between PRAL and urinary calcium, oxalate, and urate was shown. Daily urinary calcium (R=0.186, P=0.011) and uric acid (R=0.157, P=0.033) were significantly related to the dietary intake of protein. Daily urinary citrate was significantly related to the intakes of copper (R=0.178, P=0.015), riboflavin (R=0.20, P=0.006), piridoxine (R=0.169, P=0.021) and biotin (R=0.196, P=0.007). The regression analysis by stepwise selection confirmed the significant negative correlation between PRAL and urinary citrate (P=0.002) and the significant positive correlation between riboflavin and urinary citrate (P=0.000). Urinary citrate excretion of renal stone formers (RSFs) is highly dependant from dietary acid load. The computation of the renal acid load is advisable to investigate the role of diet in the pathogenesis of calcium stone disease and it is also a useful tool to evaluate the lithogenic potential of the diet of the individual patient.

Extracorporeal Shockwave Lithotripsy in Patients Treated with Antithrombotic Agents

PATIENTS AND METHODSnBetween January 1996 and December 1999, 749 patients underwent electromagnetic SWL. Among them, 23 patients, 19 with renal and 4 with ureteral stones, were receiving antithrombotic drugs (aspirin, ticlopidine, dipyridamole). According to the cardiologist and hematologist, we divided these patients into two groups: Group 1 had a low thromboembolic risk (previous myocardial infarction), and Group 2 had a high thromboembolic risk (aortocoronary bypass, atrial fibrillation, cerebrovascular disease, peripheral occlusive arterial disease). Group 1 patients discontinued their antiplatelet therapy 8 days prior to SWL to permit a sufficient number of functioning platelets to remain. Group 2 patients suspended antiplatelet therapy, and unfractioned heparin 5000 IU tid (8 a.m., 4 p.m., and 12 p.m.) was administered for the 8 days prior to SWL. On the ninth day of withdrawal, SWL was performed in all patients. Close follow-up was performed during the postoperative period (hemoglobin, hematocrit, kidney ultrasonography, plain abdominal film). The antithrombotic therapy was restored in all patients within 10 to 14 days of withdrawal.nnnRESULTSnHematomas and thromboembolic events were not observed. At 3 months follow-up, 14 patients (61%) were stone free, 3 (13%) had <4-mm fragments, and 6 (26%) had >4-mm residual fragments.nnnCONCLUSIONnOur schedules for the suspension or substitution of antithrombotic therapy, although tested in a small number of patients, allowed us to perform SWL without hemorrhagic or thromboembolic complications.

Effect of Potential Renal Acid Load of Foods on Calcium Metabolism of Renal Calcium Stone Formers

Objectives: Diet has been proposed as a causative factor of hypercalciuria in patients with calcium stones. The aim of this study was to investigate the influence of diet on calcium metabolism of renal stone formers. Methods: Thirty-five renal calcium stone formers were entered in this study. A 2-day recall of dietary intake was obtained from each subject. The food records were coded and computer analyzed for total energy, protein, fat, carbohydrate, sodium, potassium, calcium, magnesium, phosphate, oxalate, vitamin C and fiber. Daily potential renal acid load (PRAL) of the diet was calculated considering the mineral and protein composition of foods, the mean intestinal absorption rate for each nutrient and the metabolism of sulfur-containing amino acids. A fasting blood sample was drawn and a 24-hour urine collection were obtained for analyses of calcium, phosphate and creatinine. Serum osteocalcin was also analyzed. A fasting 2-hour urine sample was collected in the morning for hydroxyproline, pyridinium cross-links and creatinine. Results: The mean daily dietary PRAL of renal stone formers was 22.4 ± 15.7 (range 4.2–65.8) mEq/day. Regression analysis demonstrated that urinary calcium excretion is dependent on daily protein intake and dietary PRAL, whereas the urinary pyridinium cross-links/creatinine ratio is inversely dependent on daily calcium intake. The urinary pyridinium cross-links/creatinine ratio was significantly lower in patients on a low calcium diet (<600 mg/day) than in other patients (19.5 ± 7.8 vs. 27.3 ± 7.5 nM/mM, p = 0.008). No significant difference was observed between the 2 groups for daily urinary calcium (254 ± 109 vs. 258 ± 140 mg/day), serum osteocalcin (8.2 ± 3.3 vs. 6.2 ± 2.4 ng/ml) and urinary hydroxyproline/creatinine (14.1 ± 7.4 vs. 10.3 ± 4 mg/g). Conclusions: The urinary calcium excretion of renal stone formers seems to be dependent on dietary acid load rather than dietary calcium intake. In patients consuming an acidifying diet a restriction of calcium intake could increase bone resorption leading to a progressive bone loss.

The impact of new technology in the treatment of cystine stones

Cystinuric patients frequently require stone removing procedures because of their high tendency to have recurrent urinary calculi. In the last 20xa0years the morbidity of stone treatment has been reduced by the introduction of endourologic procedures and shock wave lithotripsy (SWL), but cystine stones are not amenable to all minimally invasive procedures. The aim of our study was to assess the impact of new technology in the treatment of cystine stones. The records of patients observed at our institutions from 1978 to 2005 were reviewed. We retrospectively analysed the previous stone histories of all the patients who presented at our institutions for stone treatment who resulted to be cystinuric at our metabolic work up. Patients were divided in two groups according to the date of our first observation: group A comprised patients observed from 1978 to 1989 who mainly experienced traditional stone treatment and group B patients observed from 1990 to present who were preferentially treated with minimally invasive therapeutic modalities. A total of 48 cystinuric patients were observed (31 in group A and 17 in group B). The mean age (38xa0±xa015 vs. 36xa0±xa013xa0years), the age at stone onset (21xa0±xa011 vs. 21xa0±xa012) and the annual recurrence rate (1.34xa0±xa02.38 vs. 1.16xa0±xa01.11 stones/year/pt) were not significantly different in the two groups. The male/female ratio was 18/13 and 8/9, respectively, in group A and B. In group A 16 patients underwent open surgical treatment for a total of 29 procedures (0.93 for patient) and four of them had nephrectomy; in group B only eight underwent open surgery but other seven had percutaneous surgery (0.47xa0+xa00.41 procedure/patient). In group B 37 SWL treatments were performed (2.17 for patient) whereas patients in group A underwent only four SWLs. Renal function was impaired in six patients (19%) in group A with a patient requiring haemodyalitic treatment and in one patient (6%) in group B. Compared to the traditional stone treatment, after 1990 fewer cystinuric patients required open surgery and none underwent nephrectomy or developed severe renal failure. Our results indicate that the actual care of patients with cystine stones should still be improved requiring a comprehensive approach in order to avoid inappropriate SWL treatments and more attention to early diagnosis and preventive measures.