Medical management for the prevention of kidney stones

The alarming fact is that approximately one out of every 10 of us will have a kidney stone during our lifetime. The increasing prevalence and associated costs of kidney stones have resulted in it being one of the most commonly encountered and impactful medical conditions. Contributing factors include, but are not limited to, diet, climate, genetics, medications, activity and underlying medical conditions. Symptoms generally parallel stone size. Treatment varies from supportive to procedural (invasive and non-invasive). Prevention remains the best way to avoid this condition especially given the high recurrence rate. First time stone formers require counselling regarding dietary adjustments. Certain risk factors ultimately require a more in-depth metabolic investigation, especially if stones are recurrent. Ultimately, management is defined by stone composition. Where appropriate, we review both pharmacologic and non-pharmacologic options. Pivotal to successful prevention is patient education and the encouragement of compliance with the appropriate regimen.

Association of Urine Findings with Metabolic Syndrome Traits in a Population of Patients with Nephrolithiasis

Background: The odds of nephrolithiasis increase with more metabolic syndrome (met-s) traits. We evaluated associations of metabolic and dietary factors from urine studies and stone composition with met-s traits in a large cohort of stone-forming patients. Methods: Patients >18 years, who were evaluated for stones with 24 h urine collections, July 2009-December 2018, had records reviewed retrospectively. Patient factors, laboratory values and diagnoses were identified within 6 months of urine collection and stone composition within 1 year. Four groups with 0, 1, 2, > 3 met-s traits (hypertension, obesity, dyslipidemia, diabetes) were evaluated. Trends across groups were tested using linear contrasts in analysis of variance and analysis of covariance. Results: 1473 patients met inclusion criteria (835 with stone composition). Met-s groups were 0=684, 1=425, 2=211, 3 and 4 =153. There were no differences among groups for urine volume, calcium or ammonium excretion. There was a significant trend (p<0.001) for more met-s traits being associated with decreasing urine pH, increasing age, calculated dietary protein, urine uric acid, oxalate, citrate, titratable acid phosphate, net acid excretion and uric acid supersaturation. The ratio of ammonium to net acid excretion did not differ among the groups. After adjustment for protein intake, the fall in urine pH remained strong, while the upward trend in acid excretion was lost. Calcium oxalate stones were most common, but there was a trend for more uric acid (p<0.001) and fewer calcium phosphate (p=0.09) and calcium oxalate stones (p=0.01) with more met-s traits. Conclusions: Stone forming patients with met-s have a defined pattern of metabolic and dietary risk factors that contribute to an increased risk of stone formation including higher acid excretion, largely the result of greater protein intake, and lower urine pH.

The relationship between ethnicity and stone composition in a large multi-ethnic London NHS Trust

Purpose Few studies have examined kidney stone composition of an ethnically diverse group living in the same location, we aimed to study this in an ethnically diverse NHS trust. Methods We reviewed all patients (n=312) with laboratory stone analysis and compared their ethnicity with their stone composition. Results Using a Chi Squared analysis there was no significant difference between stone composition in different ethnic groups (p=0.07). Uric acid stones were more common in the White-other group at 22.0% compared to 10.3% for White British, 5.2% for Asian and 9.52% for Black patients. Calcium oxalate stone were more common in the Asian population with 71.9% and Black population at 76.1%, compared with 56.7% in the White British population and 52.6% in the White-other population. Calcium phosphate stones were found commonly in the White British population (26.8%) compared to 18.6% for White-other, 16.7% for Asian and 9.5% for Black patients. Cystine and Struvite stones were found at low levels of between 0-3.4% in each group. Repeat stone formers with calcium oxalate, uric acid or cystine stones formed the same stone again 100.0% of the time. The odds for the Black population having a stone analysed (OR 0.62, CI 0.39-0.97, p=0.04) was significantly lower than the local population, and for the Asian population this was significantly higher (OR 1.31, CI1.05-1.62, p=0.01), Conclusion Uric acid stones are found more frequently in the White-other population and calcium oxalate stones are found more frequently in the Asian and black population. However, these results were not statistically significant. The odds ratio of having a stone was significantly higher in the Asian population and lower in the Black population.

Dual Energy Computed Tomography (DECT) for Determination of Renal Calculi Composition - In-Vivo Analysis and In-Vitro Comparison with Qualitative Chemical Analysis - A Prospective Comparative Study at a Single Centre at SDM Medical College and Hospital – Dharwad, Karnataka

BACKGROUND Dual energy computed tomography (DECT) is a new method of computed tomography (CT) imaging which allows to determine stone composition in addition to assessing stone morphology. The purpose of this study was to evaluate the role of dual energy CT (DECT) preoperatively to assess the composition of urinary stones and to compare it with post-operative in vitro qualitative chemical analysis as reference standard. METHODS Forty patients (18 male and 22 female) who presented with symptoms of renal stones in the department of urology were included in the study. All 40 patients who were diagnosed to have renal stones clinically and by ultrasonography (USG) kidney, ureter and bladder (KUB) region were subjected to dual energy CT. The stone composition assessed in vivo using DECT preoperatively and in vitro by chemical analysis post operatively after stone extraction by surgical procedure. The results were compared by statistical analysis. Sensitivity, specificity and positive predictive value (PPV) were calculated and descriptive study done using Statistical Package for Social Sciences (SPSS) 20.00 version. Data was analysed by comparing it with correlative qualitative chemical analysis. RESULTS In our study, in vivo analysis using DECT showed most common type of stone was calcium oxalate seen in 20 cases compromising 50 % of total cases. Next common stone type was uric acid stone (22.5 %) followed by cysteine (17.5 %) and calcium hydroxyapatite (10 %) respectively. When the same stones were subjected to ex vivo chemical analysis, one of the calcium oxalate stone came out to be calcium phosphate and one of the cysteine stone came out to be mixed stone. Thus, out of 40 stones, 38 stones were found to have the same result in ex vivo chemical analysis as that of in vivo analysis by dual energy CT. Hence, accuracy of dual energy CT in diagnosis of renal stones was found to be 100 % with CI 91.19 % - 100 %. CONCLUSIONS With dual energy CT, it is possible to determine the composition of renal calculi in vivo non-invasively (with specificity of 100 % in our present study). Therefore, this helps in deciding the modality of treatment pre-operatively whether the stone is amenable to medical management (e.g., Uric acid stones) or requires extracorporeal shock wave lithotripsy (ESWL) or surgical intervention can be determined preoperatively. This helps to reduce the unnecessary financial burden and is found to be time saving. KEYWORDS Renal Calculus, Dual Energy CT, Stone Composition, Uric Acid Stones, Non-Uric Acid Stones, Attenuation, Hounsfield Units HU, Chemical Analysis of Stones.

Stone composition of renal stone formers from different global regions

Objective: To study urinary stone composition patterns in different populations around the world. Materials and methods: Data were collected by reviewing charts of 1204 adult patients of 10 countries with renal or ureteral stones (> 18 years) in whom a stone analysis was done and available. Any method of stone analysis was accepted, but the methodology had to be registered. Results: In total, we observed 710 (59%) patients with calcium oxalate, 31 (1%) with calcium phosphate, 161 (13%) with mixed calcium oxalate/calcium phosphate, 15 (1%) with carbapatite, 110 (9%) with uric acid, 7 (< 1%) with urate (ammonium or sodium), 100 (9%) with mixed with uric acid/ calcium oxalate, 56 (5%) with struvite and 14 (1%) with cystine stones. Calciumcontaining stones were the most common in all countries ranging from 43 to 91%. Oxalate stones were more common than phosphate or mixed phosphate/oxalate stones in most countries except Egypt and India. The rate of uric acid containing stones ranged from 4 to 34%, being higher in Egypt, India, Pakistan, Iraq, Poland and Bulgaria. Struvite stones occurred in less than 5% in all countries except India (23%) and Pakistan (16%). Cystine stones occurred in 1% of cases. Conclusions: The frequency of different types of urinary stones varies from country to country. Calcium-containing stones are prevalent in all countries. The frequency of uric acid containing stones seems to depend mainly on climatic factors, being higher in countries with desert or tropical climates. Dietary patterns can also lead to an increase in the frequency of uric acid containing stones in association with high obesity rates. Struvite stones are decreasing in most countries due to improved health conditions.