Stesura Seveso 307Archivio Italiano di Urologia e Andrologia 2021; 93, 3 ORIGINAL PAPER No conflict of interest declared. BACKGROUND Most data on chemical stone composition have been col- lected in the Western world (1-8). It is well known that stone composition is dependent on lifestyle and diet, which in turn is dependent on country, climate and cul- ture. Therefore, it is of interest to establish a more glob- alised map of chemical stone composition around the globe. U-merge, an association gathering urologists from all over the world, is the ideal platform for this task. For this reason, the scientific office of U-Merge launched a study to collect the results of urinary stone analyses among different populations in the countries of its members. MATERIALS AND METHODS All members of U-merge were invited to join in the study. Data were collected by reviewing charts of adult patients (> 18 years) with renal or ureteral stones observed in each participating center who had chemical analysis of the stone available. Gender, age, country and stone composi- tion of each patient were recorded in an Excel data base. Any method of stone analysis was accepted, but the methodology had to be known and registered. A mini- mum number of 30 patients per center was required. Stones analyzed by wet chemical were classified as calci- um oxalate (CaOx) (unspecified), calcium phosphate (CaP) (unspecified), mixed calcium oxalate/calcium phosphate (CaOx/CaP), struvite, uric acid (UA), mixed uric acid/cal- cium oxalate (UA/CaOx) and cystine. Stones analysed by infrared spectroscopy or X-ray diffrac- tometry were classified as CaOx dihydrate (> 50%), CaOx monohydrate (> 50%), CaP (> 50%), mixed CaOx/CaP (if CaP > 10%), struvite (> 50%), carbonate apatite (50%), UA anhydrous (> 50%), UA dihydrate (> 50%), ammonium Objective: To study urinary stone composi- tion 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. Calcium- containing stones were the most common in all countries rang- ing 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 con- taining stones in association with high obesity rates. Struvite stones are decreasing in most countries due to improved health conditions. KEY WORDS: Urinary calculi; Epidemiology; Gender; Age; Calcium oxalate; Calcium phosphate; Uric acid; Struvite; Cystine. Submitted 18 August 2021; Accepted 25 August 2021 Stone composition of renal stone formers from different global regions Adam Haliński 1, Kamran Hassan Bhatti 2, Luca Boeri 3, Jonathan Cloutier 4, Kaloyan Davidoff 5, Ayman Elqady 6, Goran Fryad 7, Mohamed Gadelmoula 6, Hongyi Hui 8, Kremena Petkova 9, Elenko Popov 5, Bapir Rawa 10, Iliya Saltirov 9, Francisco R. Spivacow 11, Belthangady Monu Zeeshan Hameed 12, Alberto Trinchieri 13, Noor Buchholz 13 1 Private Medical Center "Klinika Wisniowa" Zielona Gora; Poland; 2 Urology Unit, City Hospital Pakpattan, Pakistan; 3 Department of Urology, IRCCS Ca’ Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy; 4 CHU de Québec, Laval University, Québec City, Canada; 5 Acibadem City Clinic Tokuda Hospital, Sofia, Bulgaria; 6 Urology Department, Assiut University, Assiut, Egypt; 7 Shar Teaching Hospital, Sulaymanyah City, Iraq; 8 Department of Urology, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China; 9 Department of Urology and Nephrology, Military Medical Academy, Sofia, Bulgaria; 10 Smart Health Tower, Sulaymaniyah, Kurdistan region, Iraq; 11 Instituto de Investigaciones Metabólicas (IDIM Department of Urology), Buenos Aires, Argentina; 12 Department of Urology, Kasturba Medical College, Manipal, Karnataka, India; 13 U-merge Ltd (Urology for emerging countries), London, UK. DOI: 10.4081/aiua.2021.3.307 Summary Archivio Italiano di Urologia e Andrologia 2021; 93, 3 A. Haliński, K. Hassan Bhatti, L. Boeri, et al. 308 urate (> 50%), sodium urate (> 50%), mixed UA/CaOx, cystine. The Statistical Package for the Social Sciences (SPSS) ver- sion 11.5 for Windows was used for statistical analysis. Comparisons were considered to differ significantly if p < 0.05. RESULTS In total, 1204 renal stone formers (RSFs) were considered (776 males, 428 females) from 10 countries (Argentina, Bulgaria, Canada, China, Egypt, India, Iraq, Italy, Pakistan and Poland). Twelve institutions from 10 countries have joined the survey as listed below: - Department of Urology, Instituto de Investigaciones Metabólicas, Buenos Aires (Argentina) - Acibadem City Clinic Tokuda Hospital, Sofia (Bulgaria) - Department of Urology and Nephrology, Military Medical Academy, Sofia (Bulgaria) - CHU de Québec, Laval University, Québec City (Canada) - Dep of Urolotgy, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai (China) - Urology Department, Assiut University, Assiut (Egypt) - Department of Urology, Kasturba Medical College, Manipal, Karnataka (India) - Urology Department, Sulaymaniyah Surgical Teaching Hospital, Sulaymaniyah (Iraq) - Shar Teaching Hospital, Sulaymanyah City (Iraq) - Department of Urology, IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan (Italy) - City Hospital Pakpattan, Pakpattan (Pakistan) - Private Medical Center Klinika Wisniowa, Zielona Gora (Poland) The average age of patients was 49.3+14.4 and the M/F ratio was 1.81. The number, average age and M/F ratio of RSFs from different countries are shown in Table 1. The average age of RSFs in Italy and Canada was greater than that of the RSFs of Argentina (p = 0.000), Bulgaria (p = 0.000 and p = 0.001), Egypt (p-0.000), Iraq (p = 0.000, and Pakistan (p = 0.000). The average age of RSFs in Italy was higher than that of the RSFs in China (p = 0.011). The lowest average age was observed in Egypt, Iraq, and Pakistan, where the average age of RSFs was lower than those of RSFs in Canada (p = 0.000), Italy (p = 0.000) and China (p = 0.000, p = 0.000 and p = 0.001). In Egypt and Iraq, the average age of the RSFs was also lower than in Bulgaria (p = 0.001, p = 0.002), Poland (p = 0.020, p = 0.007) and India (p = 0.009 and p = 0.004). The frequency of the disease was slightly higher in women in Poland (52%), whereas it tended to be higher in men in Canada (56%), Argentina (59%), Italy (63%), China (64%) and Bulgaria (67%). Highest rates in men were observed in Pakistan (86%), Egypt (78%), India (74%) and Iraq (72%). The spectrum of stone composition by gender and age is shown in Table 2. In total, we observed 710 (59%) patients with calcium oxalate, 31 (1%) with calcium phos- phate, 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. In the calcium-containing group, calcium oxalate stones accounted for 77% and phosphate or mixed calcium phosphate/calcium oxalate stones for the remaining 23%. The frequency of calcium phosphate or mixed calcium phosphate/calcium oxalate ranged from 9 to 74%. The great variability depends on the different methods of analyzing stones and reporting the results. In 403 patients with calcium oxalate stones analyzed by infrared spectroscopy, calcium oxalate monohydrate stones (COM) were more frequent than calcium oxalate dihydrate (COD) stones. Frequency of calcium oxalate stones was equal in women and men (58% vs 59%), whereas frequency of uric acid containing stones was lower in women than in men (13% vs 21%) and frequency of calcium phosphate and mixed calcium phosphate/calcium oxalate stones (21% vs 14%) and frequency of struvite stones were higher in women. Frequency of COM stones tended to be higher in men than in women (78 vs 71%) and to increase with age (18- 39 =78%, 40-59 = 80%, > 60% = 85%). Table 1. Average age and M/F ratio of RSFs from different countries. Argentina Bulgaria Canada China Egypt India Iraq Italy Pakistan Poland N° 300 183 50 90 73 35 36 360 44 33 M 179 (59%) 122 (67%) 28 (56%) 58 (64%) 57 (78%) 26 (74%) 26 (72%) 226 (63%) 38 (86%) 16 (48%) F 121 (41%) 61 (33%) 22 (44%) 32 (36%) 16 (22%) 9 (26%) 10 (28%) 134 (37%) 6 (14%) 17 (52%) Age 45+12 48+13 56+14 50+12 40+12 50+12 38+13 56+14 40+8 50+17 Age p = 0.000; M/F p = 0.002. Table 2. Spectrum of stone composition by gender and age. Gender Age class Males Females 18-39 40-59 > 60 Total CaOx 461 (59%) 249 (58%) 200 (59%) 318 (57%) 192 (62%) 710 (59%) COM 223 105 73 136 119 328 COD 52 23 20 34 21 75 CaOx/CaP 89 (11%) 72 (16%) 46 (13%) 80 (14%) 35 (11%) 161 (13%) CaP 18 (2.3%) 13 (3.0%) 12 (3.5%) 14 (2.5%) 5 (1.5%) 31 (3%) Carbapatite 4 (0.5%) 11 (2.5%) 5 (1.5%) 8 (1.5%) 2 (0.5%) 15 (1%) Ca-containing 572 (74%) 345 (80%) 263 (77%) 420 (76%) 234 (76%) 917 (76%) UA 84 (11%) 26 (6%) 22 (6.4%) 49 (8.8%) 39 (12.6%) 110 (9%) Urate 4 (0.5%) 3 (0.7%) 0 (0%) 4 (0.5%) 3 (1%) 7 (0.5%) UA/CaOx 75 (10%) 25 (6%) 25 (7%) 55 (10%) 20 (6%) 110 (9%) UA-containing 163 (21%) 54 (13%) 47 (14%) 108 (19%) 62 (20%) 217 (18%) Struvite 33 (4.2%) 23 (5.4%) 23 (7%) 22 (4%) 11 (3.5%) 56 (5%) Cystine 8 (1.1%) 6 (1.4%) 8 (2.5%) 4 (0.5%) 2 (0.5%) 14 (1%) Total 776 428 341 554 309 1204 309Archivio Italiano di Urologia e Andrologia 2021; 93, 3 Worldwide renal stone composition Frequency of uric acid stones was higher in males and tended to increase with age. The distribution of the different types of stones in RSFs in different countries is described in Table 3. Calcium-con- taining stones were the most common in all countries. Among calcium-containing stones, calcium oxalate stones were more frequent in all countries except in Egypt and India where the frequency of calcium phosphate or mixed calcium phosphate/calcium oxalate was 74% in Egypt and 53% in India, respectively. Among calcium oxalate stones, the rate of COM stones was 100% in Egypt, 83% in Italy, 81% in Bulgaria, 75% in China, and 69% in Iraq. The rate of uric acid containing stones ranged 4 to 34% in most countries with the highest rates observed in Egypt, India, Poland, and Bulgaria. Struvite stones were less than 5% in all countries but India (23%) and Pakistan (16%). Cystine stones were less than 2%. DISCUSSION Stone composition by age and sex In the present study, calcium-containing stones were the most frequent, followed by uric acid-containing stones, while struvite and cystine are less frequent. In accordance with previous reports (9), uric acid con- taining stones were more frequent in males and in older ages, whereas phosphate stones were more frequent in women. The average age of RSFs in different countries varies but these differences reflect those that are observable in the general population of their countries, which averaged about 20 years lower (Figure 1). M/F ratio is different in countries, being balanced between men and women or slightly in favor of men in the countries of North America, Europe, South America and China but heavily weighted in favor of men in Egypt, Pakistan, India and Iraq. This finding confirmed the ten- dency to an increase of stone formation in women of Western countries (9), and more recently of China (10), while in Egypt, Pakistan, India and Iraq the ratio of males to females is still similar to what was observed in Western countries forty years ago (11). This trend can be explained by the so-called nutrition transition, that is the change in dietary habits across the world with a conver- gence towards an increased consumption of unhealthy Table 3. Spectrum of stone composition in different countries. Argentina Bulgaria Canada China Egypt India Iraq Italy Pakistan Poland Tot CaOx 239 (80%) 97 (53%) 23 (46%) 65 (72%) 12 (16%) 7 (20%) 16 (44%) 214 (59%) 21 (48%) 16 (49%) 710 (59%) COM - 79 - 49 12 11 178 - COD - 18 - 16 0 5 36 - CaOx/CaP 12 (4%) 17 (9%) 11 (22%) 11 (12%) 34 (47%) 8 (23%) 7 (20%) 57 (16%) 0 (0%) 4 (12%) 161 (13%) CaP 7 (2%) 0 (0%) 2 (4%) 6 (7%) 0 (0%) 0 (0%) 0 14 (4%) 2 (4%) 0 31 (3%) Carbapatite 0 (0%) 3 (2%) 10 (20%) 0 (0%) 0 (0%) 0 (0%) 2 (5%) 0 (0%) 0 (0%) 0 15 (1%) Ca-containing 258 (86%) 117 (64%) 46 (92%) 82 (91%) 46 (63%) 15 (43%) 25 (69%) 285 (79%) 23 52% 20 61% 917 (76%) Ox % 92% 85% 50% 79% 26% 46% 64% 72% 91% 80% 77% UA pure 27 (9%) 8 (4.5%) 1 (2%) 5 (5%) 0 (0%) 5 (14%) 8 (22%) 39 (10.5%) 11 (25%) 6 (18%) 110 (9%) UA urate 0 (0%) 6 (3.5%) 0 (0%) 0 (0%) 0 (0%) 0 (0%) 0 (0%) 1 (0.5%) 0 (0%) 0 (0%) 7 (1%) UA/CaOx 6 (2%) 39 (21%) 1 (2%) 1 (1%) 22 (30%) 7 (20%) 1 (3%) 18 (5%) 0 (0%) 5 (15%) 100 (8%) UA - containing 33 (11%) 53 29% 2 (4%) 6 6% 22 (30%) 12 (34%) 9 (25%) 58 (16%) 11 (25%) 11 (33%) 217 (18%) Struvite 9 (3%) 10 (5.4%) 1 (2%) 2 (3%) 4 (5.5%) 8 (23%) 1 (3%) 12 (3,5%) 8 (18%) 1 (3%) 56 (5%) Cystine 0 (0%) 3 (1.6%) 1 (2%) 0 (0%) 1 (1.5%) 0 (0%) 1 (3%) 5 (1.5%) 2 (5%) 1 (3%) 14 (1%) Total 300 183 50 90 73 35 36 360 44 33 1204 Figure 1. Average age in RSFs and general population. Archivio Italiano di Urologia e Andrologia 2021; 93, 3 A. Haliński, K. Hassan Bhatti, L. Boeri, et al. 310 foods that is the cause of the increase in non-communi- cable diseases in almost all regions of the world in both sexes (12). Consumption of unhealthy foods is still limit- ed in some regions of North Africa and South Asia that maintain dietary patterns with a lower risk of urinary stones forming. Moreover, in some countries the charac- teristics of family structure and cultural rules still present a nutritional disadvantage for women (13). Stone composition by country The spectrum of composition of urinary stones is quite variable in different countries. Differences could be attrib- utable to the different characteristics by age and gender of the populations studied, reflecting the distribution by age and gender in the general population of each country. On the other hand, the modality of stone analysis and report- ing in the different centers may be a confounding factor (14). For this reason, the most robust data are those com- paring the rates of calcium-containing with those of uric acid containing stones, whereas it is less significant to compare the results of different countries in relation to the specific crystallographic composition, which should be compared between patients whose stones have been ana- lyzed and reported in the same laboratory. Calcium-containing stones were the most common in vast majority of countries with a rate ranging from 52 to 91%. The highest rates of calcium-containing stones were observed in North America, South America, China and some European countries. In most countries, calcium oxalate stones (in particular, COM stones) were the more frequent calcium-containing stones, although calcium phosphate and mixed calcium oxalate/calcium phosphate stones were more frequent than pure calcium oxalate stones in some countries such as Egypt and India. This trend agrees with previous observation in North America where a tendency has been reported of an increase in oxalate stones and a decrease in phosphate stones during the last two decades (4, 5). The highest rates of acid uric con- taining stones were observed in Iraq, Pakistan, India, Egypt and Poland and Bulgaria. In general, uric acid-con- taining stones should be more fre- quent in older male patients, but sur- prisingly in our study the highest rates of uric acid-containing stones were observed in two countries with the lowest mean age, namely Egypt and Iraq. This result can be explained by the finding that the fre- quency of a type of stone is not a measure of the prevalence of the dis- ease in the population, but is the result of the prevalence of different types of urinary stones. In other words, a high frequency of uric acid stones may be due to an increase in the prevalence of uric acid stones but, alternatively, a lower prevalence of other types of stones in the popu- lation studied. On the other hand, the impact of environmental factors could be decisive, considering that high temperatures and high humidi- ty cause a decrease of urinary vol- umes and urinary pH values result- ing in an increase of urinary uric acid saturation and of the incidence of uric acid stones (15, 16). In fact, the highest values of uric acid-containing stones were observed in countries with high mean temperatures (17) and tropic or hot desert climates such as Egypt, India, Pakistan and Iraq (Table 4) (Figure 2). Our data con- firm previous evidence in the litera- ture showing a high rate of uric acid- containing stones in Pakistan, Egypt, and Iraq (18-21). In the present Figure 2. Rate of uric-acid containing stones and mean temperature. Table 4. Mean temperature, precipitation fall and climate classification in the countries involved in the study. Country Town Temperature Precipitation Climate Köppen-Geiger climate mean fall classification system Argentina Buenos Aires 16.8 °C. 1040 mm Warm temperate Cfa Bulgaria Sofia 10.2 °C 581 mm Warm temperate Cfb Canada Quebec 4.8 °C. 1101 mm Cold temperate Dfb China Shanghai 16.1 °C. 1066 mm Warm temperate Cfa Egypt Asyut 22.6 °C. 2 mm Hot desert BWh India Karnataka 26.7 °C 4866 mm Tropical Am Pakistan Pakpattan 24.8 °C 234 mm Hot desert BWh Iraq Sulaymaniyah 16.2 °C 906 mm. Warm temperate Csa Italy Milan 13.1°C 1013 mm Warm temperate Cfa Poland Zielona Gora 8.8 °C 572 mm Warm temperate Cfb 311Archivio Italiano di Urologia e Andrologia 2021; 93, 3 Worldwide renal stone composition study, the prevalence of uric acid containing stones was also high in Southern India in accordance with previous reports. In fact, the frequency of uric acid-containing stones was reported low (4.28%) or very low (< 1%) in North Western India (22, 23), but higher in Southern India (24). This difference can be explained by different region- al eating habits: in the Northern and Western regions, a more traditional vegetarian diet is consumed with exclu- sive consumption of fruit, vegetables and legumes, where- as in the Southern regions the consumption of sweets, snacks and pork meat is common (25). On the other hand, in our study the lowest rate of uric acid containing stones was observed in Canada, the country with the low- est mean temperature. Intermediate rate values were observed in countries with a temperate climate, such as China and Italy. The high frequency of uric acid-contain- ing stones in Poland is less easily explained, mainly because it contrasts with previous findings showing lower rates of uric acid stones in a series of stones analyzed by infrared spectroscopy (26). Possible explanations are high obesity rate of the population (45%) and unfavorable dietary patterns (27). In fact, the adherence to the tradi- tional Polish dietary pattern, characterized by high intake of refined grains, potatoes, sugar and sweets is associated with a higher risk of abdominal obesity and hypertriglyc- eridemia (28). Similarly, in Bulgaria the frequency of uric acid-containing stones is associated with obesity rates which are among the highest in Europe (46%) (27), and with an unhealthy nutritional pattern characterized by high consumption of fatty meats and meat products, high- fat milk and a high alcohol intake (29). The rate of struvite stones is generally lower than described in the past, due to improved health conditions and early diagnosis and treatment of urinary tract infec- tions by urease-producers, although in some countries such as Pakistan and India it still accounts for a quarter of cases. Cystine stone rates are similar in all countries, with similar rates than those reported in the literature. In conclusion, the frequency of different types of urinary stones varies from country to country. Calcium-containing stones are the most frequent in all countries, with fre- quencies of up to 90%. The frequency of uric acid con- taining stones seems to depend mainly on climatic factors, being more frequent in warmer countries with desert or tropical climates although 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 except India and Pakistan. REFERENCES 1. Daudon M, Donsimoni R, Hennequin C, et al. Sex- and age-relat- ed composition of 10 617 calculi analyzed by infrared spectroscopy. Urol Res. 1995; 23:319-26. 2. Trinchieri A, Rovera F, Nespoli R, Currò A. Clinical observations on 2086 patients with upper urinary tract stone. Arch Ital Urol Androl. 1996; 68:251-62. 3. Knoll T, Schubert AB, Fahlenkamp D, et al. Urolithiasis through the ages: data on more than 200,000 urinary stone analyses. J Urol. 2011 Apr;185(4):1304-11. doi: 10.1016/j.juro.2010.11.073. 4. Gault MH, Chafe L. Relationship of frequency, age, sex, stone weight and composition in 15,624 stones: comparison of resutls for 1980 to 1983 and 1995 to 1998. J Urol. 2000; 164:302-7. 5. Moses R, Pais VM Jr, Ursiny M, et al. Changes in stone composi- tion over two decades: evaluation of over 10,000 stone analyses. Urolithiasis. 2015; 43:135-9. 6. Singh P, Enders FT, Vaughan LE, et al. Stone composition among first-time symptomatic kidney stone formers in the community. Mayo Clin Proc. 2015; 90:1356-65. 7. Xu LHR, Adams-Huet B, Poindexter JR, et al. Temporal changes in kidney stone composition and in risk factors predisposing to stone formation. J Urol. 2017; 197:1465-1471. 8. Kittanamongkolchai W, Vaughan LE, Enders FT, et al. The chang- ing incidence and presentation of urinary stones over 3 decades. Mayo Clin Proc. 2018; 93:291-299. 9. Lieske JC, Rule AD, Krambeck AE, et al. Stone composition as a function of age and sex. Clin J Am Soc Nephrol. 2014; 9:2141-6. doi: 10.2215/CJN.05660614. 10. Zeng G, Mai Z, Xia S, et al. Prevalence of kidney stones in China: an ultrasonography based cross-sectional study. BJU Int. 2017; 120:109-116. doi: 10.1111/bju.13828. Epub 2017 Mar 21. 11. Johnson CM, Wilson DM, O'Fallon WM, et al. Renal stone epi- demiology: a 25-year study in Rochester, Minnesota. Kidney Int. 1979; 16:624-31. 12. Imamura F, Micha R, Khatibzadeh S, et al. Global Burden of Diseases Nutrition and Chronic Diseases Expert Group (NutriCoDE) Dietary quality among men and women in 187 countries in 1990 and 2010: a systematic assessment. Lancet Glob Health. 2015; 3:e132-42. 13. Rao T, & Pingali P. The role of agriculture in women's nutrition: Empirical evidence from India. PloS one 2018; 13:e0201115. 14. Siener R, Buchholz N, Daudon M, et al. Quality Assessment of Urinary Stone Analysis: Results of a Multicenter Study of Laboratories in Europe. PloS one 2016; 11:e0156606. 15. Stuart RO 2nd, Hill K, Poindexter J, Pak CY. Seasonal variations in urinary risk factors among patients with nephrolithiasis. J Lithotr Stone Dis. 1991; 3:18-27. 16. Baker PW, Coyle P, Bais R, Rofe AM. Influence of season, age, and sex on renal stone formation in South Australia. Med J Aust. 1993; 159:390-2. 17. https://it.climate-data.org/ 18. Rafique M, Bhutta RA, Rauf A, Chaudhry IA. Chemical compo- sition of upper renal tract calculi in Multan. J Pak Med Assoc. 2000; 50:145-8. 19. Sheir KZ, Mansour O, Madbouly K, et al. Determination of the chemical composition of urinary calculi by noncontrast spiral com- puterized tomography. Urol Res. 2005; 33:99-104 20. Afaj AH, Sultan MA. Mineralogical composition of the urinary stones from different provinces in Iraq. Scientific World Journal. 2005; 5:24-38. 21. Popov E, Almusafer M, Belba A, et al. Obesity rates in renal stone formers from various countries. Arch Ital Urol Androl. 2021; 93:189-194. 22. Bhat A, Singh V, Bhat M, et al. Spectrum of urinary stone com- position in Northwestern Rajasthan using Fourier transform infrared spectroscopy. Indian J Urol. 2018; 34:144-148. doi: 10.4103/ iju.IJU_363_16. 23. Ansari MS, Gupta NP, Hemal AK, et al. Spectrum of stone com- position: structural analysis of 1050 upper urinary tract calculi from northern India. Int J Urol. 2005; 12:12-6. Archivio Italiano di Urologia e Andrologia 2021; 93, 3 A. Haliński, K. Hassan Bhatti, L. Boeri, et al. 312 24. Marickar YMF. Epidemiology of stone disease in Kerala, South India. In Talati J, Tiselius H-G, Albala DM, Ye Z (eds.) Urolithiasis: basic science and clinical practice, Springer Verlag, London, pp 47-51. 25. Green R, Milner J, Joy EJ, et al. Dietary patterns in India: a sys- tematic review. Br J Nutr. 2016; 116:142-8. doi: 10.1017/ S0007114516001598. 26. Wrobel A, Rokita E, Taton G, Thor P. Chemical composition and morphology of renal stones. Folia Med Cracov. 2013; 53:5-15. 27. Kotseva K, Wood D, De Bacquer D, et al. A European Society of Cardiology survey on the lifestyle, risk factor and therapeutic man- agement of coronary patients from 24 European countries. Eur J Prev Cardiol. 2016; 23:636-48. doi: 10.1177/2047487315569401. 28. Suliga E, Kozieł D, Ciesla E, et al. Dietary patterns in relation to metabolic syndrome among adults in Poland: a cross-sectional study. Nutrients. 2017; 9. pii: E1366. doi: 10.3390/nu9121366. 29. ncpha.government.bg/files/hranene-en.pdf Correspondence Adam Haliński, MD adamhalinski@gmail.com Private Medical Center "Klinika Wisniowa" Anieli Krzywon street 2; 65-001 Zielona Gora (Poland) Kamran Hassan Bhatti, MD kamibhatti92@gmail.com City Hospital Pakpattan (Pakistan) Luca Boeri, MD dr.lucaboeri@gmail.com Department of Urology, IRCCS Ca’ Granda Ospedale Maggiore Policlinico University of Milan, Milan, Italy Kaloyan Davidoff, MD shennyp@yahoo.com Elenko Popov, MD shennyp@yahoo.com Acibadem City Clinic Tokuda Hospital - Sofia, Bulgaria Sofia, bul N. Vaptzarov 51 B Ayman Elqady, MD Mohamed Gadelmoula, MD mgad73@aun.edu.eg Urology Department - Assiut University - Assiut (Egypt) Goran Fryad, MD goranfryad@yahoo.com Shar Teaching Hospital - Malik Mahmood Circle street, Sulaimani City (Kurdistan Region-Iraq) PO Box: Baxtyary 36B Hongyi Hui, MD 1095340463@qq.com Department of Urology, Renji Hospital, Shanghai Jiaotong University School of Medicine No.160, Pujian Road, Shanghai, 200127, China Kremena Petkova, MD dr_petkova@yahoo.com Iliya Saltirov, MD saltirov@vma.bg Department of Urology and Nephrology, Military Medical Academy 3, Georgi Sofiiski blvd, 1606 Sofia, Bulgaria Bapir Rawa, MD dr.rawa@yahoo.com Smart Health Tower, Sulaymaniyah, Kurdistan region, Iraq Francisco R Spivacow, MD frspivacow@gmail.com Instituto de Investigaciones Metabólicas (IDIM) Libertad 836, 1° piso, Ciudad Autónoma de Buenos Aires (Argentina) Belthangady Monu Zeeshan Hameed, MD zeeshanhameedbm@gmail.com Kasturba Medical College, Manipal Department of Urology, KMC Hospital, Manipal-576104, Karnataka, India Alberto Trinchieri, MD alberto.trinchieri@gmail.com Noor Buchholz, MD (Corresponding Author) noor.buchholz@gmail.com U-merge Ltd. (Urology for emerging countries), London, UK