{'fraction_non_alphanumeric': 0.040479140850888065, 'fraction_numerical': 0.02734407269723255, 'mean_word_length': 4.8909975669099754, 'pattern_counts': {'":': 0, '<': 2, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Epidemiology and composition of nephrolithiasis in a Lebanese tertiary care center: A descriptive study

Introduction: Nephrolithiasis is a common affliction with a prevalence of 12% in men and 7% in women. The incidence rate diverges with geographic location. Arab countries report high nephrolithiasis prevalence rates, with Saudi Arabia being the highest (20.1%). To date, there is little knowledge about the demographics and composition of stones in Lebanon. Methods: A retrospective chart review was performed on stone composition at the American University of Beirut Medical Center, between 2005 and 2018. Patients’ demographics and stone characteristics were obtained from electronic medical records. Analysis of frequencies and Chi-square test were adopted for potential risk factor correlations by the Statistical Package for the Social Sciences (SPSS). Results: A total of 626 stone analyses were performed. Male patients predominated (69%). The mean age was 46.58 ± 16.5 years, and mean body mass index was 28.63 ± 5.6, for both sexes. Calcium oxalate was the most predominant stone in both sexes (70%). Uric acid stones followed (~16%), and calcium oxalate phosphate stones were the third most common (5%). Incidence of kidney stones peaks in the summer, with 11.86% presenting in July. Around 60% presented with flank pain to the Emergency Department, and 32% ended up with spontaneous passage of stones by medical expulsive therapies alone, with no further surgical intervention. Diabetes and hypertension were significantly correlated with stone recurrence in our cohort. Conclusion: There is a significant gender disparity in stone prevalence in Lebanon. Calcium oxalate is the most common type in both sexes. Future investigations of dietary and environmental factors are recommended from our region.

In 2009, 1.3 million ED visits in the US were linked to symptomatic kidney stones. [2] This variation is expected to be due to the increasing prevalence of the metabolic syndrome in the population. [4] It is also a widespread illness in other regions such as 5%-9% in Europe and 1%-5% in Asia. [5] The primary age group afflicted is the working-age population. The Urological Disease in America Project estimated the direct costs of stones to be 4.5 billion dollars in 2000 due to common ED visits, hospitalization and lost working hours. [2] The relapsing rate for secondary stone formation is about 10%-23% per year; 50% in the next 5-10 years, and 75% in 20 years, in those who do not apply metaphylaxis. [1] A few epidemiological elements showed an augmented risk for stone formation such as genetics, sex, climate, geographic location, and weight. [1] Once diagnosed with the first kidney stone, about 50% will experience another episode in the following 10 years. [2] There is a paucity of studies about the prevalence and composition of kidney stones from the Middle Eastern and the Levant countries. The following descriptive study aims to determine the prevalence of kidney and ureteral stones from a cohort of patients presenting to a tertiary care center in Beirut, Lebanon. The composition of stones has been emphasized along with the numerous risk factors that could prompt stone recurrence.

METHODS
The aim of this paper is to present and describe the epidemiology and composition of stones in Lebanon, part of the Middle Eastern, and North African countries. Lebanon is one of the Levant countries, facing the Mediterranean Sea. A retrospective review was performed of all adult patients who had the composition of their upper urinary tract calculi analyzed at the American University of Beirut Medical Center between 2005 and 2018. Patients' electronic medical records were accessed, and their demographics were obtained. The following information was collected: Sex, age, and seasonal time from which the stone was extracted and analyzed, weight and body mass index (BMI), among others.
Following the descriptive study, analysis of frequencies and Chi-square testing was done by the IBM SPSS Statistics for Windows, version 26 (IBM Corp., Armonk, N.Y., USA), to check for any statistically significant correlation between patients' comorbidities and the risk for developing stones. We anticipated different results, secondary to the diverse patients' genetics, comorbidities, dietary habits, and even due to the different geographical locations within the same country.

RESULTS
A total of 626 patients were included in the cohort study. The mean age of patients was 46.6 years. Most of the patients were from Beirut-the capital and the most populated area of Lebanon. Over two-thirds of patients were males (69%); 47.8% were active smokers, and 44.2% were hypertensive [ Table 1]. There were 80.3% of patients with BMI of or <25 kg/m 2 . Stone distribution according to patients' age for both genders is presented in Table 2. The overall Male:female (M:F) ratio was 2.28. The M:F ratio was the highest in the elderly in their 7 th decade of life, whereas it was the lowest in extreme elderly in their 9 th decade of life. The highest number of calculi was observed in the age group 40-49 years, in both males and females.
Calcium oxalate was the most frequently isolated type of calculi in both sexes (70% of all stones). Calcium phosphate was by far the least abundant component (0.5%) in both sexes (0.2% in males and 1.2% in females). Uric acid stones, accounting for a relative proportion of 16.0%, were the second most abundantly isolated composition [ Table 3]. The struvite stones were almost twice as common in females as in males, and cysteine stones were twice as abundant in males as in females. Figure 1 shows the variation of stone composition in terms of age and between sexes. Calcium oxalate is the most abundant type of calculi across all ages. Its occurrence seemed to increase with age to reach two peaks in the following age groups: 40-49 and 60-69 years. Calcium oxalate was the most abundantly isolated type of calculi in every age class from 10 years up to 89 years in both sexes. Struvite stones were seen to affect females at a younger age than male counterparts, mainly in the age group of 30-49 years among most age groups.

BMI: Body mass index
The incidence of symptomatic stones, over the months of the year, was witnessed to peak during July (11.9% of stones analyzed) [ Figure 2]. Geographical location of patients who had their ureteral/kidney stone(s) analyzed at our medical center, was also identified and analyzed. Figure 3 represents the density of calculi in terms of the original Mohafaza (Governorate) of those patients, expressed per 10,000 population. Lebanon has 8 governorates in total and Beirut is the capital and a governorate. The density was calculated by the ratio of participants coming from a given Mohafaza to the total number of the Mohafaza population (as estimated by the Central Administration of Statistics). Beirut had by far the highest stone density of 7.92 per 10,000 population. Interestingly, 87.5% of all cystine stones came from the region of Mount Lebanon.
Approximately, 60% of patients presented with flank pain to the Emergency Department, while the remaining patients were diagnosed on a nonemergent basis. One-third of patients (32%) passed their stones through conservative medical expulsive therapy, with 42% of patients requiring at least one endourological intervention, regardless of the type of stone. Figure 4 shows the several management options for the patients, including the different treatments utilized such as medical expulsive therapies, extracorporeal shock wave lithotripsy (ESWL), and ureteroscopy, etc. Calcium oxalate stones required either ESWL or ureteroscopy in 10% and 60% of the cases, respectively. Around two-thirds of calcium phosphate stones (66.7%) were passed spontaneously on medical expulsive therapy. Of the pertinent medical risk factors, ordinal logistic regression analysis of our cohort highlighted that both diabetes and hypertension were related to an increased risk of kidney stones recurrence with an odds ratio of 1.8 (95% confidence interval [CI] 1.18-2.78), and 1.4 (95% CI 1.21-2.13), respectively.

DISCUSSION
Urolithiasis distresses all age groups, sexes, and  races. [1] Notwithstanding the extensive improvements in the development of novel therapies, the incidence of urolithiasis is mounting across the globe. [1] The National Health and Nutrition Examination Survey examined stone epidemiology in North America (n = 12,110) during 2007 and 2010. [4] The prevalence of stone disease was 8.4% (95% CI, 7.7-9.0). Men were more like to have a history of stone disease than women.
In the weighted analysis, BMI was linked to a history of stone disease. The prevalence of kidney stones was more in obese individuals (11.2% [95% CI, 10.0-12.3]) and overweight individuals (9.2% [95% CI, 7.9-10.5]), versus individuals with normal weight (6.1% [95% CI, 4.8-7.2]) (P < 0.001). [4] Data on the chemical composition of stones are helpful in determining pathogenesis, indicating the type of treatment, and avoiding recurrence. The chemical composition of urinary stones comprises crystals and noncrystalline phases, i.e., the organic material (the matrix). Calcium is the major component of most stones in our Lebanese cohort, present in about 80% of the total urinary calculi. The same was also noted in studies from other countries such as Tunisia, Morocco, Oman, Kuwait, and Iraq. [6][7][8][9][10][11] The proportion of calcium stones may account for pure calcium oxalate (CaOx) (50%), calcium phosphate (CaP, termed as apatite) (5%), and a mixture of both (45%). [1] There are several elements that cause CaOx stone formation (hypercalciuria, hyperuricosuria,   that help discover silent stones. This study represents one of the largest characterizations of stone composition in the Middle East and the first in Lebanon. There is a notable gender difference in stone prevalence in Lebanon, with males afflicted to a significantly larger extent. Calcium oxalate is the most prevalent kind of stone irrespective of gender and in agreement with the literature. Future research on dietary and environmental factors can help add value to these preliminary epidemiologic findings. Classifying stone formers according to their clinical presentation and stone composition can antedate the risk of future symptomatic stone episodes and help in personalization of stone prevention strategies.

Financial support and sponsorship
Nil.

Conflicts of interest
There are no conflicts of interest.
hyperoxaluria, hypocitraturia, and hypomagnesuria). Stones are formed due to urinary infection or sepsis. Struvite stones or magnesium ammonium phosphate, account for 10%-15% and are known as infection stones or triple phosphate stones. Those are generally caused by urease-producing organisms such as Proteus, Pseudomonas, Klebsiella, and Staphylococcus aureus that make the urine alkaline.
Very few cohort studies from the MENA region have described the incidence of stones and their compositions [ Table 4]. A study conducted in Tunisia analyzed 1,301 urolithiasis patients (6 months to 92 years old), 60% males and 40% females, and showed that average annual incidence of new stone formation was 31.7 per 100,000 population. Calcium oxalate monohydrate was the most recurrent stone constituent, and bladder stones were seen in 18.2% of cases. [6] Another large series from Kuwait of 1191 patients indicated that the average yearly incidence of new stone formation was 23.9/100,000 inhabitants. Calcium oxalate was the most prevalent stones (65.8%). [12] An increase in total dietary protein and sodium intake, obesity, sedentary lifestyle, and global warming may contribute to our results. In addition, other key agents may play a role like the noteworthy change in food behaviors, emphasis on industrialized diet, and preponderance of metabolite-related diseases in the MENA region.

CONCLUSION
There is a surge in urolithiasis incidence and prevalence worldwide predominantly due to the increase in diagnostic advancements and improvements in imaging techniques