Renal stone disease or nephrolithiasis is a frequent urological condition where solid crystalline material develops in the urinary tract and kidneys. Such deposits form when urine becomes supersaturated with stone forming substances, which allow for the formation of crystals, aggregation, growth and retention within the urinary system. Renal stone disease is a big clinical and public health problem as it may lead to major flank pain, haematouria, urinary obstruction, recurrent urinary infection and even in complicated cases to impaired renal function.

The incidence of urolithiasis is far different in different parts of the world depending upon environmental conditions, food habits, socioeconomic status, genetic susceptibility, and diagnostic methods. Therefore, knowledge on the epidemiology of renal stones is crucial to optimize clinical treatment and to design preventive measures [1–3].

Renal stone disease has become more prevalent in several populations over the past few decades, but the rate of increase differs with each population studied and the techniques employed in stone detection. There is strong evidence today to suggest that urolithiasis is a considerable problem in the world, influenced by geographical location, sex, age, and diagnostic criteria. Excessive sweating, low urine output, and high concentration of lithogenic substances in urine may be responsible for the enhanced risk for stone formation that may occur in hot climates. Also, low fluid intake, diets high in sodium, animal protein, obesity, diabetes mellitus and metabolic syndrome can help lead to stone formation. Personal susceptibility is also affected by family history and inherited metabolic abnormalities. All these interacting factors lead to renal stone disease being a multifactorial disease that needs clinical assessment as well as population specific epidemiological investigation [1,2,4].

Renal stones can occur at any age, but vary in terms of incidence and type across different age groups. In many populations, adult males have been found to suffer from stone disease more often than females; however, the extent to which they differ geographically and in time varies. Age differences are also significant, as diet habits, metabolism, urine chemistry and related health issues can affect stone formation. For instance, calcium stones are very common in adults, and some inherited or metabolic conditions can lead to the development of stones at an early age. Likewise, uric acid stones are related to prolonged acid urine and often are related to metabolic abnormalities. Analysis of age and sex distribution of renal stones can thus be used as a tool to gain information on the population affected by renal stones most commonly, and to identify population groups that might benefit from preventive measures. [2,4,5]

Chemical composition is an important feature of renal stone disease as stones develop due to different biochemical mechanisms and treatment and prevention strategies may be different from stone type to stone type. The main types of kidney stones are calcium oxalate, calcium phosphate, uric acid, struvite, and cystine stones. The major component of many populations is calcium oxalate, which is associated with hypercalciuria, hyperoxaluria, hypocitraturia and low urinary volume. Some renal tubular diseases and hypercalciuria are associated with the formation of calcium phosphate stones and may be present. Uric acid stones are often linked with acidic urine, hyperuricosuria, obesity and insulin resistance. Struvite stones form with the presence of urease-producing urinary pathogens, while cystine stones arise from a genetic defect in amino acid transport in renal tubules [6–8].

Another point is that stones of the kidneys often consist of more than one chemical component. Several metabolic abnormalities; alteration of urinary pH, infection and changes in the urinary environment over time may all contribute to the development of mixed stones. They can be made up of various mixtures of calcium oxalate and calcium phosphate, or other mineral components. So, stones that are just considered based on one main stone component may not truly reflect the stone's composition. An assessment of the whole and mixed stones may offer a more accurate representation of the chemical patterns that are found in a specific population. Large-scale studies of stones have shown significant difference in the number and percentage of stone constituents, underscoring the need for proper laboratory method when characterizing urinary stones [9,10].

Accurate stone analysis is crucial to understanding the mechanisms of stone formation and to making future clinical decisions. The mineral composition of urinary calculi can be determined using the well known analytical methods of fourier-transform infrared spectroscopy (FTIR) and x-ray diffraction. The added value of FTIR spectroscopy is its ability to elucidate the different crystalline and organic components and to determine mixed compositions. However, conventional wet chemical analysis is limited in the identification of particular mineral phases and the discrimination of complex mineral mixtures. Recent urologic guidelines recommend testing stone whenever stone is available, especially following the first stone episode and when recurrence or alterations in clinical situations indicate the need for re-evaluation. The chemical composition may be useful in directing metabolic studies, dietary adjustments, pharmacological prevention, and follow-up [6,7,11].

Renal stone composition in Pakistani population should be studied. During Northern Pakistan in a reference-laboratory study, Bibi and co-workers found that the main component of stones was calcium oxalate, followed by uric acid and other less common components. Another study conducted in Lahore and its vicinity on FTIR spectroscopy of stone samples also showed significant differences in compositions of stone based on age and gender. The results indicate that local data may be used to better describe the distribution of stone types and the differences in stone type for certain populations that are relevant to clinical practice. The results of reference laboratories cannot, however, be regarded as being representative of all patients seen by the individual hospital since referral patterns, specimen availability, geographical distribution of the laboratories and patient characteristics may vary [12, 13].

Although progress has been made in the diagnosis of stones and an analysis of their composition, the incidence and chemical nature of renal stones may not be the same in different healthcare facilities. Reported distributions may be affected by differing climates, dietary practices, availability of medical care, population features and laboratory methods. Furthermore, the composition of one region cannot be extrapolated to another as the relative amount of calcium-containing, uric acid, infection-related, and other stones may vary. Investigations in a hospital can thus be of value in defining local patterns, especially if the stone composition can be analysed by a method that is both reliable and widely used. These studies can also yield baseline data for future research on the association of stone type, demographic, clinical presentation and recurrence risk [3,9,12,13].

The present study titled, “Frequency and Chemical Composition of Renal Stones in Patients Presenting to a Tertiary Care Hospital” aims of this study are to find the frequency of various types of renal stones in patients attending a tertiary care hospital and to describe their chemical composition. The findings of the distribution of main stone constituents, and if applicable, their correlation with age and sex, will be of value as local epidemiological evidence. The results may help doctors determine the most common type of stone and help them decide what metabolic tests to order and which preventive actions to take. Overall, if more detail is available of the frequency and composition of renal stones in the study population, this could aid in better patient care and more effective strategies to reduce the recurrence of renal stones and the associated health burden [5,11,14,15].

The study was a descriptive cross-sectional hospital-based study carried out in Department of Urology, Ayub Teaching Hospital Abbottabad, Pakistan during a period of six months from March to September 2026. The purpose of the study was to find the prevalence and chemical constituents of renal stones in patients attending the hospital. Renal calculi diagnosed based on clinical assessment and suitable radiological investigations were taken for inclusion. Patients irrespective of sex and age were included if a specimen of the retrieved renal stone was available for chemical analysis. Patients with incomplete clinical records, no stone specimens, or stone specimens not suitable for analysis were not included.

With informed consent, structured data collection form was used to gather the relevant demographic and clinical data. The variables were age, sex, clinical presentation, history of renal stones and available relevant medical history. Stone samples were collected and sent to the laboratory for chemical analysis. Calcium oxalate, calcium phosphate, uric acid, struvite, cystine, and mixed stones (if present) were the major stone types evaluated. Documentation of the method for stone analysis was done in the laboratory according to the facilities and procedures available in the hospital. The stones were classified by the composition identified and mixed stones were noted in cases where more than one composition could be determined.

The data were input and analysed using the IBM SPSS Statistics software version 27. Data from categorical variables such as sex and stone composition were reported as frequencies and percentages. Age was a continuous variable summarised using mean and standard deviation or median and interquartile range (IQR) depending on the distribution of the data. The chi square test or Fisher's exact test was used to determine associations with stone type and demographic variables such as age group and sex, as appropriate. A value of p < 0.05 was deemed to be statistically significant. The ethical approval is obtained from the relevant institutional ethics review committee prior to the data collection and patient confidentiality was ensured throughout the study.

The study was conducted at Ayub teaching hospital, Abbottabad from March to September 2026, which included 60 patients with renal stones. The outcomes were tabulated by patients' demography and the number and chemical composition of renal stones. This illustrative distribution will be provided in the following tables; the numbers are made up and must be substituted with the actual findings from the study before submission.

Table 1. Demographic characteristics of patients (n = 60)

Sixty patients with renal stones were enrolled in the study. There were 38 male (63.3%) and 22 female (36.7%) subjects in the study. The age group with the most patients was 31-40 years (18 (30.0%)), followed by 41-50 years (16 (26.7%)). Twelve (20.0%) patients were aged 18–30 years, nine (15.0%) were aged 51–60 years, and five (8.3%) were older than 60 years.

Table 2. Frequency and chemical composition of renal stones (n = 60)

The most common stone composition was calcium oxalate with a frequency of 32 cases (53.3%). Eight patients (13.3%) had calcium phosphate stones and seven (11.7%) had uric acid stones. Six (10.0%) patients had stones of mixed composition, followed by struvite stones (5, 8.3%). Cystine stones were the rarest, occurring in two (3.3%) cases. In general, the calcium containing stones were the most common type in this illustrative distribution.

Table 3. Distribution of stone composition according to sex (n = 60)

Of the patients with calcium oxalate stone, 68.8% (22) were males and 31.3% (10) were female. Similarly, uric acid stones were more common in males, with six of seven stones (85.7%) being in males. By comparison, struvite stones occurred more often in females, three of five (60.0%). The distribution of calcium phosphate, cystine and mixed-composition stones was approximately equal between the sexes. The results of this description indicate that there was variation in stone composition between the sexes, but it is not possible to demonstrate that statistically without the appropriate statistical test on the verified stone level data.

The present study assessed the frequency, chemical composition and prevalence of stones in the kidneys among 60 patients who attended the Ayub Teaching Hospital in Abbottabad. Calcium oxalate (53.3%) was the most common stone type followed by calcium phosphate stones (13.3%), uric acid stones (11.7%), mixed-composition stones (10.0%), struvite stones (8.3%) and cystine stones (3.3%) in the illustrative results. The results indicate that the most common type of renal stone among the studied population was calcium-containing stones.

The overall calcium oxalate predominance was in line with the general knowledge that one of the larger proportions of urinary calculi in many populations is due to calcium stones. The factors that affect stone formation are urinary supersaturation, calcium and oxalate excretion, citrate concentration, urine volume, and the presence of substances that either facilitate or inhibit crystal formation. They said that insufficient water intake, hypercalciuria, hyperoxaluria and hypocitraturia are all factors that contribute to the development of kidney stones [16]. If the calcium oxalate stones were common, then it would be good to consider metabolic abnormalities in the involved patients. However, stone composition is not enough to determine which specific metabolic disturbance might have led to a patient's stone.

The demographic distribution  showed that males represented 63.3% of the patients, compared with 36.7% females. The pattern is similar to the epidemiological literature, which suggests that there is an increased prevalence of nephrolithiasis among men in some populations, but this difference varies by geographical region and over time. Shoag and colleagues discussed the influence of demographic characteristics and associated systemic conditions on the changing epidemiology of nephrolithiasis [17]. Some variations between the sexes may be due to differences in diet, heat-exposure at work, fluid intake and metabolic risk factors. However, the findings of the present study would be limited in generalizability to the larger population in Abbottabad and Pakistan, due to the small sample size and hospital setting.

The following are other factors considered in the epidemiological evaluation of renal stones: The illustrative results showed that patients between 31 and 40 years of age were the largest age group (30.0%), followed by those in the age range of 41–50 years (26.7%). This trend may be an indication of the clinical burden in the tertiary care setting amongst the adult population, but should not be viewed as a representation of the age-specific incidence of renal stones. The samples collected in the hospital are not considered to be representative of the general population because they are only those who go to the hospital for care and are diagnosed. Therefore, the distribution observed could be affected by the referral process, access to treatment, and the chances of stone retrieval and analysis [17,18].

The chemical composition can also vary significantly from area to area. In a study of 1,005 patients from northwest Rajasthan, Bhat and co-workers found that calcium oxalate was the most common component and that stones made up of mixed materials was a significant number of cases [18]. Likewise, a large study on urinary stone composition in central China showed that there were variations in stone profiles according to clinical and demographic features [19]. The results confirm the need for regional studies, not to rely on the composition reported from one population being the same elsewhere. Variations between studies could be due to differences in climate, diet, hydration, metabolic disorders and analytical methods.

It is important to also consider the occurrence of calcium phosphate and uric acid stones. Hypercalciuria, alkaline urine and some metabolic disorders are associated with calcium phosphate stones, while persistently acidic urine and metabolic disorders are strongly associated with uric acid stones. However, Lin et al. in a systemic review and meta-analysis, found correlations between nephrolithiasis and some modifiable risk factors such as obesity, sodium intake, animal protein intake and fluid intake [20]. These findings underscore the need to evaluate the dietary and metabolic risk factors in renal stone patients. The descriptive design of the present study, however, cannot infer causal relationships between the chemical composition of stones and lifestyle factors.

The importance of struvite stones is that they are frequently associated with urinary tract infections due to organisms that produce urease. If they are identified it may be necessary to evaluate for chronic infection and to treat accordingly so as to minimise the risk of further stone formation. Cystine stones are a relatively rare type of kidney stone that is linked to a genetic defect in amino acid transport, and can be very difficult to manage in the long-term. However, the identification of these less common stone types is still relevant as their prevention and follow-up may be different to the calcium containing stones [21,22].

Another important point of renal stone analysis that is relevant is the identification of mixed-composition stones. Mineral constituents can be present in a stone in more than one form; this reflects the changes in the chemistry of the urine during stone formation. He and colleagues showed that stones found in the upper urinary tract have different mineral content throughout, with stones in the centre being different to those in the rim; so that may be multiple minerals in a single stone, differing between the core and the rim [23]. In this regard, laboratory methods that can determine more than one constituent could yield better information than methods that just identify a stone by its major constituent. Observations of the proportion of mixed stones are interpreted according to the analytical method used.

To move epidemiological findings from research to practice, reliable chemical analysis is crucial. The constituents of urinary calculi are well known by using infrared spectroscopy and X-ray diffraction. Multiple and significant variations in stone composition and from one age group to another and region to region have been well documented with FTIR studies [18,19,24]. If resources allow, validated analytical techniques can be used to enhance classification and help the clinician to plan metabolic assessment and preventive treatment. The method adopted in the present study in Ayub Teaching Hospital explicitly reported to enable easy comparison with other investigations.

Previous studies also show that stone composition could relate to patient's age, gender, past history of stones, stone's anatomical location and urinary pH. In a retrospective analysis of 858 stone samples, Wang and colleagues found that calcium oxalate stones were more prevalent, and found differences in composition related to demographic and clinical variables [24]. Likewise, Zhang et al. found significant differences in stone composition amongst 3,684 samples collected from Eastern Shandong, with a large number of uric acid and mixed composition stones [25]. The results confirm the importance of local stone analysis in order to gain an understanding of regional patterns and direct appropriate preventative measures.

Interpretation of the findings of the present study, taking into consideration some limitations. The first limitation of the study is that only 60 patients were included in the sample from a single tertiary care hospital, and therefore results may not be generalizable. Secondly, the brief study period may not adequately reflect the seasonal variation in stone presentation or composition. Thirdly, a thorough metabolic investigations and detailed dietary and hydration history were not available, so the underlying risk factors could not have been properly assessed. Last but not least, the percentages shown are illustrative and cannot form any basis for definitive conclusions because there are no verified patient-level results or confirmed laboratory methods in the current draft. Larger studies, with standardized stone-analysis and detailed clinical and metabolic evaluation are recommended

Renal stone disease continues to be a significant urological condition, given its ability to result in significant pain, urinary obstruction, recurrent infection, and renal function impairment. The purpose of this study was to find out the frequency and chemistry of stone in patients coming to Ayub Teaching Hospital, Abbottabad. Calcium oxalate is the common type of stone followed by calcium phosphate stones and uric acid stones, and struvite and cystine stones were less frequent in illustrative results presented. The majority of patients in this study were males. But these were hypothetical results which have been provided for the purpose of drafting the manuscript and should not be viewed as study results until confirmed by the actual patient records and laboratory reports collected from the study. Chemical analysis was shown to be a key tool in determining common stones and suitable clinical management.

Recommendations

Chemical analysis of retrieved kidney stones should be encouraged as a routine procedure to enable targeted stone prevention measures. Renal stone patients should be counselled to drink sufficient water, to reduce water and salt consumption as well as food intake according to their clinical and metabolic evaluation. When clinically warranted, urinary and serum metabolic testing should be performed to further investigate, such as in patients with recurrent stones, bilateral stones or atypical stone composition. If patients are suspected of having infection-related stones, they will need the appropriate evaluation and treatment of their urinary infection. Further, larger multicenter studies with longer follow-up periods and standardized analytical techniques are needed to determine the regional variations in renal stone composition and to assess whether age, sex, diet, hydration, and metabolic risk factors are associated with renal stone composition

1. Stamatelou K, Goldfarb DS. Epidemiology of kidney stones. Healthcare (Basel). 2023;11(3):424. https://doi.org/10.3390/healthcare11030424
2. Sorokin I, Mamoulakis C, Miyazawa K, Rodgers A, Talati J, Lotan Y. Epidemiology of stone disease across the world. World J Urol. 2017;35(9):1301–1320. https://doi.org/10.1007/s00345-017-2008-6
3. Alelign T, Petros B. Kidney stone disease: an update on current concepts. Adv Urol. 2018;2018:3068365. https://doi.org/10.1155/2018/3068365
4. Soucie JM, Thun MJ, Coates RJ, McClellan W, Austin H. Demographic and geographic variability of kidney stones in the United States. Kidney Int. 1994;46(3):893–899. https://doi.org/10.1038/ki.1994.347
5. Basiri A, Tahvildari A, Naji M, Ziaeefar P, Kashi AH. Determination of the kidney stone composition using infrared spectroscopy in Iran at a national referral center during 2019–2023. Asian J Urol. 2025;12(1):72–78. https://doi.org/10.1016/j.ajur.2024.07.004
6. European Association of Urology. European Association of Urology guidelines on the diagnosis and treatment of urolithiasis. Eur Urol. 2025;88(1):64–75. https://doi.org/10.1016/j.eururo.2025.03.011
7. Skolarikos A, Somani B, Neisius A, Jung H, Petřík A, Tailly T, et al. Metabolic evaluation and recurrence prevention for urinary stone patients: an EAU guidelines update. Eur Urol. 2024;86(4):343–363. https://doi.org/10.1016/j.eururo.2024.05.029
8. Khan SR, Pearle MS, Robertson WG, Gambaro G, Canales BK, Doizi S, et al. Kidney stones. Nat Rev Dis Primers. 2016;2:16008. https://doi.org/10.1038/nrdp.2016.8
9. Siener R, Rüdy J, Herwig H, Schmitz MT, Schaefer RM, Lossin P, et al. Mixed stones: urinary stone composition, frequency and distribution by gender and age. Urolithiasis. 2024;52:24. https://doi.org/10.1007/s00240-023-01521-8
10. Daudon M, Jungers P. Clinical value of crystalluria and quantitative morphoconstitutional analysis of urinary calculi. For methodological background on infrared stone analysis, see: J Endourol. 2004;18(3):209–218. https://doi.org/10.1089/089277904323011966
11. Türk C, Petřík A, Sarica K, Seitz C, Skolarikos A, Straub M, et al. EAU guidelines on diagnosis and conservative management of urolithiasis. Eur Urol. 2016;69(3):468–474. https://doi.org/10.1016/j.eururo.2015.07.040
12. Bibi A, Aamir M, Riaz M, Haroon ZH, Kirmani SI, Javaid H. Assessment of frequency and composition of renal stones in a reference laboratory of Pakistan. Pak Armed Forces Med J. 2023;73(2):341–344. https://doi.org/10.51253/pafmj.v73i2.6798
13. Zubair M, Zoha R. A chemical odyssey: exploring renal stone diversity by age and sex in Punjab, Pakistan. J Biomed Res. 2024;38(5):516–518. https://doi.org/10.7555/JBR.38.20240039
14. Mitchell T, Kumar P, Reddy T, Wood KD, Knight J, Assimos DG, et al. Dietary oxalate and kidney stone formation. Am J Physiol Renal Physiol. 2019;316(3):F409–F413. https://doi.org/10.1152/ajprenal.00373.2018
15. Pearle MS, Goldfarb DS, Assimos DG, Curhan G, Denu-Ciocca CJ, Matlaga BR, et al. Medical management of kidney stones: AUA guideline. J Urol. 2014;192(2):316–324. https://doi.org/10.1016/j.juro.2014.05.006
16. Peerapen P, Thongboonkerd V. Kidney stone prevention. Adv Nutr. 2023;14(3):555–569. https://doi.org/10.1016/j.advnut.2023.03.002
17. Shoag J, Tasian GE, Goldfarb DS, Eisner BH. The new epidemiology of nephrolithiasis. Adv Chronic Kidney Dis. 2015;22(4):273–278. https://doi.org/10.1053/j.ackd.2015.04.004
18. Bhat A, Singh V, Bhat M, Kumar V, Bhat A, Khandelwal N, et al. Spectrum of urinary stone composition in Northwestern Rajasthan using Fourier transform infrared spectroscopy. Indian J Urol. 2018;34(2):144–148. https://doi.org/10.4103/iju.IJU_363_16
19. Zhang H, He Z, Zhang J, Zheng J, Jing Z, Hu C, et al. Urinary stone composition analysis and clinical characterization of 1520 patients in central China. Sci Rep. 2021;11:4636. https://doi.org/10.1038/s41598-021-85723-3
20. Lin BB, Lin ME, Huang RH, Hong YK, Lin BL, He XJ. Dietary and lifestyle factors for primary prevention of nephrolithiasis: a systematic review and meta-analysis. BMC Nephrol. 2020;21:267. https://doi.org/10.1186/s12882-020-01925-3
21. Gamage KN, Jamnadass E, Sulaiman SK, Pietropaolo A, Aboumarzouk O, Somani BK. The role of fluid intake in the prevention of kidney stone disease: a systematic review over the last two decades. Turk J Urol. 2020;46(Suppl 1):S92–S103. https://doi.org/10.5152/tud.2020.20155
22. Aizezi X, Xie L, Xie H, et al. Epidemiological and clinical characteristics of stone composition: a single-center retrospective study. Urolithiasis. 2022;50:37–46. https://doi.org/10.1007/s00240-021-01274-2
23. He Z, Jing Z, Jing-Cun Z, Hu C, et al. Compositional analysis of various layers of upper urinary tract stones by infrared spectroscopy. Exp Ther Med. 2017;14(4):3165–3169. https://doi.org/10.3892/etm.2017.4864
24. Wang B, Zheng X, Xiong J, Sun Z. Characteristics of urinary stone composition among patients with urolithiasis: a retrospective study in China. BMJ Open. 2024;14(11):e079431. https://doi.org/10.1136/bmjopen-2023-079431
25. Zhang X, Ma J, Wang N, Lin C. Urinary stone composition analysis of 3684 patients in the eastern Shandong region of China. J Int Med Res. 2020;48(3):300060519887266. https://doi.org/10.1177/0300060519887266