Risk Factors for Kidney Stone Disease in Nimroz, Afghanistan: A Retrospective Case–Control Study, 2021

ABSTRACT

Background

Kidney stone disease affects many people annually, impairing the quality of their life and health. Several risk factors such as family history, chronic diseases and diet have been reported to cause kidney stones. Reports and data show that there is an increasing pattern in the incidence of kidney stones.

Aims

This study aimed to determine the risk factors associated with kidney stone disease in Nimroz province of Afghanistan.

Methods and Materials

This hospital‐based case‐control study was conducted in Red Crescent Hospital (RCH) in Nimroz province during June–August 2021. Case was any patient with kidney stone diagnosed by ultrasonography and the control was a patient without kidney stone. Both were attending outpatient department of the target hospital at the time of data collection. The nonprobability purposive sampling technique was used. A face‐to‐face interview was carried out using a structured questionnaire. Bivariate and multi‐variate analysis using Chi‐square test, t‐test, and multiple logistic regressions were performed to calculate p‐values and odds ratio with 95% confidence interval.

Results

A total of 378 participants were interviewed (188 cases and 190 controls). The mean of age was 34.4 with 11.5 SD. The bivariate analysis in the study revealed a statistically significant association between kidney stones and occupation, BMI, family history, kidney disease, heart disease, blood pressure, and asthma. in addition, the multiple logistic regression results showed that daily use of salt and water, weekly use of eggs and diary, and age were also associated with kidney stones after adjustment of confounders.

Conclusion

The risk of kidney stones was found high among those with positive family history, > 30 BMI, and chronic ill patients. Cases who used more eggs and diary on a weekly base, and drunk less water and consumed excessive salt on a daily base were also more likely to have developed kidney stones. Families and the community should be educated about the modifiable risk factors of kidney stones.

1. Introduction

Kidney stones (nephrolithiasis) also known as renal stone or renal calculi are solid crystals which are formed from dissolved minerals in urine [1]. The disease has been reported to affect the quality of life with an increased annual incidence rate [2]. Kidney stones are common in different geographical settings with a higher prevalence in developed countries [3]. The prevalence of stone formation is reported to vary across the world [4]. Europe, America, Egypt, India, Pakistan, Indonesia, Saudi Arabia, Thailand, and other tropical and subtropical region have reported higher rates of kidney stone diseases [5, 6, 7]. Many studies have reported sociodemographic factors, diet, infections, genetics, poor fluid‐intake, lifestyle, climate, dehydration, and chronic diseases as potential predisposing factors for nephrolithiasis [8, 9, 10, 11].

Risk factors of kidney stones include, but are not limited to dehydration, diet, family history and poor fluid‐intake. Indeed, these risk factors can be categorized into dietary and non‐dietary factors [12]. Men are reported to suffer more from kidney stones; however, data suggest increased rates of kidney stones among both sexes [13, 14]. It is also reported that middle aged people are more affected by this disease [1]. Another group of risk factors found from different studies are alcohol consumption, smoking, physical activity, obesity, education, water quality and high intake of vitamin D and C [1, 15, 16, 17].

Kidney stone disease is well known as a systemic disorder that is associated with chronic kidney disease, nephrolithiasis‐induced bone disease, increased risk of coronary artery disease, hypertension, type 2 diabetes mellitus, and the metabolic syndrome (MS) [18]. In addition, End Stage Renal Disease (ESRD) and chronic kidney disease are also reported to be associated with kidney stones [19]. As a painful urological disorder, kidney stones could be asymptomatic and with sever signs and symptoms among patients, leading to hospitalization and mostly surgery depending on the size of the stones. The stones present as sudden severe unilateral colicky flank pain that may radiate anteriorly to the lower abdomen, groin, testes, or labia and usually associated with hematuria. It may also come with nausea, vomiting, dysuria, frequency, or passage of gravel [20, 21]. Evidence suggests the importance of preventive strategies for lowering the prevalence of kidney stones [21]. Considering the recurrence of stone formation, managing the most common risk factor could decrease the risk of stone formation and its recurrence. Recurrence of kidney stones have also been reported to be prevalent with high burdens of financial expenditures.

Afghanistan health system lacks data on kidney stones, however, the findings of Afghanistan Health Survey 2018, has shown that kidney problem including kidney stones are common among older ages [22]. The gap of data might be due to neglection of non‐communicable disease and priority for communicable diseases. A retrospective hospital‐based study on urinary tract samples of patients in Khost province showed that most of the stones were kidney stones and male patients were affected more [11]. Evidence also suggests the wide prevalence of kidney diseases in Afghanistan and the lack of nephrologists and diagnostic equipment [23], meanwhile, Afghanistan is shown to be among the countries with rapid decline in kidney stone incidence and this decline is indicated to be linked with incomplete data registry systems in the country [24]. Considering the upsurge in number of kidney stone patients in Nimroz province, this study aimed to find the risk factors associated with kidney stones in this province.

2. Methods and Materials

2.1. Design and Setting

This hospital‐based case–control study was conducted during June–August 2021 in Iranian Red Crescent Society Hospital in Zaranj city of Nimroz province. This 32 beds hospital has general operating room, gynecology, pediatrics, dental departments, dermatology, maternity and midwifery services, ultrasound, laboratory, nursing services, vaccinations, pharmacy, general practitioner, and specialist. In addition, the patients with kidney stones also visit this hospital for diagnosis and treatment. Most of the patients who visited this hospital were females at the time of data collection.

2.2. Selection of Cases and Controls

Cases were the patients with kidney stone disease who visited the target hospital. All the patients with kidney stone confirmation and signs and symptoms were included in the study except under 18 years old patients, rejecting to cooperate and attend the study, and pregnant women. Controls were defined as those patients who visited the hospital because of other health conditions and had no kidney stone problem. After screening, we selected all potential respondents who were available in the hospital during the study period.

2.3. Sample Size and Sampling

A total of 362 samples were calculated for the present study considering 95% confidence interval (CI), 20% proportion in the case group and 80% power using the Epi Info software version 7.2.1. The sample size was adjusted for a 5% nonresponse rate as well. One control per one case was considered for the study. The total number of cases and controls were 188 and 190, respectively. The controls were selected from the same community which is under the catchment area for the Iranian Red Crescent Society Hospital. Due to lack of hospitals in the Nimroz province, most of the people are referred to this hospital for tertiary services.

2.4. Study Tool and Variables

The study used a predefined questionnaire to interview the cases and controls. The questionnaire developed by the authors after modification of previous questionnaires consisted of questions regarding sociodemographic characteristics like age, sex, marital status, literacy, residence, BMI, dietary habits, such as frequency of consumption of water, weekly intake of certain foods (beans, eggs, meat, chicken, salt, tomatoes, potatoes, vegetables, and vitamins), smoking, frequency of urination, chronic diseases, family history of kidney stones, medical examination, and exercise habits. The questionnaire was translated in local languages, piloted, and modified before the data collection process. The dependent variable for the study was set to be the kidney stone while sociodemographic factors, dietary habits, medica, examination, family history, chronic diseases and daily exercise were independent variables.

2.5. Data Collection

Data was collected from cases and control through a face‐to‐face interview by trained data collectors after the consent was taken from the participant. Data was collected for 3 months starting in June 2021 and ending in August 2021. The structured questionnaire along with the details of the study were explained to the cases and control before starting the interview, and each interview tool a minimum of 15 min.

2.6. Ethical Considerations

Clearance and approval of the Institutional Review Board (IRB) of the Ministry of Public Health was obtained before initiation of the study. Informed consent was taken from all participants before the interview and privacy was ensured during the interview. All information was coded and stored electronically.

2.7. Statistical Analysis

The descriptive statistics on demographic and background characteristics of cases and controls are presented as percentages. Associations between the kidney stone as a “dependent” variable and each of the ‘independent’ variables such as age, sex, occupation, drinking water, exercise, urination frequency and dietary practices were carried out using out by using bivariate analysis.

The frequency of consumptions of various food are also showed in percentage and analyzed in two categories. Frequency of risk factors for kidney stones including family history and existence of other chronic diseases are shown in tables. The association between the dependent variable and each independent variable was quantified using odds ratios (OR) along with 95% CI. Finally, multiple logistic regressions were carried out to get the final model of risk factors for kidney stones by adjusting the confounders. All the variables used for bivariate analysis were pulled for multivariate analysis. To show association, the p < 0.05 is considered significant. The data management process including data entry, cleaning and analysis were done using MS. Excel, SPSS 24.0, and Epi Info 7.2.1. Tables are used to visualize main findings.

3. Results

A total of 378 participants were interviewed for this study among which 188 (49.74%) were cases and 190 (50.26%) were controls. The total number of male participants were 18 (4.76%) and females were 360 (95.24%) with 20:1 female male ratio. The male participants in case group were 6 (3.19%) and females were 182 (96.81%), additionally in the control group the male participants were 12 (6.32%) and females were 178 (93.68). Most of the participants 117 (30.95%) were between 25 and 35 years old. The mean of age for cases were 33.8 with 12.5 SD and for controls 35 with a 10.5 SD. Most of cases and controls, 327 (86.51%) were jobless and 259 (68.52%) were illiterate (Table 1).

Table 1.

Sociodemographic characteristics of the respondents n = 378.

Demographic characteristics	Count (N)	Percent (%)
Age in years
< = 25	98	25.93%
26–35	117	30.95%
36–45	99	26.19%
46–55	39	10.32%
> 55	19	5.03%
Gender
Male	18	4.76%
Female	360	95.24%
Occupation
Employed	51	13.49%
Jobless	327	86.51%
Marital status
Married	321	84.92%
Single	56	14.81%
Divorced	1	0.26%
Literacy
Yes	119	31.48%
No	259	68.52%
Economic status
Good	71	18.78%
Middle	228	60.32%
Poor	79	20.90%
Current residence
Urban	215	56.88%
Rural	163	43.12%

228 (60.32%) of the participant reported their economic status to be middle and 321 (84.92%) were married. In terms of current residence, 215 (56.88%) of the respondents were living in urban areas of Nimroz province. The data collectors also collected the height and weight of the respondents to calculate their body mass index (BMI). BMI of 202 (53.44%) respondents was normal, and 56 (14.81%) were obese.

Associations between kidney stone and occupation OR 9.41 (CI 95%: 3.90–22.68) was found in the study. The results showed that the odds of kidney stone occurrence among employed participants were 9.4 times higher than jobless respondents, however, no association between kidney stone disease and other sociodemographic and socioeconomic variables was found (Table 2).

Table 2.

Sociodemographic and socioeconomic variables and their association with kidney stone disease.

Variables	Cases N (%)	Controls N (%)	OR (CI 95%)	p value
Occupation
Employed	6 (3.19)	45 (23.68)	9.41	p < .001
Jobless	182 (96.81)	145 (76.32)	(3.90–22.68)
Age
Under 35 years	114 (62.64)	101 (53.16)	1.47	0.032
35 Years and above	68 (37.36)	89 (46.84)	(0.97–2.23)
Gender
Male	6 (3.19)	12 (6.32)	2.04	0.082
Female	182 (96.81)	178 (93.68)	(0.75–5.56)
Literacy
Yes	55 (29.26)	64 (33.68)	1.22	0.17
No	133 (70.74)	126 (66.32)	(0.79–1.89)
Residence
Urban	102 (54.26)	113 (59.47)	1.23	0.15
Rural	86 (45.74)	77 (40.53)	(0.82–1.86)
Economic status
Good	143 (76.06)	156 (82.11)	0.69	0.075
Poor	45 (23.94)	34 (17.89)	(0.42–1.14)

Abbreviations: CI, confidence interval; OR, odds ratio.

The study team also collected information of risk factors of kidney stones among participants. Data was collected on height and weight (BMI), family history of kidney stones and kidney stone history among family members and close relatives, chronic disease history (kidney disease, heart disease, diabetes, asthma, and blood pressure), diet (use of beans, eggs, diary, salt, meat, tomatoes, vegetables, and Vit C), drinking water and type of drinking water, smoking, urination in 24 h, and daily exercise.

In bivariate analysis, among risk factors, associations between kidney stone and BMI OR 1.84 (CI 95%: 1.02–3.29), family history OR 6.09 (CI 95%: 3.85–9.64), kidney disease OR 8.74 (CI 95%: 1.98–38.58), heart disease OR 4.63 (CI 95%: 1.29–16.52), blood pressure OR 2.26 (CI 95%: 1.23–4.15), and asthma OR 6.05 (CI 95%: 2.46–14.88) were seen after analysis (Table 3).

Table 3.

Risk factors and their association with kidney stone disease.

Variables	Cases	Controls	OR	p values
	N (%)	N (%)	(CI 95%)
BMI
Over 30	35 (18.62)	21 (11.05)	1.84	0.03
Under 30	153 (81.38)	169 (88.95)	(1.02–3.29)
Family history
Yes	115 (61.17)	39 (20.53)	6.09	0.001
No	73 (38.83)	151 (79.47)	(3.85–9.64)
Family history (father)
Yes	30 (15.96)	7 (3.68)	4.96	0.001
No	158 (84.04)	183 (96.32)	(2.12–11.61)
Family history (mother)
Yes	25 (13.30)	7 (3.68)	4	0.001
No	163 (86.70)	183 (96.32)	(1.68–9.51)
Kidney disease
Yes	16 (8.51)	2 (1.05)	8.74	0.001
No	172 (91.49)	188 (98.95)	(1.98–38.58)
Heart disease
Yes	13 (6.91)	3 (1.58)	4.63	0.005
No	175 (93.09)	187 (98.42)	(1.29 – 16.52)
Blood pressure
Yes	36 (19.15)	18 (9.47)	2.26	0.003
No	152 (80.85)	172 (90.53)	(1.23–4.15)
Asthma
Yes	31 (16.49)	6 (3.16)	6.05	p < 0.001
No	157 (83.51)	184 (96.84)	(2.46–14.88)

Abbreviations: BMI, body mass index; CI, confidence interval; OR, odds ratio.

The results showed that the odds of kidney stone occurrence among obese participants were 1.8. The risk of developing kidney stones among cases with a family history of kidney stone was six times higher than the cases with no family history of kidney stones. The findings revealed that kidney stone history among parents (father and mother) of cases were higher than controls. Cases with a history of chronic diseases such as kidney diseases, heart diseases, blood pressure and asthma had developed kidney stone disease 8.7, 4.6, 2.2, and six times more than cases with no history of the mentioned diseases.

The multiple logistic regression results after adjustment of confounders confirmed the outcomes of chi‐square test and in addition showed that other variables such as age p = 0.02 (CI 95% 1.07–3.27), daily use of salt p = 0.04 (CI 95% 1.01–3.02), daily drinking water p = 0.00 (CI 95% 0.07–0.32), weekly egg consumption p = 0.00 (CI 95% 1.42–3.35), and weekly diary consumption p = 0.00 (CI 95% 1.81–6.22) were significantly associated with kidney stones. The results indicate that participants with older ages, excessive daily salt intake, less water consumption in a day, and high consumption of eggs and dairy in a week were more likely to have developed kidney stones (Table 4).

Table 4.

Multiple logistic regression outcomes for kidney stones and independent variables.

Variables	Number	Percentage	Adjusted OR	p values
			(CI 95%)
Age
Under 30	148	39.2	1.87	p < 0.001
30 and above	230	60.8	(1.07–3.27)
Occupation
Employed	51	13.5	0.07	p < 0.001
Jobless	327	86.5	(0.02–0.22)
Family history of KS
Yes	154	40.7	4.66	p < 0.001
No	224	59.3	(2.67–8.13)
Kidney disease
Yes	18	4.8	4.96	0.062
No	360	95.2	(0.92–26.72)
Asthma
Yes	37	9.8	3.36	p < 0.001
No	341	90.2	(1.17–9.64)
Daily salt intake
Over 5 g	218	57.7	1.75	p < 0.001
Under 5 g	160	42.3	(1.01–3.02)
Daily drinking water
0–2 glass	74	19.6	0.15	p < 0.001
3–10 glass	304	80.4	(0.07–0.32)
Weekly consumption of eggs
Never	88	23.3	2.18	p < 0.001
1–2 piece	202	53.4
			(1.42–3.35)
> = 3 piece	88	23.3
Weekly diary intake
Never‐once	110	29.1	3.35	p < 0.001
Twice‐more than three times	268	70.9	(1.81–6.22)

Abbreviations: BMI, body mass index; CI, confidence interval; KS, kidney stones; OR, odds ratio.

4. Discussion

Understanding the epidemiology and risk factors of kidney stones is important to determine the significance of the disease at the community level [25]. In the present study we found that high BMI, having family history of kidney stones, being unemployed, chronic conditions (asthma, kidney diseases, blood pressure, and heart disease), high daily salt intake, less daily water consumption, high eggs and diary consumption in a week, and being old are risk factors for kidney stones.

Older ages were found to be associated with the development of kidney stones in the current study. Studies in different settings suggest different ages to be at risk of kidney stones. The findings of two studies in tertiary care hospitals in Pakistan showed that kidney stones were more prevalent among patients aged 15–30 years with is in contrary to the findings of this study [26, 27]. Evidence suggest that men are at a greater risk of kidney stones compared to women [4, 28, 29, 30, 31]. The current study included more female participants, with a female to male ratio of 20:1. This is because most of the visitors of the target hospital are females, however considering the female to male ratio of the study, 33.33% of men in case group had kidney stones which is higher considering the total number of male participants. In Addition, the study also found that employed participants were at a higher risk of kidney stone disease, however a similar hospital‐based case–control study in India found that laborers were more likely to have developed kidney stones [32]. This could be due to Some occupations which prevent individuals from drinking enough fluids to maintain a dilute urine or to void when they need to, poor access to fluids, and bathrooms, and doing sedentary jobs.

Literature suggests significant association between obesity, body mass index, waist circumference, and kidney stones, with an increased risk of developing kidney stones among obese women [33, 34, 35]. The present study also found association between kidney stone development and BMI OR 1.84 (CI 95%: 1.02–3.29). The exact mechanism is unknown; however, it is reported that obesity is associated with insulin resistance and compensatory hyperinsulinemia, metabolic derangements that may lead to the formation of calcium‐containing kidney stones [34].

In the present study, kidney stones developed more frequently among participants with a family history of kidney stones than in those without a family history. We found that 77.68% of the cases had a family history, either among their parents, siblings, or close relatives. The results of several studies are in accord with our findings and suggest that family history increase the risk of developing kidney stones among individuals, even men with a family history of kidney stones are three times more likely to develop kidney stones compared to men with no family history. In addition, evidence suggest that dietary calcium restriction may increase the risk of stone formation, even among individuals with a family history of kidney stones. Those with a family history of stones have an increased incidence of multiple and early recurrences as well [36, 37, 38].

Kidney stones are not only related to family history, diet, and hydration, but also to some chronic conditions such as metabolic syndrome, heart diseases, diabetes, blood pressure and chronic kidney diseases as well [9, 39, 40, 41]. The current study findings showed that participants with chronic kidney disease, heart diseases, blood pressure and asthma were more likely to have developed kidney stones. The effect of kidney stones on deterioration of renal function has not been extensively studied in the epidemiologic literature; however, evidence suggest that kidney stones are associated with increased risk of chronic kidney diseases. Additionally, recurrence of kidney stones should be avoided not only because of their immediate clinical manifestations but also because of their long‐term predisposition to CKD progression [42, 43]. Moreover, 6.91% of the present study case group reported to have heart diseases, which is high compared to the control group (1.58%). The potential explanation for kidney stone and heart disease association could be the prevalence and incidence of heart diseases risk factors such as hypertension, diabetes and metabolic syndrome, influence of dietary factors and deterioration of kidney function among kidney stone patients [44, 45, 46].

Hypertensive individuals have a greater risk of renal stone formation, especially when hypertension is associated with excessive body weight [47]. These patients have an increased 24‐h urinary calcium output due to defective tubular reabsorption of calcium [48]. Including the findings of this study, literature also indicates on association between hypertension and formation of kidney stones [41, 47, 48, 49]. In the present study asthma was found to be associated with kidney stone disease OR 6.05 (CI 95%: 2.46–14.88). It has been proposed that epithelial dysfunction and inflammation may predispose patients to kidney stone formation. Asthma is another chronic condition related to epithelial dysfunction and inflammation [50]. There is lack of evidence on asthma and kidney stones among adults; however, a few studies confirm association between asthma and development of kidney stones [50, 51, 52].

Data of various sorts, demonstrate that diet is an important contributor to the prevalence of kidney stones. Excessive salt intake has been focused on in the last few years as one of the main elements that influence health status including formation of kidney stones. Increased amounts of dietary sodium intake increase the risk of kidney stones [53]. Some studies focusing on dietary habits of idiopathic calcium stone formers have clearly demonstrated that these individuals have a significantly higher daily intake of salt and a more frequent consumption of salty foods, than healthy controls, especially among younger females [54, 55]. In addition, animal protein and calcium have shown to have role in stone formation [56, 57]. Moreover, existing data suggest that low fluids intake, especially water contributes to a faster formation of stones [58]. Low volume and high urine concentration are both regarded as risk factors for the formation of stones [59]. In the current study, participants who consumed less than three glass of water per day have developed kidney stones more than people with higher water intake, which is the same with the findings of a study among patients in India [1]. Warmer climate conditions, low access to fluids, poor hydration cultures, and lack of facilities for urination in many areas in the country and Nimroz province, could be a reason in formation of stones among people.

The current study has strengths and limitations. This study was a case‐control hospital‐based study which is a desirable design for finding the risk factors of kidney stones among two groups (cases and controls). Considering lack of data on kidney stones risk factors in Afghanistan and the increased number of kidney stone patients in Nimroz province this study was conducted in a remote and usually neglected area in the country to provide accurate data and evidence. On the other hand, small number of male participants and recall bias in responding to the relevant questions could be the study limitations.

5. Conclusion

This study showed that age, employment status, BMI, family history, chronic conditions (kidney disease, heart diseases, blood pressure and asthma), and dietary habits (salt intake, less water consumption, and high weekly consumption of eggs and diary) were significantly associated with kidney stone disease. Therefore, education and raising awareness of the public on kidney stones and their risk factors, and other preventive measures could be helpful in reducing the kidney stone cases.

Author Contributions

Khwaja Mir Islam Saeed: conceptualization, investigation, funding acquisition, writing – original draft, methodology, validation, visualization, writing – review and editing, software, formal analysis, data curation, resources, supervision, project administration. Mir Salamuddin Hakim: validation, visualization, writing – review and editing, software, formal analysis, data curation. Ajmal Zahed: conceptualization, funding acquisition, methodology, validation, visualization, software, formal analysis, data curation, resources, project administration. Khatera Safi: conceptualization, funding acquisition, methodology, validation, visualization, software, formal analysis, data curation, resources, project administration. Fatema Hasazada: conceptualization, investigation, funding acquisition, methodology, validation, visualization, software, formal analysis, data curation, resources, project administration. Hafiz Rasooly: conceptualization, methodology, validation, visualization, writing – review and editing, software, formal analysis, data curation, resources, supervision, project administration. Sayed Attaullah Saeedzai: conceptualization, methodology, validation, visualization, writing – review and editing, formal analysis, data curation, resources, supervision.

Conflicts of Interest

The authors declare no conflicts of interest.

Transparency Statement

The lead author Khwaja Mir Islam SAEED affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request. The data that support the findings of this study are available from the corresponding author upon reasonable request from Afghanistan National Public Health Institute and Field Epidemiology Training Program in the country.