Urolithiasis analysis in a multiethnic population at a tertiary hospital in Nairobi, Kenya
© The Author(s) 2017
Received: 16 April 2016
Accepted: 1 April 2017
Published: 20 April 2017
Urolithiasis is a global problem whose incidence is reported to be on the rise across the world. Previously, urolithiasis was reported as being rare among the indigenous African population but recent data suggest otherwise. This study reviewed the demographic and clinical characteristics of patients with urolithiasis seen at the Aga Khan University hospital Nairobi (AKUHN) as well as the chemical composition of the stones and the modalities of therapy used.
This was a retrospective study which utilized patients’ clinical and laboratory records from 2013 to 2014. Sixty-seven symptomatic patients with confirmed urolithiasis formed the study. This study aimed to describe the clinical characteristics of patients, modalities of treatment as well as the chemical composition of renal stones from patients diagnosed and managed for urolithiasis during a duration spanning 17 months. Wet chemistry was utilized for analyzing the chemical composition of the urinary calculi. Data on age, sex, symptoms, radiological investigations done, location of the calculi, chemical composition of calculi and therapeutic procedures instituted were extracted and analyzed.
Ages ranged from 3 to 87 years with a median of 42; males were the majority (79%) and the commonest presenting symptoms were flank pain (91%) and dysuria (19%). The majority of the stones were located in the ureters (46%) and at the pelvi-ureteric junction (25%). A statistically significant difference in frequency of lodgment at the pelvi-ureteric site between males and females was noted. However, the number of female patients in this study was small and studies with larger numbers of female participants are required to confirm this observation. All stones contained calcium and oxalate, often as the only constituents (72%). In the remainder of the stones, other constituents such bicarbonate, ammonium, phosphorous, magnesium, uric acid and cystine occurred in varying combinations with calcium oxalate. Laser lithotripsy was the most performed therapeutic procedure (77.6%).
Males formed the majority of patient with urolithiasis. Overall, most of the calculi were located in the ureters except in women where the pelviureteric location was commoner. Stones containing calcium oxalate only were predominant across the age groups and in both sexes. Lithotripsy was the commonest mode of management.
Urolithiasis refers to a condition characterized by the formation or occurrence of calculi in the urinary tract. The incidence and prevalence rates for urolithiasis vary across different regions of the world with higher rates reported in countries such as Spain and Turkey . A rise in the incidence of urolithiasis has also been documented in United States of America . Urolithiasis in tropical Africa, though less common than in Western world, is increasingly being appreciated as a problem of growing importance. Studies conducted in Kenya and in the larger East Africa region demonstrate arise in the reported cases of urolithiasis in the past 30 years [3, 4]. Underdiagnosis however remains a major challenge . In addition, most of the local studies do not describe the chemical composition of the renal calculi.
Certain factors have been noted to predispose to development of urinary calculi. Metabolic conditions such as hypercalciuria, hyperoxaluria, hyperuricosuria, cystinuria and hypocitraturia have been identified as important risk factors [6, 7]. Age is another risk factor, with a significant rise in incidence of urolithiasis noted after the age of 40 years [1, 8]. Gender is yet another significant risk factor with men predisposed to developing urolithiasis compared to women [1, 8]. Race has also been proposed to be significant with higher rates noted in Caucasians compared to African-Americans and Asians [1, 9]. Aberrations in urinary pH, as well as presence of urinary tract infections are additional factors that have been implicated in urolithiasis.
Various studies investigating the composition of renal stones in African populations revealed calcium oxalate as the commonest compound across the various age groups [10–12]. The prevalence of calcium oxalate calculi in adults has been shown to be comparable between industrialized and non-industrialized countries but purine and struvite stones are commoner in the non-industrialized countries .
In previous studies conducted in Kenya, the commonest presenting clinical features in patients with urolithiasis were pain and haematuria while the commonest modes of imaging were ultrasonography and plain abdominal radiographs . The majority of calculi were located in the renal pelvis and ureters with extracorporeal shock wave lithotripsy (ECSWL) the commonest mode of treatment .
Various methods are available for stone analysis and they include wet chemical analysis, thermogravimetry, scanning electron microscopy, optic polarizing microscopy, spectroscopy, infrared spectroscopy, X-ray powder diffraction and elementary distribution analysis. Wet chemical analysis is still the most widely utilized technique for calculi analysis in clinical routine laboratories in Africa . This method has lower costs of operation but is time-consuming and only suitable for relatively large stone specimen. In addition, it has the disadvantage of only being able to identify the presence of individual ions without differentiating specific compounds. .
This study aims to describe the clinical characteristics of patients, modalities of treatment as well as the chemical composition of renal stones from patients diagnosed and managed for urolithiasis during a duration spanning slightly over 1 year, utilizing wet chemical analysis.
This was a retrospective study conducted at AKUHN, a teaching hospital serving a multi-ethnic population, in which patients’ clinical and laboratory records were reviewed. Clinical and laboratory records for all patients with confirmed urolithiasis at AKUHN, during the period spanning from January 2013 to May 2014 were included: sixty-seven symptomatic patients with confirmed urolithiasis formed the study. Data relating to demographic characteristics, clinical features, modalities of diagnosis and treatment were extracted from the clinical records. Data concerning stone composition was extracted from corresponding laboratory records.
The analytical method used to analyze stones at AKUHN was wet chemistry. In brief, the stones were pulverized into fine powder and mixed with different liquid reagents to detect various chemical components through observation of effervescence and color changes.
In statistical analysis, continuous variables were expressed as means and medians. Categorical data were summarized into percentages. Differences in categorical variables between groups were assessed using Chi square test or Fisher’s exact test as appropriate. P values less or equal to 0.05 were interpreted as statistically significant. Statistical analysis was performed using SPSS Statistics software version 22 (IBM, Armonk, USA).
Demographic and clinical characteristics of patients
Demographic and clinical characteristics
(n = 67)
Age, median (years)
Male, n (%)
Female, n (%)
Presenting clinical features, %
Anatomical sites involved in lodgment of calculi, %
Anatomical site of lodgment of calculi, %a
Imaging modalities, %
Computerized tomography (CT KUB)
Among the imaging studies performed, computerized tomography of kidney, ureters and bladder (CT KUB) was the most commonly used mode of evaluation (Table 1).
Composition of urinary calculi
Constituents, n (%)
(n = 67)a
Calcium oxalate only
Calcium oxalate + bicarbonate
Calcium oxalate + ammonium
Calcium oxalate + phosphate
Calcium oxalate + ammonium + bicarbonate
Calcium Oxalate + ammonium + bicarbonate + phosphate uric acid + cystine
Composition of calculi by age and gender
<42 years (n = 32)
≥42 years (n = 35)
Male (n = 53)
Female (n = 14)
Calcium oxalate only
Calcium oxalate + bicarbonate
1 (1.9) (1)
There was no statistically significant difference in composition of calculi by gender or by age (P > 0.05, Table 3).
Location of calculi by age and gender
<42 years (n = 33)b
≥42 years (n = 38)b
Male (n = 57)b
Female (n = 14)b
Modes of treatment for urolithiasis
Modes of treatment for urolithiasis
Frequency of modality used, n (%)
(n = 67)
Ureteroscopy/cystoscopy and laser lithotripsy
Ureteroscopy/cystoscopy and Dormia basket extraction
Percutaneous nephrolithotomy (PCNL)
Spontaneous passage of calculi in urine
Patients in whom stenting was also done
Our study demonstrated that the majority of patients with urolithiasis were male and that the commonest presenting feature was flank pain. These findings are consistent with previous studies from various parts of the world [1, 3, 4]. It therefore seems advisable that male patients presenting with flank pain be properly evaluated for urolithiasis, as various studies have alluded to underdiagnosis being of major concern . The majority of the stones were located in the ureter and pelviureteric junction. Again, these findings are consistent with a previous study by Ngugi et al. that showed the ureter and renal pelvis to be the commonest anatomical sites of involvement . There was no statistically significant difference in anatomical location of lodgment between the two age groups analyzed. A statistically significant difference in frequency of lodgment at the pelviureteric site between males and females was noted (P = 0.01). However, the number of female patients was quite low . Studies with larger numbers female participants are required to confirm this observation.
The major constituents of the stones were calcium and oxalate, findings which are in keeping with previous studies conducted across various parts of the world [7, 10, 11]. There was no statistical difference in chemical composition of the stones when comparing patients by age or gender.
This study goes beyond previous local studies by including analysis of the chemical composition of the renal calculi. Information on the composition of renal calculi is important in understanding the pathophysiology of urolithiasis. For instance, struvite stones usually occur against a background of urinary tract infection while uric acid stones tend to form in unduly acidic urine . Information on the chemical composition of stones may also influence mode of therapy chosen: brushite (calcium hydrogen phosphate dihydrate) and cystine stones are harder and therefore more resistance to shock wave lithotripsy [15, 16]. Similarly, chemical agents such as sodium citrate or potassium citrate may be used to alkalinize urine as part of medical management in patients with uric acid stones [16, 17].
Laser lithotripsy was the commonest modality of treatment which again is consistent with the results of the study done by Ngugi et al. .
One drawback of this study was the method of stone analysis utilized. Wet chemical analysis suffers the handicap of only being able to identify the presence of individual ions without differentiating specific compounds in different stone types and mixtures. As a result, this method will not, for example differentiate between calcium oxalate monohydrate and calcium oxalate dihydrate stones. Another limitation is the relatively small sample size involved in this study.
We analyzed renal calculi from sixty seven patients using wet chemistry technique. Male patients were the majority with a male to female ratio of 3.8:1. Overall, the majority of the calculi were located in the ureters except in women where the pelvi-ureteric location was the commonest. A statistically significant difference in frequency of lodgment at the pelvi-ureteric site between males and females was noted. Stones containing calcium oxalate only were predominant across the age groups and in both sexes. Larger studies are however recommended to confirm this observation due to the small number of female patients involved in this study. Lithotripsy was the commonest mode of management.
Aga Khan University Hospital Nairobi
- CT KUB:
computerized tomography of kidney, ureters and bladder
extracorporeal shock wave lithotripsy
FW reviewed medical records of the patients with urolithiasis and extracted data pertaining to clinical presentation, radiological investigations, chemical composition of calculi and modalities of treatment. FW also participated in data analysis and preparation of the manuscript with a view to publishing, in conjunction with the other co-authors. AW performed wet chemical analysis of the urinary stones and participated in drafting the manuscript. DM was involved in formulation of the initial concept, data analysis and preparation of the final manuscript for submission. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
Availability of data and materials
The dataset supporting the conclusions of this article is available in the ‘figshare’ repository (https://figshare.com/s/eb06aa3144a11224fa55).
Ethical authorization was sought and granted by the Health Research Ethics Committee of the Aga Khan University, Nairobi (REC Ref: 2015/REC-42 [vl]).
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