Mode of presentation and first line of management of non-recurrent urolithiasis in Kuwait

Epidemiology of urolithiasis in Asia

In Asia, about 1%-19.1% of the population suffer from urolithiasis. However, due to variations in socio-economic status and geographic locations, the prevalence and incidence have changed in different countries or regions over the years. The research for risk factors of urinary tract stones is of predominant importance. In this review, we find the prevalence of urolithiasis is 5%-19.1% in West Asia, Southeast Asia, South Asia, as well as some developed countries (South Korea and Japan), whereas, it is only 1%-8% in most part of East Asia and North Asia. The recurrence rate ranges from 21% to 53% after 3-5 years. Calcium oxalate (75%-90%) is the most frequent component of calculi, followed by uric acid (5%-20%), calcium phosphate (6%-13%), struvite (2%-15%), apatite (1%) and cystine (0.5%-1%). The incidence of urolithiasis reaches its peak in population aged over 30 years. Males are more likely to suffer from urinary calculi. Because of different dietary habits or genetic background, differences of prevalence among races or nationalities also exist. Genetic mutation of specific locus may contribute to the formation of different kinds of calculi. Dietary habits (westernized dietary habits and less fluid intake), as well as climatic factors (hot temperature and many hours of exposure to sunshine) play a crucial role in the development of stones. Other diseases, especially metabolic syndrome, may also contribute to urinary tract stones.

Clinical relevance of seasonal changes in the prevalence of ureterolithiasis in the diagnosis of renal colic

Ureterolithiasis is one of the most frequently diagnosed urologic diseases worldwide. Its annual incidence in Japan increased three-fold from 1965 to 2005. Ureterolithiasis incidence is affected by numerous factors, including race, sex, body weight, fluid intake, and climate. Here, we aimed to address the latter by considering the effect of seasonal variation on stone incidence and incorporating this information into a predictive model for differential diagnosis of ureteral stone from other conditions with similar presentations. We retrospectively identified 491 patients in our emergency department computer database who complained of back, flank, or lower abdominal pain during 2007-2015. Among them, 358 had stones, as confirmed by computerized tomography or plain abdominal X-ray of kidney-ureter-bladder. We also charted the mean ambient temperatures in our city for a year. The cases of ureteral stones paralleled the ambient temperatures, peaking during the hottest weather. Univariate analysis identified 13 factors associated with ureteral stones. Multivariate analysis narrowed the number to eight: age <60 years, male sex, short duration of pain (<6 h), nausea/vomiting, hydronephrosis, hematuria, history of urinary stone(s), and summer (July-September in Japan). Pain appearing during summer was nine times more likely to be due to a ureteral stone than was pain appearing during other seasons. We incorporated the eight variables identified into a predictive logistic regression model, which yielded good prediction of ureteral stones. Awareness that hot weather is associated with increased incidence of ureterolithiasis could facilitate differential diagnosis, and our prediction model could be useful for screening for ureterolithiasis.

Interpreting the results of chemical stone analysis in the era of modern stone analysis techniques

INTRODUCTION AND OBJECTIVE

Stone analysis should be performed in all first-time stone formers. The preferred analytical procedures are Fourier-transform infrared spectroscopy (FT-IR) or X-ray diffraction (XRD). However, due to limited resources, chemical analysis (CA) is still in use throughout the world. The aim of the study was to compare FT-IR and CA in well matched stone specimens and characterize the pros and cons of CA.

METHODS

In a prospective bi-center study, urinary stones were retrieved from 60 consecutive endoscopic procedures. In order to assure that identical stone samples were sent for analyses, the samples were analyzed initially by micro-computed tomography to assess uniformity of each specimen before submitted for FTIR and CA.

RESULTS

Overall, the results of CA did not match with the FTIR results in 56 % of the cases. In 16 % of the cases CA missed the major stone component and in 40 % the minor stone component. 37 of the 60 specimens contained CaOx as major component by FTIR, and CA reported major CaOx in 47/60, resulting in high sensitivity, but very poor specificity. CA was relatively accurate for UA and cystine. CA missed struvite and calcium phosphate as a major component in all cases. In mixed stones the sensitivity of CA for the minor component was poor, generally less than 50 %.

CONCLUSIONS

Urinary stone analysis using CA provides only limited data that should be interpreted carefully. Urinary stone analysis using CA is likely to result in clinically significant errors in its assessment of stone composition. Although the monetary costs of CA are relatively modest, this method does not provide the level of analytical specificity required for proper management of patients with metabolic stones.

Stone formation in the Middle Eastern Gulf States: A review

Objectives

To review the possible causes of the high incidence of urolithiasis in the oil-rich Gulf States.

Methods

Data were extracted from published reports on the incidence of urolithiasis, affluence and diet in the Gulf States, various Western countries and China.

Results

There are strong relationships: (a) between the life-expectancy of stones in men and the Gross National Income (GNI) per capita of these countries; and (b) between the daily consumption of animal protein and GNI per capita. Together these data suggest that the occurrence of stones is proportional to the intake of animal protein, although they also indicate that there are additional factors that further increase the risk of urolithiasis in the populations of the Gulf. The consumption of oxalate in the Gulf is three times higher and that of calcium a half of what it is in Western countries. Thus, the average oxalate/calcium ratio in the intestines of the Gulf populations is five to six times higher than that in Western populations, leading to enteric hyperoxaluria and an increased risk of calcium-oxalate stone formation. The risk is further accentuated by the lower urine volumes, due to the hot, dry climate of the region, and lower excretions of citrate, from the highly acidic urine resulting from the high intake of animal protein. There is a high incidence of uric acid-containing stones from the acidic urine and the hyperuricosuria caused by the high intake of purine.

Conclusions

The high incidence of urolithiasis in the Gulf is due to an adverse combination of dietary and environmental factors.