The heavy metal cadmium (Cd) is known to be a widespread environmental contaminant and a potential toxin that may adversely affect human health. Exposure is largely via the respiratory or gastrointestinal tracts; important non-industrial sources of exposure are cigarette smoke and food (from contaminated soil and water). The kidney is the main organ affected by chronic Cd exposure and toxicity. Cd accumulates in the kidney as a result of its preferential uptake by receptor-mediated endocytosis of freely filtered and metallothionein bound Cd (Cd-MT) in the renal proximal tubule. Internalised Cd-MT is degraded in endosomes and lysosomes, releasing free Cd(2+) into the cytosol, where it can generate reactive oxygen species (ROS) and activate cell death pathways. An early and sensitive manifestation of chronic Cd renal toxicity, which can be useful in individual and population screening, is impaired reabsorption of low molecular weight proteins (LMWP) (also a receptor-mediated process in the proximal tubule) such as retinol binding protein (RBP). This so-called 'tubular proteinuria' is a good index of proximal tubular damage, but it is not usually detected by routine clinical dipstick testing for proteinuria. Continued and heavy Cd exposure can progress to the clinical renal Fanconi syndrome, and ultimately to renal failure. Environmental Cd exposure may be a significant contributory factor to the development of chronic kidney disease, especially in the presence of other co-morbidities such as diabetes or hypertension; therefore, the sources and environmental impact of Cd, and efforts to limit Cd exposure, justify more attention.

Renal stone disease covers kidney and lower urinary tract stones caused by a variety of conditions, including metabolic and inherited disorders, and anatomical defects with or without chronic urinary infection. Most cases are idiopathic, in which there is undoubtedly a genetic predisposition, but where environmental and lifestyle factors play an important role. Indeed, it is becoming apparent that renal stone disease is often part of a larger ‘metabolic picture’ commonly associated with type 2 diabetes, obesity, dyslipidaemia, and hypertension. Renal stone disease is a growing problem in the UK (and other developed and developing populations) with a cross-sectional prevalence of ∼1.2%. This means that there are currently ∼720,000 individuals with a history of kidney stones in the UK. Almost 40% of first-time stone formers will form a second stone within 3 years of the first episode if no prophylactic measures are instituted to prevent stone recurrence, since removal or disintegration of the first stone does not treat the underlying cause of stones in the majority of patients. The age of onset is getting younger and the sex ratio (until recently more men than women) is becoming almost even. Metabolic screening remains an important part of investigating renal stone disease, but to the disappointment and frustration of many doctors, medical treatment is still essentially pragmatic, except perhaps in cystinuria, and to a limited extent in primary hyperoxaluria (if pyridoxine-sensitive); although newer treatments may be emerging. This review summarizes current thinking and provides a practical basis for the management of renal stone disease.

Background. Mutations in the 4-hydroxy-2-oxoglutarate aldolase (

Similar to obese KSF, OW KSF show clear alterations in metabolic urinary profiles that are associated with increased overall risk of stone formation. This greater risk is primarily due to raised U.UA and U.Na, lower U.pH and higher prevalence of hypercalciuria, along with unchanged levels of the commonly measured urinary lithogenesis inhibitors. Moreover, our study established a higher incidence of uric acid, but not calcium, stones in OW KSF. Thus, appropriate evaluation and follow-up may be warranted even in OW patients who are at risk of increased stone formation. Whether modest weight loss in OW KSF will have a favourable impact on their metabolic urinary profiles and thereby diminish the risk of further stone formation needs exploring.

While vitamin D (vitD) deficiency is thought to contribute to poor health in a variety of ways and should be corrected, there is still concern about giving vitD supplements to patients with a history of nephrolithiasis. The aim is to study the prevalence of vitD deficiency and the effect on stone risk of cholecalciferol (vitD3) supplementation in a cohort of idiopathic stone formers (ISF). We screened for vitD deficiency and urinary measures of stone risk, comparing vitD deficient (serum 25-OH vitD ≤30 nmol/L; ≤12 ng/mL) with vitD insufficient (31–75 nmol/L; 13–30 ng/mL) or vitD replete (>75 nmol/L; >30 ng/mL); we investigated the effect of giving vitD3 (20,000 IU orally, weekly for 4 months) to 37 of the vitD deficients. Thirty-one percent (142/456) were vitD deficient, 57% (259/456) vitD insufficient, and the rest (12%) vitD replete (55/456). Comparison among the groups showed that baseline 24-h urinary measures related to stone risk expressed as concentration ratios over urine creatinine (Cr), such as U. Calcium/Cr, U. Oxalate/Cr, U. Citrate/Cr, and U. Uric acid/Cr were not significantly different. VitD3 supplementation did significantly increase serum 25-OH vitD levels and U. Phosphate/Cr ratios, as well as reduce serum parathyroid hormone (PTH) concentrations. Following vitD3 supplementation, there was an overall rise in 24-h urine calcium excretion, but it failed to reach statistical significance (p = 0.06). U. Calcium/Cr increased in 22 out of 37 patients (average increase +0.07 mmol/mmol), decreased in 14 (average decrease −0.13 mmol/mmol), and remained unchanged in 1; 6 out of 26 initially normocalciuric ISF developed hypercalciuria; and 6 out of 9 patients who became vitD replete were hypercalciuric after supplementation. It is appropriate to monitor urinary Ca excretion in vitD-supplemented stone formers, because it may reveal underlying hypercalciuria in some treated patients.

Our findings in a large cohort of patients attending a London-based stone clinic over the past 20 years show differences in distributions of risk factors for stones for men and women, as well as metabolic profiles and stone composition. The impact of most risk factors for stones appeared to change over time.

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