Hypokaliuria - a Neglected Variable in the Equation of Lithogenesis in Young Patients?

Abstract

Nephrolithiasis in young patients is today a public health problem with an increasing prevalence in industrialized nations. Between 01 January 2016 and 1 September 2018, we have evaluated patients aged between 18 and 40 years old referred to our clinic and diagnosed with urinary stones. After 30 days at least, it was confirmed using imaging stone-free status of the patient and then the 24h urine composition was performed. We have enrolled 110 patients, 58 males and 52 females, with a mean age of 29.55 years. Surprisingly, in 71 cases (64.54%), patients had hypokaliuria, 37 normokaliuria cases (33.63%) and two cases of hyperkaliuria (1.81%). We divided the patients into two main groups: those with hypokaliuria and those without. In those with hypokaliuria, the mean concentration was 22.53 mmol/L, while in the other group 52.77 mmol/L. Patients with low urinary potassium level had a slightly acid urinary pH (5.6 vs. 5.86) and lower urinary density (1012.96 vs. 1016.15 kg/m3) than in others, however higher than the recommended levels in lithiasic patients. Urinary magnesium level was lower (3.68 mmol/24h vs 3.87 mmol/24h) in the hypokaliuria group. Therefore, hypokaliuria was positively correlated with two protective factors. Patients with hypokaliuria revealed low urinary levels of lithogenic factors. Natriuria was significantly lower in patients with hypokaliuria (67.81 vs. 120.77 mmol/L, p [ 0.05). In addition, we noticed the same thing on urinary calcium level (4.02 mmol/24h vs 4.98 mmol/24h) but with no statistical significance (p = 0.16). Hypophosphaturia was more common in those with hypokaliuria (18.89 vs. 26.72 mmol/24h, p [ 0.05). The 24-hour urine analysis remains an important component of the metabolic workup for recurrent renal lithiasis. It seems that many of the young lithiasic patients in our geographic area have a low urinary potassium. Paradoxically, patients with hypokaliuria seems to have also hyponatriuria and hypophosphaturia. Through this study, we hope to make correlations between the risk of recurrent lithiasis -being a recognized high risk among young patients - and changes in 24-hour urine parameters found in the initial assessment.