Urinary stones are a frequent problem. The NHANES study identified that 19% of men and 9% of women will have experienced a urolithiasis at the age of 70 years [1, 2]. The main complication is the renal colic, which led to 120 000 admissions in an emergency department in France in 2019 [3], excluding all the cases treated out of the hospital by the general practionner. The prevalence in the whole population increased since the 70’s, from 3,8% between 1976 and 1980, to 5,2% between 1988 and 1994, and 8,8% between 2007 and 2010 [4]. Several risk factors have been identified: age (19,7% of men after 80 years-old, vs 5,1% of men from 20 to 39 years-old), sex (similar incidence before 40 years-old, but more frequent among men after 40 years), race (more frequent in White ascendance), and geography (more frequent in the south-east of the USA) [5]. The studies on the composition of the lithiasis show a high prevalence of calcium oxalate (70 to 80%), calcium phosphate (15%; apatite more frequent than brushite), uric acid (8%), cystine (1–2%), struvite (1%), and others (< 1%) [6]. The recurrence rate is very high, from 10–30% 3 to 5 years after an idiopathic oxalo-calcic lithiasis, and up to 50% at 10 years among men [7, 8, 9]. The determination of the lithiasis composition is very important because it leads to specific treatment and dietetic advises [8, 9] associated with less recurrence [10]. Some urinary biochemical anomalies have been associated with certain types of lithiasis, but the link is sometimes weak. For example, some values as calciuria may have contestable normal range. Phospho-calcic and oxalo-calcic lithiasis share risk factors (low urinary volume, hypercalciuria, hypocitraturia). Hyperoxaluria is a risk factor for oxalo-calcic lithiasis. High urinary pH is a risk factor for phospho-calcic lithiasis, although low urinary pH favors uric acid lithiasis. Moreover, the stone analysis can differentiate the nucleus from the cortical zone, to identify the pathologic process leading to the nucleus formation. For all these reasons, the preventive and curative treatment cannot be based only on urinary biochemical analyses. The morphologic and spectrophotometric analysis of the lithiasis is essential [11]. Several studies insist on the need of these two pillars to make the right diagnosis [12, 13, 14]. All these data led to a strong recommendation (grade A) of the European Society of Urology to make the morphologic and spectrophotometric analyze, and to measure the urinary pH at the time of the renal colic, even if it is the first episode (15].
Nephrologists often see lithiasis patients after the renal colic. In our experience, we observed a low prevalence of stone analysis, for several reasons: the patient may have not seen the stone, may have not found convenient to catch it with a compress, and sometimes have not been advised of the main interest of this analysis. The measure of the urinary pH at the time of crisis is exceptionally done.
We used a novel device, Calcustop® to facilitate the capture of the stone and its conservation until it is brought safely to the laboratory. It also includes a cycle measurement of the urinary pH. Considering the crisis as a key point in retrieving the kidney stone, we tried to evaluate the interest of Calculstop® as a clinical tool to improve urolithiasis management.