Dear Editor,

The Consensus Conference Group recently published an article in Urolithiasis highlighting the importance of urine and stone analysis in the metabolic evaluation of kidney stone formers (KSF) [1]. Indeed, each kidney stone contains the imprints of the conditions which created them during their ‘lifetime in the kidney’.

The morpho-constitutional classification method (MCC) established by Prof Michel Daudon correlates the morphological characteristics of stones with specific metabolic disorders [2]. Briefly, it distinguishes 7 types and 21 subtypes according to the crystalline composition and shape, color and structure of stones identified using an optical stereo-microscope (Table 1). This very specific method is easy to learn and provides the opportunity to quickly identify highly recurrent diseases, sometimes serious in their clinical consequences. Indeed, subtypes Ic, Ie, IIId, IVa2 and V are pathognomonic of specific clinical entities corresponding to primary hyperoxaluria type 1, enteric hyperoxaluria, hyperuricosuria with diarrhea, distal tubular acidosis and cystinuria, respectively. In 2019, the International COllaborative NEtwork on Kidney sTones (ICONEKT) encouraged medical community to integrate this method for rapid identification of disorders responsible for the highly recurrent diseases [3]. Despite growing evidence of the robust diagnostic value of Daudon’s MCC and its benefits in drawing up individualized treatment plans, this simple tool unfortunately still remains underexplored. Given the increasing prevalence of KSF and the worrying rise in cases in groups previously considered to be at lower risk of stones (for example, women and children), the aim of our “call to action letter” is to support the position of accurate stone analysis elegantly highlighted by the Consensus Conference that you recently published [1]. In this way, we hope to raise interest and encourage more physicians to consider Daudon’s MCC as a priority in their clinical practice in order to improve the care of KSFs.

Table 1 Daudon’s morpho-constitutional classification of kidney stones, main characteristics and corresponding etiologies
Full size table