Classifying Renal Pyelocaliceal System: A Complete Literature Overview of All Existing Classification Approaches

Our comprehension of the actual diversity of kidney pyelocaliceal system (PCS) is lacking and many crucial features have been overlooked in the existing literature on this subject. The purpose of this review is to provide a concise summary of the current understanding of the structure of the pelvicalyceal system, considering both anatomical and surgical perspectives, as well as to highlight any limitations or inconsistencies in these approaches. A full review of all the literature on the anatomical and surgical methods used to classify pelvicalyceal system was conducted in several databases in August 2024. This included all the articles that talked about classifications for the whole pelvicalyceal system, minor calyces, and morphometric measurements within the pelvicalyceal system. Despite over a century of studying this anatomical zone and numerous approaches, some classifications still rely on pelvic branching or the division site related to the renal sinus. However, no single classification has incorporated both aspects. In addition, despite the consensus regarding the number of minor calyces, there are many approaches to determining their orientation. Finally, researchers have described a sufficient number of morphometric measurements within the pelvicalyceal system, considering their prognostic value before endourological interventions and their correlation with individual patterns of the structure of pelvicalyceal system. However, these measurements often lead to contradictions in interpreting the anatomical favorability of the same pelvicalyceal system using different approaches. Despite the numerous approaches to identify pelvicalyceal system from both morphological and surgical perspectives, there are significant gaps in our understanding of the real anatomy of the renal cavity that, even after more than a century, remain unanswered. There needs to be more correlation of anatomy with modern minimally invasive clinical interventions for stone disease.