Association Between Randall's Plaque Stone Anchors and Renal Papillary Pits

Advancements in stone classification: unveiling the beauty of urolithiasis

PURPOSE

Urolithiasis has become increasingly prevalent, leading to higher disability-adjusted life years and deaths. Various stone classification systems have been developed to enhance the understanding of lithogenesis, aid urologists in treatment decisions, and predict recurrence risk. The aim of this manuscript is to provide an overview of different stone classification criteria.

METHODS

Two authors conducted a review of literature on studies relating to the classification of urolithiasis. A narrative synthesis for analysis of the studies was used.

RESULTS

Stones can be categorized based on anatomical position, size, medical imaging features, risk of recurrence, etiology, composition, and morphoconstitutional analysis. The first three mentioned offer a straightforward approach to stone classification, directly influencing treatment recommendations. With the routine use of CT imaging before treatment, precise details like anatomical location, stone dimensions, and Hounsfield Units can be easily determined, aiding treatment planning. In contrast, classifying stones based on risk of recurrence and etiology is more complex due to dependencies on multiple variables, including stone composition and morphology. A classification system based on morphoconstitutional analysis, which combines morphological stone appearance and chemical composition, has demonstrated its value. It allows for the rapid identification of crystalline phase principles, the detection of crystalline conversion processes, the determination of etiopathogenesis, the recognition of lithogenic processes, the assessment of crystal formation speed, related recurrence rates, and guidance for selecting appropriate treatment modalities.

CONCLUSIONS

Recognizing that no single classification system can comprehensively cover all aspects, the integration of all classification approaches is essential for tailoring urolithiasis patient-specific management.

2022 Recommendations of the AFU Lithiasis Committee: Endoscopic description of renal papillae and stones

Endoscopic observation is performed during treatments by flexible ureteroscopy to differentiate in situ between renal papillary abnormalities and stones based on their concordance with Daudon's morphological/composition descriptions adapted to endoscopy. These intraoperative visual analyses are now an integral part of the urinary stone disease diagnostic approach in addition to the morphological/structural and spectrophotometric analysis that remains the reference exam, but that loses information on the stone component representativeness due to the development of in situ laser lithotripsy. These are the first practical recommendations on the endoscopic description of renal papillae and stones. METHODOLOGY: These recommendations were developed using two methods: the Clinical Practice Recommendations (CPR) and the ADAPTE method, depending on whether the question was considered in the European Association of Urology (EAU) recommendations (https://uroweb.org/guidelines/urolithiasis [EAU Guidelines on urolithiasis. 2022]) and their adaptability to the French context.

Stone morphology distinguishes two pathways of idiopathic calcium oxalate stone pathogenesis

Introduction About 1-in-11 Americans will experience a kidney stone, but underlying causes remain obscure. The objective of the present study was to separate idiopathic calcium oxalate stone formers by whether or not they showed positive evidence of forming a stone on Randall's plaque (RP). Materials and Methods In patients undergoing either percutaneous or ureteroscopic procedures for kidney stone removal, all stone material was extracted, and analyzed using micro computed tomographic imaging (micro CT), in order to identify those attached to RP. 24-hour urines were collected weeks after the stone removal procedure and off of medications that would affect urine composition. Endoscopic video was analyzed for papillary pathology (RP, pitting, plugging, dilated ducts, loss of papillary shape) by an observer blinded to the data on stone type. Percent papillary area occupied by RP and ductal plugging was quantified using image analytic software. Results Patients having even 1 stone on RP (N=36) did not differ from Non-RP patients (N=37) in age, sex, BMI, or other clinical characteristics. Compared to the Non-RP group, RP stone formers had more numerous but smaller stones, more abundant papillary RP, and fewer ductal plugs, both by quantitative measurement of surface area (on average, 3 times more plaque area, but only 41% as much plug area as Non-RP) and by semi-quantitative visual grading. Serum and blood values did not differ between RP and Non-RP stone formers by any measure. Conclusions Growth of many small stones on plaque seems the pathogenetic scheme for the RP stone forming phenotype, whereas the Non-RP phenotype stone pathogenesis pathway is less obvious. Higher papillary plugging in Non-RP suggests that plugs play a role in stone formation, and that these patients have a greater degree of papillary damage. Underlying mechanisms that create these distinctive phenotypes are presently unknown.

Endoscopic Papillary Abnormalities and Stone Recognition (EPSR) during Flexible Ureteroscopy: A Comprehensive Review

Introduction: The increasing efficiency of the different lasers and the improved performance of endoscopic devices have led to smaller stone fragments that impact the accuracy of microscopic evaluation (morphological and infrared). Before the stone destruction, the urologist has the opportunity to analyze the stone and the papillary abnormalities endoscopically (endoscopic papillary recognition (EPR) and endoscopic stone recognition (ESR)). Our objective was to evaluate the value for those endoscopic descriptions. Methods: The MEDLINE and EMBASE databases were searched in February 2021 for studies on endoscopic papillary recognition and endoscopic stone recognition. Results: If the ESR provided information concerning the main crystallization process, EPR provided information concerning the origin of the lithogenesis and its severity. Despite many actual limitations, those complementary descriptions could support the preventive care of the stone formers in improving the diagnosis of the lithogenesis mechanism and in identifying high-risk stone formers. Conclusion: Until the development of an Artificial Intelligence recognition, the endourologist has to learn EPSR to minimize the distortion effect of the new lasers on the stone analysis and to improve care efficiency of the stone formers patients.

Automatic detection of calcium phosphate deposit plugs at the terminal ends of kidney tubules

Kidney stones are a common urologic condition with a high amount of recurrence. Recurrence depends on a multitude of factors the incidence of precursors to kidney stones, plugs, and plaques. One method of characterising the stone precursors is endoscopic assessment, though it is manual and time-consuming. Deep learning has become a popular technique for semantic segmentation because of the high accuracy that has been demonstrated. The present Letter examined the efficacy of deep learning to segment the renal papilla, plaque, and plugs. A U-Net model with ResNet-34 encoder was tested; the Letter examined dropout (to avoid overtraining) and two different loss functions (to address the class imbalance problem. The models were then trained in 1666 images and tested on 185 images. The Jaccard-cross-entropy loss function was more effective than the focal loss function. The model with the dropout rate 0.4 was found to be more effective due to its generalisability. The model was largely successful at delineating the papilla. The model was able to correctly detect the plaques and plugs; however, small plaques were challenging. Deep learning was found to be applicable for segmentation of an endoscopic image for the papilla, plaque, and plug, with room for improvement.