Matrix Calculi in the Urinary Tract- A Prospective Cohort Study

Abstract

Introduction: Matrix calculi are infrequently encountered in the urinary tract. Their biochemical composition and unusual radiological appearance make it difficult to differentiate them from fungal balls or tumours of the urinary tract. Aim: To study radiological, biochemical and microbiological characteristics of matrix calculi in the urinary tract and their management. Materials and Methods: This prospective observational cohort study was conducted at a tertiary care hospital, from July 2016 to August 2019. Analysis of the clinical, radiological and biochemical profiles of patients who were found to have matrix renal or ureteric calculi was done. These patients underwent Percutaneous Nephrolithotomy (PCNL) or Ureteroscopic Lithotripsy (URSL) and the stone material evacuated was sent for analysis. Data was analysed using Microsoft Excel, version 2016. Results: Matrix urinary stones were found in a total of 21 patients, out of which 15 were renal matrix calculi and six were ureteric matrix calculi. Mean age of the patient population was 44.5 years. Male to female ratio was 1.33:1. Total 7 (33.3%) patients were found to have Chronic Kidney Disease (CKD). The mean radiodensity of all the stones was 403 Hounsfield Unit (HU). Six patients also had a concomitant crystalline calculus. Histopathological analysis of these matrix calculi revealed an amorphous lamellated appearance. The postoperative course of all the patients was uneventful. One patient presented with a non matrix stone in the opposite kidney after one year of follow-up. Conclusion: Matrix calculi of the urinary tract are usually radiolucent on plane radiographs and have a low radiodensity on Computerised Tomography (CT) scan. Biochemical analysis of these calculi shows protein to be the predominant component. These calculi are more often seen in patients with Diabetes Mellitus (DM) or CKD and are frequently associated with a positive urine culture. They can be managed successfully with a combination of PCNL and URSL. Complete clearance is necessary to minimise recurrence.