Study of differences in urine and stone microbiome and stone composition in patients with staghorn and non-staghorn renal calculi

Abstract Background: Urolithiasis is one of the most common afflictions of modern society, yet there is a paucity of data regarding the differences, if any, in the composition and urine and stone microbiome of staghorn and non-staghorn calculi. Hence, this study aimed to compare the two in patients with urolithiasis. Methods: A cross-sectional study was done during the period July 2022 to December 2023. Patients who were diagnosed with renal stones on imaging and subjected to stone retrieval surgery were included in the study. Mid-stream urine obtained preoperatively and calculi collected during surgery (washed in sterile normal saline) were sent for investigation. The following variables were compared: prevalence, patient characteristics, urine and stone culture and stone composition. Results: Data from 213 patients 159 (74.6%) with non-staghorn and 54 (25.4%) with staghorn calculus were analysed. Bacterial growth in pre-operative urine culture was seen more often in the staghorn calculus group (27.8% Vs 15.8%; P =0.07). Stone culture yield of bacterial growth was almost similar in both groups (48.2% in the staghorn Vs 46.6% in the non-staghorn group; P =0.962). Metabolic stones were more frequently found than infective stones in patients with staghorn and non-staghorn calculus ( P =0.0012). The most common stone composition was calcium oxalate, both in cases of staghorn (68.5%) as well as non-staghorn calculi (84.2%). Conclusions: Our study suggests that the difference between staghorn and non-staghorn calculi in terms of urine, stone microbiome and stone composition is less significant than previously believed.