Category: Clinical Stones: Outcomes

MP8-5 - What defines a Struvite stone?

Fri, Sep 21
10:00 AM - 12:00 PM

Introduction & Objective :

Struvite stones constitute only a small fraction of urinary stones, but their medical and economic burden are disproportionally higher. The definition of struvite stone varies widely across the literature, thus, the implications of finding a struvite stone are inconsistent. We aimed to study the association between a stone's struvite content and clinical outcomes and to determine a clinically significant cutoff for defining struvite stones.

Methods :

A retrospective study of all patients who underwent ureteroscopy or PCNL at our institution between 2012 and 2017, and had any comp onent of struvite in the stone analysis. Patients were divided into four groupsĀ  based on percent struvite content: A(1%-25%), B(26%-50%), C(51%-75%), and D(76%-100%). Bacterial characteristics were compared between groups. Univariate and multivariate analyses were performed to evaluate the association between struvite content and postoperative SIRS. Log-rank test was used to compare between the four groups' recurrence rates.

Results :

A total of 123 patients were included in the study. Positive preoperative urine culture was found in 31%, 81%, 87%, and 90% of patients from group A,B,C, and D, respectively. E.Coli was the most common pathogen in group A (54%), while Proteus was the most common pathogen in groups C (53%) and D (47%). Enterococci isolation rates remained similar between groups A-D, ranging from 23% to 33%. Postoperative SIRS occurred in 2.4%, 26.7%, 21.3%, and 47.4% of the patients from groups A,B,C and D, respectively, and was associated with struvite content and age on multivariate analysis. Increasing struvite content was associated with higher 2-years recurrence rate.

Conclusions :

Higher struvite content is associated with a higher frequency of traditional urea splitting bacteria in urine culture, higher risk for postoperative SIRS, and higher recurrence rate. Struvite content greater than 25% can be used to define a clinically significant struvite stone.

Omar Ayyash

Department of Urology, University of Pittsburgh Medical Center, Pittsburgh
Pittsburgh, Pennsylvania

Amihay Nevo

clinical instructor
Department of Urology, University of Pittsburgh Medical Center, Pittsburgh
Tel Aviv, Tel Aviv, Israel

Mohammed Shahait

Division of Urology, University of Pennsylvania
Philadelphia, Pennsylvania

Advanced Robotic Urology, University of Pennsylvania.
Interested in outcome research, new imaging modalities

Anup Shah

Department of Urology, University of Pittsburgh Medical Center, Pittsburgh
Pittsburgh, Pennsylvania

Stephen Jackman

Endourology Faculty
University of Pittsburgh
Pittsburgh, Pennsylvania

Timothy Averch

Chief, Division of Urology
Palmetto Health - University of South Carolina
University of South Carolina
Columbia, South Carolina