Evaluating factors that dictate struvite stone composition: A multi-institutional clinical experience from the EDGE Research Consortium

Abstract

Introduction: Struvite stones account for 15% of urinary calculi and are typically associated with urease-producing urinary tract infections and carry significant morbidity. This study aims to characterize struvite stones based on purity of stone composition, bacterial speciation, risk factors, and clinical features. Methods: Retrospective data was collected from patients diagnosed with infection stones between 2008 and 2012. Stone analysis, perioperative urine cultures, bacterial speciation, and clinical data were collected and analyzed. The purity of struvite stones was determined. Statistical comparisons were made among homogeneous and heterogeneous struvite stones. Results: From the four participating centres, 121 struvite stones were identified. Only 13.2% (16/121) were homogenous struvite. Other components included calcium phosphate (42.1%), calcium oxalate (33.9%), calcium carbonate (27.3%), and uric acid (5.8%). Partial or full staghorn calculi occurred in 23.7% of cases. Urease-producing bacteria were only present in 30% of cases. Proteus, E. coli, and Enterococcus were the most common bacterial isolates from perioperative urine, and percutaneous nephrolithotomy was the most common modality of treatment. Only 40% of patients had a urinalysis that was nitrite-positive, indicating that urinalysis alone is not reliable for diagnosing infection stones. The study's limitations is its retrospective nature; as such, the optimal timing of cultures with respect to stone analysis or treatment was not always possible, urine cultures were often not congruent with stone cultures in the same patient, and our findings of E. coli commonly cultured does not suggest causation.

Current insights into the mechanisms and management of infection stones

“…These findings suggest that future work should evaluate the effect of therapies for metabolic diseases on the incidence of struvite stone formation 45 . A retrospective study with 121 recovered struvite stones showed that only ~13% were homogenously composed of struvite, whereas ~87% contained struvite admixed with other mineral components, the order of abundance of which was calcium phosphate, calcium oxalate, calcium carbonate, and uric acid 47 . On average, ~35% of recovered struvite stones are composed of struvite with or without carbapatite, and ~65% comprise struvite stones admixed with calcium oxalate 45,46,48 .…”

First Report of Pathogenic Bacterium Kalamiella piersonii Isolated from Urine of a Kidney Stone Patient: Draft Genome and Evidence for Role in Struvite Crystallization

“…Urease negative bacteria such as Enterococcus spp., E. coli , Streptococcus spp., Citrobacter spp., Peptostreptococcus spp. and Bacteroides fragilis are commonly identified in the urine of struvite stone patients [ 5 , 34 ].…”

“…The stone can grow rapidly occupying the renal calyces and pelvis damaging significantly the epithelium of the internal renal walls [ 4 ]. Data on the bacteriology of struvite stone cultures and urine cultures agree largely on the presence of infection agents [ 5 , 6 ]. Patients with kidney stone disease are more likely to have urinary tract infection (UTI) due to the invasion of uropathogens and their colonization in bladder or ascending infection to kidney.…”

Struvite stones causing recurrent pain in a child with cerebral palsy: a lesson for a pragmatic approach to pain in children with cerebral palsy and cognitive impairment.

“…Remarkably, these patients are prone tobe affected byurinary stones, due to several predisposing factorssuch ashypercalciuria, bone demineralization,dehydration 5 andtopiramate treatment forconcomitant epilepsy 6 .Struvite stones are a subset ofkidney stones, composed of magnesiumammonium phosphate (struvite)and calcium carbonate-apatite, whichform as a result of urinarytract infections with urease-producingpathogens. It is known thatthis type of stone is formed quickly,within a few weeks, in thepresence of urease producingbacteria 7 , from generasuch as Proteus,Providencia, Klebsiella, Staphylococcus. When theproduction ofammonia increases and the urine pH is high, thesolubility ofphosphate decreases, and struvite stones candevelop.…”