Can we predict the presence of struvite stones based on clinical factors?

■ Understanding the composition of urinary calculi is essential for guiding long-term treatment strategies.
■ This is the first study to correlate clinical data with crystallographic analysis of urinary stones.
■ Clinical criteria allow for a high likelihood of accurately identifying stone composition.
■ Clinical findings can serve as valuable tools for guiding treatment decisions.

ABSTRACT

Objective:

This study aimed to evaluate whether clinical, laboratory, and radiological data could effectively identify struvite stones without the need for crystallographic analysis.

Methods:

Stone fragments obtained using endourological procedures were subjected to crystallographic analysis. A prospective evaluation and comparison were conducted between patients with and without struvite stones. Sex, age, comorbidities, Hounsfield Unit Coefficient, stone size, urine culture, and urinary pH were analyzed.

Results:

Among the 221 stones enrolled, 18% were struvite. Among patients with struvite stones, 95% were women, whereas in the group without struvite stones, 51% were women. The average age was 40.6 years among patients with struvite stones, and 51.5 years in the other group (p<0.001). The stone size in the struvite group (24.9 mm) was significantly larger than that in the non-struvite group (15.6 mm) (p<0.001). The urinary pH was significantly higher in the struvite group than in the non-struvite group (p<0.001). Patients with a positive urine culture had a 3.78 times greater chance of having a struvite stone than those with a negative urine culture (p<0.01). Multivariate analysis considering pH, age, and stone size yielded an AUC value of 0.83, sensitivity of 0.39, specificity of 0.95, and accuracy of 0.85. There was no significant difference between the groups in terms of the Hounsfield Unit Coefficient and comorbidities.

Conclusion:

Our analysis further supports the conclusion that characteristics such as pH, age, stone size, and urine culture have notable specificity but low sensitivity for identifying struvite stones.