Prospective Evaluation of Ureteral Wall Thickness as a Means to Predict Spontaneous Stone Passage: Is It Beneficial?

Purpose: Ureteral wall thickness (UWT) was proposed as a potential predictor for spontaneous stone passage (SSP). In earlier studies, the effect could not be isolated from stone size. Accordingly, we sought to determine whether UWT, alone or combined with stone size, could enhance SSP predictability. Material and Methods: In total, 199 patients with acute renal colic and a single ureteral stone visible on noncontrast computerized tomography (NCCT) who opted for SSP were prospectively enrolled. A reviewer, blinded to the enrollee's stone passage status, analyzed NCCTs for both stone metrics (linear measurements, area, volume, density) and ureteral parameters (UWT at the point of greatest soft-tissue thickness, location, hydronephrosis). Logistic regression models were used to evaluate the relationship between these factors and SSP. Results: In a univariate analysis, longer (odds ratio [OR] = 0.285; 95% confidence interval [CI]: 0.375-0.608), wider (OR = 0.477; 95% CI: 0.375-0.608), denser (OR = 0.997; 95% CI: 0.995-0.998) stones with larger surface areas (OR = 0.920; 0.890-0.951), larger volumes (OR = 0.984; 95% CI: 0.977-0.990), and greater depth (OR = 0.538; 95% CI: 0.427-0.676), as well as those surrounded by a thicker UWT (OR = 0.665; 95% CI: 0.504-0.878), were less likely to pass spontaneously. In a multivariate analysis, UWT actually lost its significance. Indeed, in the multivariate analysis, only the largest linear stone measurement retained significance (OR = 0.454; 95% CI: 0.343-0.600). Conclusion: Although significant in a univariate analysis, in a prospective cohort study that adjusted for stone size, UWT lost significance in the multivariate model. SSP of a ureteral calculus was best predicted by its maximum linear measurement.