Preoperative Prostate MRI Predictors of Urinary Continence Following Radical Prostatectomy

Abstract

Background Urinary continence after radical prostatectomy (RP) is an important determinant of patient quality of life. Anatomic measures at prostate MRI have been previously associated with continence outcomes, but their predictive ability and interrater agreement are unclear in comprehensive clinical models. Purpose To evaluate the predictive ability and interrater agreement of MRI-based anatomic measurements of post-RP continence when combined with clinical multivariable models. Materials and Methods In this retrospective cohort study, continence outcomes were evaluated in men who underwent RP from August 2015 to October 2019. Preoperative MRI-based anatomic measures were obtained retrospectively by four abdominal radiologists. Before participation, these radiologists completed measure-specific training. Logistic regression models were developed with clinical variables alone, MRI variables alone, and combined variables for predicting continence at 3, 6, and 12 months after RP; some patient data were missing at each time point. Interrater agreement of MRI variables was assessed by using intraclass correlation coefficients (ICCs). Results A total of 586 men were included (mean age ± standard deviation: 63 years ± 7). The proportion of patients with incontinence was 0.2% (one of 589) at baseline, 27% (145 of 529) at 3 months, 14% (63 of 465) at 6 months, and 9% (37 of 425) at 12 months. Longer coronal membranous urethra length (MUL) improved the odds of post-RP continence at all time points (odds ratio per 1 mm: 0.86 [95% CI: 0.80, 0.93], P < .001; 0.86 [95% CI: 0.78, 0.95], P = .003; and 0.79 [95% CI: 0.67, 0.91], P = .002, respectively) in models that incorporated both clinical and MRI predictors. No other MRI variables were predictive. Age and baseline urinary function score were the only other predictive clinical variables at every time point. Interrater agreement was moderate (ICC, 0.62) for MUL among readers with measure-specific prostate MRI training and poor among those without the training (ICC, 0.38). Conclusion Preoperative MRI-measured coronal membranous urethra length was an independent predictor of urinary continence after prostatectomy. © RSNA, 2022 Online supplemental material is available for this article.

Graphical abstract

Figure 1:

Study flowchart. MUSIC = Michigan Urological Surgery Improvement Collaborative.

Figure 2:

T2-weighted fast spin-echo MRI scans in (A) sagittal view and (B, C) coronal views with (B) and without (C) annotation illustrate membranous urethra length (MUL) measurement technique. MUL was defined as the distance from the prostate apex to the urethral entry into the penile bulb. The yellow line in A and B represents the MUL.

Figure 3:

(A) Axial and (B, C) sagittal T2-weighted fast spin-echo MRI scans demonstrate anatomic measurement techniques. (A) Axial image shows the inner levator distance (dots) and outer levator distance (arrows). (B, C) Sagittal images show the angle between membranous urethra and prostatic axis (B) and pubourethral angle (C). Inner levator distance was measured in the axial plane and was defined as the narrowest distance between the inner borders of the levator muscles just below the caudal margin of the prostatic apex. Outer levator distance was measured in the axial plane and was defined as the distance between the outer borders of the levator muscles at the same level as the inner levator distance measurement. The angle between the membranous urethra and prostatic axis was measured in the sagittal plane and defined as the angle between the membranous urethra length and a line drawn through the prostatic axis. The pubourethral angle was measured in the sagittal plane and defined as the angle between a line drawn from the anterior bladder neck to the lower border of the pubic symphysis and a line drawn from the upper to lower border of the pubic symphysis.