Dynamic MR of the pelvic floor. Influence of alternative methods to draw the pubococcygeal line (PCL) on the grading of pelvic floor descent

Objective: To evaluate the impact of the pubococcygeal line (PCL) position on hiatal descent grading, comparing the method recommended by the official guidelines with the other two most common methods reported in literature. Methods: Female patients prospectively included performed dynamic-MR (1,5 T) in supine position. Rectum and vagina were filled with ultrasound gel. MR protocol included TSE T2 weighted sequences on axial/sagittal/coronal planes and steady-state sequences (FIESTA) on midsagittal plane during three phases (rest, strain and defecation). On each phase, the posterior point of PCL was traced in the region recommended by the official guidelines (last coccygeal joint or PCLcc) and in the other two regions: coccyx's tip (PCLtip) and sacrococcygeal joint (PCLsc). The resulting grades of pelvic floor descent (according to HMO-System) were compared. Inter-reader and intra-reader agreement were evaluated. Results: The final population consisted of 60 patients (56yy±10). No significant differences in grading were observed using PCLtip and PCLcc in all phases (p = 0.3016/0.0719/0.0719 during rest/strain/defecation). Using PCLsc, the grading was significantly overestimated compared to PCLcc in all phases (p = 0.0041/0.0001/0.0001 during rest/strain/defecation). Inter-reader and intra-reader agreement were significantly higher using PCLtip (p < 0.05). Conclusions: PCLtip is a reliable and highly reproducible option to the official PCLcc to correctly grade the pelvic floor descent and could be used when the PCLcc is not clearly visible. The use of PCLsc overestimates the grading compared to the official PCLcc and should not be used to avoid wrong patients’ management.