Dynamic magnetic resonance imaging for grading pelvic organ prolapse according to the International Continence Society classification: which line should be used?

Aims: To assess and compare the reliability of dynamic MRI to quantify pelvic organ prolapse (POP) according to the International Continence Society (ICS) using two different reference lines, and to determine which line gives the best concordance with clinical examination.
Methods: Forty-seven patients with genital prolapse underwent physical examination and dynamic MRI. Five nulliparous, symptom-free female volunteers underwent dynamic MRI as control subjects. Two distinct observers performed the MRI measurements of POP according to the ICS using two distinct reference lines: the mid-pubic line and a new one, the perineal line that provides a better match with the hymen plane. Measurements were repeated twice according to each line. The intra-class coefficient was used to estimate intra-observer and inter-observer reliability; the Altman and Bland plot was used to assess the agreement between MRI and clinical measurements.
Results: The intra-observer and inter-observer reliability of MRI measurements were in general excellent. Intra-class coefficients were better for the mid-pubic line than the perineal line. Although the MRI measurements correlate significantly with the physical measurements, the Altman and Bland plot shows an unacceptable magnitude of discrepancy between clinical and MRI examinations.
Conclusions: Although dynamic MRI shows excellent inter- and intra-observer reliability, its agreement with clinical examination is poor whatever the line used.
((c) 2007 Wiley-Liss, Inc.)