Dynamic MR Defecography: Assessment of the Usefulness of the Defecation Phase

OBJECTIVE. The purpose of this study was to assess the usefulness of the defecation phase during dynamic MR defecography. MATERIALS AND METHODS. The images from 85 MR defecographic examinations (83 patients; age range, 20-88 years; mean, 52.7) were retrospectively reviewed in consensus by two observers. Images from each of four phases (rest, maximal sphincter contraction and squeezing, maximal straining, and defecation) were evaluated and scored independently with a modified previously published grading system. Features evaluated included the presence and degree of bladder, vaginal, and rectal descent and the presence and size of rectocele, enterocele, and intussusception. Statistical analysis was performed with a variety of tests. RESULTS. Compared with images obtained in the other phases, defecation phase images helped in identification of additional cases of abnormal bladder descent in 43 examinations (50.6%), abnormal vaginal descent in 52 examinations (61.2%), and abnormal rectal descent in 11 examinations (12.9%). Similarly, only defecation phase images depicted previously undetected rectoceles 2 cm or larger in 31 examinations (36.5%), enteroceles in 34 examinations (40%), and intussusceptions in 22 examinations (25.9%). The number of additional cases of abnormalities identified on defecation phase images was significantly greater than the number identified on images obtained in the other phases (p < 0.005). The average total scores for the rest, squeeze, strain, and defecation phases were 1.4, 0.7, 2.3, and 6.6. The average total defecation phase score was significantly greater than the average total score in any of the other phases (p < 0.001). CONCLUSION. During dynamic MR defecography, defecation phase imaging yields important additional information on the presence and degree of pelvic floor abnormalities and is therefore an essential component of MR defecographic examinations.