EC Gastroenterology and Digestive System

Background: With the exception of anal endosonography, imaging of fecal incontinence (FI), has had a limited role in the clinical practice until recently.

Aim: (a) To describe an MR imaging protocol tailored to patients with FI and (b) to validate an MR 1-5point confidence rating scale useful for the diagnosis and therapy planning.

Method: Bi-phasic MR-defecography has been performed in two groups of patients with similar demographic characteristics regarding their age (55.3 ± 10.7 yr vs 57.9 ± 14.6 yr, p 0.4489) who differ only for presence/absence of fecal incontinence. Image interpretation is performed twice by the same observer blind to patient’s clinical features with a 1-week interval between readings. The examiner reports his diagnosis taking into account the following two categories of changes: A = involuntary loss of rectal contrast, anal gaping at rest, poor squeezing and inability to interrupt the stream of contrast on command (main changes); B = pelvic organ prolapse, levator ani hiatus ballooning, uncompliant rectal ampulla, hasty emptying, anal sphincter defect, hyperactive sigmoid colon and pudendal nerve neuropathy (additional changes). Based on the combination of various changes, a 1-5 rating confidence rating scale for FI is developed with 1 indicating certainly present, 3 equivocal, and 5 certainly absent for the purpose of ROC curve and accuracy rates according to the various thresholds. In addition, intraobserver agreement between first and second readings and its statistical significance is calculated.

Results: At MR defecography, the unvoluntary loss of contrast, anal gaping at rest and poor squeeze test were the best discriminants between the two groups of patients (optimal cutoff ≤ 2, sensitivity 0.5652, specificity 0.8947, accuracy 0.7705) with good agreement between the first and second reading (weighted K value 0.6834, SE 0.054, CI 0.5775 - 0.7893).

Conclusion: MR defecography is suitable for application in patients with FI due to its diagnostic accuracy and promise for robust diagnostic criteria.

 Keywords: Fecal Incontinence; Quality of Life; Diagnosis; Endoanal Ultrasonography; Magnetic Resonance Imaging; MR-Defecography

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