The Utility of the Functional Sphincter Area: A Novel Functional Lumen Imaging Probe Parameter for the Assessment of...

: The functional lumen imaging probe (FLIP) is a unique tool to measure the anal sphincter during distension. Using detailed geometric data generated by FLIP, we present the functional sphincter area (FSA), a novel measurement of sphincter morphology with potential clinical utility in the investigation of fecal incontinence (FI).

: Parous female patients with FI presenting to a tertiary pelvic floor unit were prospectively recruited. FLIP measurements were obtained alongside endoanal ultrasound and high-resolution anorectal manometry.

: Thirty-one parous female patients with FI (median age: 62) were recruited. On endoanal ultrasound, 14 (45.2%) were found to have a sphincter defect in either the external sphincter (n = 10), or in both the external and internal sphincter (n = 4). The FSA demonstrated a consistent pattern of change during distension of the FLIP bag in all patients. At rest, the FSA was greater in those without anal sphincter defects at 30 mL (72.6 vs 53.2 mm²; P = 0.029) and 40 mL (71.5 vs 45.5 mm²; P = 0.048) bag volumes. The same pattern was observed during voluntary squeeze at 30 mL (67.8 vs 42.8 mm²; P = 0.044) and 40 mL (61.2 vs 38.6 mm²; P = 0.040) bag volumes. By contrast, there were no differences in symptom severity or manometry measurements between the 2 groups.

: The FSA may offer a clinically useful parameter and, in combination with other FLIP measurements, could become a useful tool to assess the structure and function of the anal canal in FI.