Zifan A¹, Mittal RK², Kunkel DC³, Swartz J³, Barr G⁴, Tuttle LJ⁴. Am J Physiol Gastrointest Liver Physiol. 2019 Nov 18. doi: 10.1152/ajpgi.00164.2019. [Epub ahead of print]

Author information

1 Medicine, University of California San Diego.

2 Medicine, University of California, San Diego, United States.

3 University of California San Diego.

4 School of Exercise and Nutritional Sciences, San Diego State University, United States.

Abstract

BACKGROUND AND AIMS: Cardiac loops have been used extensively to study myocardial function. With changes in cardiac pump function, loops are shifted to the right or left. Functional luminal imaging probe (FLIP) recordings allow for loop analysis of anal sphincter and puborectalis (PRM) function. The goal was to characterize anal sphincter area-pressure/tension loop changes in fecal incontinence (FI) patients.

METHODS: 14 healthy subjects and 14 patients with FI were studied. Custom-designed FLIP was placed in the vagina and then in the anal canal, and deflated in 20ml steps, from 90-30ml. At each volume, subjects performed maximal voluntary squeezes. Area-pressure (AP) and area-tension (AT) loops were generated for each squeeze cycle. 3D-US imaging of the anal sphincter and PRM were obtained to determine the relationship between anal sphincter muscle damage and loop movements.

RESULTS: With an increase in bag volume, AP-loops and AT-loops shifted to the right and upwards in normal subjects (both anal and vaginal). The shift to the right was greater, and upwards movement less in FI patients. The difference in the location of AP-loops and AT-loops was statistically significant at volumes of 50ml to 90ml (p<0.05). Similar trends were found in the vaginal loops. There is a significant relationship between the damage to the anal sphincter and PRM, and loop location of FI patients.

CONCLUSION: We propose AP and AT-loops as novel ways to assess anal sphincter and PRM function. Such loops can be generated by real-time measurement of pressure and area within the anal canal.