High‐frequency ultrasound imaging of the anal sphincter muscles in normal subjects and patients with fecal incontinence

Abstract

Introduction The current “gold standard” to diagnose anal sphincter morphology and disruptions utilizes low‐frequency (3‐9 MHz) ultrasound (US) imaging techniques that provide a general outline of the sphincter muscles, but not their microstructural details. High‐frequency US transducers (7‐15 MHz) have been used to study the muscle architecture (direction of muscle fascicles) in the limb muscle. Aims The goal of our study was to visualize the microstructural anatomy of the anal sphincters, specifically the external anal sphincter (EAS), using high‐frequency US imaging. Methods Studies were conducted in asymptomatic female and male subjects and patients with fecal incontinence. US images were acquired using a low‐frequency US (3‐9 MHz) and high‐frequency (7‐15 MHz) US transducer. The latter was placed intra‐anally to image the anal canal at 12, 9, 3, and 6 o'clock positions. Results The low‐frequency US images revealed the general outline of the anal sphincter muscles. On the other hand, high‐frequency imaging visualized muscle fascicles and connective tissue inside the external anal sphincter (EAS). In FI patients, there was loss of muscle fascicles and alteration in the echo‐intensity pattern in the region of damaged EAS suggestive of muscle fibrosis. Conclusion High‐frequency ultrasound imaging is a powerful tool to visualize the microstructural details of the EAS. Our studies show that damage to the EAS muscle results in the alteration of its myoarchitecture, that is, loss of muscle fascicles and increase in the muscle connective tissue.

Fecal incontinence patients categorized based on anal pressure and electromyography: Anal sphincter damage and clinical symptoms

“…However, our studies show that the myoarchitecture of the EAS is organized like a "purse string." [25][26][27] The EAS muscles from the right and left sides of the anal canal cross in the perineal body and continue as the transverse perinea and bulbospongiosus muscles. These two muscles originates from the pubic rami anteriorly and are inserted into the coccyx posteriorly.…”

Prospects of Intraoperative Multimodal OCT Application in Patients with Acute Mesenteric Ischemia

“…Using MM OCT, we managed to achieve a high quality of visualization of the complex of serous and muscle layers and the vascular network localized within them. It should be emphasized, that useful and clinically significant results of the study of muscle fibers have previously been demonstrated by high-frequency ultrasound scanning of the rectal muscular layer [ 71 ]. However, CP OCT technology is an improvement as it offers imaging of individual muscle bundles and intermuscular spaces with higher resolution and contrast.…”

Establishing a novel method for assessing elasticity of internal anal sphincter using ultrasonic real‐time tissue elastography

“…It is used for evaluating EAS defects caused by vaginal delivery injury, 21 repair sites of EAS after surgical reconstruction 22 anal fistulae, haemorrhoids and perianal abscesses 23 . High‐frequency EAUS imaging with a 7–15 MHz transducer has been used to visualize the microstructural details of the EAS, such as its muscle fascicle and connective tissue 24 . However, conventional EAUS provides only morphologic information, and consequently does not allow for the evaluation of the degree of tissue hardness objectively.…”