Introduction Esophageal multiple intraluminal impedance (MII) measurement has been in used to detect gastroesophageal reflux and bolus transport. It is not clear if MII can detect changes in luminal cross sectional area (CSA) during bolus transport. Aims Intraluminal ultrasound (US) images, MII and high resolution manometry (HRM) were recorded simultaneously to determine temporal relationship between CSA and impedance during esophageal bolus transport and to define the relationship between peak distension and nadir impedance. Methods Studies were conducted in five healthy subjects. MII, HRM and US images were recorded 6 cm above LES. Esophageal distensions were studied during swallows and injections of 0.5 N saline bolus into the esophagus. Results Temporal change in esophageal CSA correlates with changes in impedance (r value: mean ± SD = −0.80 ± 0.08, range: −0.94 to −0.66). Drop in impedance during distension occurs as a two step process; initial large drop associated with onset of CSA increase, followed by a small drop during which majority of the CSA increase occurs. Peak CSA and nadir impedance occur within 1 s of each other. Increase in swallow and injection volumes increased the CSA, had no effect on large drop but increased the small drop amplitude. We observed a significant correlation between peak CSA and nadir impedance (r = − 0.90, p<0.001) and a better correlation between peak CSA and inverse impedance (r = 0.94, p<0.001). Conclusion Further studies are needed to confirm that intraluminal impedance recordings may be used to measure luminal CSA during esophageal bolus transport.

Mittal RK, Bhargava V, Sheean G, Ledgerwood M, Sinha S. Purse-string morphology of external anal sphincter revealed by novel imaging techniques. Am J Physiol Gastrointest Liver Physiol 306: G505-G514, 2014. First published January 23, 2014 doi:10.1152/ajpgi.00338.2013.-The external anal sphincter (EAS) may be injured in 25-35% of women during the first and subsequent vaginal childbirths and is likely the most common cause of anal incontinence. Since its first description almost 300 years ago, the EAS was believed to be a circular or a "donut-shaped" structure. Using three-dimensional transperineal ultrasound imaging, MRI, diffusion tensor imaging, and muscle fiber tracking, we delineated various components of the EAS and their muscle fiber directions. These novel imaging techniques suggest "purse-string" morphology, with "EAS muscles" crossing contralaterally in the perineal body to the contralateral transverse perineal (TP) and bulbospongiosus (BS) muscles, thus attaching the EAS to the pubic rami. Spin-tag MRI demonstrated purse-string action of the EAS muscle. Electromyography of TP/BS and EAS muscles revealed their simultaneous contraction and relaxation. Lidocaine injection into the TP/BS muscle significantly reduced anal canal pressure. These studies support purse-string morphology of the EAS to constrict/close the anal canal opening. Our findings have implications for the effect of episiotomy on anal closure function and the currently used surgical technique (overlapping sphincteroplasty) for EAS reconstructive surgery to treat anal incontinence. external anal sphincter muscle architecture; anal incontinence; childbirth-related injury; magnetic resonance diffusion tensor imaging AN UNDERSTANDING OF THE MORPHOLOGY of the external anal sphincter (EAS), one of the superficial muscles of the pelvic floor, is important, since damage to this muscle may occur in 25-35% of women during vaginal childbirth (34). Injury to the EAS muscle is an important cause of anal incontinence, which has a devastating effect on an individual's quality of life (8). Morphology of the EAS has intrigued many investigators. From the original description by Santorini at the turn of 18th century (27) to the most current texts (2, 19), the EAS is described as a three-component (subcutaneous, superficial, and deep) circular muscle structure (2, 19). Others have argued that the deep part of the EAS is actually the puborectalis muscle (PRM) (7,14,23,25). MRI studies of Hussain et al. (14) and our recent three-dimensional (3-D) ultrasound (US) images, combined with high-definition manometry maps (25), support the idea that the deep part of the EAS is indeed the PRM, because it has a "sling" shape. On the basis of 3-D US images and anal canal pressures obtained by high-definition manometry (HDM), our study shows that the increase in pressure with voluntary contraction of the proximal and distal halves of the anal canal is related to contraction of the PRM and EAS, respectively (25).Another aspect of EAS morphology that has never been questi...

Esophageal axial shortening is caused by longitudinal muscle (LM) contraction, but circular muscle (CM) may also contribute to axial shortening because of its spiral morphology. The goal of our study was to show patterns of contraction of CM and LM layers during peristalsis and transient lower esophageal sphincter (LES) relaxation (TLESR). In rats, esophageal and LES morphology was assessed by histology and immunohistochemistry, and function with the use of piezo-electric crystals and manometry. Electrical stimulation of the vagus nerve was used to induce esophageal contractions. In 18 healthy subjects, manometry and high frequency intraluminal ultrasound imaging during swallow-induced esophageal contractions and TLESR were evaluated. CM and LM thicknesses were measured (40 swallows and 30 TLESRs) as markers of axial shortening, before and at peak contraction, as well as during TLESRs. Animal studies revealed muscular connections between the LM and CM layers of the LES but not in the esophagus. During vagal stimulated esophageal contraction there was relative movement between the LM and CM. Human studies show that LM-to-CM (LM/CM) thickness ratio at baseline was 1. At the peak of swallow-induced contraction LM/CM ratio decreased significantly (Ͻ1), whereas the reverse was the case during TLESR (Ͼ2). The pattern of contraction of CM and LM suggests sliding of the two muscles. Furthermore, the sliding patterns are in the opposite direction during peristalsis and TLESR. muscularis propria; gastroesophageal reflux; unequal shortening of muscle layers THE ESOPHAGUS IS A RELATIVELY straight tube with simple functions, to transfer swallowed contents either from the mouth to the stomach or from the stomach toward the mouth as happens during vomiting, belching, and reflux. Prior studies have shown two distinct motor patterns in the esophagus: peristalsis that transports the swallowed contents aborally and transient lower esophageal sphincter (LES) relaxation (TLESR) that allows gastric contents to move into the esophagus toward the mouth. Inner circular muscle (CM) and outer longitudinal muscle (LM) layers play a key role in both oral and aboral movements of the bolus. Studies show that during peristalsis CM and LM contract together cranial to the bolus (ascending contraction), to propel the bolus in the aboral direction, and they relax together around and caudal to the bolus (descending relaxation) (11), to receive the bolus. On the other hand, during TLESR, a unique LM contraction that starts in the distal esophagus and progresses in the cranial direction is observed (1, 15). There is no significant contraction of the CM during TLESR.Axial stretch of esophagus in the oral direction activates neurologically mediated LES relaxation and possibly descending relaxation of the esophagus (7). Therefore, it is hypothesized that longitudinal muscle contraction related axial stretch is of fundamental importance in the descending relaxation of the peristaltic reflex. Axial esophageal shortening is generally thought to be caused b...

Background Studies show that intraluminal impedance recordings of the esophagus allow one to measure the luminal distension during peristalsis, an important parameter for calculation of the biomechanical properties of esophageal wall. The goal was to determine the effect of subject posture and bolus viscosity on the biomechanical properties of esophageal wall, and the rate of bolus flow along the length of the esophagus during primary peristalsis. Methods High‐resolution manometry impedance recordings were obtained in 14 normal healthy subjects. Swallows of 10 ml saline and viscous bolus were recorded in the supine and Trendelenburg positions. User identified the region of interest, and a custom‐designed software extracted parameters of interest such as bolus flow rate, esophageal wall tension, and esophageal wall distensibility in four equal segments of the esophagus. Key Results Bolus flow rate decreases along the length of the esophagus, being slowest in the distal esophagus. Bolus flow rate is smaller in the Trendelenburg position and with viscous bolus as compared with supine position and saline bolus. Esophageal wall tension is greater in the Trendelenburg position and with viscous bolus as compared with the supine position and saline bolus. The esophageal wall distensibility is larger in the distal as compared with proximal esophagus, which is true for both the saline and viscous bolus. Conclusions & Inferences We report, for the first time, bolus flow rate and biomechanical properties of the esophageal wall during swallow‐induced primary peristalsis. Future studies may investigate biomechanical basis of esophageal motility disorders using the methodology described.