Hypertrophic smooth muscle in the partially obstructed opossum esophagus. Excitability and electrophysiological properties

Role of mechanoregulation in mast cell-mediated immune inflammation of the smooth muscle in the pathophysiology of esophageal motility disorders

Major esophageal disorders involve obstructive transport of bolus to the stomach, causing symptoms of dysphagia and impaired clearing of the refluxed gastric contents. These may occur due to mechanical constriction of the esophageal lumen or loss of relaxation associated with deglutitive inhibition, as in achalasia-like disorders. Recently, immune inflammation has been identified as an important cause of esophageal strictures and the loss of inhibitory neurotransmission. These disorders are also associated with smooth muscle hypertrophy and hypercontractility, whose cause is unknown. This review investigated immune inflammation in the causation of smooth muscle changes in obstructive esophageal bolus transport. Findings suggest that smooth muscle hypertrophy occurs above the obstruction and is due to mechanical stress on the smooth muscles. The mechanostressed smooth muscles release cytokines and other molecules that may recruit and microlocalize mast cells to smooth muscle bundles, so that their products may have a close bidirectional effect on each other. Acting in a paracrine fashion, the inflammatory cytokines induce genetic and epigenetic changes in the smooth muscles, leading to smooth muscle hypercontractility, hypertrophy, and impaired relaxation. These changes may worsen difficulty in the esophageal transport. Immune processes differ in the first phase of obstructive bolus transport, and the second phase of muscle hypertrophy and hypercontractility. Moreover, changes in the type of mechanical stress may change immune response and effect on smooth muscles. Understanding immune signaling in causes of obstructive bolus transport, type of mechanical stress, and associated smooth muscle changes may help pathophysiology-based prevention and targeted treatment of esophageal motility disorders.NEW & NOTEWORTHY Esophageal disorders such as esophageal stricture or achalasia, and diffuse esophageal spasm are associated with smooth muscle hypertrophy and hypercontractility, above the obstruction, yet the cause of such changes is unknown. This review suggests that smooth muscle obstructive disorders may cause mechanical stress on smooth muscle, which then secretes chemicals that recruit, microlocalize, and activate mast cells to initiate immune inflammation, producing functional and structural changes in smooth muscles. Understanding the immune signaling in these changes may help pathophysiology-based prevention and targeted treatment of esophageal motility disorders.

Esophageal anatomy and physiology vary across spastic and non-spastic phenotypes of disorders of esophagogastric junction outflow

BACKGROUND

Pathophysiologic mechanisms of disorders of esophagogastric junction (EGJ) outflow are poorly understood. We aimed to compare anatomic and physiologic characteristics among patients with disorders of EGJ outflow and normal motility.

METHODS

We retrospectively evaluated adult patients with achalasia types 1, 2, 3, EGJ outflow obstruction (EGJOO) or normal motility on high-resolution manometry who underwent endoscopic ultrasound (EUS) from January 2019 to August 2022. Thickened circular muscle was defined as ≥1.6 mm. Characteristics from barium esophagram (BE) and functional lumen imaging probe (FLIP) were additionally assessed.

KEY RESULTS

Of 71 patients (mean age 56.2 years; 49% male), there were 8 (11%) normal motility, 58 (82%) had achalasia (5 (7%) type 1, 32 (45%) classic type 2, 21 (30%) type 3 [including 12 type 2 with FEPs]), and 7 (7%) had EGJOO. A significantly greater proportion of type 3 achalasia had thickened distal circular muscle (76.2%) versus normal motility (0%; p < 0.001) or type 2 achalasia (25%; p < 0.001). Type 1 achalasia had significantly wider mean maximum esophageal diameter on BE (57.8 mm) compared to type 2 achalasia (32.8 mm), type 3 achalasia (23.4 mm), EGJOO (15.9 mm), and normal motility (13.5 mm). 100% type 3 achalasia versus 0% type 1 achalasia/normal motility had tertiary contractions on BE. Mean EGJ distensibility index on FLIP was lower for type 3 achalasia (1.2 mmHg/mm2 ) and EGJOO (1.2 mmHg/mm2 ) versus type 2 (2.3 mmHg/mm2 ) and type 1 achalasia (2.9 mmHg/mm2 ).

CONCLUSIONS

Our findings suggest distinct pathologic pathways may exist: type 3 achalasia and EGJOO may represent a spastic outflow phenotype consisting of a thickened, spastic circular muscle, which is distinct from type 1 and 2 achalasia consisting of a thin caliber circular muscle layer with more prominent esophageal dilation.

Esophageal Symptoms and Lumbosacral Back Pain

BACKGROUND AND AIMS

Esophageal symptoms, that is, heartburn, regurgitation, dysphagia, and chest pain are common in the general population. Also common are symptoms of back pain related to pathology in the lumbosacral spine. The right crus of the diaphragm that forms the esophageal hiatus, originates from lumbar spine, may be affected by lumbar spine pathology resulting in esophageal symptoms. We studied whether there was an association between esophageal symptoms and spine symptoms.

METHODS

Two patient groups of 150 each were investigated: group 1 (ES); patients referred to the esophageal manometry study for assessment of esophageal symptoms, group 2 (SC); patients undergoing screening colonoscopy (control group). Both groups completed standardized questionnaires assessing esophageal and spine symptoms.

RESULTS

Back pain was reported by 74% of patients in the ES group as compared to 55% of patients in the SC group. Thirty percent of patients in the SC group reported one or more esophageal symptoms and these patients were regrouped with the ES group, resulting in 2 groups, ES1 and SC1, with and without esophageal symptoms, respectively. The ES1 group was 3.3 times more likely to experience back pain compared to the SC1 group (95% confidence interval: 1.95-5.46). Thoracolumbar was the most common site of pain in both groups. Pain score was greater for the group with esophageal symptoms compared to controls. Narcotic intake for most patients in the ES1 group was for back pain.

CONCLUSION

A strong association between esophageal symptoms and thoracolumbar back pain raises the possibility that structural and functional changes in the esophageal hiatus muscles related to thoracolumbar spine pathology lead to esophageal dysmotility and symptoms.

Functional luminal imaging probe in the evaluation of esophago-gastric junction outflow obstruction

PURPOSE OF REVIEW

Esophagogastric junction outflow obstruction (EGJOO) comprises a heterogeneous group of conditions that demonstrate impaired deglutitive relaxation of the esophagogastric junction (EGJ) with intact esophageal peristalsis on high-resolution manometry. Functional luminal imaging probe (FLIP) panometry is a powerful tool that can help to clarify the etiology of this manometric diagnosis. The aim of this review is to summarize the use of FLIP for the evaluation and management of EGJOO.

RECENT FINDINGS

FLIP panometry provides measures of esophageal compliance at the EGJ and information on esophageal body contractile responses to balloon distention that have important implications for the management of patients with EGJOO. After excluding anatomic causes of impaired EGJ distensibility, FLIP panometry is useful in differentiating true lower esophageal sphincter dysfunction from manometric artifact. FLIP panometry has been shown to be useful in determining the need for invasive treatment in patients with EGJOO, and in intraoperative tailoring of myotomy procedures.

SUMMARY

FLIP panometry is easy to perform during endoscopy and provides useful information for characterizing the EGJOO population. FLIP panometry can be used to guide treatment and improve outcomes in the management of patients with EGJOO.

Esophageal hypercontractility is abolished by cholinergic blockade

BACKGROUND

Esophageal hypercontractility (EHC) is considered a major esophageal motor disorder of unclear etiology. Different mechanisms have been proposed, including an imbalance in inhibitory and excitatory esophageal innervation. We hypothesized that patients with EHC suffer from cholinergic hyperactivity.

AIM

To interrogate the excitatory and inhibitory neurotransmission in EHC by assessing the esophageal motor response to atropine (ATR) and cholecystokinin (CCK), respectively, in EHC patients.

METHOD

We retrospectively reviewed patients who underwent high-resolution manometry (HRM) with pharmacologic challenge in a tertiary referral center between 2007 and 2017. We identified 49 EHC patients who were categorized based on frequency of hypercontractile peristaltic sequence into "frequent" and "infrequent" and motility diagnosis groups. Deglutitive pressure metrics and esophageal motor responses to ATR (12 mcg/kg iv) and CCK (40 ng/kg iv) were analyzed across groups.

RESULTS

Atropine abolished hypercontractility across all groups studied, converting nearly half of patients to a motor pattern of ineffective esophageal motility. Abnormal CCK responses primarily occurred in the patient groups with concomitant outflow obstruction.

CONCLUSIONS

Hypercontractility is cholinergically mediated in all esophageal motor disorders. Most patients with isolated EHC appear to have excessive cholinergic drive, rather than loss of inhibitory innervation, and might be candidates for treatment with anticholinergic agents.

Three-Dimensional Pressure Profile of the Lower Esophageal Sphincter and Crural Diaphragm in Patients with Achalasia Esophagus

BACKGROUND & AIMS

Smooth muscles of the lower esophageal sphincter (LES) and skeletal muscle of the crural diaphragm (esophagus hiatus) provide the sphincter mechanisms at the esophagogastric junction (EGJ). We investigated differences in the 3-dimensional (3D) pressure profile of the LES and hiatal contraction between healthy subjects and patients with achalasia esophagus.

METHODS

We performed a prospective study of 10 healthy subjects (controls; 7 male; mean age, 60 ± 15 years; mean body mass index, 25 ± 2) and 12 patients with a diagnosis of achalasia (7 male; mean age, 63 ± 13 years; mean body mass index, 26 ± 1), enrolled at a gastroenterology clinic. Participants underwent 3D high-resolution manometry (3DHRM) with a catheter equipped with 96 transducers (for the EGJ pressure recording). A 0.5-mm metal ball was taped close to the transducer number 1 of the 3DHRM catheter. EGJ pressure was recorded at end-expiration (LES pressure) and at the peak of forced inspiration (hiatal contraction). Computed tomography (CT) scans were performed to localize the circumferential location of the metal ball on the catheter. Esophagus, LES, stomach, right and left crus of the diaphragm, and spine were segmented in each CT scan slice images to construct the 3D morphology of the region.

RESULTS

The metal ball was located at the 7 o'clock position in all controls. The circumferential orientation of metal ball was displaced 45 to 90 degrees in patients with achalasia compared with controls. The 3D-pressure profile of the EGJ at end-expiration and forced inspiration revealed marked differences between the groups. The LES turns to the left as it entered from the chest into the abdomen, forming an angle between the spine and LES. The spine-LES angle was smaller in patients with achalasia (104°) compared with controls (124°). Five of the 10 subjects with achalasia had physical breaks in the left crus of the diaphragm CONCLUSIONS: Besides LES, the 3D pressure profile of the EGJ can indicate anatomic and functional abnormalities of the crural diaphragm muscle in patients with achalasia esophagus. Further studies are needed to define the nature of hiatal and crural diaphragm dysfunction in patients with achalasia of the esophagus.

Jackhammer esophagus: Observations on a European cohort

BACKGROUND

With the advent of high-resolution manometry (HRM), a new diagnosis, jackhammer esophagus, was introduced. Little is known about this rare condition, and the relationship between symptoms and hypercontractility is not always straightforward. The aim of our study was to describe a large cohort of patients with jackhammer esophagus and to investigate whether manometric findings are associated with the presence of symptoms.

METHODS

All patients from 06, 2014 until 12, 2015 seen at two tertiary centers with at least one hypercontractile swallow (distal contractile integral [DCI] >8000 mm Hg/s/cm) on HRM were analyzed. Patients with ≥20% premature swallows, or patients with another diagnosis explaining their symptoms were excluded.

KEY RESULTS

Of the 34 patients identified with jackhammer esophagus, most suffered from dysphagia (67.6%) and/or chest pain (47.1%). The symptom chest pain was not associated with any of the manometric findings, whereas dysphagia was associated with the DCI of the hypercontractile swallows and with intrabolus pressure. In addition, all patients who had an isolated DCI of the lower esophageal sphincter (LES) zone >2000 mm Hg/s/cm had dysphagia. The differences in HRM and clinical characteristics between subgroups based on the contraction type (single- or multi-peaked) or based on meeting criteria of the Chicago Classification v3.0 and v2.0 were limited.

CONCLUSIONS & INFERENCES

The symptom dysphagia is accompanied with strong contractions of the LES, signs of a possible outflow obstruction, and a very high DCI. The presence of a multipeaked contraction seems to be of limited relevance, and caution is warranted in labeling patients with one hypercontractile swallow as normal.

Selective inhibition of nitric oxide synthase causes increased muscle thickness in rat esophagus

AIM

Achalasia is a primary motor dysfunction of esophagus which can be created experimentally by nitric oxide synthase (NOS) inhibition. Although several theories have been suggested, mechanism of increased esophageal muscle thickness in achalasia is still unclear. An experimental study was performed to evaluate the esophageal muscle thickness after selective inhibition of NOS in rats.

MATERIALS AND METHODS

Wistar albino rats (n=18) weighing 150-200g of both sexes were included in the study. After anesthetization with ketamine hydrochloride, esophageal body and distal esophagus were sampled in control group (CG, n=6). In sham group (SG, n=6), intraperitoneal saline (1ml) injection was performed for 21days. l-NAME (l-nitroarginin metyl ester, selective inhibitor of NOS) group (LNAMEG, n=6) received 100mg/kg/d l-NAME intraperitoneally for 21days. The esophageal body and distal esophagus were removed for histopathological analysis in each group. All samples were evaluated for total and circular muscle thickness with hemotoxylene-eosine (HE) staining.

RESULTS

None of the samples showed pathologic finding in esophageal mucosa. There was no difference between CG and SG for total and circular muscle thickness in esophageal body and distal esophagus. LNAMEG had higher median levels of both total and circular muscle thickness than CG and SG in esophageal body (P<0.05). However, in distal esophageal segments, only total muscle thickness was statistically higher in LNAMEG than CG and SG (P<0.05).

CONCLUSION

Selective inhibition of NOS causes increased total smooth muscle thickness in esophageal body and distal esophagus. However, this effect could not detected in circular muscle in the distal esophagus. We suggest that NOS inhbition not only increases esophageal peristalsis but also causes muscle hypertrophy in esophagus.

The spectrum of achalasia: lessons from studies of pathophysiology and high-resolution manometry

High-resolution manometry and recently described analysis algorithms, summarized in the Chicago Classification, have increased the recognition of achalasia. It has become apparent that the cardinal feature of achalasia, impaired lower esophageal sphincter relaxation, can occur in several disease phenotypes: without peristalsis, with premature (spastic) distal esophageal contractions, with panesophageal pressurization, or with peristalsis. Any of these phenotypes could indicate achalasia; however, without a disease-specific biomarker, no manometric pattern is absolutely specific. Laboratory studies indicate that achalasia is an autoimmune disease in which esophageal myenteric neurons are attacked in a cell-mediated and antibody-mediated immune response against an uncertain antigen. This autoimmune response could be related to infection of genetically predisposed subjects with herpes simplex virus 1, although there is substantial heterogeneity among patients. At one end of the spectrum is complete aganglionosis in patients with end-stage or fulminant disease. At the opposite extreme is type III (spastic) achalasia, which has no demonstrated neuronal loss but only impaired inhibitory postganglionic neuron function; it is often associated with accentuated contractility and could be mediated by cytokine-induced alterations in gene expression. Distinct from these extremes is progressive plexopathy, which likely arises from achalasia with preserved peristalsis and then develops into type II achalasia and then type I achalasia. Variations in its extent and rate of progression are likely related to the intensity of the cytotoxic T-cell assault on the myenteric plexus. Moving forward, we need to integrate the knowledge we have gained into treatment paradigms that are specific for individual phenotypes of achalasia and away from the one-size-fits-all approach.

Phenotypes and clinical context of hypercontractility in high-resolution esophageal pressure topography (EPT)

OBJECTIVES

This study aimed to refine the criteria for esophageal hypercontractility in high-resolution esophageal pressure topography (EPT) and to examine the clinical context in which it occurs.

METHODS

A total of 72 control subjects were used to define the threshold for hypercontractility as a distal contractile integral (DCI) greater than observed in normals. In all, 2,000 consecutive EPT studies were reviewed to find patients exceeding this threshold. Concomitant EPT and clinical variables were explored.

RESULTS

The greatest DCI value observed in any swallow among the control subjects was 7,732 mm Hg-s-cm; the threshold for hypercontractility was established as a swallow with DCI >8,000 mm Hg-s-cm. A total of 44 patients were identified with a median maximal DCI of 11,077 mm Hg-s-cm, all with normal contractile propagation and normal distal contractile latency, thereby excluding achalasia and distal esophageal spasm. Hypercontractility was associated with multipeaked contractions in 82% of instances, leading to the name "Jackhammer Esophagus." Dysphagia was the dominant symptom, although subsets of patients had hypercontractility in the context of esophagogastric junction (EGJ) outflow obstruction, reflux disease, or as an apparent primary motility disorder.

CONCLUSIONS

We describe an extreme phenotype of hypercontractility characterized in EPT by the occurrence of at least a single contraction with DCI >8,000 mm Hg-s-cm, a value not encountered in control subjects. This phenomenon, branded "Jackhammer Esophagus," was usually accompanied by dysphagia and occurred both in association with other esophageal pathology (EGJ outflow obstruction, reflux disease) or as an isolated motility disturbance. Further studies are required to define the pathophysiology and treatment of this disorder.

Morphometric evaluation of oesophageal wall in patients with nutcracker oesophagus and ineffective oesophageal motility

The pathogenesis of nutcracker oesophagus (NE) and ineffective oesophageal motility (IEM) is unclear. Damage to the enteric nervous system or smooth muscle can cause oesophageal dysmotility. We tested the hypothesis that NE and IEM are associated with abnormal muscular or neural constituents of the oesophageal wall. Oesophageal manometry was performed in patients prior to total gastrectomy for gastric cancer. The oesophageal manometries were categorized as normal (n = 7), NE (n = 13), or IEM (n = 5). Histologic examination of oesophageal tissue obtained during surgery was performed after haematoxylin and eosin (H&E) and trichrome staining. Oesophageal innervation was examined after immunostaining for protein gene product-9.5 (PGP-9.5), choline acetyltransferase (ChAT) and neuronal nitric oxide synthase (nNOS). There were no significant differences in inner circular smooth muscle thickness or degree of fibrosis among the three groups. Severe muscle fibre loss was found in four of five patients with IEM. The density of PGP-9.5-reactive neural structures was not different among the three groups. The density of ChAT immunostaining in the myenteric plexus (MP) was significantly greater in patients with NE (P < 0.05) and the density of nNOS immunostaining in the circular muscle (CM) was significantly greater in IEM patients (P < 0.05). The ChAT/nNOS ratio in both MP and CM was significantly greater in NE patients. NE may result from an imbalance between the excitatory and inhibitory innervation of the oesophagus, because more than normal numbers of ChAT-positive myenteric neurones are seen in NE. Myopathy and/or increased number of nNOS neurones may contribute to the hypocontractile motor activity of IEM.

Smooth muscle remodeling of the gastroesophageal junction after endoluminal gastroplication

BACKGROUND

Endoluminal gastroplication has been shown to reduce symptoms of gastroesophageal reflux disease and to induce focal hypertrophy of the gastroesophageal junction (GEJ) muscularis propria. Despite suture loss, some patients have persistent symptomatic resolution.

OBJECTIVE

This study was designed to examine the durability of smooth muscle hypertrophy after suture removal.

DESIGN

Seven pigs underwent upper endoscopy with endoscopic ultrasonography (EGD/EUS) at baseline to evaluate GEJ muscularis propria layer. Endoluminal gastroplication was performed at week 1 with placement of 2 sutures at the GEJ. Repeat EGD/EUS was performed at week 3 and week 5. Three of the 7 pigs were killed for histologic analysis. The remaining 4 pigs had sutures removed and survived for 9, 11, and 13 weeks; serial weekly EGD/EUS was performed until the animal was killed.

RESULTS

The GEJ muscularis propria thickness by EUS was 1.1+/-0.1 mm at baseline, 4.7+/-1.9 mm at week 3, and 4.4+/-1.1 mm at week 5. The muscularis propria thickness by histologic examination in the 3 animals with sutures intact were 6.2+/-0.3 mm near the suture site and 4.7+/-0.5 mm at the opposing wall to the suture site. For the 4 animals with sutures removed, the measurements were 6.9+/-0.2 mm (suture site) and 4.7+/-0.5 mm (opposing wall), respectively.

CONCLUSIONS

The GEJ smooth muscle cell hypertrophy induced by endoluminal gastroplication persisted after removal of mucosal sutures. These changes may be responsible for persistent symptomatic response despite suture loss in patients.

Oesophageal wall stress and muscle hypertrophy in high amplitude oesophageal contractions

Excessive wall stress is a known stimulus for muscle growth. We recently reported a thickened muscularis propria in patients with high amplitude oesophageal contractions (HAEC). The goal of this study was to determine oesophageal wall stress in normal subjects and patients with HAEC. A manometry catheter equipped with a high frequency ultrasound (US) transducer was used to record pressure and US images simultaneously in 10 healthy subjects and 11 patients with HAEC. Recordings were obtained at 2 and 10 cm above the lower oesophageal sphincter during water swallows. The changes in circumferential wall stress during oesophageal contraction in both groups are relatively small because of an increase in the wall thickness-to-radius ratio during contraction. Patients show a greater muscle thickness than normal subjects at rest and at the peak of contraction. The wall stress in patients is elevated at the 2 cm but not at the 10-cm level as compared to normal subjects. Wall strain is not different between the two groups. Increase in wall thickness during oesophageal contraction maintains low wall stress. A greater wall stress in patients with HAEC may be a stimulus for the increased wall thickness.

Gastroesophageal junction smooth muscle remodeling after endoluminal gastroplication

OBJECTIVES

Endoluminal gastroplication (ELGP) is an endoscopic mucosal suturing procedure for the treatment of gastroesophageal reflux disease. The antireflux mechanism of the mucosal suture remains poorly understood. The aim of this study is to investigate any morphologic changes in the smooth muscle layer induced by the mucosal sutures placed at the gastroesophageal junction.

METHODS

ELGPs were performed using endoscopic suturing devices with placement of two or three circumferential sutures within 2 cm of the squamocolumnar junction. Eight patients with subsequent symptom resolution underwent endoscopic ultrasound (EUS) to evaluate the muscularis propria layer at the gastroesophageal junction. A swine model was used for EUS and histopathologic correlation study. Six control and 15 ELGP pigs were evaluated with EUS and histological examination of the gastroesophageal junction smooth muscle layer.

RESULTS

Focal thickening of the muscularis propria layer near the suture region (2.3 +/- 0.4 mm vs 1.4 +/- 0.3 mm, p < 0.01) was found in eight patients with symptomatic resolution. In ELGP pigs, the smooth muscle layer thickness increased by 2.6 mm near the suture site by EUS. By histology, the total and circular smooth muscle layer thickness increased by 2.1 mm and 1.9 mm, respectively.

CONCLUSIONS

Focal thickening of smooth muscle layer occurs at the gastroesophageal junction after ELGP in patients with gastroesophageal reflux disease. This finding was reproduced in a swine model and localized hypertrophy was found to be entirely due to an increase in the circular smooth muscle layer.

Hypertrophy of the muscularis propria of the lower esophageal sphincter and the body of the esophagus in patients with primary motility disorders of the esophagus

OBJECTIVES

Patients with diffuse esophageal spasm (DES) and nutcracker esophagus/high amplitude esophageal contraction (HAEC) have a thicker esophageal muscularis propria than do healthy subjects. The goals of this study were to determine the esophageal muscle cross-sectional area (MCSA), a measure of muscle mass, in patients with achalasia of the esophagus; and to compare it with that in patients with DES, patients with HAEC, and normal subjects.

METHODS

Using a high-frequency ultrasound probe catheter, concurrent manometry and ultrasound images of the esophagus were recorded in four subject groups: normal volunteers, patients with HAEC, patients with DES, and patients with achalasia of the esophagus. Recordings were obtained from the lower esophageal sphincter (LES) and multiple sites in the esophagus 2, 4, 6, 8, and 10 cm above the LES.

RESULTS

The LES and esophageal muscle thickness as well as esophageal MCSA were greater in all three patient groups than in the normal subject group. Muscle thickness and MCSA were observed to be greatest in patients with achalasia, which were greater than in patients with DES, which were greater than in those with HAEC, which in turn were greater than in normal subjects.

CONCLUSIONS

We propose that an increase in the MCSA is an important feature of patients with primary motility disorders of the esophagus. The degree of increase in muscle mass may be an important determinant of the type and the severity of esophageal motor dysfunction.

Role of altered responsiveness of hypertrophic smooth muscle in manometric abnormalities of the obstructed opossum oesophagus

The movements of the obstructed oesophagus are abnormal, but whether this relates to the disease causing the obstruction, to the altered load conditions or to abnormal neuromuscular functions in hypertrophic smooth muscle is unclear. In an opossum model of chronic oesophageal obstruction, we compared the mechanical responsiveness of hypertrophic smooth muscle in vitro to in vivo manometric function. Related to their greater thickness, strips of hypertrophic muscle generated greater force in response to electrical stimulation and to stretch than control strips. Hypertrophic muscle often generated repetitive contractions; spread of contractions orad from the stimulus site was common in hypertrophic oesophageal bands. On manometry, the obstructed oesophagus generated abnormally high pressures proximally, and highly variable pressure amplitudes in the middle and distally; pressure waves often occurred simultaneously throughout the oesophagus, were repetitive or multi-peaked and led to a lasting rise of oesophageal pressure. Alterations in the intrinsic neuromuscular functions of hypertrophic smooth muscle including generation of greater force, repetitive or spontaneous contractions, and retrograde spread of contractions explain many, but not all, of the manometric abnormalities seen in the chronically obstructed oesophagus.