Endoscopic sclerotherapy in porcine esophagus changes luminal cross-sectional area and wall distensibility dose- and time-dependently

Biomechanical properties of the layered oesophagus and its remodelling in experimental type-1 diabetes

Passive biomechanical properties in term of the stress-strain relationship and the shear modulus were studied in separated muscle layer and mucosa-submucosa layer in the oesophagus of normal and STZ (streptozotocin)-induced diabetic rats. The mucosa-submucosa and muscle layers were separated using microsurgery and studied in vitro using a self-developed test machine. Stepwise elongation and inflation plus continuous twist were applied to the samples. A constitutive equation based on a strain energy function was used for the stress-strain analysis. Five material constants were obtained for both layers. The mucosa-submucosa layer was significantly stiffer than the muscle layer in longitudinal, circumferential and circumferential-longitudinal shear direction. The mechanical constants of the oesophagus show that the oesophageal wall was anisotropic, the stiffness in the longitudinal direction was higher than in the circumferential direction in the intact oesophagus (P < 0.001) and in the muscle layer (P < 0.05). Diabetes-induced pronounced increase in the outer perimeter, inner perimeter and lumen area in both the muscle and mucosa-submucosa layer. The growth of the mucosa-submucosa layer (P < 0.001) was more pronounced than the muscle layer (P < 0.05). Furthermore, the circumferential stiffness of the mucosa-submucosa layer increased 28 days after STZ treatment. In conclusion, the oesophagus is a non-homogeneous anisotropic tube. Thus, the mechanical properties differed between layers as well as in different directions. Morphological and biomechanical remodelling is prominent in the diabetic oesophagus.

Functional oesophago-gastric junction imaging

Despite its role in disease there is still no definitive method to assess oesophago-gastric junction competence (OGJ). Traditionally the OGJ has been assessed using manometry with lower oesophageal sphincter pressure as the indicator. More recently this has been shown not to be a very reliable marker of sphincter function and competence against reflux. Disorders such as gastro-oesophageal reflux disease and to a lesser extend achalasia still effects a significant number of patients. This review looks at using a new technique known as impedance planimetry to profile the geometry and pressure in the OGJ during distension of a bag. The data gathered can be reconstructed into a dynamic representation of OGJ action. This has been shown to provide a useful representation of the OGJ and to show changes to the competence of the OGJ in terms of compliance and distensibility as a result of endoluminal therapy.

Torque properties of a rat oesophagus for physiological and diabetic conditions

In this paper the torque of an oesophagus is studied for physiological and diabetic conditions. Since the function of the oesophagus is mainly mechanical, this work is focused on providing quantitative measurement of the passive biomechanical properties of the oesophagus torque. The oesophagus was treated as a membrane when calculating the stress and strain. The torque versus twist-angle relation was approximated to be linear at a specified pressure and longitudinal stretch ratio. Thus, the shear modulus can be computed by the torque, twist angle and polar moment of inertia in this state. The shear modulus varies greatly with the changing inflation pressure and longitudinal stretch ratio. When the longitudinal stretch ratio or transmural pressure is constant, the shear modulus is increased after 28 days of diabetes.

Morphologic and biomechanical changes of rat oesophagus in experimental diabetes

AIM: To study morphologic and biomechanical changes of oesophagus in diabetes rats.

METHODS: Diabetes was induced by a single injection of streptozotocin (STZ). The type of diabetes mellitus induced by parenteral STZ administration in rats was insulin-dependent (type I). The samples were excised and studied in vitro using a self-developed biomaterial test machine.

RESULTS: The body mass was decreased after 4 d with STZ treatment. The length of esophagus shortened after 4, 7, 14 d. The opening angle increased after 14 d. The shear, longitudinal and circumferential stiffness were obviously raised after 28 d of STZ treatment.

CONCLUSION: The changes of passive biomechanical properties reflect intra-structural alteration of tissue to a certain extent. This alteration will lead to some dysfunction of movement. For example, tension of esophageal wall will change due to some obstructive disease.

Esophageal motility changes after endoscopic intravariceal sclerotherapy with absolute alcohol

Endoscopic sclerotherapy (EST) leads to structural and motility changes in the esophagus; the former are thought to be commoner after EST with absolute alcohol (AA), which is a commonly used sclerosant in India as it is cheap and effective. There are no previous studies on changes in esophageal motility after EST with AA. Accordingly, we studied patients with portal hypertension before (n = 24) and after (n = 22) variceal obliteration by EST with AA using a water perfusion esophageal manometry system. Contraction amplitude in the distal esophagus was reduced in the post-EST group compared with the pre-EST group (63.4 +/- 24.9 vs. 18.2 +/- 14.3 mmHg, p < 0.01). Duration of esophageal contraction in both the proximal and distal esophagus became prolonged in the post-EST compared with the pre-EST group (3.3 +/- 0.8 vs. 5.4 +/- 2.6 and 4.3 +/- 1.1 vs. 6.6 +/- 2.3 s, p < 0.001 for both). Lower esophageal sphincter (LES) pressure was reduced in the post-EST compared with the pre-EST group, although the difference was not significant statistically. Abnormal contraction waveforms were more frequent in the post-EST group. One patient in the post-EST group had persistent dysphagia in the absence of endoscopically documented stricture at the time of manometric study. This study shows frequent occurrence of esophageal dysmotility after EST with AA; however, esophageal dysmotility after EST was infrequently associated with motor dysphagia.