Biomechanical wall properties and collagen content in the partially obstructed opossum esophagus

A specially designed probe was used to investigate biomechanical wall properties of the esophagus in opossums with distal esophageal banding. A balloon was stepwise inflated and deflated 6 cm above the lower esophageal sphincter before the banding and at 2 weeks postoperatively. After animals were killed, collagen content of the esophageal wall was determined. Preoperatively, cross-sectional area and wall tension at maximal inflation of the balloon, compliance, and hysteresis were 108.04 +/- 7.23 mm2, 5.8 +/- 0.3 cm H2O/m, 0.664 +/- 0.081 mm2/cm H2O, and 101.14 +/- 18.89 mm2, respectively. Postoperatively, the parameters increased to 357.45 +/- 54.22 mm2 (P < 0.001), 10.5 +/- 1.4 cm H2O/m (P < 0.001), 2.402 +/- 0.420 mm2/cm H2O (P < 0.001), and 225.86 +/- 44.56 mm2 (P < 0.05), respectively. The collagen content was 0.065 +/- 0.004 and 0.104 +/- 0.009 mg/mg dry defatted weight in the mid and distal normal esophagus, respectively, compared with 0.110 +/- 0.012 and 0.121 +/- 0.012 mg/mg in the banded group (P < 0.05 in the middle part). A positive correlation was shown between the maximal cross-sectional area and the collagen content in the mid-esophagus (P < 0.05). In conclusion, biomechanical wall properties were altered significantly, indicating dilatation and decreased ability of the esophageal wall to resist intraluminal pressure.