Watters, David Allan Kilpatrick

2019-02-15T14:26:14Z

2019-02-15T14:26:14Z

1983

The mechanical properties of the large bowel have been largely neglected to date. A method was established using the rat colon to mechanically test colonic tissue. The method involved 10 mm rings of colon being tested mechanically at right angles to the long axis of the colon. Tests chosen to measure "strength" were burst strength and tensile strength. "Stretch" was measured by percentage elongation and width of the colon at burst. The internal diameter of the colon at zero stress and the thickness of the colon wall, at rest were taken as reference dimensions. Viscoelastic properties were measured by stress relaxation and hysteresis in the rat and stress -relaxation in the human.

Post-mortem material was the only practical source of non -diseased colonic tissue across the spectrum of age. The tests used were not affected significantly by death or time after death. Because colons required to be transported from Uganda to be tested in Edinburgh, a method of preserving mechanical properties during storage had to be devised. The method of choice was salt, mechanical properties as tested being well preserved for at least 35 days.

Twenty -tw adult Edinburgh colons (age range 19 to 81) and 17 adult Kampala colons (age range 14 to 62) were studied. In addition, 10 Edinburgh children's colons (age range 28 weeks gestation to 4 years) and 3 Kampala children's colons (age range 36 to 40 weeks gestation) were tested. Segments from an ascending, transverse, descending and sigmoid colons were tested in each case.

The tensile strength of the human colon declined with age (P < 0,05). Once adult life was reached its capacity to stretch remained fairly constant, except in the sigmoid colon, where there was a fall in stretch capacity with age (P <0,001. ). The diameter of the colon fell with increasing age in adult life (P <0,05), this was most pronounced in the Edinburgh colon. Viscoelastic properties were unaffected by age. There were no consistent sex differences in mechanical properties.

The Kampalan colon had a significantly greater tensile strength than its Edinburgh counterpart (P <0,05). The distal but not the proximal colon had a greater stretch capacity in the Kampala group (P <0,001). The viscoelastic property of stress relaxation was similar in both groups. Children's colons were similar in the two race groups.

Comparing those colons with and without diverticular disease in the Edinburgh over 50 group, no differences were found in mechanical properties.

The results are discussed in the light of the few mechanical or structural studies previously reported for the colon and also mechanical studies of other tissues. Their relevance to the high incidence of diverticular disease in Edinburgh compared with Kampala is discussed, together with theories for the aetiology of diverticular disease.

http://hdl.handle.net/1842/34374

The University of Edinburgh

Annexe Thesis Digitisation Project 2019 Block 22

Mechanical properties of the large bowel in health and disease

Thesis or Dissertation

Doctoral

ChM Master of Surgery