The effect of stapler diameter and proximal colostomy on narrowing at experimental circular stapled large bowel anastomoses.

The effect of stapler diameter and proximal colostomy on large bowel anastomotic narrowing was studied in 23 ewes, to test the hypotheses that stapler diameter is inversely proportional to narrowing and that a colostomy increases narrowing. Large bowel anastomoses were performed with ILS Proximate circular staplers of 25, 29 and 33 mm diameter (six in each group), and assessed at 12 weeks for anastomotic narrowing, hydroxyproline content and histology. In five animals a proximal loop colostomy was added after anastomosis with the 29 mm stapler and similarly assessed at 6 weeks. Neither radiological nor clinical anastomotic leaks occurred and there were no deaths. Comparison of narrowing indices showed no statistically significant difference between the three stapler diameters. Colostomy significantly increased narrowing. Hydroxyproline content was greater at all anastomoses compared with controls. Anastomoses with the 25 mm staplers had a significantly reduced hydroxyproline content compared to the 29 and 33 mm staplers, which may be explained by anastomotic dilatation. The tendency for stapled anastomoses to develop narrowing should not necessarily influence the surgeon's choice of stapler diameter when performing large bowel anastomoses. Moreover, dilatation by faeces may be a factor in reducing staple anastomotic narrowing and, when safe, a proximal colostomy is best avoided.