[The healing influenced by hypothyroidism and elderly. Study of intestinal anastomosis healing in rats]. / O processo de cicatrização influenciado pelo hipotireoidismo e pelo envelhecimento. Estudo da cicatrização de anastomoses intestinais, em ratos.

PURPOSE: The aging of the population has led to an increased number of interventions in elderly patients, with hypothyroidism, even at the subclinical level, being a common situation among these patients. The objective of the present study was to determine the influence of hypothyroidism on the healing process of colon anastomoses in aged rats. METHODS: 96 male Wistar rats were used, 48 of them young and 48 old. Half the young animals and half the old ones were euthyroid and half were hypothyroid. Hypothyroidism was obtained by total thyroidectomy. Thirty days after surgery the animals were submitted to median laparotomy followed by transverse colotomy of the left colon with end-to-end anastomosis and laparorrhaphy. Six animals from each group were submitted to euthanasia by drawing lots on the 3rd, 7th and 14th postoperative day and submitted to macroscopic, resistance, and histopathological analysis of the anastomoses. RESULTS: No dehiscence was observed and the gain of resistance and the general histological evolution in terms of epithelialization and inflammatory reaction was similar in all groups. Analysis of total collagen content revealed that the anastomoses of young and old animals showed the same behavior on the 3rd day, although less collagen was observed in hypothyroid animals (YN x YH p = 0.0000; ON x OH p = 0.0000). This behavior persisted on the 7th and 14 day. Less collagen I was present in the anastomoses of hypothyroid animals on the 3 (YN x YH p = 0.0015; ON x OH p = 0.0000), 7th (YN x YH p = 0.0006; ON x OH p = 0.0001) and 14th day (YN x YH p = 0.0181; ON x OH p = 0.0057), the same occurring for collagen III on the 3rd (x YH p = 0.0007; ON x OH p = 0.0260), 7th (YN x YH p = 0.0160; ON x OH p = 0.2670) and 14th day (YN x YH p = 0.0000; ON x OH p = 0.0030). CONCLUSION: Analysis of the results permitted us to conclude that lower collagen concentration du to low synthesis and delayed scar maturation in the anastomoses occurred and was much more due to hypothyroidism than to aging.