Postoperative changes in a bronchial stump following covering with free fat tissue in a rat model

OBJECTIVES: Covering the bronchial stump with free fat tissue has been used as minimally invasive prophylaxis against bronchial stump fistulas; however, postoperative changes in the bronchial stump have not been well validated. Our goal was to examine changes in the bronchial stump in response to covering with free fat tissue in a rat model.METHODS: A left pneumonectomy was performed on 16 Wistar/ST rats, 12 of which had a bronchial stump covered with free subcutaneous fat tissue. Four rats that underwent a left pneumonectomy alone were sacrificed on postoperative day 7, and the 12 rats whose bronchial stumps were additionally covered with fat tissue were sacrificed on postoperative days 7, 14 and 56. Macroscopic and histological changes and pressure resistance of the bronchial stumps due to coverage with free fat tissue were examined.RESULTS: None of the rats showed macroscopic infection or necrosis in the thoracic cavity at the time of the rethoracotomy. The normal bronchial stumps remained mostly exposed, whereas the bronchial stumps covered with fat tissue were well-coated with tissue mass. Histologically, fibrous connective tissue containing microvessels gradually formed around the bronchial stump covered with fat tissue, and some of the tissue masses still had normal fat structures 56 days postoperatively. Covering with fat tissue significantly increased the pressure resistance of the bronchial stump 7 days postoperatively and further increased with time.CONCLUSIONS: Covering the bronchial stump with free fat tissue formed fibrous connective tissue around the bronchial stump and reinforced its closure.