[A microsurgical approach to drainage of the thoracic duct in the rat]

Study of thoracic lymph flow is still of interest in gastrointestinal absorption and lymph distribution of different drugs or in immunological studies. A microsurgical experimental model for cannulation of the thoracic duct in rats is described. The principle of the method is the end fistula described by Bollman, allowing the sampling of the total thoracic duct lymph output. A simple method of collecting lymph under free moving conditions was used. The lymph cannulations were one with 0.9 mm outer diameter silicone tubing in 24 Sprague-Dawley rats with an average preoperative weight of 300 +/- 30 g. The daily lymph output measured for up to 10 days in the awake and unrestrained rats varied between 24.4 ml and 97.7 ml/day (average 45.6 ml/ day). The hourly lymph output varied between 0.55 ml and 5.8 ml (average 1.9 ml/h). Patency of the lymph fistulas was 87.5% at five days and 64.3% at the end of the experiment. The rats with failed fistulas presented various degrees of thickening of the lymphatic vessel wall. The average weight loss at the time of euthanasia was 72 g (24%). An accurate technique under the operation microscope and the use of silicone tubing may offer a reliable method in experiments requiring the sampling of the whole thoracic duct lymph output for limited periods of time.