LAUSR

Dear Editor, The lymphaticovenous anastomosis (LVA) has become an increasingly common procedure for the surgical treatment of the lymphedema, even in advanced stages (Koshima et al., 2004). However, it requires specific training because of the small vessel diameter, the variety of anastomosis techniques and the change thickness of the lymphatic vessel wall depending on the lymphedema stage (Mihara et al., 2012). There are few published articles describing a LVA training model in rats (Leuzzi et al., 2018; Yamamoto et al., 2017). Although they are really useful, anastomoses described were only end-to-end between veins and normofunctional lymphatic vessels and sometimes the mean lymphatic vessel diameter was smaller than 0.27mm (Leuzzi et al., 2018; Yamamoto et al., 2017). We are presenting here a new training model in rats to practice end-to-end and end-to-side anastomoses similar to LVAs in advanced stages of lymphedema. After general anesthesia of the rat, the animal was placed in supine position. A midline abdominal laparotomy was made and the ureter (mean diameter 0.61 mm [range, 0.5–0.8 mm]) and the iliolumbar vein (mean diameter 0.38 mm [range, 0.3–0.5 mm]) were dissected (Figure 1a). The iliolumbar vein was temporary clamped and the ureter was cut 0.5 mm proximal. We recommend not clamping the ureter in order to avoid its spasm. An orifice was performed in the vein and an end-to-side anastomosis was performed using 11-0 nylon. The suture should be hermetic so at least six stitches should be performed (Figure 1b). Once the patency had been assessed removing the clamp, the ureter and the iliolumbar vein were cut keeping them as long as possible and an end-to-end anastomosis was performed between them with 6–7 simple stitches. After checking the anastomosis, the ureter was cut again and was anastomosed end-to-end to the proximal ureter segment with 5–7 simple stitches. This anastomosis was checked injecting saline or methylene blue. We consider this model is appropriate for LVA training because of the similarity in the color, the fragility, the diameter (range, rat ureter 0.3–0.5 mm, human lymphatic vessels 0.2–0.8 mm) and the ratio wall-lumen compared to advanced lymphedema cases: in Stages IIb and III, the human lymphatic vessel wall is thickened and lumen is progressively narrowed (Mihara et al., 2012). Similarly, the ureter of the rat has a thicker wall and narrower lumen than the veins or the normofunctional lymphatics. Besides, the identification of the ureter is