Conventional reanastomosis versus laser welding of rat uterine horns Arthur G. Shapiro, M.D., Mel Carter, A. Ahmed, and Marek W. Sielszak, M.D. Miami Beach, Florida In this study we compared conventional surgical techniques with those of low-power C0 2 lasers (output 140 mW; spot size 0.4 mm) used to weld transected rat uterine horns. On one side a microanastomosis was made by standard surgical technique of 8-0 nylon; the other side was "welded" either after doing the anastomosis with 8-0 sutures or without any anastomotic sutures. Histologic sections obtained from rats' uteri treated with conventional and laser surgery showed that on the laser-treated sutured side there was less necrosis and inflammatory and giant cells. The animals that underwent laser welding without suturing had no necrosis, suppuration, or granulation; giant cells were not present. We conclude that in the tissue from the laser-treated animals, when compared with conventional and laser-with-suture surgery, histologic features indicate healing process by primary intention via an aseptic noninflammatory reaction. (AM J 0BSTET GYNECOL 1987;156:1006-9.) Key words: Welding, laser, microanastomosis, fallopian tubes Recent evaluations of the use of laser for reanasto- mosis have documented that this modality can be used for welding of blood vessels and other organs such as vas deferens. 1 In 1978 Klink et al.2 described a suc- cessful pregnancy rate of 70% with end-to-end reanas- tomosis of rabbit uterine horns using laser power den- sities of 64 W/cm 2 • Latest studies'·' have failed to show that the C0 2 laser was able to weld uterine tubes in animals. Of note is that these latter studies used power densities of 600 to 900 W/cm 2 • In the present study we compared conventional surgical reanastomosis of tran- sected rat uterine horns with welding the tissue using very low C0 2 laser with a power output of 150 mW (power densities of < 100 W /cm 2 ). Methods In six adult female rats, the uterine horn was tran- sected through an abdominal incision. On one side a microreanastomosis was performed by standard micro- surgical technique with 8-0 nylon; the other side was welded with either the laser after completing the re- anastomosis with 8-0 nylon suture or without any an- astomotic sutures. In a latter case, two temporary un- tied stay sutures, one at 12 and one at 6 o'clock, were used only to help approximate the tissue and were re- moved after the welding was completed. A Shaplan laser No. 743 (Laser Industries, Tel Aviv, Israel) was From the Departments of Obstetrics and Gynecology and Medicine, Pulmonary Division, Mount Sinai Medical Center. Received for publication December 26, 1985; revised June 6, 1986 and December 8, 1986; accepted December 19, 1986. Reprint requests: Arthur G. Shapiro, M.D., Department of Obstetrics and Gynecology, Mount Sinai Medical Center, 4300 Alton Rd., Miami Beach, FL 33140. 1006 adjusted with a special kit (supplied by Dr.Jacob Dagan, Advanced Surgical Technologies, Allendale, New Jer- sey) to give an accurate low-power output in the mil- liwatt range. Laser was used with outputs of 0.15 W, a spot size of 0.4 mm. The welding was done with a micromanipulator and in a continuous fashion; slight blanching of the tissue was noted as the laser was passed over the anastomotic edges. Histologic sections of the anastomotic sites were obtained 1, 3, 4, and 10 weeks after the procedure. Material was immediately fixed in buffered neutral formalin and processed via routine paraffin technique. Tissue slides were stained with hematoxylin-eosin and parallel slides for iron deposits (Pearl's method) to determine the presence of macro- phages containing hemosiderin as an indication of bleeding at the operative site. The parameters studied were the type and localization of necrosis, suppuration, presence and type of inflammatory cells, and presence and localization of giant cells. Numbers of macrophages containing hemosiderin and inflammatory and giant cells were determined by light microscopy (Olympus BH2 Microscope) with a 40 x objective lens (0.456 mm field diameter = one high-power field). For analysis, 10 high-power fields were randomly selected from the welding area 1, 3, 4, and 10 weeks after surgery. The numbers of cells per 10 high-power field were graded as follows: 0 to 20 cells ( + ), 21 to 40 ( + + ), >41 (+++).Also, the pres- ence and localization of necrosis or suppuration were determined in the welding area. Results The results are summarized in Table I. The material from rats that underwent conventional surgery showed