Experimental Diaphragmatic Hernia and Tracheal Ligation in a Fetal Rabbit Model

ABSTRACT

Despite of advances in perinatal management and treatment modalities, congenital diaphragmatic hernia (CDH) remains a frustrating problem. Although the sheep has been the most reliable experimental animal of fetal surgery in CDH, the rabbits has some possible advantages over sheep; lower cost, smaller body size, year-round availability, high number of fetuses per pregnancy, and short gestational period. The purpose of this study is to evaluate the feasibility of the animal model of CDH in rabbits. Twenty seven pregnant New Zealand rabbits underwent hysterotomy and fetal operation on gestational day 24 or 25. Two fetuses of each pregnant rabbit were operated. In the fetus of one end of bicornuate uterus, left diaphragmatic hernia was created by excision of fetal diaphragm through open thoracotomy (DH Group). In the fetus of the other end of bicornuate uterus, left diaphragmatic hernia was created and tracheal ligation by small-sized Surgiclip(R) (USSC, Norwalk, Conn., USA) was performed through cervical incision (TL Group). Among twenty seven pregnant rabbits, twelve were born alive with diaphragmatic hernia and eight were born alive with diaphragmatic hernia & tracheal ligation. The most commonly herniated abdominal organ was the left lobe of liver. In DH group, the lungs were hypoplastic with a decrease in lung weight/body weight ratio, a reduction in number of alveoli, an increase of vascular medial wall thickness of pulmonary arteries. The alveoli were immature with thick alveolar septum and increased interstitium. In TL group, the alveoli were more mature than that of DH group and no significant difference from control group was existed. Thus this study demonstrates that (1)Diaphragmatic hernia can be created in rabbits by fetal surgery, (2)Tracheal ligation can be performed in rabbits by fetal surgery, (3)Experimental diaphragmatic hernia results in pulmonary hypoplasia, (4)Concurrent tracheal ligation prevents pulmonary hypoplasia that resulted from diaphragmatic hernia. The above mentioned results show that pregnant New Zealand rabbit is appropriate as the animal model of CDH.