Experimental tracheal ligation (TL) has been shown to reverse the pulmonary hypoplasia associated with congenital diaphragmatic hernia (CDH) and to normalize gas exchange. The purpose of this study was to determine whether the TL would correct the surfactant deficiency present in the fetal rabbit model of CDH by using lamellar body count. Lamellar bodies are synthesized and secreted by the type II pneumocytes of fetal lung. The phospholipids present in these bodies constitute the major component of pulmonary surfactant. Twenty-one pregnant New Zealand rabbits underwent hysterotomy and fetal surgery on gestational day 24. Two fetuses of each pregnant rabbit were operated. In the fetus of one end of bicornuate uterus, left DH was created by excision of fetal diaphragm through open thoracotomy (DH Group). In the fetus of the other end of bicornuate uterus, left DH and TL were created (TL Group). The fetuses were delivered by Cesarean section on gestational day 31. Fourteen in control group, 12 in the DH group and 13 in TL group were born alive. En bloc excision of lungs, bronchi and trachea was done in all newborn rabbits. A five Fr catheter was inserted through trachea and repeated irrigations with 10 cc normal saline were done. The irrigated fluid was centrifuged at 280 xg for 5 minutes and the lamellar bodies were counted with the upper level fluid in platelet channel of electronic cell counter. The average lamellar body counts were 37.1 ± 14.2 × 10³/µL in control group, 11.5 ± 4.4 × 10³/#x00B5;L in DH group, and 6.5± 0.9 × 10³/#x00B5;L in TL group. Lamellar body count in DH group was lower than in control group and did not increase after TL. This study shows TL has no therapeutic effect on decreased surfactant level of CDH and the pregnant rabbit is appropriate for the animal model of CDH.

Despite of advances in perinatal management and treatment modalities congenital diaphragmatic hernia(CDH) remains a frustrating problem. Although the sheep has proven to be a reliable experimental model for the production of intrauterine CDH, the rabbit may have some advantages. These include lower cost, smaller body size, year-round availability, high number of fetuses per pregnancy, and short gestational period. To evaluate the feasibility of the rabbit model of CDH, twenty-seven pregnant New Zealand rabbits were utilized. Hysterotomy and an operative procedure for creating a diaphragmatic defect on gestational day 24 or 25, in two fetuses of each pregnant rabbit were performed. In one fetus of one cornu of the uterus, the left fetal diaphragm was excised through an open thoracotomy(DH group). In another fetus in the other cornu, CDH was created and the trachea clipped(Surgiclip, USSC, Norwalk, Conn., USA) (TL group). Delivery was by Cesarean section on 30 days of gestation. Among twenty- seven pregnant rabbits, 12 in the DH group and eight in the TL group were born alive. The most common herniated organ was the left lobe of the liver. In thee DH group, the lungs were hypoplastic with decreased lung weightlbody weight ratio, reduced numbers of alveoli, thicker media of the pulmonary arteries, and immature alveoli. In TL group, the alveoli were more mature and did not differ from the control animals. In conclusion, (1) pulmonary hypoplasia develops in the fetal rabbit diaphragmatic hernia model and (2) simultaneous tracheal ligation prevents pulmonary hypoplasia.