The structural and functional impact of microsurgical anastomosis on the rabbit oviductal isthmus.

Microsurgical transection and anastomosis of the left isthmus in 7 rabbits caused fertility to be reduced 40%. Following rebreeding artificial eggs were introduced into the anastomosed and control oviducts. Sixty-three to 65 hours after mating, direct in vivo observations disclosed varied forms of motion of the artificial eggs within the isthmus, including both small oscillations and occasionally, large precipitous excursions covering more than 1 cm. Subsequent clearing of the genital tracts revealed that the anastomosis in the isthmus had detained most of the natural and artificial eggs, whereas both forms of ova were predominantly past the equivalent site on the control side; yet all anastomosed oviducts were fully patent. We conclude that the decreased fertility after isthmic anastomosis is due not to a physical obstacle but to an inability of the isthmus near the anastomosis to dilate as do other regions of the tube.