Transcervical artificial insemination in dogs and cats: review of the technique and practical aspects.

The technique of transcervical catheterization for artificial insemination has gained practical importance over the last 3 and 1 decades in bitches and queens, respectively. The vagina of both species has a thickening of the dorsal aspect called dorsal medial fold, which restricts the lumen of the paracervix, making catheterization of the cervix difficult both with manual and endoscopic techniques. Manual catheters have been used initially in the bitch and are now gradually being replaced by rigid endoscopy through the adaptation of human cystoscopes and ureteroscopes. Cystoscopes provide excellent imaging of the vagina, but cervical catheterization is more difficult due to the oblique 30° viewing angle of its telescope and may not be long enough to catheterize large size bitches. Ureteroscopes allow an acceptable view of the vaginal mucosa and offer advantages such as the possibility to catheterize the cervix of bitches of all body sizes, manipulate the cervical tubercle when the external cervical os is not visible, offer a better visualization of the cervix using the shunt (a large Foley catheter which allows insufflation and distention of the vagina). Feline cervical catheterization has been achieved with three different types of catheters; the last one, developed following careful anatomical studies of how the feline vaginal lumen changes during estrus, allows cervical catheterization thanks to digital manipulation of the cervix through the rectum.