Influence of the peripheral progesterone level on uterine distension during hysteroscopy in the horse

Hysteroscopy, an established method for diagnosis and surgery treatment in equine gynecology, requires on adequate distension of the uterus. To define standard values of the necessary pressure for distension as well as of the pressure limits nine mores during anestrus and ten mores during diestrus w ere examined endoscopically. Using a defined scheme for insufflation the pr essure being necessary for total uterine distension (p(arb), = pressure for optimal working conditions, standard pressure), the limiting pressure for the cervical closure (p(efflux)), and the maximum pressure (p(max)) were de termined. Especially the influence of the peripheral progesterone level on the measured pressures was tested. The passage through the cervix as well a s the establishment of total visibility of endouterine structures were poss ible in all examinations. With increasing progesterone level the necessity of a manual occlusion of the cervix to obtain enough pressure for optimal w orking conditions (p(arb)) decreased (logical regression). The mares were assigned in groups according to the progesterone level in th e serum (group A: < 1 ng/ml, n=7; group B: > 1 ng/ml, n=12); the cervix of mores of group B resisted to significantly higher uterine pressure (p(efflu x): 65 +/- 10,11 mmHg; p < 0,05, Wilcoxon-test) compared to the mores of gr oup A (p(efflux): 48,22 +/- 8,07 mmHg). Furthermore, the maximum pressure ( p(max)) was significantly higher during progesterone influence (group A: 90 ,5 +/- 30,79 mmHg; group B: 110,28 +/- 16,66 mmHg). The results of the present study show that a hysteroscopy is a feasible met hod during anestrus as well as diestrus. During predominating progesterone influence the cervix is lightened up and allows a more efficient distension of the uterus as shown with the aid of concrete values in the present stud y. However, the risk of unintentionally superelevated pressure values incre ases with a high progesterone level. To avoid strain of the circulatory sys tem and unnecessary pain of the patient a controlled method of insufflation is recommended.