[Development of an intrauterine distension pressure for hysteroscopy in the horse].

Diagnostic and operative hysteroscopy have offered an advance in equine fertility diagnostic and equine fertility surgery. A distension of the uterine cavity and an establishment of a continuous intrauterine pressure are basic requirements for complete visualisation of intrauterine structures and safe and efficient surgical procedures. Superelevated pressure and resorption of distension media may result in fatal complications. Intrauterine pressure was monitored in 28 healthy di- or anestrus mares during hysteroscopy via a transcervically inserted catheter. Mares were sedated with xylazine and levornethadon and fixed in a stock. The pressure which was elementary for complete visualisation Parb, the pressure with onset of transcervical efflux of distension medium Pcerv and the maximum intrauterine pressure Pmax that could be obtained were determined. Complete visualisation of intrauterine structures could be achieved with a mean pressure of 17.8 +/- 5.5 mm Hg (mean +/- s) and a range of 12.8 to 28.6 mm Hg. Spontaneous efflux of distension media was registered in mares following further insufflation at a significantly higher (p < 0.001) intracavitary pressure of 62.5 +/- 10.0 mm Hg (mean +/- s). Maximum pressure Pmax that could be obtained was found to be significantly higher (p < 0.001) than Parb but also significantly higher than Pcerv with 101.6 +/- 24.4 mm Hg (mean +/- s). Clinical or cardiological signs of discomfort or affection on the circulatory system were only registered while Pmax was applicated. The results indicate, that a safe and efficient hysteroscopy can be performed with a mean pressure of 17.8 mm Hg and an upper pressure limit of 30 mm Hg.