Hysteroscopes are available in two basic types—ﬂexible and rigid. Flexible hysteroscopes are self-contained in that they do not require a sheath; the single integrated channel is used to transmit gas or ﬂuid to the endometrial cavity for distention. As a result, these instruments are generally of smaller diameter than rigid systems. In addition, they can be designed to be “steerable,” allowing angled viewing. Flexible hysteroscopes utilize fiberoptic bundles rather than lenses to transmit the image to the observer and, consequently, have lower resolution than rigid instruments of a similar diameter and typically do not have a channel with a caliber suitable for most hand instruments. Rigid hysteroscopes are more durable and provide a superior image. The most commonly used hysteroscopes are 3 to 4 mm in diameter, although those using fibers can be smaller than 2 mm in diameter.
Rigid endoscopes require an angled (fore-oblique) lens to provide the angled view useful for operative hysteroscopy and are available in 0-degree, 12-to 15-degree, and 25-to 30-degree models (Fig. 23.26). The 0-degree telescope provides a panoramic view and is best for diagnostic procedures. Hysteroscopes with 25-to 30-degree angles are most often used for cannulation of the fallopian tubes or placement of sterilization devices, whereas 12-to 15-degree designs are a suitable compromise useful for diagnosis and ablation or resection. The utility of endoscopes with larger fore-oblique views may be offset by the tendency of resectoscopic electrodes to leave the visual field on full extension.
Adequate illumination of the endometrial cavity is essential. Because it runs from a standard 110-or 220-volt wall outlet, the light source requires no special electrical connections. For most cameras and endoscopes, the element must have at least 150 watts of power for direct viewing and preferably 250 watts or more for video and operative procedures (219).
Although diagnostic hysteroscopy may be performed with direct visualization, it is best to use video guidance for prolonged operations. Video imaging is important for teaching and recording pathology and procedures. The camera must be sensitive because of the narrow diameter of the endoscope and the frequently dark background of the endometrial cavity, particularly when it is enlarged or when blood is in the field. (Fig. 23.25).
A small video camera can be used to teach and to coordinate the procedure with the operating room team. It allows the acquisition of still or video images for future reference or teaching. When a video recorder is used, the camera should be attached directly to the recorder to preserve the image quality. A number of video recording formats are available, each with inherent advantages and disadvantages. Some video printers provide images suitable for a medical record. Newer high-definition digital cameras provide high-quality video still images as well as high-resolution digital video, suitable for publication or teaching.
Figure 23.27 Resectoscope. The assembled resectoscope is shown, with two electrodes in the foreground. Manipulation of the electrode is via the white handle in the proximal portion of the device.
The instruments available for use through operative hysteroscopes include biopsy, grasping, cutting, and punch-biopsy devices. These tools are narrow and ﬂexible enough to navigate the 1-to 2-mm diameter operating channel (Fig. 23.25). Although their value is limited by their small size and ﬂimsy construction; the scissors can divide adhesions, the biopsy forceps can sample targeted lesions, and the grasping forceps can remove small polyps or intrauterine devices. Some operative hysteroscopes are designed to allow passage of fibers for the conduction of Nd:YAG laser energy, although this modality is generally superseded by electrosurgical electrodes.