The first examination of the uterine lining was performed in 1869 using a cystoscope-type instrument during uterine bleeding. Hysteroscopy is currently less widely used in clinical practice, but the conditions for its use have undoubtedly been created: fiber optics provide good illumination of the object, and a variety of instruments has paved the way for complex surgical interventions equivalent to those performed by surgeons (Fig. 1). To address these issues, researchers have continually sought methods to increase uterine volume and improve conditions for examining its lining. Specifically, the effectiveness of stretching the uterine walls with various liquids, gases, and mechanical means (balloons) has been evaluated. Indications and contraindications: Hysteroscopy as a diagnostic procedure is indicated in clinical situations such as spotting and uterine bleeding, pain of unknown etiology, and suspected neoplasms. Thanks to its high resolution, it allows for the diagnosis of various diseases, benign and malignant tumors, developmental anomalies, and residual fertilized egg after abortion (adenomyosis), and to evaluate the effectiveness of their medical and surgical treatment. Surgical hysteroscopy is indicated for the removal of tumors, bleeding control, foreign bodies, septum removal, and other interventions. Contraindications to hysteroscopy include acute infectious diseases (tonsillitis, influenza), acute inflammatory diseases of the genital organs, and grades III–IV vaginal cleanliness. Equipment and instruments. Although hysteroscopy is a natural examination, there is a risk of infection during its performance. The uterine wound surface and the abdominal cavity, where optical media (gas and liquid) enter, can be entry points for infection. This fact requires hysteroscopy to be performed with strict adherence to aseptic and antiseptic precautions in a well-equipped mini-gynecological operating room. The following equipment and instruments are required for hysteroscopy: a hysteroscopic kit, including an endoscope body, a set of optical tubes (hysteroscopes [ https://eleps.ru/katalog/gisterorezektoskopiya-i-ginekologiya-optika/ ]) with viewing angles from 0 to 120°, a vacuum adapter for the cervix with a guidewire, a diathermy coagulator probe, catheters for tube bougienage, scissors, forceps and other instruments; a light source; insufflators for introducing gas (CO2) and liquids into the uterine cavity; a high-frequency current generator, etc.; a gynecological device. The equipment and instruments are located to the right of the gynecological chair. The hysteroscopy room must have an oxygen system, anesthesia equipment and medications for providing emergency care in the event of cardiopulmonary disorders. Increasing the volume of the uterine cavity and allowing a detailed examination of its walls are achieved by introducing gas (CO2) and fluids such as isotonic sodium chloride solution, high-molecular-weight dextrans, silicone, and others. Gas is delivered through an insufflator system with complex electronic devices that regulate the rate of gas delivery and the pressure in the uterine cavity. The abundant blood supply to the uterus and the outflow of venous blood into large vessels—the iliac and inferior vena cava—create conditions for the development of gas embolism if the gas administration technique is improper. At a uterine pressure of no more than 21.3–24.0 kPa (160–180 mmHg) and a gas delivery rate of 80–100 ml/min, the gas, even if it enters the uterine vessels, is completely utilized by the body and does not cause embolism. Fluid is delivered through a special system in a jet or in portions. At a pressure of 13.3–16.0 kPa (100–120 mmHg), fluid does not enter the tubes or the abdominal cavity, preventing irritation of the pelvic peritoneum. Patient preparation, premedication, and anesthesia are included. Before a scheduled hysteroscopy, patients must prepare their bowels with a cleansing enema on the morning of the procedure, shave the external genital hair, empty the bladder, and sanitize the vagina (the vagina is washed with a 1:5000 furacilin solution both in the evening and morning of the procedure). Premedication is mandatory. The choice of medication and its dosage are determined individually. Anxiety and other negative emotions can be suppressed by administering tranquilizers 30–40 minutes before the hysteroscopy. The choice of anesthesia method is based on the nature of the examination, in particular, on such procedures as cervical canal dilation, endometrial curettage, removal of large polyps and myomatous nodes, and tubal bougienage. General anesthesiology is considered the optimal anesthesia option for nulliparous women [Savel'eva G. M. et al., 1983]. In women who have given birth, local paracervical anesthesia is sometimes sufficient for hysteroscopy, since the hysteroscope passes through the cervical canal without dilating it. Technique. The patient is positioned in the gynecological chair as for a routine gynecological examination. The legs are fixed on supports. The external genitalia and vagina are treated with a 5% iodine alcohol solution or 96% alcohol. The technique of hysteroscopy largely depends on the type of optical medium. Hysteroscopy using liquid media. The cervix is ??fixed with bullet forceps, the uterine cavity is probed, and the cervical canal is dilated using standard techniques using Hegar dilators up to size 11. This is necessary for subsequent diagnostic curettage, removal of endometrial polyps, and other interventions. Fluid flows through the hysteroscope channel under pressure, spreading the uterine walls, washing the uterine cavity, and freely draining out through the space between the cervical canal wall and the hysteroscope body, the diameter of which corresponds to a Hegar dilator size 6-7. This removes blood clots and liquid blood from the uterine cavity, improving examination conditions. After dilating the cervical canal, the hysteroscope, connected to the irrigation system and light guide, is inserted into the uterine cavity through the internal os. When performing a hysteroscopy with a liquid optical medium, the nurse prepares a sufficient amount of solution, assembles the system for fluid administration, and prepares the endoscopic and gynecological instruments. This technique uses gas-assisted hysteroscopy. Carbon dioxide is used as the optical medium. After dilating the cervical canal, the hysteroscope body, without the optical tube, is inserted into the uterine cavity. The uterine cavity is flushed of blood by injecting and then aspirating 40-50 ml of isotonic sodium chloride solution through the hysteroscope body. The optical tube is then inserted, an insufflator is connected to one of the valves in the body, and a pressure of 160-180 mmHg is created in the uterine cavity by injecting CO2 for 20-25 seconds, which is necessary for dilation of the walls. A diagnostic examination is performed. Before performing the procedure, the nurse must check the presence of gas, the tightness of the system, and the operation of the sensors. Uterine perforation, development of pain syndrome due to irritation of the peritoneum when fluid or CO2 enters the abdominal cavity, and exacerbation of the inflammatory process are possible.