Monitoring the water and electrolyte balance is an integral part of diagnostics and designing an effective therapy of many diseases. Sodium and potassium play a crucial role in the diagnosis of water and electrolyte disorders. The study was conducted to demonstrate the relationship between the occurrence of electrolyte disturbances in women undergoing hysteroscopy due to pathological uterine bleeding. Medical records of 543 patients aged 21-88 (52.8 ± 11.8 years) hospitalized in the Gynecology and Obstetrics Department of the Provincial Specialist Hospital in Biała Podlaska, who underwent hysteroscopic diagnostics due to pathological bleeding from the uterus were collected. 212 women (39.04%) were diagnosed with pathological bleeding from the uterus, 147 women (27.07%) had endomentrial hyperplasia, 104 women (19.15%) were diagnosed with an endometrial polyp,  62 women (11.42%) suffered from heavy menstruations and  18 women (3.3%) had uterine fibroids. The sodium and potassium concentrations were measured using an automated Cobas® 8000 analyzer (Roche). The average concentration of sodium in the serum was 139.84 ± 2.13 mmol L-1 (χ 2=35.079; P < 0.001), and the average potassium concentration was 4.44 ± 0.37 mmol L-1 (χ 2=36.019; P < 0.001).  Higher values ​​for sodium were recorded in the group of patients with adenomyosis (140.41 ± 2.27 mmol L-1) and patients with uterine fibroids (140.11 ± 1.94) mmol L-1). Statistically significant differences were found in mean sodium concentration values depending on the causes of patients’ hospitalization (H=33.914; P < 0.001), and the biggest differences were between patients with ovulation disorders and patients with adenomyosis: 138.86 ± 0.21 mmol L-1 vs. 140.41 ± 2.27 mmol L-1 (Z =5.169; P < 0.001). It seems important add measurements of sodium and potassium concentrations to the profile of tests performed in the diagnosis of gynaecological patients referred for hysteroscopy for the reasons presented in the study in order to reduce the risk of complications associated with the loss of these elements.  

25.3.2020