Overhydration (OH) is a prevalent medical problem that occurs in patients with kidney failure, but a specific marker has still not been found. Patients requiring kidney replacement therapy suffer from a water imbalance, which is correlated with mortality rates in this population. Currently, clinicians employ techniques such as bioimpedance spectroscopy (BIS) and ultrasound (USG) markers of overhydration or markers of heart and kidney function, namely NT-pro-BNP, GFR, or creatinine levels. New serum markers, including but not limited to Ca-125, galectin-3 (Gal-3), adrenomedullin (AMD), and urocortin-2 (UCN-2), are presently under research and have displayed promising results. Ca-125, which is a protein mainly used in ovarian cancer diagnoses, holds great potential to become an OH marker. It is currently being investigated by cardiologists as it corresponds to the volume status in heart failure (HF) and ventricular hypertrophy, which are also associated with OH. The need to ascertain a more precise marker of overhydration is urgent mainly because physical examinations are exceptionally inaccurate. The signs and symptoms of overhydration, such as edema or a gradual increase in body mass, are not always present, notably in patients with chronic kidney disease. Metabolic disruptions and cachexia can give a false picture of the hydration status. This review paper summarizes the existing knowledge on the assessment of a patient’s hydration status, focusing specifically on kidney diseases and the role of Ca-125.

Overhydration (OH) is a prevalent medical problem occuring in patients with kidney failure, but a specific marker has still not been found. Currently, clinicians employ techniques such as bioimpedance spectroscopy (BIS), ultrasound (US) markers of fluid overload or markers of heart and kidney function such as NT-pro-BNP, GFR or creatinine levels. New serum markers, including but not limited to Ca-125, Galectin-3 (Gal-3), Adrenomedullin (AMD) and Urocortin-2 (UCN-2), are presently under research, displaying promising results. The necessity to ascertain a more precise marker of overhydration is urgent mainly because physical examination is exceptionally imprecise. Signs and symptoms of fluid overload, like edema or gradual increase of body mass, are not always present, notably in patients with chronic kidney disease. This review paper summarizes actual knowledge of a patient's hydration status estimation, focusing specifically on kidney diseases.