Non-invasive urine volume estimation in the bladder by electrical impedance-based methods: A review

Urinary incontinence is prevalent among elderly people and associated with a substantial decrease in quality of life. Recent clinical studies have suggested the importance of tailored continence care based on urine volume measurement in the bladder. However, an accurate sensor for continuous urine volume measurement remains unavailable. Electrical impedance measurement represents a promising method to accurately estimate urine volume. This review highlights the recent progress in and future research on electrical impedance-based urine volume estimation. There are two basic electrical impedance-based urine volume estimation methods: bioelectrical impedance analysis and electrical impedance tomography. The research on systems for bioelectrical impedance analysis is dedicated to developing portable or wearable devices. The research on electrical impedance tomography-based methods primarily utilizes computer simulation models, and several algorithms for urine volume estimation have been proposed. Only a few reports exist on volume estimation performance evaluation in humans. Further research in this field will include the development of a wearable urine volume sensor utilizing textrodes and the evaluation of estimation accuracy in long-term measurement under real-life conditions.