Electrical impedance measurement of urinary bladder fullness

Area of Science:

• Biomedical Engineering
• Urology
• Physiology

Background:

• Monitoring urinary volume is crucial for managing bladder function.
• Existing methods for assessing bladder fullness can be invasive or inconvenient.
• Electrical impedance offers a non-invasive approach to track physiological changes.

Purpose of the Study:

• To investigate the feasibility of using tetrapolar electrical impedance measurements to monitor urinary volume changes in healthy adults.
• To determine the correlation between electrical impedance and urinary bladder filling/emptying.
• To evaluate the predictive accuracy of the cumulative sum (CUSUM) test for voiding events.

Main Methods:

• A tetrapolar 75-kHz constant-current electrical impedance system was employed.
• Measurements were taken over 12 four-hour sessions in 40 healthy subjects (20 male, 20 female).
• Electrodes were placed on the lower abdomen, and impedance, skin temperature, and urine specific gravity were recorded periodically.

Main Results:

• Urinary bladder impedance decreased significantly with filling and increased upon voiding (p ≤ 10⁻¹⁰).
• Baseline impedance varied based on individual subject characteristics (e.g., skinfold thickness, circumference).
• The CUSUM test accurately predicted voiding events in 78.9% of cases and non-voiding in 66.8%, achieving 74.6% overall accuracy (p ≤ 0.05).

Conclusions:

• Tetrapolar electrical impedance measurement is a viable method for monitoring urinary volume changes.
• Impedance changes correlate reliably with bladder filling and voiding.
• The CUSUM test demonstrates potential for predicting voiding behavior non-invasively.