Implantable Bladder Sensors: A Methodological Review

Abstract

The loss of urinary bladder control/sensation, also known as urinary incontinence (UI), is a common clinical problem in autistic children, diabetics, and the elderly. UI not only causes discomfort for patients but may also lead to kidney failure, infections, and even death. The increase of bladder urine volume/pressure above normal ranges without sensation of UI patients necessitates the need for bladder sensors. Currently, a catheter-based sensor is introduced directly through the urethra into the bladder to measure pressure variations. Unfortunately, this method is inaccurate because measurement is affected by disturbances in catheter lines as well as delays in response time owing to the inertia of urine inside the bladder. Moreover, this technique can cause infection during prolonged use; hence, it is only suitable for short-term measurement. Development of discrete wireless implantable sensors to measure bladder volume/pressure would allow for long-term monitoring within the bladder, while maintaining the patient’s quality of life. With the recent advances in microfabrication, the size of implantable bladder sensors has been significantly reduced. However, microfabricated sensors face hostility from the bladder environment and require surgical intervention for implantation inside the bladder. Here, we explore the various types of implantable bladder sensors and current efforts to solve issues like hermeticity, biocompatibility, drift, telemetry, power, and compatibility issues with popular imaging tools such as computed tomography and magnetic resonance imaging. We also discuss some possible improvements/emerging trends in the design of an implantable bladder sensor.

Localization and Tracking of Implantable Biomedical Sensors

“…In implantable bladder sensors, hermiticity, bio-compatibility, drifting, telemetry, power transfer and compatibility issues still require more research for enhanced patient comfort and long-term monitoring. The study [15] indicates that the wireless communication distance is an essential factor for such sensors, since RF signals rapidly spread in the human body, but inductive coupling necessitates alignment and appropriate localization of both interior and exterior coils for effective power transmission.…”

Suppression of Urinary Voiding “on Demand” by High-Frequency Stimulation of the S1 Sacral Nerve Root in Anesthetized Rats

“…For the individual with urinary urge incontinence, the opportunity to activate their stimulator at the onset of urge sensation and suppress imminent involuntary voids would restore autonomy over their bladder emptying. As implantable sensor technology develops , it may become possible to incorporate a stimulator into a device, which would detect bladder fullness and/or sharp rises in bladder pressure and then alert the individual to the need to empty their bladder while at the same time activating the stimulator to suppress the imminent void and prevent an incontinent episode. Such a “smart” device could have applications for those with impaired bladder sensation, for example, after spinal cord injury, as well as patients with urinary urge incontinence.…”

Towards a Chipless and Wireless Passive System for Real‐Time Encoding of the Bladder Volume

“…These methods are thus suitable in clinical settings, and always for a short time. [ 10 ] Other techniques based on advanced imaging are also used in clinical facilities, but systems suitable for homecare, able to provide a real time and continuous monitoring of the bladder filling state, are not yet available. Recently, portable ultrasound equipment have been specifically designed for accurate volume bladder monitoring, especially for postvoid residual volume assessment.…”