Although utilized as the gold standard for the diagnosis of functional bladder disorders for decades, the challenges of urodynamics are clear: lack of reproducibility, variable diagnostic accuracy, artifacts, infections, and the need for invasive catheters. Several groups, including our own, performed urodynamics studies (UDS) on normal healthy volunteers without lower urinary tract symptoms. These studies found high rates (∼70%) of artifactual and inaccurate diagnoses, likely due to irritation from catheters and supraphysiologic fill rates.¹ In terms of the voiding phase, UDS performs fairly well. However, filling phase data are more limited, only providing information about involuntary detrusor contractions and compliance. The problem is that a great deal of patient-reported lower urinary tract symptoms (ie, urgency and frequency) occur during the filling phase where UDS may not provide clinically useful data. Bottom line: we need to do better, and here’s a sneak peek at some new ideas.

Sensation

During UDS, the way we measure sensation is to prompt patients to report verbal sensory thresholds. However, there are insufficient guidelines for what these thresholds mean or what is considered normal. To address this, our group developed a tablet-based sensation meter (Figure 1) which allows patients to record real-time sensation from 0% to 100%.² The data are then used to generate sensation-capacity curves, and we have shown that curve slopes and how they change are associated with different sensory phenotypes. Furthermore, this technology is simple, cheap, and can be incorporated into UDS equipment or used in stand-alone natural filling studies.

Micromotion

Bladder wall micromotion, or spontaneous low amplitude rhythmic detrusor contractions, are thought to be involved in overactive bladder pathophysiology. In fact, investigators have shown that changes in rhythmic activity are associated with increased urgency.³ Unfortunately, techniques to identify micromotion during UDS are limited. In one study, investigators used a urinary catheter with balloon-mounted electrodes inflated to the bladder diameter and demonstrated increased micromotion in women with urgency,⁴ but the invasivity and discomfort with this technique limits its use. Our group developed an automated detection algorithm during UDS and identified a clear subgroup of patients (∼15%) with micromotion.⁵ We, and others, have also developed techniques to identify bladder wall micromotion, noninvasively, using linear (M-mode) ultrasound (Figure 2).⁶

Noninvasive Urodynamics

The goal of a well-done urodynamic study is to reproduce a patient’s functional bladder pathology. In this regard, catheters are problematic, and the ideal UDS upgrade would be catheter free. Our group, and others, have used ultrasound to identify bladder biomechanical properties including shape⁷ and micromotion.⁶ Newer technologies include a wireless bladder insert that can record bladder pressures⁸ and even functional MRI techniques.⁹ Ultrasound has also been used to measure bladder wall thickness¹⁰ and wall elasticity using ultrasonic waves in a technique called vibrometry.¹¹

Preclinical Urodynamics

There are a few groups (including ours) that are successfully using a working in vitro porcine bladder as a model for UDS. We have used this preclinical method to develop new UDS techniques that can be readily translated into human clinical studies. Using this model, we have shown how blood flow and ischemia can alter wall tension,¹² how compliance can be acutely regulated,¹³ and have even shown how upstream afferent nerve signaling can be recorded as a surrogate measure of bladder sensation.¹⁴

Conclusion

Unlike many other diagnostic techniques in urology and other areas of medicine, UDS has not evolved much in the last few decades. However, researchers are now working on upgrades to measure sensation, micromotion, and to noninvasively evaluate bladder function using ultrasound and other techniques. There are also multiple groups exploring the brain-bladder axis with functional MRI and near-infrared spectroscopy. While this sneak peek only scratches the surface, hold on, because next-generation UDS upgrades are already in development.