Michael Chancellor, MD highlights that we are beginning stages of understanding the pathophysiology of underactive bladder. His involvement with the Aikens Center for Neurourology Research at Beaumont has a significant research interest in this topic. There is an NIDDK grant allocated to address this issue. Dr. Chancellor began to describe the pathophysiology by comparing overactive bladder (OAB) to UAB. He states that detrusor under activity is important but may encompass only a smaller component of UAB. We are in need of animal models to mimic it, in order to better understand it. Several factors come into play with UAB, which include non-neural (diseases affecting smooth muscle of the bladder), neural, and aging (degeneration, biochemical micro damages).
Alan Wein, MD had done research on UAB dating back to 2005, using diabetes mellitus as a model. UAB has also been studied in Streptozotocin-induced rats. Rat models have been performed on aging rates, showing that voiding detrusor pressures decrease with aging, with concomitantly increased pressure thresholds, and an increase in non-voiding bladder contractions. Several animal models for UAB currently exist a DM model, aging model, obstruction and overdistention, ischemia and oxidative stress, and neurogenic model with pelvic nerve and spinal cord injury. There is now ongoing research on genetic mutations to study UAB as well. It has been shown that OAB and UAB share symptoms, such as nocturia, and both are associated with common underlying etiologies (aging, BOO, DM). There continues to be an accelerated interest in research on this topic and we look to future advancements in the understanding of UAB.
Dr. Alan J. Wein then discussed the future of UAB. Currently, basic science advancements are ahead of our clinical understanding. At this time, we are unable to exactly define or quantitate it. We know there is either a difficulty of the bladder to empty or to store, but no routine successful therapy is known at present. UAB is a clinical condition which consists of symptoms, bothersome or non-bothersome, with objective measurements, found on UDS.
Dr. Wein advocates for the development of a specific symptom set, with measurements with regard to age, gender, and etiology. We then need to be able to characterize it with severity scores and standardized quality of life scores, to judge response to treatment.
An International Incontinence Society (ICS) working group recently developed the definition that “UAB is characterized by a slow urinary stream, hesitancy, and straining to void with or without a feeling of incomplete bladder emptying, sometimes with storage symptoms.” UAB is a symptom complex often associated with UDS finding of detrusor underactivity (DU), but does not always correlate with this. Data has been collected finding that there is no symptom specific to UAB, in both men and women, therefore, making it often difficult to make the diagnosis. DU is quantitative on UDS, but the problem of what is “normal” varies with age, gender, and etiology. Although you can measure Pdet Qmax on UDS, contraction strength, speed, and duration are harder to measure (and not routinely done). In research, there are so many different definitions used for DU, no standardized definition has been established.
BCI (bladder contractility index) has been used to determine DU, but it is measured only in men. We still do not know the true consequences of UAB, with very little data available, in regard to bladder deterioration over time, upper tract damage and UTI. Studies have shown that patients with DU do well with outlet reduction procedures (TURP, HoLep). In the end, the future of UAB should include an agreed upon definition for UAB and DU, as well as indications for treatment, and indicators for success.
Michael B. Chancellor, MDL Pathophysiology of Underactive Bladder
Alan J. Wein, MD, Ph.D. (hon), FACS: The Future of Underactive Bladder
Moderated by: Brian J. Flynn, MD
Written by: Cristina Palmer, DO, Female Urology, Pelvic Reconstruction, Voiding Dysfunction Fellow, Department of Urology, UC Irvine Medical Center, Orange, California at the Society of Urodynamics, Female Pelvic Medicine & Urogenital Reconstruction Winter Meeting (SUFU 2018), February 27-March 3, 2018, Austin, Texas