- The International Continence Society definition of underactive bladder (UAB) clarifies that it is a symptom syndrome, whereas detrusor underactivity is a urodynamically defined condition
- Urodynamic testing is not usually necessary for women with lower urinary tract symptoms because bladder outlet obstruction is uncommon in women
- Behavior modification therapy is useful for patients with UAB and impaired bladder sensation who may not sense bladder distension
- Monotherapy with cholinergic drugs, including bethanechol, is not recommended for UAB, but one study showed that the combination of urapidil and a cholinergic drug (bethanechol or distigmine) was superior to either monotherapy in women with UAB
- Sacral neuromodulation is an effective and durable way for patients with UAB to improve voluntary voiding
Underactive bladder (UAB) affects up to 45% of women, and the prevalence increases with age. This condition has received little attention in medical literature, partly due to a lack of consistent definitions and diagnostic criteria.
The International Continence Society (ICS) revised its definition for UAB, which is expected to guide research and therapeutic innovations. In the Indian Journal of Urology, Massachusetts General Hospital Urologist Tammer Yamany, MD, Ajay K. Singla, MD, urologist at Mass General and director of the Harvard Urologic Surgery Residency Program, and colleagues explain that definition and review what is known to date about the diagnosis and management of UAB.
Categorizing Underactive Bladder Function
The ICS states that UAB is a syndrome "characterized by a slow urinary stream, hesitancy and straining to void, with or without a feeling of incomplete bladder emptying, sometimes with storage symptoms." Examples of storage symptoms are nocturia, frequency and urgency.
Thus, the diagnosis of UAB is made based on symptoms. This distinguishes it from detrusor underactivity (DU), a diagnosis that is based on the results of urodynamic studies.
DU is defined by the ICS as a bladder contraction of reduced strength and/or duration resulting in prolonged or incomplete emptying of the bladder. UAB and DU coexist in many patients.
Diagnosis of UAB
The presentation of UAB is highly variable, but patient complaints often overlap those of patients with general lower urinary tract symptoms (LUTS). As such, the initial evaluation should be similar:
- History and physical examination, with attention to bowel habits, prior abdominal or pelvic surgeries, prior traumas, medications, neurologic history and pelvic floor examination
- Postvoid residual
- Uroflowmetry is particularly useful to identify women with low flow. No cutoff for maximum flow rate in UAB has been defined, but typical findings are a slow take-off with low maximum flow rate, prolonged voiding time and multiple intervals
- Urodynamic testing is not usually necessary because bladder outlet obstruction (BOO) is uncommon in women with LUTS. Still, because there is no noninvasive diagnostic algorithm for UAB, urodynamic testing is often performed and may demonstrate DU, delayed start of contraction and delayed urine flow despite a desire to void
A small number of women with LUTS have both DU and BOO. In women for whom the etiology of LUTS is uncertain, and for those who don't respond to first-line therapies, urodynamic testing may be helpful to identify combined DU and BOO.
UAB Management Strategies
Clean intermittent catheterization is the most commonly used management strategy for UAB. It should be considered for patients with incomplete emptying and high postvoid residual volumes. Catheterization reduces many of the risks associated with incomplete emptying, including urinary tract infections, upper tract deterioration and overflow incontinence.
2. Behavior Modification
Behavior modification therapy is useful for patients with impaired bladder sensation who may not sense bladder distension.
- Timed voiding and double voiding can help avoid overdistension, assist with incomplete emptying and reduce frequency and/or incontinence
- Voiding diaries can be important for identifying patients who chronically overhydrate and might benefit from a fluid restriction program
- Pelvic floor physiotherapy and biofeedback has shown benefit in children with nonneuropathic UAB but has not been studied in adult women with UAB
- Parasympathomimetics (also called cholinergic drugs, such as bethanechol, carbachol and distigmine) are not recommended for treating UAB. They have had mixed results in randomized controlled trials; there is no definitive evidence of their efficacy in UAB. In addition, they can have significant side effects including blurred vision, bronchospasm and bradycardia
- Alpha-adrenergic antagonists, such as tamsulosin, decrease the pressure against which the bladder needs to empty, which may allow increased emptying. The alpha-blocker urapidil was studied in women with UAB in a randomized trial. The combination of urapidil and a cholinergic drug (bethanechol or distigmine) was more efficacious than either monotherapy with regard to improving voiding parameters and symptoms
Sacral neuromodulation is approved by the U.S. Food and Drug Administration for patients with UAB as a way to improve voluntary voiding. The theory is that sacral neuromodulation increases detrusor contractility while decreasing outflow resistance.
A meta-analysis concluded that the therapy decreases postvoid residual volumes and the number of self-catheterization episodes per day. The results of sacral neuromodulation with an implanted device appear to be durable—in a retrospective study, >80% of patients demonstrated >50% improvement in symptoms after five years.
Surgery has not been studied in women with UAB, although various surgical procedures for DU have met with some success. Surgical options for DU include Botox injections to the urethral sphincter, transurethral incision of the bladder neck and myoplasty.
Although UAB is receiving increased recognition, large gaps in the research base are evident. Future developments will hopefully include validated patient symptom scales that can be used to diagnose UAB and targeted therapies that are based on pathophysiologic mechanisms.
Visit the Department of Urology
Refer a patient to the Department of Urology