Pelvic Prime's Anatomy Academy Series
Overactive Bladder
Understanding Overactive Bladder
Overactive bladder is a condition where a person suddenly and strongly feels the need to urinate, leading to frequent trips to the bathroom and waking up at night to urinate. It can also cause urine leakage when this urge happens, which is called urgency urinary incontinence. This condition usually occurs without any infection or other clear health problems.
Overactive bladder affects a lot of people and can impact their daily life and health. It's more common as people get older. Studies suggest between 2% and 53% of adults might have overactive bladder, with most estimates around 10% to 20%.
What Causes Overactive Bladder?
The sensation of urgency in overactive bladder happens when there are unexpected bladder contractions. These contractions can be triggered by different signals from the bladder and urethra to the brain, which can cause the sudden urge to urinate.
Normally, the bladder gradually fills up and sends signals to the brain about needing to urinate. In overactive bladder, these signals can become more intense and frequent, leading to the urgent feeling to urinate even when the bladder isn't full.
Normal Bladder Filling and Voiding Process
Bladder filling is a smooth process. When the bladder fills with urine from the kidneys, the tension in the bladder wall increases slowly to match the amount of urine coming int. As the bladder stores urine, certain nerve fibers in the bladder wall get activated. These signals travel up the spinal cord to a part of the brain that controls urination.
In response, the brain sends signals back to the bladder to keep the urine stored by tightening the urethra sphincter muscles and the muscles around the bladder and relaxing the bladder muscle itself. These actions help prevent accidental urination.
When it's time to urinate, the brain sends signals to relax the muscles around the urethra and tighten the bladder muscle. This allows urine to flow out.
Causes of Urinary Urgency
Urgency is the sudden, strong need to urinate and can happen with a small amount of urine in the bladder. This happens because of changes in the way the bladder and the nervous system communicate. There are seven main causes that affect the way the bladder and brain communicate.
Bladder Wall Changes: When the bladder's connective tissues stretch, they send signals to the brain that increase the feeling of needing to urinate. This can happen even if the bladder isn't very full.
Nerve and Muscle Interaction: The bladder and its nerves interact in complex ways. For example, cold stress can trigger nerves that make the bladder muscles contract, causing urgency.
Stress and Emotions: Stress and anxiety can make the need to urinate more frequent and urgent. This is because the nervous system responds to stress by affecting bladder signals.
Aging and Health Conditions: Older people and those with conditions like diabetes, neurological diseases, or cognitive impairments may experience urgency due to changes in how their bladder and nervous system function.
Bladder Outlet Obstruction: Blockages that increase pressure in the bladder can lead to frequent and urgent urination. This might be due to nerve or muscle changes in the bladder.
Muscle Changes: Changes in bladder muscle structure can lead to overactivity and urgent urination. This includes increased sensitivity and contractions of bladder muscles.
Neurological Issues: Damage or disease affecting the brain or spinal cord can disrupt normal bladder control, leading to urgency. Conditions like multiple sclerosis or spinal cord injuries can cause these problems.
Bladder Muscle Overactivity and Sensitization
There are two types of sensitization that can lead to bladder muscle (detrusor muscle) overactivity:
1. Central Sensitization:
This happens when the pathways in the central nervous system get tired or overworked and stop working properly.
It often results from long-term stress, chronic fatigue, or fibromyalgia.
This can lead to increased sensitivity in the spinal cord, causing nerve reactions that lead to urgency.
2. Peripheral Sensitization:
During bladder filling, chemicals like acetylcholine can be released, which makes the bladder muscles contract more.
This release can increase the activity of the nervous system, causing the feeling of urgency.
Local inflammation can also make the nerve endings more sensitive, leading to pain and urgency.
Indication for Physical Therapy
Research shows that the symptom of urgency is complex and affects many different types of patients. This makes it hard to determine when physical therapy is needed for urgency and urge urinary incontinence. Physical therapy is usually recommended for patients whose urgency, frequency, nocturia (nighttime urination), and urge urinary incontinence cannot be explained by anatomical issues or diseases.
Physical Therapy Techniques
Physical therapy aims to reduce urgency and control the micturition reflex. These techniques help modulate nerve activity and can be effective in managing symptoms.
Electrostimulation: Uses electrical signals to stimulate nerves and muscles.
Percutaneous Tibial Nerve Stimulation: A type of neuromodulation that targets specific nerves.
Pelvic Floor Muscle Training: Strengthens and relaxes the pelvic floor muscles.
Detrusor Overactivity and β2-Adrenoceptors
β2-adrenoceptors are special parts of our cells, like tiny switches, that help control how muscles work. They are found in different parts of the body, including the bladder. When these switches are turned on by certain signals from the nervous system, they help relax the muscles. This is important because it helps keep the muscles from being too active. In the bladder, this helps control when we need to pee. If these switches don't work well, the bladder muscles can become too active, making it hard to control when we go to the bathroom.
In some people, the β2-adrenoceptors in the bladder may be downregulated. When these receptors are downregulated, they become less responsive or fewer in number. As a result, the bladder muscles can become overactive and contract too much because they aren't getting the right signals from the nervous system to control their activity properly. Similar to the muscles getting too much electric power making the muscle contract too much. Physical therapy focusing on muscle relaxation techniques may improve bladder control.
Non-Relaxation of Pelvic Floor Muscles
Some patients with overactive bladder syndrome experience pelvic floor muscles that do not relax properly. This condition is often linked to constipation and painful intercourse. "Down-training" physical therapy can help by teaching pelvic floor awareness and relaxation techniques. Physical therapy is an attractive first-line treatment for urgency due to its low side effects and compatibility with other treatments.
Bladder Training for Overactive Bladder
Bladder training has been a treatment for overactive bladder symptoms like urgency, frequency, urgency incontinence, and nighttime urination since the late 1960s. It's also recommended for mixed and stress urinary incontinence. Bladder training is best for motivated adults without cognitive or physical impairments. The goal is to restore normal bladder function through education and a voiding schedule that gradually increases the time between bathroom trips.
The exact way bladder training works is unclear. One idea is that it strengthens the brain's control over bladder sensations and the closure of the urethra. Another idea is that people learn to change their behavior to increase their bladder's capacity and avoid leakage.
Bladder training is simple, relatively cheap, and doesn't have unpleasant side effects, making it a good option for older adults, especially those on multiple medications who might have adverse effects from overactive bladder medications. It can be used alone or with other treatments like pelvic floor muscle training. Many professional societies recommend bladder training as a first-line treatment for urinary incontinence in both men and women, including frail older adults.
Bladder training usually includes three main parts:
Education: Learning about the bladder, how to maintain continence, and strategies to suppress urgency.
Scheduled voiding: Following a schedule that gradually extends the time between bathroom trips.
Positive reinforcement: Support from a healthcare professional.
In the past, bladder training often involved 5 to 13 days in the hospital with a strict bathroom schedule. Nowadays, it’s more common to have outpatient programs that last 6 to 12 weeks. Patients start with a voiding schedule based on their current patterns and gradually increase the time between trips.
Education on urgency suppression techniques, like distraction or pelvic floor muscle contractions, is also important. Patients might keep a diary of their voiding habits, and they may get advice on fluid intake, caffeine reduction, and diet changes if needed.
Clinical Recommendations for Physical Therapists
In clinical practice, many patients with overactive bladder are treated with a mix of lifestyle changes, pelvic floor muscle training with or without biofeedback, electrical stimulation, bladder training, or medication. Often, these methods are combined, making it hard to determine which intervention causes which effect. Most systematic reviews on pelvic floor muscle training for urinary incontinence mix studies of stress urinary incontinence, urgency urinary incontinence, and mixed urinary incontinence. This makes it difficult to understand the true effect of each intervention on each condition.
While some theories suggest pelvic floor muscle dysfunction as a common cause of stress urinary incontinence urge incontinence, the mechanisms behind pelvic floor muscle dysfunction in these conditions are not well understood. The causes might be different, such as childbirth-related pelvic floor damage for stress incontinence and caffeine related for urge incontinence in older women.
Ideally, physical therapy should target the underlying condition. Pelvic floor muscle training may have different success rates for stress incontinence an urge incontinence, and combining different patient groups in reviews can obscure the true cure rate for each diagnosis. Moreover, the best pelvic floor muscle training approach might differ for each condition.
Rationale for the Effect of Pelvic Floor Muscle Training
The idea behind using pelvic floor muscle training to treat overactive bladder symptoms is based on observations from electrical stimulation and urodynamic assessments during pelvic floor muscle contractions. During urine storage, bladder distension causes low-level nerve firing, which stimulates sympathetic and pudendal outflow, helping to maintain continence. Sympathetic firing also inhibits bladder muscle contraction. This balance of responses, occurring through spinal reflex pathways, promotes continence.
It has been found that pelvic floor muscle contractions increase urethral pressure and decrease bladder pressure, with a larger effect in healthy participants. It was concluded that pelvic floor muscle contractions could help reduce bladder pressure and encourage pelvic floor muscle contractions to treat overactive bladder. Patients can also manage urgency and bladder contractions by walking, bending forward, crossing their legs, using hip adductor muscles, or consciously contracting their pelvic floor muscles.
Two main hypotheses explain how pelvic floor muscle training might treat urgency incontinence:
intentional pelvic floor muscle contraction during urgency until the urge to void disappears
strength training of PFMs to make lasting changes in muscle structure, stabilizing nerve activity.
However, no studies have shown if these inhibitory mechanisms change after pelvic floor muscle training. More research is needed, and there is no consensus on the best exercise protocol to treat overactive bladder. The theoretical basis for pelvic floor muscle training in treating overactive bladder is still unclear.
Medications for Overactive Bladder
Doctors have found that surgery doesn't help much for people with overactive bladder and urgency urinary incontinence. Finding the right treatment is important because medicines often disappoint, working for only 60-70% of adults and 25-75% of older adults, and they have side effects that make them hard to keep using.
Long-term studies are rare, so we don't know much about how well these medicines work over time. Combination therapy might be better, but it also has side effects that lead to people stopping the treatment.
Electrical Stimulation for Overactive Bladder
Electrical stimulation is another possible treatment for overactive bladder. It might help by making the pelvic floor muscles stronger, which could control the bladder better. Different physical therapy treatments are based on theories about what causes overactive bladder, but experience shows they can help most people with overactive bladder.
The information about electrical stimulation for overactive bladder is hard to understand because it's based on complex biology. Electrical stimulation may help by stimulating the pudendal nerve, which controls the pelvic floor muscles and the external urinary sphincter, leading to better bladder control. Electrical stimulation requires the pelvic floor muscles to be at least partially intact to work. Electrical stimulation should be done carefully to avoid pain by not over-stimulating small nerve fibers. Whether external or internal, electrical stimulation aims to reduce bladder activity by stimulating large nerve fibers.
Electrical Parameters:
Current: Most trials used alternating current
Frequency: Ranged from 5 Hz to 150 Hz.
Pulse Duration: Varied from 0.1 ms to 320 ms.
Duty Cycle: Some trials used a 1:2 or 2:1 duty cycle.
Intensity: Ranged from 5 to 25 mA.
Mode of Delivery: Most used vaginal electrodes or other placements on the body.
Length and Number of Treatments: Ranged from one session to several months of daily sessions. The longest treatment lasted 4 months, while the shortest was a single session.
Is Electrical Stimulation Better Than No Treatment, Control, or Placebo Treatment?
Studies showed that electrical stimulation alone improved bladder control compared to no treatment or placebo. Electrical stimulation alone led to better daily life activities control and significant improvement in bladder control in some studies.
Some studies compared electrical stimulation with pelvic floor muscle training, biofeedback, and medication. Results varied, with some showing electrical stimulation as effective as medication. However, side effects were higher in medication groups. Electrical stimulation combined with other treatments like pelvic floor muscle training or medication also showed mixed results.
References: Bo, K., Berghmans, B., Mørkved, S., & Van Kampen, M. (Eds.). (2023). Evidence-Based Physical Therapy for the Pelvic Floor (3rd ed.). Elsevier.