Overactive Bladder Syndrome: Evidence-Based Management in Clinical Practice

Overactive Bladder (OAB)

Overactive Bladder (OAB), also known as overactive bladder syndrome or irritable bladder, is a syndrome characterized by a sudden, uncontrollable urge to urinate, urinary incontinence, increased urinary frequency, and nocturia (nighttime urination). The hallmark symptom of OAB is a sudden, compelling urge to urinate that is difficult for the patient to suppress. The sound or sight of running water and other external stimuli may provoke a sudden and intense urge to urinate. Involuntary contractions of the bladder muscle may prevent patients from reaching the toilet in time.

According to studies conducted in various countries, OAB affects approximately 17% of women and 16% of men. No specific epidemiological studies have been conducted on the prevalence of OAB in Lithuania, but it is believed that the prevalence is similar to that reported in other countries. Clinically, OAB is characterized by:

• a sudden onset of frequent and imperative urges to urinate;
• in some cases, the urge to urinate becomes so strong that the patient is unable to control it, resulting in urinary incontinence.

Symptoms of OAB are more common in older women who are overweight. A typical situation described by patients is returning home with groceries, inserting the key into the front door, and suddenly experiencing such a strong urge to urinate that they can no longer hold it. According to Dr. S. Auškalnis, in patients with OAB, a sudden imperative urge to urinate may be accompanied by episodes of urinary incontinence. According to the current definition, patients with OAB urinate more than eight times during the day and approximately twice at night. Kaunas-based urologist Dr. Stasys Auškalnis states that OAB is closely related to urinary incontinence from a pathophysiological perspective. Accordingly, two forms of OAB are distinguished: 1) "dry" OAB (without urinary incontinence) and 2) "wet" OAB (with urinary incontinence).

Most patients report the bothersome symptoms of lower urinary tract symptoms (LUTS) to their physician, usually first to their family doctor. However, some patients are reluctant to discuss these symptoms, so physicians should actively inquire about LUTS whenever they are suspected. For example, this may be appropriate if the physician notices an unpleasant urine odor, particularly when urinary incontinence is also present.

According to Dr. S. Auškalnis, the problem is that many patients with LUTS, especially older women, do not regard this urinary disorder as a disease, believing it to be a "normal part of aging," and therefore do not seek medical attention. In reality, LUTS is a significant medical condition. Urinary incontinence may lead to irritation of the skin around the external genitalia, eczema, hygiene problems, anxiety, and depression. In some cases, patients rushing to the toilet may fall and sustain hip fractures. Embarrassed by their urinary symptoms and unpleasant odor, patients often become socially withdrawn, avoid public places such as theatres, and refrain from taking longer bus trips.

Even the simplest trip from home to the store requires careful planning. Patients often use the bathroom before leaving home, mentally map out their route, and plan their journey according to the availability of public toilets. Overactive bladder syndrome is diagnosed based on the patient's symptoms and objective clinical findings. According to Dr. S. Auškalnis, OAB may have many different causes. Idiopathic OAB is diagnosed when no specific cause of the urinary disorder can be identified, such as infection, inflammation, or structural abnormalities of the bladder.

Symptoms of OAB may be caused by:

• neurological disorders;
• medications (diuretics, antihypertensive drugs, etc.);
• bladder diseases (cystitis, bladder cancer, etc.);
• comorbid conditions (diabetes mellitus, hyperthyroidism, etc.);
• prostate disorders (prostatitis, benign prostatic hyperplasia);
• physiological conditions (pregnancy, etc.).

A detailed medical history, including underlying medical conditions, current medications, smoking status, and a history of pelvic radiotherapy, helps determine the cause of OAB. Valuable diagnostic information is obtained from routine urinalysis (to detect urinary tract infections or hematuria), ultrasound examination (to assess post-void residual urine volume, bladder morphology, bladder wall abnormalities, tumors, stones, prostate size and structure, and other morphological changes), and a patient-completed voiding diary documenting urinary frequency, circumstances of voiding, urgency, the severity of urgency, and episodes of urinary incontinence.

In certain cases, additional diagnostic procedures, such as cystoscopy, urodynamic studies, or MRI/CT, may be required. According to Dr. S. Auškalnis, idiopathic OAB is diagnosed by exclusion, meaning that other possible causes of voiding dysfunction, particularly organic causes, must first be ruled out.

OAB can be diagnosed if:

• the patient urinates more than eight times during the day;
• urinary urgency is present;
• episodes of urinary incontinence may or may not be present;
• there are no other factors that could explain increased urinary frequency (such as excessive fluid intake or the use of diuretics);
• if more than 3 liters of urine are produced per day, the condition is considered polyuria, and its underlying cause should be investigated.

It has been observed that patients with OAB tend to urinate approximately the same number of times during the day and at night. Therefore, one of the effective treatment approaches is behavioral therapy, which includes gradually extending the interval between voids and consciously suppressing the urge to urinate.

Treatment

According to Dr. S. Auškalnis, the treatment of OAB consists of first-line and second-line therapies.

First-line treatment includes behavioral therapy, bladder training, establishing regular voiding habits by gradually extending the interval between voids, pelvic floor muscle training (Kegel exercises), fluid intake management (avoiding caffeinated beverages, beer, and carbonated drinks), weight reduction in overweight patients, and maintaining regular bowel function. If these measures are ineffective, pharmacological treatment is initiated. Antimuscarinic agents are considered the most effective first-line medications.

Second-line treatment is recommended when first-line therapy (behavioral therapy combined with medication) is ineffective or provides insufficient symptom relief. Treatment options include intradetrusor botulinum toxin injections and neuromodulation (sacral nerve stimulation), which may occasionally also be used as primary therapy.

In patients with severe voiding dysfunction (for example, neurogenic OAB following spinal cord injury or congenital spinal defects), electrodes can be implanted through the sacral foramina to stimulate the sacral nerves. Botulinum toxin may also be injected into the bladder wall during cystoscopy. If necessary, surgical treatment may be considered, such as bladder augmentation using a segment of the intestine. In very severe cases, when all other treatment options have failed, cystectomy may be required.

Drug therapy

For many patients with OAB, pharmacological treatment is effective. It offers several advantages: it is convenient, non-invasive, and well accepted by most patients.

Antimuscarinic agents are the first-line pharmacological treatment for OAB and are effective in many patients. However, their use is associated with dose-dependent adverse effects. The higher the dose, the more frequent and severe the adverse effects become. The severity of adverse effects also depends on the route of administration. One of the safest and best-tolerated formulations is the transdermal antimuscarinic patch, although it is not available in Lithuania.

There are relatively few direct comparative studies of antimuscarinic agents used to treat OAB. Available evidence indicates that these medications have similar efficacy. Current drug development is focused primarily on improving safety and tolerability. Solifenacin is one of the successful outcomes of these efforts, demonstrating a more favorable safety and tolerability profile.

Antimuscarinic agents reduce bladder overactivity by blocking muscarinic acetylcholine receptors within the parasympathetic nervous system. Five muscarinic receptor subtypes have been identified, distributed throughout various organs and tissues, including the iris, bronchi, intestines, stomach, and heart. The less selective an antimuscarinic agent is, the more receptor subtypes it blocks, increasing the likelihood of adverse effects in multiple organ systems.

The most common adverse effects of antimuscarinic therapy include:

• dry mouth;
• constipation;
• impaired visual accommodation;
• tachycardia.

Antimuscarinic agents are contraindicated in patients with angle-closure glaucoma, uncontrolled open-angle glaucoma, persistent constipation, or a high post-void residual urine volume.

Antimuscarinic agents provide symptomatic treatment. They reduce symptoms of voiding dysfunction and improve quality of life but do not eliminate or cure the underlying cause of OAB. Consequently, symptoms usually recur after treatment is discontinued.

Historically, oxybutynin was the first antimuscarinic agent used to treat OAB. However, it has the poorest tolerability profile and is associated with the highest incidence of adverse effects.

Tolterodine is more selective than oxybutynin and is therefore generally better tolerated. Both oxybutynin and tolterodine are available as immediate-release and extended-release formulations. Extended-release formulations are more convenient and are generally associated with better tolerability. Both medications are reimbursed in Lithuania for the treatment of urinary incontinence and OAB.

According to Dr. S. Auškalnis, solifenacin, a safe and selective antimuscarinic agent, is available in Lithuania but is not reimbursed, making it accessible only to patients who can purchase it themselves.

A meta-analysis of clinical trials found that solifenacin has a favorable tolerability profile, which is associated with improved patient quality of life.

The STAR study directly compared the efficacy and safety of solifenacin and tolterodine in the treatment of OAB. Solifenacin was significantly more effective than tolterodine in reducing the key symptoms of OAB, including urinary urgency, the severity and frequency of urge urinary incontinence episodes, and was also better tolerated, with fewer adverse effects.

According to another study published in 2012, patients with OAB preferred solifenacin over other antimuscarinic agents because they tolerated it better, were more likely to continue treatment, and discontinued therapy less frequently due to adverse effects.

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