Introduction:
The urinary tract is composed of components like the kidney, ureter, bladder, and urethra. All these components work together for the production of urine and the elimination of urine from the body. The function of the kidney is the production of urine, and the ureter works for the transportation of urine from the kidney to the urinary bladder. The urinary bladder works as a temporary storage unit for urine. The urinary bladder is a hollow, pear-shaped, and muscular organ of the urinary tract. This organ not only works as a temporary site for the urinary tract but also helps pass urine from the body. Any abnormality of the urinary bladder causes the involuntary passing of urine.
What Is Overactive Urinary Bladder?
The urinary bladder is a pear-shaped hollow organ that is situated in front of the pelvic cavity. The urinary bladder is divided into four parts. These are; the apex, body, fundus, and neck. The apex is the most anterosuperior part that points towards the abdominal wall. The fundus is the posteroinferior part, and the body joins the fundus and the apex. The neck of the bladder is the most constricted part that connects the urethra. Urine enters the urinary bladder through the right and left ureter and moves out through the neck of the urinary bladder. The usual volume of the urinary bladder is 400 to 600 millimeters. The urinary bladder is composed of three layers. The innermost layer is the mucous membrane, and the second layer is the submucosa layer. The third layer is the muscular layer. The muscle fibers are oriented in multiple directions. These smooth muscles that maintain the urinary bladder's structural integrity are smooth muscles known as detrusor (bladder) muscles. The internal urethral sphincter is located at the junction of the urethra and urinary bladder. It is under the control of the autonomic nervous system and provides involuntary control of urinary flow. The external urethral sphincter is a striated skeletal muscle that provides voluntary control over urinary outflow.
Overactive bladder is a chronic disorder that affects both men and women. This is characterized by hyperactivity of the detrusor muscle. The term was first used in 1988.
Pathophysiology:
Detrusor overactivity is the primary reason for overactive bladder. Several risk factors play a crucial role in the development of overactive bladder. In women, lower estrogen levels of postmenstrual women, prolapse of the pelvic floor, and stress urinary incontinence (surgery to prevent accidental leakage of urine) are considered risk factors. In males, factors like obesity, low levels of testosterone, inflammatory disorders or oxidative stress, and anxiety and depression act as risk factors. Other than this, diseases such as gastrointestinal disorders like irritable bowel syndrome, nerve disorders, autoimmune disorders, and obstructive sleep apnea are related to this condition. Habits like smoking and alcoholism also affect the activity of the detrusor muscle. All these factors lead to the following changes:
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According to neurogenic theory, a reduction in the inhibitory neural impulses and an increase in the afferent impulses trigger the voiding activity of the urinary bladder.
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In some cases, the detrusor muscle becomes more sensitive toward the cholinergic stimulation that leads to the spontaneous stimulus.
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Increased muscarinic stimulation and spontaneous urinary bladder contraction during filling are also responsible for bladder overactivity.
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Chronic urinary tract infection, which leads to chronic urinary retention, leads to detrusor under activity.
Symptoms:
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The sudden urge to urinate.
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Increased frequency of urination and low volume of urine. The increased frequency is mainly seen in the daytime. Also, in some cases, the urgency of urination at night time can be observed.
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A sudden increase in intraabdominal pressure may cause leakage of the urine.
What Are the Treatment Options?
The first line of treatment option is bladder training exercises. Exercises such as pelvic floor training exercises or kegel exercises are beneficial. These exercises are responsible for strengthening the pelvic floor muscles and increasing the contractile ability of the muscles. Increased muscle contraction increases the pelvic floor's volume and lifts the levator plate. Stiffness due to the contraction of muscles is responsible for increased intraabdominal pressure.
Oxybutynin, Tolterodine, Fesoterodine, and Propiverine are antimuscarinic drugs. These drugs reduce the spontaneous activity in the resting detrusor muscle. This helps in decreasing the frequency and intensity of the detrusor muscle contraction. The adverse effects of these drugs are dry mouth, blurred vision, and constipation. To over such complications, transdermal patches of Oxybutynin can be applied.
What Are the Novel Therapies?
These are the newer therapies that can improve the condition of such patients.
1. Phosphodiesterase-5 Inhibitors: These drugs are mainly used for the treatment of erectile dysfunctions. These drugs reduce smooth muscle tone by increasing intracellular cyclic guanosine monophosphate. These drugs are sometimes used in cases of both erectile dysfunction and bladder obstructions. Sometimes these drugs are used in combination with Alpha-1-adrenergic receptors inhibitors.
2. Botulinum Neurotoxin: This drug causes the relaxation of the bladder relaxation. Intra-detrusor injection of this toxin reduces the release of calcitonin gene-related peptide (CGRP; a release of vasoactive peptides) that improves n the intervals between bladder contractions. 200 U and 300 U of Botulinum toxin are effective in neurogenic bladder disorder.
3. Beta-3 Adrenergic Agonist: Mirabegron is a drug that belongs to this group. The activation of beta-3 receptors causes the relaxation of detrusor smooth muscle. This causes an increase in the bladder's storage capacity, which help reduce frequency and urgency.
4. Posterior Tibial Nerve Stimulation: In this process, the method of neuromodulation is used for the improvement of urinary symptoms. Percutaneous tibial nerve stimulation (PTNS) is given through needles, and transcutaneous tibial nerve stimulation (TTNS) is given through pads in this procedure. A weekly 30-minute therapy for 12 weeks can be helpful.
5. Sacral Neuromodulation: Sacral nerve control the neural stimulation to the bladder, pelvic floor, and bowel. A neurostimulator is a pacemaker-like device that uses electrical stimulus. These electrical stimuli modulate neural activity and influence the behavior of the pelvic floor, lower urinary tract, and urinary bladder. This implantable device also acts on the pontine micturition center of the brain and modulates the sensation of urination.
Conclusion:
The urinary bladder acts as a storage site for urine. It also helps in the passage of urination. Various conditions like obesity, anxiety, autoimmune disorders, and post-menopausal conditions are associated with altered activity of the detrusor muscle. This altered activity of the detrusor muscle causes an overactive bladder. This causes an increased urge to urinate. Modern therapies include injection of botulinum neurotoxin, phosphodiesterase-5 Inhibitors, and sacral neuromodulation that can be helpful in reducing symptoms of overactive bladder.
