bubble_chart Overview

Urinary incontinence is the involuntary leakage of urine due to injury of the bladder sphincter or neurological dysfunction, resulting in the loss of voluntary control over urination.

bubble_chart Etiology

Medical history is an important part of diagnosing urinary incontinence. The causes of urinary incontinence can be divided into the following categories: ①Congenital disorders, such as epispadias. ②Trauma, such as childbirth injuries in women, pelvic fractures, etc. ③Surgery, including prostate surgery and urethral stricture repair in adults, and posterior urethral valve surgery in children. ④Neurogenic bladder caused by various factors.

bubble_chart Pathogenesis

The control of urine in normal males relies on the following two parts of the urethra:

1. Proximal urethral sphincter: Includes the bladder neck and the prostatic urethra above the verumontanum.

2. Distal urethral sphincter: Can be divided into two parts: ① The posterior urethra below the verumontanum. ② The external urethral sphincter.

In both males and females, the bladder neck (the smooth muscle of the urethra controlled by sympathetic nerves) is the primary force preventing urine leakage. In males, if the proximal urethral sphincter is completely dysfunctional (e.g., after prostate surgery) but the distal urethral sphincter remains intact, normal urination control can still be maintained. If the distal urethral sphincter is also impaired, varying degrees of urinary incontinence may occur depending on the severity of the damage. In females, complete dysfunction of the bladder neck can lead to stress urinary incontinence. Complete loss of function of the external urethral sphincter, which is controlled by somatic nerves (pudendal nerve), does not cause incontinence in males if the urethral smooth muscle functions normally, but can result in stress urinary incontinence in females.

3. Detrusor areflexia: In such patients, both detrusor contraction strength and urethral closure pressure (i.e., urethral resistance) are reduced to varying degrees. The detrusor cannot actively expel urine completely, and urination relies on increased abdominal pressure. When residual urine volume is high and urethral resistance is low, stress urinary incontinence may occur; overflow incontinence can also occur during urinary retention.

4. Detrusor hyperreflexia: Detrusor hyperreflexia may sometimes lead to three different types of urinary incontinence: ① Complete upper motor neuron lesions can result in reflex incontinence. ② Incomplete upper motor neuron lesions may cause urgency incontinence in some patients, often accompanied by severe symptoms of frequency and urgency. ③ Some patients may experience uninhibited detrusor contractions triggered by coughing, leading to urine leakage with symptoms resembling stress urinary incontinence. These patients do not have frequency, urgency, or urgency incontinence, and surgical treatments for stress incontinence are ineffective. Criminal punishment examination methods cannot distinguish this from true stress urinary incontinence, but synchronous bladder pressure-uroflowmetry can provide an accurate diagnosis. Bates et al. termed this "cough-urgency incontinence" (Coughurge incontinence).

5. Detrusor-sphincter dyssynergia: Sometimes, two different types of incontinence may occur. One type involves persistent spasm of the external sphincter during detrusor contraction, leading to urinary retention and subsequent overflow incontinence. The other type involves sudden uninhibited relaxation of the external urethral sphincter (with or without detrusor contraction) caused by upper motor neuron lesions, resulting in incontinence. Such patients often have no residual urine.

bubble_chart Clinical Manifestations

The clinical manifestations of urinary incontinence can be divided into five categories: overflow incontinence, non-resistant incontinence, reflex incontinence, urge incontinence, and stress incontinence. Overflow incontinence is caused by severe mechanical (such as benign prostatic hyperplasia) or functional obstruction of the lower urinary tract leading to urinary retention. When the intravesical pressure rises to a certain level and exceeds the urethral resistance, urine continuously drips from the urethra. The bladder in these patients is distended. Non-resistant incontinence occurs when urethral resistance is completely lost, preventing the bladder from storing urine, and the patient loses all urine through the urethra while standing. Reflex incontinence is caused by complete upper motor neuron lesions, with urination relying on spinal reflexes. The patient experiences involuntary intermittent urination (intermittent incontinence) without sensation. Urge incontinence can result from partial upper motor neuron lesions or intense local stimuli such as acute cystitis. Patients exhibit severe symptoms of frequent urination and urgency, with incontinence occurring due to strong, uninhibited detrusor contractions. Stress incontinence is characterized by urine leakage from the urethra when abdominal pressure increases (such as during coughing, sneezing, climbing stairs, or running). The disease causes of this type of incontinence are complex and require thorough examination.

bubble_chart Auxiliary Examination

Urinary incontinence, especially that caused by neurogenic bladder, should undergo the following examinations: ① Measure residual urine volume to distinguish between incontinence caused by high urethral resistance (lower urinary tract obstruction) and low resistance. ② If residual urine is present, perform voiding cystourethrography to observe whether the obstruction is at the bladder neck or the external urethral sphincter. ③ Cystometry to check for uninhibited contractions, bladder sensation, and detrusor areflexia. ④ Standing cystography to observe whether the posterior urethra is filled with contrast. In individuals with normal urethral function, the contrast is blocked at the bladder neck. If the sympathetic nerves controlling urination are impaired, the smooth muscles of the posterior urethra relax, and the proximal 1–2 cm of the posterior urethra may show contrast filling on imaging, as this part lacks striated muscles. ⑤ Urethral pressure profile. ⑥ When necessary, conduct synchronous examinations of bladder pressure, urine flow rate, and electromyography to diagnose stress-urgency incontinence, detrusor-sphincter dyssynergia, and incontinence caused by uninhibited sphincter relaxation. ⑦ Dynamic urethral pressure profile: Use a specially designed double-lumen catheter with two distal openings—one placed in the bladder and the other in the posterior urethra. In individuals with normal urethral function, urethral pressure increases when bladder pressure rises (e.g., during coughing) to prevent urine leakage. In some patients with stress incontinence, urethral pressure does not rise with increased bladder pressure, leading to urine leakage.

bubble_chart Treatment Measures

Treatment based on different mechanisms of disease:

1. A large amount of residual urine can cause stress incontinence or overflow incontinence. The treatment principle for this type of incontinence is to reduce urethral resistance by surgical methods (such as bladder neck or external urethral sphincter incision) to decrease residual urine.

2. Detrusor hyperreflexia or an unstable bladder can cause urge or reflex incontinence, and sometimes even cough-induced urge incontinence. The treatment principle is to suppress the uninhibited contractions of the bladder using medications (e.g., verapamil), sacral nerve block, sacral nerve surgery, or bladder denervation.

3. Insufficient sphincter function—Patients with this condition have residual urine. The treatment principle is to increase urethral resistance through medications (e.g., ephedrine, propranolol) or surgical methods. For patients with resistance-free incontinence, options include implanting an artificial urinary sphincter, urethral lengthening, urethral clamps (for females), or penile clamps.