Свръхактивен пикочен мехур

Etiology
OAB is primarily a neuromuscular problem in which the detrusor muscle contracts inappropriately during bladder filling (ie, storage phase). These contractions often occur regardless of the amount of urine in the bladder. OAB may result from a number of different causes, both neurogenic and nonneurogenic.

Neurologic injuries that may cause OAB include the following:

Spinal cord injury
Stroke
Neurologic diseases that may cause OAB include the following:

Multiple sclerosis
Dementia
Parkinson disease
Medullary lesions
Diabetic neuropathy
Detrusor overactivity can also occur in the absence of a neurogenic etiology. Contractions can be spontaneous or induced by rapid filling of the bladder, postural changes, or even walking or coughing. Because these causes are nonneurogenic, the pressing need to urinate can be contained for a few minutes after it is first sensed.

Idiopathic OAB is OAB in the absence of any underlying neurologic, metabolic, or other causes of OAB, or conditions that may mimic OAB, such as urinary tract infection, bladder cancer, bladder stones, bladder inflammation, or bladder outlet obstruction.

Certain medications may lead to symptoms of OAB. Diuretics can cause urge incontinence because of increased bladder filling, stimulating the detrusor. Bethanechol can also cause urge incontinence through its stimulation of bladder smooth-muscle contraction.

Heart failure or peripheral venous and vascular disease can also contribute to symptoms of OAB. During the day, such individuals have excess fluid collect in dependent positions (feet and ankles). When they recline to go to sleep, much of this fluid becomes mobilized and increases renal output, thereby increasing urine output. Many of these patients describe increased nocturia that manifests as OAB.

Only in rare cases does it prove impossible to identify a specific cause (idiopathic OAB).

Risk factors
Several risk factors are associated with OAB. White people, persons with insulin-dependent diabetes, and individuals with depression are 3 times as likely to develop OAB. Other risk factors include the following [10] :

Age > 75 years
Arthritis
Use of oral hormone replacement therapy
High body mass index (BMI)
The physiologic changes associated with aging, such as decreased bladder capacity and changes in muscle tone, favor the development of OAB when precipitating factors intervene. [11, 12, 13, 14, 15] In postmenopausal women, many of these changes are related to estrogen deficiency. Estrogen deprivation therapy in younger women with breast cancer has also been associated with increased risk for OAB. [16] Perhaps the most important age-related change in bladder function that leads to incontinence is the increased number of involuntary bladder contractions (detrusor instability).

Any disruption in the integration of musculoskeletal and neurologic responses can lead to loss of control of normal bladder function and to urge incontinence.