**2.2.3 Idiopathic etiologies**

Idiopathic detrusor overactivity is a diagnosis of exclusion of all other known causes. Mechanisms that have been proposed for idiopathic detrusor overactivity include myogenic, urothelial and muscarinic.

### **2.2.3.1 Myogenic**

Mills et al, noted that denervation is consistently found in detrusor biopsies from patients with non-neurogenic detrusor overactivity. (Mills et al, 2000) They hypothesize that partial denervation of the detrusor alters the properties of smooth muscle, which leads to increased excitability and increased coupling between cells. Thus, myogenic changes in the bladder increase contractility locally.

#### **2.2.3.2 Urothelial**

Another mechanism that has garnered interest in idiopathic detrusor overactivity is the roles of the urothelium and suburothelial myofibroblasts in afferent activation. The C-fiber afferents have endings in the suburothelial layer of the bladder wall, and may reach the urothelium. (Koelbl et al, 2009) Upon bladder distention ATP has been shown to be released from the urothelium. (Ferguson et al, 1997) ATP receptors on afferent nerve terminals are stimulated by ATP release to evoke a neural discharge. It has been proposed that there is up-regulation of the afferent activation mechanisms(eg. an increased generation/release of ATP increased sensitivity of afferent nerves to mediators, increased number of afferent nerves) can cause the symptoms of OAB. (Koelbl et al, 2009)

Diagnosis and Treatment of Overactive Bladder 167

Bladder diaries are an excellent tool that can be utilized to assess the frequency of daytime and nighttime voiding, as well as the timing of incontinence episodes and pad usage. Recently, bladder diaries have been developed that reliably assess the rate and severity of urinary urgency and are readily available. (Abrams et al, 2009) Despite some limitations,

A thorough history should inquire about the onset, duration, severity, and bother of lower urinary tract symptoms. In addition, a medical, surgical, gynecological, and obstetrical history should be obtained. Inquire about current medications which affect bladder function, particularly diuretics, alcohol, caffeine, narcotics, and calcium channel blockers.

The physical examination should be focused on the abdominal and genitourinary examinations. The pelvic examination is used to evaluate the strength of the muscles of the pelvic floor and to assess for pelvic organ prolapse, urethral mobility, and stress urinary incontinence. The rectal examination is used to assess for any masses and to evaluate for constipation and anal tone. A simple, focused neurologic examination to evaluate pelvic reflexes, innervation of the lower extremities, and the patient's mental status completes the

Because some patients who present with acute symptoms of frequency and urgency have a urinary tract infection, a urinalysis (UA) is performed. In addition a UA will detect

A post-void residual (PVR) is performed as a rough evaluation of as a measurement of the efficiency of evacuation of the bladder. This can be measured by bladder ultrasonography or post-void catheterization. Although there is no universally accepted definition of an abnormally elevated PVR, a high post-void residual (greater than 100 cc) may be cause for further, more complex testing. In addition, patients with high PVR's are at high risk for

Urodynamic studies can provide additional insight into bladder pathophysiology and can be a key to making the diagnosis of OAB and destrusor overactivity. Urodynamic studies are a series of clinical tests, such as flow studies, filling cystometry, pressure-flow studies and/or urethral function measurements. These can be combined with electromyography (EMG) recording and/or imaging by either X-rays or ultrasound. (Abrams et al, 2009)

urinary retention, especially when anticholinergic medications are prescribed.

bladder diaries do provide a baseline with which to compare treatment efficacy.

**4.2 Bladder diaries** 

**4.3 History** 

**4.4 Physical Examination** 

physical examination.

hematuria or glucosuria.

**4.6 Postvoid residual** 

**4.7 Urodynamic studies** 

**4.5 Urinalysis** 
