Typically, patients who have failed conservative therapies such as behavioral modification and anticholinergic or beta agonist therapy or patients who have contraindications to oral anticholinergic therapies are good candidates for injection therapy. Patients should be formally evaluated prior to undergoing an injection of onabotulinum toxin A. Patients presenting with refractory overactive bladder with symptoms of urinary urgency, frequency, with or without urge urinary incontinence should always be attempted on conservative therapy prior to considering procedural therapy for their condition. A formal history to ascertain that patients have failed conservative therapy such as behavioral modification and adequate oral therapy, including dietary history, should be ascertained when evaluating patients for onabotulinum toxin A injection. A 24–48 h voiding diary can often provide insight to voiding symptoms, and daily intake of caffeine and other fluids should be recorded. A basic urologic evaluation consisting of a detailed and proper pelvic exam, residual volume measurement, and urinalysis should be performed. Patients presenting with bacteriuria should be treated appropriately prior to considering injection. Pelvic floor muscle rehabilitation or biofeedback should be attempted as first-line therapy for voiding symptoms. Typically, patients should be tried on oral anticholinergics or beta-agonist therapy prior to being scheduled for onabotulinum toxin A injection.

Once patients have been selected to undergo detrusor injection of onabotulinum toxin A, they must be counseled specifically about the risks of injection, which are discussed elsewhere in this chapter. Because the risk of urinary retention exists, patients should consider learning intermittent catheterization prior to injection, should they experience difficulty when the toxin exerts its effect on the detrusor. It is recommended that patients are started on a flouroquinolone antibiotic or trimethoprim-sulfamethoxazole 1–3 days prior to the procedure. Patients should avoid concurrent aminoglycoside administration, as the effects of onabotulinum toxin A have been reported to be potentiated with concomitant aminoglycoside administration in prior studies [18]. Patients should discontinue antiplatelet agents or other anticoagulants prior to injection, if possible.

Intradetrusor injection of onabotulinum toxin A is performed through a cystoscope, in either the office or ambulatory setting. Both rigid and flexible cystoscopes can be used, and there are a variety of needles which are available for injection. There are also rigid cystoscopes designed specifically for needle injection which are small and quite tolerable to the patient with only local anesthesia. Typically, needle gauges range from 21 to 25 gauge. When using needles through a flexible cystoscope, one must be careful not to damage the scope by threading the exposed needle tip through the scope. Therefore, a variety of sheaths and retractable needle tips are available for use during flexible cystoscopy (Fig. 17.5a–d).

Anesthetic choice is surgeon-dependent, and patients should be offered no anesthesia, local anesthesia, intravenous sedation, or general anesthesia. Special considerations may be made in the patient presenting with NDO and a history of autonomic dysreflexia, as patients may require preoperative blockade to prevent unopposed sympathetic efferent discharge [19]. In the author’s experience, most healthy patients with idiopathic OAB tolerate injection in the office setting with simple local anesthetic. Such local anesthetic is in the form of 30–50 mL of 1 % lidocaine, which is instilled via catheter into the bladder. The solution is left for approximately 20 min in order to allow the anesthetic to exert its maximal effect. On the contrary, patients with multiple sclerosis, spinal cord injury with limited mobility may be better served under general anesthesia in order to allow for better positioning during the procedure. The patient is positioned in the lithotomy position, and genitalia should be prepped with sterile solution. The patient is draped, and anesthetic is administered if necessary.

Proper mixing onabotulinum toxin A is of utmost importance, as improper handling prior to the procedure may render the toxin ineffective. Onabotulinum toxin is stored in single-use 100 or 200 unit vials and is commercially available (BOTOX, Allergan Inc., Irvine, CA, USA). The vials themselves contain freeze-dried toxin which is in crystallized form, and is often not visible to the human eye. Botox is reconstituted by instilling 0.9 % normal saline into the vacuum-sealed vials. Total saline reconstituted depends on the total units being administered, in addition to anatomical and clinical considerations. One must remember not to shake the vial, as this can disrupt the delicate disulfide bonds within the toxin, rendering it ineffective. Therefore, careful rotation and mixing of the vial is all that is needed for proper reconstitution.

Cystoscopy is briefly performed to map patient anatomy, visualize the trigone and ureteral orifices, and to rule out any papillary mass or lesion. The bladder should be filled with at least 100 mL of sterile water or saline. The reconstituted drug is then injected at a depth of 2 mm, under direct vision at 20–30 equally spaced sites throughout the detrusor, sparing the trigone (Fig. 17.6). The trigone is extremely sensitive especially in patients with only local anesthesia. Furthermore, there exists the theoretical risk of new-onset vesicoureteral reflux if the trigone is injected. Sites should be spaced approximately 1 cm apart. A superficial bleb occurs if the injection is done superficially in the submucosa, whereas no visual change will occur if the drug is injected too deep. A proper injection should result in a subtle visual change and rise of the mucosa under the injection site. The author’s technique is to proceed from a left to right (or right to left) manner, beginning each column of injection sites at the bottom, to avoid any minor bleeding from a previous injection site seeping downward and preventing good visualization of the next injection site. For the final injection, 0.5–1 mL of sterile saline is injected in order to inject the remaining toxin, which remains within the needle sheath.

In patients not already on intermittent catheterization, prior to being discharged after the injection procedure, patients should be able to void spontaneously. It is recommended that patients receive 1–3 days of antibiotics posttreatment in order to minimize the chance of urinary tract infection [Allergan PI]. Patients should be counseled that urinary tract infection is common, and they may have dysuria, or hematuria, as with any cystoscopic procedure.