January 6, 2009 1 Comment
Bladder augmentation is the addition of a segment of bowel to the in situ bladder to increase capacity, improve compliance, or abate uncontrollable detrusor contractility. It is frequently used in the reconstruction of neurogenic bladders that have failed medical therapy or other conservative therapies. Augmentation cystoplasty has replaced cutaneous urinary diversion in this group of patients because of decreased morbidity of the procedure, fewer postoperative complications, the widespread use of clean intermittent catheterization (CIC), and improved postoperative quality of life. Additionally, it has been shown that patients with cutaneous urinary diversions, draining continuously via any segment of bowel, have a worse long-term outcome with regard to infections and upper tract deterioration than patients with a large low-pressure reservoir that uses the urethra as the continence mechanism. In some cases, such as chronic, intractable interstitial cystitis with a small bladder capacity and severe symptoms, a supratrigonal cystectomy may be performed, and the bladder replaced by a bowel segment.
Although we prefer ileum in most cases, many different bowel segments have been used, each with its own specific advantages and disadvantages. However, no bowel segment is clearly superior in all circumstances. The most important factor is detubularization of the bowel to reduce intravesical pressure from peristalsis or mass contractions.
In most cases of neuropathic vesical dysfunction, the simplest low-pressure continent reservoir to construct involves the addition of bowel to augment the in situ bladder, utilizing the patient’s own urethra as the continence mechanism.
Before consideration is given for an augmentation cystoplasty, all medical therapies and conservative treatments directed at improving detrusor compliance and increasing capacity should be exhausted. When these therapies have failed, the basic evaluation includes a cystometrogram, preferably using fluoroscopy, to evaluate bladder compliance, status of the bladder neck (open or closed at rest), and presence of vesicoureteral reflux. The bladder’s functional characteristics such as capacity and compliance can sometimes dictate the type and length of bowel required.
The evaluation of urethral function is problematic, particularly in patients with poor compliance or a defunctionalized bladder, where the urethra may deceptively appear worse than it truly is. The abdominal leak point pressure (ALPP) is a good method of determining urethral resistance to abdominal pressure as an expulsive force.5 If, in addition to the augmentation cystoplasty, one of the goals of the operative procedure is to achieve continence, the abdominal pressure required to cause leakage is essential. If that pressure is very low, 0 to 60 cm H2O, then a sling procedure, an artificial urinary sphincter, or an injectable agent will be required to prevent leakage. If the resistance to abdominal pressure is high, perhaps 140 to 150 cm H2O or more, then no procedure to improve urethral function is usually necessary. In the middle range, 60 to 140 cm H2O, any of the above treatments and perhaps a urethral suspension in women, can be used to treat stress incontinence. It is important to recognize that creation of outlet resistance that completely resists intrareservoir pressure is inherently dangerous to the upper tracts and may contribute to rupture of the augmentation.6 An upright cystogram, which demonstrates that continence is maintained at the bladder neck, can be a useful adjunct to the ALPP. Even if both studies are done and the urethra appears functional, leakage may still occur after augmentation cystoplasty when the bladder is very full and high intra-abdominal pressure is applied.
Another important urethral function is that it must function as a compliant voiding conduit. If the patient is neurologically normal and voiding is anticipated after augmentation cystoplasty (as in selected patients with interstitial cystitis), the urethra should open normally on a voiding urodynamic study. Voiding pressures less than 30 to 40 cm H2O usually indicate that the conduit opens normally with voiding, and CIC may not be required postoperatively. Voiding pressures greater than 40 cm H2O generally indicate poor conduit function, and the patient will often require CIC after the augmentation cystoplasty.
It is now clear that ureteral size (or dilation) has little to do with ureteral function, whereas, if ureteral peristalsis is present, as seen by ultrasound, fluoroscopy, or during a Whitaker perfusion test, the ureters will function adequately when placed into a low-pressure reservoir.
INDICATIONS FOR SURGERY
Bladder augmentation is a useful technique for the following indications:
- Uncontrolled bladder contractility, most commonly for multiple sclerosis, spinal cord injury, and idiopathic urge incontinence.
- Poor bladder compliance for neuropathic conditions after pelvic radiation therapy, intravesical chemotherapy, prolonged catheter drainage, or from untreated obstructive uropathy.
- Prolonged bladder defunctionalization after long-term cutaneous vesicostomy drainage or bilateral cutaneous ureterostomy.
- Patients previously diverted who are candidates for undiversion into a large, low-pressure reservoir.
Patient selection remains an important issue before augmentation cystoplasty. Chronic renal failure (documented by creatinine clearance) is a relative contraindication to an augmentation because both small and large bowel resorb many urinary solutes that may deleteriously alter the metabolic status of the patient. In these patients, the use of stomach has been recommended.
All patients should be able, both mentally and physically, to perform CIC before a bladder augmentation, even if postoperative voiding is anticipated. This is especially important at both age extremes. If any question exists, it is better to place a cutaneous catheterizable stoma or, alternatively, a noncontinent stoma.
No bowel segment is clearly superior to another in all circumstances, and the segment used is usually based on surgeon preference. In some circumstances, restrictions may exist, however. Stomach should probably not be used in patients with peptic ulcer disease, and large bowel should not be used if a history of ulcerative colitis, previous colon cancer, or diverticulitis exists. Similarly, in cases of extensive pelvic radiation, transverse colon or stomach may be preferable to small bowel. Finally, consideration for preservation of the ileocecal valve should be given in patients with myelodysplasia, as significant problems with diarrhea and fecal incontinence have been reported.
In autoaugmentation of the bladder (also called partial detrusor myomectomy), the detrusor muscle over the dome and anterior wall is excised, which allows the bladder epithelium to distend outward, thereby improving storage capacity and detrusor compliance. In our experience, the gains in bladder capacity and compliance in patients with neuropathic voiding dysfunction are small, and we do not recommend its routine use in this group of patients. We continue to use this technique in selected patients with intractable urge incontinence, with favorable results.
For patients in whom a simple, low-pressure cutaneous diversion is preferable, a noncontinent ileovesicostomy (bladder “chimney”) can be performed. Schwartz and colleagues reported excellent long-term results in 23 patients, with few complications.
Nonautologous tissues (Gore-Tex, Dacron, bovine dura, pericardium, etc.) have all been utilized to augment the bladder; however, complications with the anastomosis, infections, or stone formation preclude their routine use.
Preparation of the patient is important, and all patients should undergo preoperative bowel preparation. In the neuropathic patient, chronic constipation is usually a problem, and 2 to 3 days of clear liquids and a full mechanical bowel preparation the day before the procedure will be necessary to insure removal of all solid stool. Nonneurogenic conditions and the use of small bowel for the augmentation may allow a less rigorous prep. If large bowel is used, oral nonabsorbable antibiotics such as neomycin and erythromycin base should be considered. Note that sometimes the desired segment of bowel is found intraoperatively to be unsuitable, and therefore, a full bowel prep is recommended for the majority of cases. A preoperative dose of IV antibiotics is also given with special consideration given to those patients with implanted prosthetic materials such as a ventriculoperitoneal shunt or orthopedic hardware.
Other considerations include preoperative normalization of any metabolic or electrolyte disorders, documentation of sterile urine, and, in selected cases where colon will be used, a preoperative barium enema or colonoscopy.
After preparation of the skin from xiphoid to genitalia, a urethral catheter is placed, a midline (preferably) or Pfannenstiel incision is made, and the retropubic space is dissected until the bladder is free of adhesions. In general, if a procedure to improve continence is necessary, it is performed first. Additionally, if low-pressure vesicoureteral reflux has been documented preoperatively, ureteral reimplantation should be considered. The ureters should be reimplanted into the bladder or into a colonic augmentation, as ureteral reimplantation into the ileum is tenuous and is not as favorable. We do not reimplant functional ureters that reflux with high bladder pressures because augmentation will decrease bladder pressures. A self-retaining retractor is placed, the bladder is filled with saline, and the peritoneum is dissected off the bladder to the level of the trigone (Fig. 26-1). Using electrocautery, a U-shaped incision is made on the bladder starting 3 cm above the ureters, effectively creating an anteriorly based bladder flap (Fig. 26-2). This technique avoids the hourglass configuration that can develop, making the augmentation little more than a poorly draining bladder diverticulum. The peritoneum is opened last to minimize third-space fluid loss and urine contamination of the peritoneal cavity. A 25- to 30-cm segment of ileum at least 15 cm away from the ileocecal valve is selected and marked with sutures. The ileum should easily reach the bladder without tension. The mesentery is cleared from both ends to create a window, and the ileum is divided using a standard stapling device.
The exact amount of ileum required varies among patients, but enough should be used to allow a minimum of 4 hours between catheterizations after the bowel is fully stretched over the ensuing months. Ileal continuity is then achieved using one of the hand-sewn or stapled techniques, and the mesenteric defect is closed. The ileal ends are oversewn with a running 2-0 chromic catgut to exclude the staples (to prevent stone formation), and the antimesenteric surface of the bowel is opened using electrocautery. Towels should be placed under the bowel, and the opened ileum irrigated into a kidney basin until clear. The posterior wall of the ileum is folded back on itself and sutured together using running 2-0 chromic catgut. The required size of the augmentation opening is roughly measured, and the superior, anterior wall is partially closed with running 2-0 chromic catgut to match this opening. A large-bore suprapubic (SP) tube is placed through the bladder wall before placement of the augmentation on the bladder. The SP tube allows reliable postoperative drainage and irrigation of mucus until the suture lines are healed. The ileal segment is then sewn onto the opened bladder using running 2-0 chromic catgut with the initial suture placement. A closed suction drain is placed near the suture line and brought through the skin on the side opposite the SP tube. The patient is closed in the usual manner. If a continence procedure has been performed, it is imperative that a catheter can be easily passed, otherwise the patient will be unable to catheterize postoperatively.
Although this technique is our preferred technique, other methods of performing an augmentation exist. One such method involves splitting the bladder sagittally from just above the bladder neck and ending near the level of the ureters posteriorly to form a clam. A 25- to 30-cm segment of ileum is isolated and divided completely along the antimesenteric border. The posterior wall of the augmentation is closed with running 2-0 chromic catgut and is then either anastomosed to the bladder as a “patch” or folded again and partially closed to form a “cup.” A cup is especially useful if the patient’s own bladder is very small but sometimes requires the use of up to 40 cm of bowel. In both cases, the anastomosis is started on the posterior wall until it is approximately one-third closed, and then the anterior wall is closed. The lateral walls are closed last, and any redundant bowel is closed to itself.
Postoperative care is generally straightforward. Fluid and electrolyte management is important because of large third-space losses and drainage from the nasogastric tube, which remains in place until bowel function returns. The drain is removed after a few days, when drainage tapers off. The bladder is irrigated at least three times per day with 30 to 60 ml of saline to clear mucus. A cystogram is performed at 2 to 3 weeks, and the Foley is removed if no extravasation is noted. The patient begins CIC with the SP tube in place until the patient is proficient at CIC. At 3 to 4 weeks, the SP tube can usually be removed, and the patient continues CIC every 2 to 3 hours during the day and twice at night. Sometimes the augmentation takes several months to stretch, during which time frequent CIC is necessary. This may be distressing to the patient; however, liberal use of anticholinergics can help in many cases. Daily irrigation to clear mucus is essential, especially for the first few months. As capacity increases, the intervals can increase, with most patients able to go 4 to 5 hours between catheterizations during the day and once at night. Patients who are able to void must document consistently small postvoid residuals. Routine electrolytes, creatinine, BUN, and upper tract studies should be performed at regular intervals.
A recent long-term study of 122 patients by Flood and colleagues reported an overall 28% early and 44% late complication rate in this difficult group of patients.3 Most of the complications were minor and involved prolonged ileus, transient urinary extravasation, or stomal problems. Surgical interventions were necessary in only 15% of patients and were mainly stomal revisions.
Small bowel obstructions occur in approximately 3% of patients. This is similar to the rate reported in urinary diversions. Bladder or kidney stones vary from study to study depending on the patient population and surgical techniques used. Stones commonly form secondary to retained mucus or exposed staples as a nidus. Routine bladder irrigation, treatment of infections, and staple exclusion at time of surgery minimize stone formation.
Reservoir perforation is perhaps the most feared complication with reported rates of approximately 6%.Fatalities are uncommon if diagnosed early.
Metabolic problems such as metabolic acidosis or vitamin B12 deficiency that are not medically treatable are uncommon if patients are properly selected and followed with appropriate labs.
Carcinogenesis in all bowel segments has been reported. Although the risk to any individual patient is small, surveillance after 10 years should be considered.
Voiding dysfunction is common even in nonneurogenic patients after augmentation cystoplasty. In a review by Flood and colleagues, 89% and 67% of neurologically intact men and women, respectively, required lifelong CIC. These numbers reinforce the need to counsel patients on the high likelihood for lifelong CIC and preoperative demonstration of proficiency at CIC.
A tabulation of success or failure after augmentation depends on the original reason for performance of the procedure. In patients with neuropathic bladders requiring improved compliance and capacity, an augmentation is almost uniformly successful. An augmentation is less successful in treating the symptoms of interstitial cystitis and, by itself, does not guarantee continence, especially in patients with high rates of intrinsic sphincter deficiency (ISD) such as myelomeningocele and radiation cystitis. A preoperative urethral evaluation is essential in diagnosing ISD in these patients.