The Mitrofanoff and Malone Antegrade Continence Enema Procedures in Pediatric Urinary Tract Reconstruction



The Mitrofanoff and Malone Antegrade Continence Enema Procedures in Pediatric Urinary Tract Reconstruction


MARK P. CAIN



MITROFANOFF PROCEDURE

The Mitrofanoff principle has now been used for over 30 years but still stands as one of the major advancements to continent urinary reconstruction for children and adults. Earlier innovations—including clean intermittent catheterization (CIC), bladder augmentation, and a variety of bladder neck tightening procedures—created the foundation that made continent bladder reconstruction possible. The technically difficult problem was creating a bladder outlet that was tight enough to ensure continence but wide enough to allow reliable catheterization over a lifetime. In addition, many of these patients have physical disabilities that prevent easy access to the urethra, making independent urethral catheterization challenging. The concept of a continent catheterizable abdominal channel was introduced by Paul Mitrofanoff in 1980 (1) and has since been widely adopted as an integral part of urinary tract reconstruction for continence in most pediatric centers worldwide. This principle involves creation of a flap-valve continence mechanism for a conduit that is tunneled into a low-pressure urinary reservoir that can then be catheterized and emptied via an abdominal stoma (Fig. 108.1).

There are multiple surgical options for creating the Mitrofanoff channel. Appendicovesicostomy has by tradition been used because of availability, the reliable blood supply, adequate lumen for catheterization, and supple muscular wall. Longterm follow-up has shown that appendicovesicostomy provides a durable channel with minimal late complications (2,3). In the absence of a suitable appendix, or in conditions where the appendix is used for an alternate procedure (such as for a Malone antegrade continence enema [MACE channel]), there are several other options that have been described. The most reliable alternatives have been the Monti-Yang ileovesicostomy, ureterovesicostomy, and continent bladder tube.



Indications for Surgery

In the past, the primary indication for bladder reconstruction was for upper urinary tract preservation. In the era of aggressive use of anticholinergics and intermittent catheterization in young patients, the more common indication for a
Mitrofanoff channel is for urinary continence and convenient, independent bladder management for the patient. All patients should undergo a trial of CIC to demonstrate that they are reliable and able to comply with a daily routine prior to bladder reconstruction.






FIGURE 108.1 Umbilical Mitrofanoff stoma allowing catheterization in the sitting or standing position.


Alternative Therapy

The most common alternative to continent bladder reconstruction with a Mitrofanoff stoma is anticholinergic therapy with clean intermittent urethral catheterization. With careful attention to catheterization schedules and fluid intake, social dryness can be achieved in many patients with neuropathic bladder and other underlying bladder pathology without the need for surgical intervention.

Less frequently used alternatives are long-term incontinent cutaneous vesicostomy, incontinent ileovesicostomy channel, and conduit urinary diversion. Although these are considered suboptimal in the era of continent urinary reconstruction, there will be a subset of patients who are unable to care for themselves because of physical, mental, or psychosocial problems, and the incontinent diversion provides a safer long-term option for these patients.

In the rare patient with a completely nonusable bladder, a continent urinary reservoir with a continent catheterizable channel is another alternative.


Surgical Technique

Many centers today have adopted outpatient oral mechanical bowel preparation with admission to the hospital the day of surgery. A urine culture should be obtained preoperatively and urinary tract infection treated. Perioperative intravenous antibiotics should be given for 24 hours. Potential sites for stomal location should be determined preoperatively, with the patient in the sitting and supine position.

Surgical exposure is usually obtained through a small lower midline transabdominal incision that, if needed, may be carried around the umbilicus to leave enough fascia to close the abdomen without compromising an umbilical stoma. A lower transverse Pfannenstiel incision will also allow adequate exposure for both bladder augmentation and the Mitrofanoff stoma in thin patients. Laparoscopy and robotic-assisted laparoscopic surgery has been used in some centers to either to assist in mobilization of the appendix and colon (allowing a smaller abdominal incision to complete the reconstruction without compromising exposure), or to complete the entire procedure, avoiding the larger abdominal incision. The robotic approach has the clear advantage over a pure laparoscopic approach of technically easier intracorporal sewing.


Appendicovesicostomy

The right colon is mobilized beyond the hepatic flexure to allow maximal freedom of the appendiceal mesentery. If the appendix is retrocecal in location, it is mobilized carefully from the cecal attachments with extra caution to avoid injuring the appendiceal artery, which is a branch of the ileocolic artery (Fig. 108.2). In some cases, there is significant peritoneal inflammation due to the presence of a ventriculoperitoneal shunt, and the peritoneal incision must be carried medial to the ileocecal valve to adequately mobilize the appendix. When the length of appendix is inadequate, it can be extended by incorporating a segment of distal cecum as described by Cromie et al. (4). Prior to detaching the appendix, the bladder is mobilized to ensure that the bladder and appendix can easily reach the chosen site for the abdominal stoma without tension. At our center, we now preferentially implant the Mitrofanoff channel in the anterior bladder wall, usually in an extravesical fashion, especially when performing the procedure without simultaneous bladder augmentation. This avoids a large cystotomy, decreasing bladder irritability postoperatively, and also allows improved fixation of the entire channel/bladder to the posterior abdominal wall. In cases where the bladder needs to be opened, the cystotomy is made to the left of the midline for a right lower quadrant appendicovesicostomy or in a wide inverted U-shaped anterior bladder incision for an umbilical stoma. The appendix is detached from the cecum either sharply or with a stapling device, and the cecum is closed with absorbable and permanent sutures. The mesentery to the appendiceal artery can be freed from the cecal mesentery to allow complete mobilization of the appendix if needed (Fig. 108.3). The terminal end of the appendix is then opened, and the channel is irrigated with antibiotic solution. A 12Fr to 14Fr catheter is passed to ensure that the appendix has an adequate lumen. If necessary, the appendix can be gently dilated with serial sounds. If bladder augmentation is to be performed, the segment of bowel is isolated, harvested, and reconfigured appropriately. If an additional segment of intestine is required for the Mitrofanoff (e.g., Monti-Yang) channel, it can be harvested simultaneously. The site of the bladder hiatus is then selected, again ensuring that it can easily reach the posterior abdominal wall fascia without tension. The site of the hiatus is opened wide enough to allow the appendix to pass without any tension, and a vessel loop is passed through the hiatus for traction. A submucosal bladder tunnel is then created using sharp dissection. Placing several traction
sutures on the bladder to flatten out the posterior bladder wall facilitates this dissection. The orientation of the tunnel should be directed away from the bladder outlet and trigone to prevent painful catheterization postoperatively. The tunnel length should be at least 2.5 cm in length. It is occasionally helpful to inject 1:200,000 epinephrine along the path of the submucosal tunnel to facilitate the dissection and minimize bleeding. The terminal end of the appendix is then passed through the bladder hiatus and submucosal tunnel. The appendix is spatulated and secured distally with two 4-0 absorbable sutures incorporating full-thickness bites of the appendix and detrusor muscle and mucosa. The remainder of the anastomosis is completed using 4-0 or 5-0 absorbable sutures, securing the bladder mucosa to the appendix. The appendix is also secured at the level of the bladder hiatus using several 4-0 absorbable sutures. The channel is catheterized with a 12Fr or 14Fr catheter to ensure that it passes easily across the hiatus and submucosal tunnel. With an extravesical technique, the detrusor muscle is incised the entire length of the proposed tunnel (3 to 4 cm) using fine needle point cautery, and lateral detrusor flaps are raised using sharp dissection. A small incision is made in the mucosa at the distal end of the tunnel, and the appendix is secured with two 4-0 sutures to the mucosa and bladder muscle. The remainder of the anastomosis is carried out in a mucosa to mucosa fashion with either 4-0 or 5-0 suture. It is helpful to place a catheter across the anastomosis during the mucosal anastomosis. The detrusor flaps are then secured over the appendix with 3-0 interrupted absorbable sutures, with occasional bites that include both detrusor and serosa of the appendix. A right-angle clamp is placed periodically within the tunnel to ensure that the closure is not too tight. The appendix is secured at two sites at the detrusor hiatus. The stomal site is then selected, again taking care to ensure that the bladder hiatus can reach the posterior fascia without tension. A U-shaped (umbilical) or V-shaped skin incision is made at the stomal site, and the flap is freed sharply to the level of the fascia. A cruciate incision is made in the fascia and widened to allow passage of an index finger. The appendix is then brought through the fascial opening and the appendiceal/bladder hiatus is secured to the posterior fascial wall using 3-0 nonabsorbable sutures, taking care not to angulate or compress the appendiceal mesentery (Fig. 108.4). This maneuver ensures a short, straight extravesical appendix channel, which will minimize the potential for traumatic catheterization and creation of a false passage. With an extravesical implant technique on the anterior bladder wall, the detrusor closure sutures can also be used to fix the bladder to the posterior abdominal wall, further securing the closure and continence mechanism. The stomal end of the appendix is then spatulated on the antimesenteric side, and if there is redundant appendix, it is amputated. The stomal anastomosis is secured using interrupted 4-0 absorbable sutures (Fig. 108.5). The stoma is then catheterized multiple times with the bladder both distended and empty to ensure that there is no angulation in the channel. A 12Fr catheter is left indwelling for 3 to 4 weeks before initiating intermittent catheterization.






FIGURE 108.2 Vascular anatomy of appendicular artery.






FIGURE 108.3 The mesentery to the appendix can be mobilized carefully, taking care not to injure the appendicular artery.






FIGURE 108.4 The bladder is secured to the posterior abdominal fascia to avoid redundancy in the extravesical channel, which can be a source of late catheterization problems.

When both Mitrofanoff and MACE channels are indicated, and the appendix is of adequate length to create both channels, it can be split, with the majority of the mesoappendix left intact with the Mitrofanoff segment, basing the blood supply to the appendiceal stump off the cecal artery. In some cases, the appendix is too short to use for both channels, but in this circumstance, the appendix can still be used for both channels, utilizing one of the described stapling techniques to extend the proximal portion of the appendix into the cecum for the MACE channel (5,6).


Monti-Yang Ileovesicostomy

The concept of retubularized ileum as a replacement for the appendicovesicostomy was introduced in 1997 (7,8), and it has quickly become the ideal alternate to appendix as a choice for the Mitrofanoff channel. Several large series with intermediate follow-up have confirmed the equivalent outcomes for the Monti-Yang channel and appendicovesicostomy (9). The growing indications for and use of the MACE channel have led to preservation of the appendix for the appendicocecostomy stoma and the need for alternatives for a bladder channel. Because some of the children will also undergo bladder augmentation at the time of reconstruction, the Monti-Yang channel can be easily constructed from a segment of the bowel harvested for augmentation.







FIGURE 108.5 The skin stoma is completed by securing the wide-based V flap of skin into the spatulated channel.

A 2.5- to 3-cm segment of intestine is harvested with a wellvascularized segment of mesentery (Fig. 108.6). If ileal augmentation is planned, the Monti-Yang segment can be easily harvested from the distal end of the segment with a shared mesentery. The ileal segment is opened on the antimesenteric side (Fig. 108.7). It can be opened slightly off the midline to provide a longer segment for implanting into the bladder. The opened segment is then retubularized transversely in two layers over a 14Fr catheter. The bowel mucosa is approximated with running 5-0 or 6-0 absorbable sutures and the muscular layer is closed with running or interrupted 4-0 absorbable sutures (Fig. 108.8A and B). The stomal end is not closed initially, providing wide spatulation of the antimesenteric side of the tube for later stomal anastomosis. The technique of implanting the tube into the bladder and creating a stoma is identical to that for appendicovesicostomy (Fig. 108.9). The Monti-Yang tube can be created out of any segment of intestine with good results. If there is inadequate bladder volume for creation of a submucosal tunnel, the tube can be implanted into a segment of bowel using an extravesical technique. Care must be taken to adequately secure the channel in the serosal tunnel. We have found that it is helpful to secure the entire tunnel length to the posterior fascial wall to prevent breakdown of the thin intestinal muscular backing during repetitive bladder filling due to effacement/breakdown of the serosal tunnel, which may be a potential cause for late incontinence. A 12Fr catheter is left across the channel for 3 to 4 weeks before initiating intermittent catheterization. The Monti channel can also be used for the MACE channel, with two channels created side by side (Fig. 108.10).

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Apr 24, 2020 | Posted by in UROLOGY | Comments Off on The Mitrofanoff and Malone Antegrade Continence Enema Procedures in Pediatric Urinary Tract Reconstruction
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