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.

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).

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.

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).