European Urology

1. Historical aspects of continent urinary diversion to the skin

An exhaustive description of one century's work in regard to urinary diversion is beyond the scope of this article. An excellent overview and critical analysis has been compiled by Studer and coworkers [1]. The interested reader is referred to this article. In brief:

2. Why is this a landmark article?

There can be no doubt that the authors have drawn the proper conclusions from a century's work on urinary diversion and picked the right moment to introduce this concept of the Mainz pouch into the modern urologist's armamentarium, when that was technically feasible, at least in departments with a major interest in urinary diversion.

From the very beginning, the Achilles heel of continent cutaneous diversion has been the outlet valve. Again, this is reported honestly by the authors: for sphincteric control, an alloplastic stomal prosthesis for simple mechanical closure was implanted or an isoperistaltic ileoileal invagination was fashioned.

A recent SIU/ICUD/World Health Organization consensus conference on bladder cancer included the evaluation of the current status of urinary diversion [2]. The Achilles heel of the Kock ileal reservoir remained the intussuscepted nipple valve. Most complications associated with the Kock ileal reservoir involve either the antirefluxing (afferent limb) nipple or the continent catheterisation (efferent limb) nipple. Despite several surgical modifications to improve on the construction of the intussuscepted nipple valve, there remained complications and a certain reoperation rate.

Several alternative techniques may be applied to create a dependable, continent catheterisable efferent limb including: (1) appendiceal techniques, (2) tapered or imbricated terminal ileum and ileocecal valve, and (3) a flap-valve technique such as the serous-lined extramural tunnel or efferent T mechanism.

Although these techniques may provide a catheterisable continence mechanism, each has its own limitations. The ideal outlet should be constructed from a readily available and surgically versatile intestinal segment without the need for synthetic materials. It should provide reliable continence and allow for easy catheterisation in the long-term. It is important to note that when revision surgery is performed for the continence mechanism, the existing reservoir portion of the urinary diversion should be maintained (and, if necessary, augmented) with the new catheterisable efferent limb providing the continent mechanism.

The appendix may provide for an effective continence mechanism as was first described by Mitrofanoff [3]. The in situ appendix can be tunnelled into a caecal tenia similarly to a ureterocolonic anastomosis (with preservation of the mesentery). The appendiceal continence mechanism has been criticised for three reasons. First, the appendix may be unavailable because of prior appendectomy. Second, the appendiceal stump may be too short to reach the anterior abdominal wall. Lastly, the calibre of the appendix may be small and may make reservoir urine and mucus more difficult to eliminate. However, if an appropriate appendix is available, it can provide an effective continence mechanism. A slight modification of the Mitrofanoff principle was described by Monti in which a 2- to 3-cm segment of ileum is used and reconfigured into a tube; this tube can then be tunnelled into the colon to provide a continence mechanism [4].

The second major type of continence mechanism that can be used for an intussuscept nipple failure is the tapered or imbricated terminal ileum and ileocaecal valve. The principle evolved from the Gilchrist procedure described in 1950 (see the original article). In this situation, imbrication and plication of the ileocaecal valve region along with tapering of the more proximal ileum can provide an acceptable continence mechanism. This technique can be easily performed. However, criticisms of this continent cutaneous mechanism include the loss of the ileocaecal valve and potential for bowel dysfunction. In addition, this outlet relies mostly on passive tubular resistance (extraluminal valve) and will leak at higher reservoir pressures.

The third general type of procedure for developing a continence mechanism incorporates a flap-valve technique. The principle of embedding a tubular structure with a serous-lined extramural tunnel was first developed by Abol-Enein and Ghoneim [5]. This is a versatile technique that was used initially and successfully for reflux prevention in conjunction with an orthotopic ileal bladder. Because the technique of embedding a tubular structure within a serous-lined extramural tunnel provides unidirectional flow of urine, the feasibility of constructing a continent cutaneous outlet was explored and confirmed experimentally in animals first.

Continence is provided by a passive mechanism derived from tubular resistance of the anchored and tapered segment and, most importantly, a dynamic mechanism that results from embedding the outlet with the wall of the reservoir—a flap-valve technique. This combination prevents leakage even at high pressures within the reservoir (intraluminal valve). A modification of the serous-lined extramural tunnel was subsequently developed and named the T mechanism. This surgical technique incorporates an extramural serous-lined flap-valve technique. This technique was first developed to eliminate the inherent problems with the intussuscept Kock nipple valve. This T mechanism was initially applied as an antireflux technique in the T pouch ileal neo-bladder [6] and subsequently applied to a continent cutaneous ileal reservoir, creating an afferent antireflux, and continent efferent catheterisable mechanism called the double-T pouch.

As previously mentioned, most reconstructive surgeons have abandoned the intussuscept nipple valve largely due to the technical difficulties of pouch construction and the association significant complication rates. Alternative and effective techniques for the creation of a continent cutaneous catheterisable mechanism have been developed. This evolution in urinary diversion must not be viewed as a condemnation of the brilliant and pioneering work. Rather, these are the natural improvements and refinement of reconstructive surgical techniques that occur over time.

3. Current practice

The members of the consensus panel [2] perform continent cutaneous diversions in only 7% of their patients (orthotopic 47%, conduit 33%, anal 10%, and 3% others). Nevertheless, important indications for continent cutaneous diversion remain:

• (1)Urethral removal is deemed necessary because of a high risk of recurrence.

• (2)Patients prefer continent diversion over orthotopic diversion because of the risk of urinary leakage with the latter.

• (3)In patients without cancer, particularly in the paediatric age group, when the closure mechanism and intact urethra are lacking, the procedure can be used.

This is in neurogenic patients (myelomeningocele) with incontinence (ecstrophy complex), loss of the urethra, and combined bladder/sphincteric dysfunction (actinic, interstitial cystitis).