The urinary tract consists of the kidneys, ureters - the tubes allowing urine to flow from the kidneys and into the bladder, a bladder, and a urethra - urinary outlet. Kidneys filter wastes, water and salts from the flood resulting in urine production. The bladder stores the urine until it is voluntarily emptied through the urethra and out of the body.
Urinary diversion, first described in 1852, is a surgical technique that diverts urine away from the bladder. The reasons for bypassing the bladder include: bladder cancer, disease, trauma, birth defects, and after bladder removal (cystectomy). Two broad categories of urinary diversion exist. A non-continent diversion is any isolated bowel segment (conduit) which allows urine to drain freely through the skin (stoma) called a urostomy. A continent diversion is a surgically created substitute for the bladder that is emptied naturally or with a catheter; e.g., continent urostomy, neobladder, ureterosigmoidostomy.
Almost every segment of the bowel or intestine has been used in the past for urinary diversion. The ileum, the end portion of the small intestine, is the most commonly used segment for urinary diversion due to technical ease and fewer metabolic side effects.
The type of diversion selected depends on a number of factors: age, general health, reason for diversion, manual dexterity, body shape, bowel disease, motivation for maintenance of body image, willingness to self-catheterize, tolerance of nighttime leaking, potential for recurrence of cancer, and prognosis of bladder disease. Regardless of the type, all diversions are associated with some short- and long-term complications, especially metabolic problems.
The oldest form of urinary diversion is ureterosigmoidostomy (U), which was first described by Smith in 1878. A U is a direct connection between the ureters and the lower large bowel or colon. Voiding or urination is via regular bowel movements. Over 60 different U techniques were reported by 1936. This was the method of choice until the 1950's when the metabolic effects and the development of secondary bowel cancers were discovered. These secondary cancers, located at the connection of the ureters and the colon, have been know to develop up to 26 years after the operation. This technique is still being used today for rectal reservoirs, however, cautiously as the long-term results are not available.
Although first described in 1911, the ileal conduit did not become the preferred method of urinary diversion until 1950. The technique of forming the ileal conduit has undergone very few changes since then. The operation is technically the simplest and one of the shortest compared to all other forms of urinary diversion. For a period of time, this was the only choice available to patients. Over the past two decades, advances have been made to develop other techniques, which eliminate the use of an external appliance. Currently, the ileal conduit remains the most popular method of urinary diversion due to its relatively few and infrequent complications.
The continent urostomy was first attempted in 1888, revised in the 1950's by Dr. Gilchrist, and successfully implemented in the 1980's. This type of diversion has a reservoir which collects and stores urine, and is emptied by inserting a catheter through a stoma located on the surface of the abdomen. Presently, there are more than 40 different types of continent urostomy diversions. Two popular stomal forms are the Kock pouch made entirely from ileum; and the Gilchrist - Indiana or Miami pouch - which is formed from the right side of the colon and a small segment of the ileum.
The stoma is designed for easy catheter insertion and must also be leak-free; i.e., continent. The continent urostomy requires a longer operation, necessitates a lengthier hospital stay, and results in a higher long-term complication rate. Long-term complications occur in approximately 15% of patients. The continent urostomy is not recommended for individuals who are of advanced age, have more severe cancer, decreased kidney function, or have had previous abdominal radiation therapy. Although the long-term results are not available, patient surveys have shown a better overall quality of life resulting from a continent urostomy as compared to the ileal conduit.
The neobladder became popular in the 1980's. The procedure involves replacing the diseased bladder with a bladder fashioned from intestine that empties through the urethra, the normal urinary opening. Careful patient selection is mandatory and is the key to success. similar to all continent diversions, there are many techniques and types available. After surgery, voiding or urinating becomes a new learned technique. Complete emptying of the neobladder may always require catheterization at the end of each void. Although the complication rates are higher, similarity to the natural voiding pattern translates into an improved quality of life compared to other forms of diversion. While long-term results are unavailable, the neobladder is currently considered to be the procedure of choice for selected patients with bladder cancer.
Not all types of diversion are suitable for every patient. There is no easy way to predict how each person will react to a particular type of diversion. However, research has shown that the selection of the most appropriate type of diversion, effective pre-operative counselling, and consulting with family members and other patients can help lead to a better quality of life.
In summary, there are several options for bypassing the diseased bladder: the ileal conduit, the continent urostomy, and the neobladder. Continuous research will shed light on the long-term effect of the different methods of urinary diversion. The future of urinary diversion looks bright. The next few decades will allow for the development of newer surgical reconstructive techniques, leading to lower complication rates and improved quality of life. The advent of gene cloning and tissue engineering will enable the growth of a new bladder. The ultimate goal of medicine is prevention. The prevention of bladder diseases is the key. We hope that in this millennium, the need for urinary diversion will hopefully be a thing of the past.
