The Michigan Vascular Access/MiDRE primer in Vascular Access

Chapter 2 - Options in renal replacement therapy

The three options for renal replacement therapy are maintenance hemodialysis, peritoneal dialysis, and renal transplantation. Currently approximately 412,000 patients are on maintenance dialysis in the United States in nearly 6000 dialysis units. Approximately 182,000 are managed by renal transplantation.

Renal transplantation

Renal transplantation is associated with the best individual survival and lowest costs of the

Renal transplant incision
three renal replacements therapies. An obvious limitation is a shortage of donor kidneys relative to the need. Living related and non–living related donor programs attempt to address this shortage by appealing to the altruism of family members, friends and strangers to donate an "extra" kidney to those in need, and in fact the first successful renal transplant was between identical twins. A recent emphasis on the long-term health issues of donors has cast a pall on living donor programs, and a more promising answer might be the expansion of cadaver donation efforts. Failure of renal transplants is also known, and it is not uncommon for a renal transplant to fail in a short time, bring the patient back to a need for peritoneal or hemodialysis. Some patients have had up to four renal transplants. Let is suffice to say that the supply of donors is currently insufficient for the management of the need.

Peritoneal dialysis

Peritoneal dialysis (CAPD) involves the placement of a catheter in the peritoneal cavity to allow the instillation of volumes of fluid into the cavity, diffusion of metabolic wastes into the fluid across the semi permeable membranes of the abdominal cavity, and removal of these wastes with frequent fluid "exchanges". CAPD is popular with those who would prefer not to be linked to a strict dialysis schedule and wish to control their schedule. CAPD is also used extensively in the management of pediatric renal failure patients in whom very small vessels make creation of fistulas and placement of grafts very difficult. It is also used as a bridge therapy in patients whose fistulas are developing slowly.

By avoiding the necessity of placing an intravenous permacath in patients who do not or cannot have either a transplant, or a "permanent" hemodialysis access, the CAPD catheter is frequently called "the ‘good’ catheter".


Continuous ambulatory peritoneal dialysis (CAPD)

Problems with fluid traversing from the abdomen into the pleural cavity, diabetes and glucose control, inadequacy of clearance, and infection in the peritoneal cavity complicate CAPD and limit the number of patients who are successful with this modality. For this reason, any patient choosing CAPD is strongly encouraged to have a fistula created as well as a backup option.

Hemodialysis

As mentioned previously, nearly 410,000 patients are on hemodialysis nationwide, with a network of nearly xxx dialysis units, usually on a Monday-Wednesday-Friday or Tuesday-Thursday-Saturday schedule three to four hours at a time. The ability to hemodialyze is dependent on a way to remove large volumes of blood from the body, run it through a filter, and give it back. Unfortunately, hemodialysis requires passing large amounts of blood through a dialysis filter three times a week: 90,000 to 120,000 milliliters; 90 to 120 liters; or 23.7 to 31.6 gallons over a session repeated three times a week). There is no vein in the human body that can withstand this amount of use without modification.

There are essentially three options that allow for this volume of blood to be drawn from the body, run thought the dialysis machine, and returned to the circulation: (1) a large catheter with two channels can be placed through the skin into one of the major veins with sufficient flow to provide this amount of blood and safely handle its return; (2) a native vein of the patient which has been conditioned by a direct connection with the arterial pressure and flow of an artery to expand, to carry sufficient flow, and to toughen enough to safely and repeatedly handle being punctured by large needles twice a week (called a "fistula"); and finally, (3) an artificial tube connecting an artery and vein, placed under the skin, and also designed to be safely punctured three times a week with large needles (called a graft).

Patient on dialysis via a forearm loop graft

All such means for hemodialysis are artificial, disturb the natural state of the circulatory system, pose risk for complications, and are inherently unstable, requiring large amounts of time and effort to maintain.

Michigan Dialysis Research and Education (MiDRE)
Saint Mary's Mercy Hospital