Dialysis is a procedure to filter the blood, made necessary when the kidneys can’t. But filter what? How does it replace what the kidneys do? What does it involve? First, why do we need kidneys (or an artificial substitute) at all?
Chemical reactions that take place during cellular activity produce waste products. Those products move through the blood into the kidneys where they are turned into urine. That then moves through the ureters down to the bladder and out the urethra. If they remained in the blood harmful effects would occur, a condition known as uremia. Symptoms include severe muscle cramps, nausea, and skin discoloration.
At the same time, the kidneys help balance electrolytes, drain excess fluid, and even regulate blood pressure. Those, too, are vital activities to keep the human body in equilibrium.
When the kidneys can not perform those functions, a substitute is necessary. Dialysis is one traditional and effective method.
There are actually two types of dialysis: hemodialysis and peritoneal dialysis. They are very different. Let’s cover them in order.
Hemodialysis is a procedure that uses a dialysis machine to remove waste products from the blood and return filtered blood back to the patient. That is done through a special insert called an access point that is surgically prepared in advance.
The access point may be a simple catheter in the case of emergency hemodialysis, usually inserted in a vein in the neck or groin. Or it may be a more long-term structure created surgically in which an artery and vein are artificially joined. The arteriovenous (AV) fistula, as it’s called, is then used to insert the pair of needles used for extraction and replacement of blood.
The dialysis machine is then connected and the patient’s blood filtered, usually about 3 times per week for 3-4 hours per session. The procedure has two stages. In one stage, waste products move through a semi-permeable membrane. In the second, filtered blood is returned through another tube.
The procedure is usually carried out in a central location staffed by professionals. Home dialysis has become somewhat more common over the years, though, as machines grew smaller and less expensive.
Peritoneal dialysis is a very different procedure and one that is much more often performed at home by the patient and/or an assistant. In this method, a sterile tube is inserted in the peritoneal cavity near the large intestine. A solution is then injected into the abdominal cavity. The tissues there perform a filtering role similar to the semi-permeable membrane described above.
Though more convenient in one way because it is performed at home, it must be carried out 4-5 times per day, or by an automated system at night. It carries a slightly higher risk of infection, primarily because most patients are less skilled than professionals in antisepsis.
In years past, dialysis (once it became necessary) was usually a lifetime commitment. Today, it is more often temporary (though ‘temporary’ can mean several months or years), thanks to kidney transplants and other permanent solutions.