Dialysis

What is dialysis?

Dialysis represents the most commonly applied kidney replacement therapy. Generally, we distinguish intra- and extracorporeal methods, depending on whether dialysis happens within or outside the body.

What functions do kidneys have?

The kidneys are a crucial organ for the body. They are made up from a complex system of small channels (called canaliculi), through which our blood is pumped around 300 times each day. During this process, the blood is cleansed from excessive or harmful substances, which are subsequently peed out. Cleansing works by means of osmosis: Within the kidney canaliculi, which act as a semipermeable membrane, certain substances are present in different concentrations compared to the adjacent tissue. These substances travel along the concentration gradient out of the blood and drag excess water with them to be excreted with the urine.

In case the kidneys fail to complete this task due to a disease or injury, these substances accumulate and damage internal organs. Once the kidneys are severely impaired in this function and no transplant is available, replacement therapy with dialysis must be performed.

For what reasons and under what conditions is dialysis performed?

Dialysis is used when kidneys can no longer carry out their filtering function. Kidney failure can have a wide range of causes with acute or chronic progression. Intoxications, certain drugs as well as trauma with severe blood loss are the most common causes of acute kidney injury.

Chronic kidney failure is most commonly caused by diabetes but may also be the result of inflammations, high blood pressure or kidney stones. Blood and urine investigations help assessing the severity of kidney damage. In case the severity is too high or the treatment of the cause is not successful, patients must undergo dialysis. In Germany, this affects around 75.000 persons.

A different kind of dialysis can be used in cases of acute intoxications – including overdosing of medications or intoxication with pesticides. However, this is only possible for a small number of toxins.

How does dialysis work and what techniques are available?

Generally, we distinguish intra- and extracorporeal methods, depending on whether dialysis happens within or outside the body. The following types of dialysis are most important:

Hemodialysis

This is the most common therapy. Patients are required to visit a dialysis center around 3 times a week. Before starting dialysis, it has to be ensured that blood can be pumped out of the circulation with sufficient speed. A specific catheter is either placed into a large vein, or an artificial connection between an artery and a vein is created, through which blood can reach higher velocities.

The latter is the method of choice when preparing patients for long-term dialysis. During the process of dialysis, this catheter is connected to a machine containing a dialysis membrane as well as a certain exchange liquid called dialysate. The membrane has holes of specific sizes that allow water, electrolytes and substances that are regularly excreted with the urine to pass through, while holding back blood cells and other larger particles. Dialysate contains water and electrolytes and its constitution is individually designed for each patient. Blood passes along the membrane.

The concentration gradients of substances what need to be excreted force them to enter the dialysate which is continuously exchanged. Electrolytes, if needed, can enter the blood which is re-introduced into the circulation. This way, the entire blood volume can be exchanged in a matter of a few hours.

Hemofiltration

This method can be applied to acute kidney injury or high blood pressure. Similar to hemodialysis, blood is directed along a filtration membrane. Due to lower pressure on the other side, water and smaller substances can exit the blood. In contrast to hemodialysis though, dialysate is not used. This way, a lot of water can be removed from the body, which must be replaced by an electrolyte solution.

Hemodiafiltration

This method combines the advantages of both hemodialysis and hemofiltration. Although more elaborate, this method is considered more effective, because hemofiltration offers removal of substances of low and medium molecular sizes from the blood.

Peritoneal dialysis

Peritoneal dialysis is another intracorporeal method. While the principle is similar to hemodialysis, instead of using an artificial membrane, the patient’s abdominal membrane (called peritoneum) is used. This layer of tissue lines the abdominal cavity and separates it from blood vessels. Here, the concentration of substances to be excreted with the urine is significantly lower. As a result, dialysate can be introduced into the abdominal cavity and exchanged after several hours. This enables harmful substances to be washed out. Peritoneal dialysis is used far less frequently than hemodialysis, as the risk of infection is greater and hemodialysis is more effective.

What needs to be considered as a dialysis patient?

In most cases, patients must follow fairly strict dietary schedules that are designed for each patient individually according to their health status and underlying diseases. Most recommendations include low salt, potassium and phosphate intake, as these substances have significant impact on the water balance in the body.

Additionally, dialysis patients should not take in more liquid than their daily excretion volume plus 500 ml. It goes without saying that life with dialysis requires discipline to undergo this procedure several times per week, because not adhering to dialysis can be life-threating after only a few days.

What side effects may be encountered?

Side effects that are frequently seen include muscle cramps and drops in blood pressure. Also nausea and headaches are possible. However, with close supervision these can be readily managed. The venous access may also be associated with hematomas and infections. A feared complication of peritoneal dialysis is inflammation of the abdominal membrane. This can be avoided by working precisely and under sterile conditions.

What is a dialysis center and how can I find an experienced nephrologist or clinic in Germany?

While peritoneal dialysis can be performed at home, hemodialysis is done in specialized dialysis centers under the supervision of experienced nephrologists and licensed nursing staff. Dialysis is an outpatient procedure and its duration can vary from patient to patient and is determined by the physician. Generally, at least 4-5 hours are required to cleanse the blood.

At PRIMO MEDICO you will exclusively find experienced nephrologists and specialized clinics in Germany.