Kidney inflammation (glomerulonephritis)

Kidney inflammation (glomerulonephritis) is an inflammation of the kidney corpuscles (glomeruli). Each kidney contains over one million of these renal corpuscles, whose function is to filter and cleanse the blood to produce urine, which is then passed through the ureter into the bladder. Glomerulonephritis (unlike pyelonephritis, which is caused by bacteria) is usually an autoimmune disease. In this case, the kidneys are attacked and damaged by the body's own immune system, which can subsequently trigger renal insufficiency (kidney weakness). A distinction is made between acute and chronic glomerulonephritis.

The most common cause of kidney inflammation is an overreaction of the body's immune system - this type of kidney inflammation is called IgA glomerulonephritis. In this case, the immune system forms so-called immunoglobulin A antibodies, which are deposited in the filter cells of the kidneys (glomeruli) and trigger an inflammation there. As a result, the kidney is restricted in its filter function, whereby it is no longer possible to successfully retain proteins and erythrocytes (red blood cells) in the blood. These are now continuously excreted through the urine instead of remaining in the body. In contrast, the excretion of toxic metabolites is restricted, resulting in the accumulation of these substances.

Unlike renal pelvic inflammation, kidney inflammation is not caused by bacteria and therefore cannot be treated with antibiotics. In addition, both kidneys are always affected in the case of kidney inflammation, whereas only one kidney is often affected in the case of pelvic inflammation.

Basically, a distinction is made between primary and secondary kidney inflammation. If only the kidneys are affected and inflamed, it is a primary glomerulonephritis. If, however, the inflammation is due to other causes (for example, if it is triggered by autoimmune diseases such as systemic lupus erythematosus or by medication), this is called secondary glomerulonephritis.

Since glomerulonephritis, unlike inflammation of the renal pelvis, is usually painless, the disease often goes unnoticed for a long time and is only discovered by chance during routine examinations. In some cases, the disease manifests itself at such a late stage that dialysis (blood washing) or transplantation is unavoidable.

In the course of the disease, the following typical symptoms occur:

• Due to the fact that the kidneys are impaired in their filtering function, there is a pathological transfer of blood (hematuria) and proteins (proteinuria) into the urine, where these substances can now be detected. If there are high concentrations of proteins, the urine may become frothy. The urine may also be stained red by the erythrocytes, which is called macrohaematuria.
• If larger amounts of proteins are excreted in the urine, this may result in a low concentration of proteins in the blood.
• Because urine production by the kidneys is impaired, there are increased concentrations of electrolytes (salts) in the body, which can cause edema (water retention in the tissues) and high blood pressure.
• Some patients experience a sudden deterioration in kidney function (acute kidney failure). However, chronic kidney failure can also occur, in which the kidneys deteriorate in function over a period of years, requiring regular dialysis.

The suspicion of a possible kidney inflammation usually arises from the laboratory examination of urine and blood samples. To confirm the diagnosis, a kidney biopsy (examination of kidney tissue under the microscope) must be performed. In addition, the kidneys are examined by means of sonography (ultrasound).

By determining the 24-hour creatinine clearance (parameter that provides information about kidney function), it is possible to find out whether and to what extent the kidneys are limited in their ability to function.

It is important to exclude a bacterial inflammation of the renal pelvis, as this could easily be treated with antibiotics.

Whether glomerulonephritis is treated depends primarily on the extent of the disease.

If only very small amounts of proteins and red blood cells are excreted in the urine and the kidney function and blood pressure are in the normal range, there is no compelling need for action. However, regular checks should be made with the doctor.

Since glomerulonephritis is often caused by an overreaction of the immune system, treatment with immunosuppressive drugs such as cortisone is necessary in these cases. However, since this weakens the entire immune system, there are numerous undesirable side effects associated with this treatment.

If the kidney inflammation is the result of another disease, treatment of the actual underlying disease usually helps. In addition, the following measures should be observed:

• Adequate drinking should be ensured (unless the kidneys are already too impaired in their function).
• High blood pressure should be treated consistently, as this puts additional strain on the filter cells in the kidneys and can thus worsen kidney function.
• In certain cases, a diet low in protein and salt can be helpful.

The prognosis of glomerulonephritis depends to a large extent on whether only the kidneys or other organs are affected.

In the case of primary kidney inflammation (in which only the kidneys are involved), the life expectancy of those affected is quite good, even with severe loss of kidney function and the need for dialysis. If a kidney transplant is possible, patients can usually lead an almost normal life afterwards. However, after some time, a new outbreak of kidney inflammation can also occur in the transplanted kidney, which in rare cases also destroys the new kidney.

Since secondary kidney inflammation primarily affects other organs and only subsequently damages the kidneys, the prognosis depends heavily on the treatment of the original disease and the extent to which other organs have already been damaged.

Although glomerulonephritis cannot be prevented with certainty, the disease can be detected and treated at an early stage through regular urine tests.