Nephritic syndrome is present when three symptoms are present:
- Hematuria (blood in the urine)
- Hypertension (high blood pressure - new onset)
- Edema (water retention in the subcutaneous tissue)
The following may also occur:
Hematuria plays a central role among all symptoms. The red blood cells are either visible in the urine or are detected in a laboratory test. In addition, proteins are excreted in the urine (proteinuria). In both cases, this occasionally goes unnoticed by those affected.
However, nephritic syndrome is only diagnosed when high blood pressure and edema (water retention) are also present. In the early stages, the latter are primarily seen in the eyelids, making the face of those affected appear swollen.
Other symptoms include flank pain as well as headaches and aching limbs. If there is a serious disturbance of the electrolyte balance, epileptic seizures may occur. If the high blood pressure is severe, this often results in shortness of breath and pulmonary oedema.
A dangerous complication of nephritic syndrome is a massive deterioration in kidney function. This can develop within a few days as a result of bilateral inflammation of the kidneys involving the renal corpuscles. In the worst case, acute kidney failure occurs.
Nephritic syndrome is usually caused by inflammation of the renal corpuscles, often following a streptococcal infection. Lupus nephritis, an autoimmune disease, can also trigger inflammation.
These pathological changes are very diverse and their causes have not yet been fully researched. For this reason, no specific risk factors for the development of the disease have yet been identified. However, autoimmune diseases such as lupus nephritis or lupus erythematosus play an important role. This initially only affects the skin, but can spread to other organs, including the kidneys.
In post-infectious inflammation of the renal corpuscles, kidney problems occur a few weeks after an infection with the bacterium Streptococcus pyogenes, which often causes tonsillitis, due to faulty immunological processes in the body. It is not the bacteria themselves that attack the kidneys, but antigen-antibody complexes (immune complexes) that attack proteins similar to the bacteria again after the infection has already been overcome. This blocks the smallest vessels of the kidney in the glomeruli. The backlog of blood flow in the renal corpuscles increases the blood pressure, as a result of which blood cells are squeezed out into the urine. In other parts of the body, water leaks out of the blocked vessels and edema forms.
Diagnosis is based on the three main symptoms of hematuria, edema and hypertension as well as other clinical aspects such as flank pain. After a detailed anamnesis (discussion about the patient's medical history), in which questions are asked about previous tonsillitis, for example, a physical examination is carried out.
This determines whether there is water retention in the tissue (edema). The blood and urine tests are also very important. An additional ultrasound examination can make the disease visible and provide more detailed information about the causes. In severe or unassessable cases of nephritic syndrome, it is necessary to take a tissue sample from the kidney as part of a kidney biopsy.
Treatment of nephritic syndrome is based on the associated symptoms. High blood pressure and the resulting proteinuria are treated with antihypertensive drugs known as ACE inhibitors.
If there are signs of water retention, a strict diet with salt and fluid restriction is prescribed. Diuretics may also be used. Those affected must also follow a low-protein diet, and physical rest and bed rest are also recommended.
In nephritic syndrome, it is important to check blood levels regularly, especially creatinine. The creatinine level in the blood provides information about the functioning of the kidneys. An increase in this blood value is an indication of incipient kidney failure.
If a streptococcal infection is the cause of nephritic syndrome, preventive treatment with the antibiotic penicillin is prescribed for a period of ten days.