Acute kidney failure often causes symptoms within a short time: The urine production usually decreases, eventually comes to a halt. Sometimes, however, the kidney still excretes urine.

Urinary substances remain in the body – recognizable by rising blood levels of creatinine and urea.
There are signs of overhydration of the body, such as fluid retention in the lungs (pulmonary edema) or in the legs.
Disorders in the salt balance (electrolyte disturbances) are possible, for example, high potassium values in the blood. Acidification (acidosis) occurs. Both can potentially be life-threatening.
With sufficient treatment, the kidneys can gradually recover, causing urine production to resume and normalize other functions (such as regulation of the electrolyte and acid-base balance). Until the kidney function has completely recovered, often weeks to months.

Symptoms of chronic renal insufficiency
Chronic renal insufficiency (CNI)develops gradually. It may initially go unnoticed or cause nonspecific symptoms such as fatigue, tiredness or loss of appetite. The blood pressure can rise. Sometimes fluid retention occurs, for example on the legs or in the lungs. The latter can cause shortness of breath.The kidneys may not be able to properly concentrate the urine. Then the amount of urine may initially increase – which does not even make sufferers think of kidney weakness. The urine is then usually bright and little colored – not very concentrated.

Doctors classify the CNI according to the functional state of the kidneys in stages. For this purpose, they use various parameters such as protein excretion in the urine or blood values with the estimated so-called glomerular filtration rate (GFR). It is the amount of blood freed from creatinine by the kidney per minute. The GFR is expressed in milliliters per minute (ml / min). Normal is a GFR greater than 90 ml / min.

An untreated kidney weakness can have many effects on the whole organism. Because the kidney fulfills important tasks, among other things, produces hormones (see overview). Possible consequences of renal insufficiency are: anemia , hypertension , bone disorders, nervous disorders ( polyneuropathy ), disorders of the sexual organs with no menstruation (amenorrhoea) or impotence , coagulation disorders with the formation of bruises. In the course of ha headache or itching occur.

Without therapy threatens finally urine poisoning (uremia) – a life-threatening condition with over-hydration of various organs, heart failure , cardiac arrhythmia and general symptoms such as nausea , vomiting , change of consciousness to coma.

Survival without the use of renal replacement therapy is not possible in the medium term. This most severe stage of renal insufficiency is irreversible (chronic renal failure).