Renal failure

Renal failure is a condition in which the kidneys insufficiently fulfill their function of maintaining a constant internal environment and their excretory function.

Distribution of renal failure
Traditionally, kidney failure is divivded into three types :


 * prerenal failure – kidney function is damaged by insufficient blood supply to the kidneys (dehydration, shock),
 * renal failure – the kidneys do not perform their function due to damage to the glomeruli or tubules,
 * postrenal failure – this is an obstruction in the urinary tract that prevents the outflow of urine.

In terms of time, kidney failure is divided into :


 * acute renal failure and
 * chronic renal failure.

Differential diagnosis
The cause of renal failure is determined from the anamnesis, medical history, physical examination, biochemical examination of blood and urine, and sonography of the kidneys. Before any diagnosis of renal failure, it is necessary to rule out both prerenal and postrenal failure. Eliminating the cause of prerenal and postrenal failure can save the patient from dialysis.

Prerenal failure
We think of prerenal failure if the uirne sediment is normal, no proteinura and EFNa < 1%. We look for reduced intravascular volume or closure of the renal vessels. Prerenal failure can also arise as a purely functional blockage of the kidney's blood supply by increased intra-abdominal pressure.

The therapy is replenishment of the intravascular volume. If patients start to urinate afterwards, even with high creatinine and urea values, it is possible to treat them conservatively and under observation. If there is no indication for other reasons (e.g. hypercalemia), they can thus save themselves unncessary dialysis. On the contrary, if they do not start to urinate, the cause must be looked for elsewhere and at the same time the excess supply of fluids must be stopped (– then even dialysis, which was initially unnecessary, could now be necessary for pulmonary edema).

Renal failure
After anamnestic detection of toxins, nephrotoxic drugs (often aminoglycosides, e.g. gentamicin) or in the case of myoglobinuria or hemoglobinuria, we think of acute tubular necrosis. This can arise as a result of tubule ischemia even after long-lasting prerenal failure.

In the presence of swelling, involvement of other organs, hypertension, abnormal sediment, proteinuria, we think of these units :


 * acute interstital nephritis  (AIN),
 * acute glomerulonephritis (AGN),
 * vasculitides,
 *  hemolytic uremic syndrome / thrombotic thrombocytopenic purpura (HUS/TTP).

In AGN and vasculitides, it is desirable to have a kidney biopsy. For unclear cases of AIN as well. In HUS/TTP as well, but due to the bleeding state, biopsy may not be feasible.

Postrenal failure
For postrenal failure, it is necessary to demonstrate urinary tract obstruction (sono of the kidneys, dilatation of the calicopelvic system). Obstruction of one ureter, however – if it is not in a solitary kidney – will not cause renal failure. (In single ureter obstruction and renal failure, another cause should be sought.)

Related articles

 * Acute renal failure • Acute renal failure (pediatrics) • Treatment of acute renal failure
 * Chronic kidney disease • Chronic kidney function disorders (pediatrics)
 * Renal failure (neonatology)