Acute renal failure (ARF) is defined as a sudden and significant decrease in the glomerular filtration rate, a value used for assessing kidney function. The filtration rate is calculated from blood creatinine levels, a protein normally excreted by the kidney. It is expressed in milliliters per minute and depends, among other factors, on the sex and age of the patient. There is talk of acute renal failure when the flow decreases suddenly, and there are three types of ARF according to the mechanism involved. The origin can the kidneys and can be the result of a disease called nephropathy: this is particularly the case of a crash in the blood supply to the kidney, responsible for necrosis (cell death), and thus the stopping of kidney functions. The cause may also be a sudden blockage in the flow of urine, which is the case when there are stones in both kidneys, or when only one kidney is working. Finally, in the case of low blood flow filtered by the kidneys, which is essentially due to dehydration, functional ARF appears. An ARF can also be secondary to many causes.
The clinical signs of acute renal failure are different depending on whether the cause is an obstruction, touching the kidney itself or lowering its perfusion capabilities. Functional ARFS is often a result of dehydration, which explains the presence of symptoms such as decreased blood pressure and tachycardia. ARF is also possible in the case of a reduction of circulating blood volume, as in some cases of advanced cirrhosis or chronic heart failure. Obstructive ARF is often manifested by the presence of abdominal or back pain, lack of urination, or blood in the urine. Lastly, in the case of a pathology affecting the renal tissue, signs may be highly variable.
The diagnosis of obstructive acute renal failure will be made following a clinical examination and confirmed by a renal ultrasound that will show a dilation of cavities of the kidneys. Sometimes an X-ray of the abdomen or a CT scan will be needed. For the other two types of ARF, a blood test will show a significant increase in blood creatinine with decreased glomerular filtration rate. The search for the cause will be aided by performing a renal ultrasound, urinalysis and possibly a renal biopsy if necessary for the diagnosis of renal disease.
The treatment also depends on the mechanism involved. In the case of obstructive renal failure, an emergency urinary diversion must be performed by various methods depending on the location of the blockage. If the ARF is due to dehydration, rehydration is necessary. The management of renal disease or other chronic diseases may help with the ARF.