Acute renal injury – classification, diagnosis and treatment

Acute renal injury (AKI) is a rapid regression of kidney function, followed by the accumulation of body waste in the blood. The syndrome can be provoked by:

  • Violation of blood circulation in the kidneys
  • Slow drainage of urea from the kidneys
  • Cirrhosis
  • Congenital renal failure

Until recently, this pathology was called acute renal failure.


According to the degree of development, the PPE is divided into 3 categories. Below are the reasons for each category of AKI.

  • Prerenal. Frequent vomiting and diarrhea, bleeding of various kinds, weakening of the muscles of the blood vessels, and relaxation of the renal muscles can cause the prerenal stage of AKI.
  • Renal. Drugs and X-ray contrast agents that affect the kidney are one of the causes of renal AKI. Other causes are vasculitis, renal vascular thrombosis, malignant hypertension, acute glomerulonephritis. Glomerulonephritis in 90% of cases progresses to renal failure.
  • Postrenal. Obstruction and stones in the ureter, as well as intratubular narrowing, lead to urinary obstruction. Postrenal AKI develops.

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    The international RIFLE classification of AKI helps to identify the damage class. The abbreviation RIFLE stands for risk, damage, failure, loss, chronic stage. To determine the AKI class, the indicators of kidney filtration and urination are used:

    • Risk – creatinine is 1,5 times higher or filtration is lower than 25% of the norm, urination <0,5 ml/kg/hour>, in 6 hours.
    • Damage – creatinine is 2 times higher or filtration is reduced by half of the norm. Urine volume <, 0,5 ml \ kg \ hour>, for 12 hours
    • Insufficiency – creatinine is 3 times higher, and filtration is 75% lower. Urination <, 0,3 ml/kg/hour>, per day.
    • Loss of kidney function – irreversible AKI, complete kidney failure.
    • Terminal renal failure is the last stage of chronic renal failure.


    The first symptoms of AKI are swelling of the extremities and weight gain. After the accumulation of body wastes appear:

    • Sudden convulsions.
    • Nausea.
    • Vomiting.
    • Malaise.
    • Epileptic seizures.
    • Clouding of the mind.
    • Coma.

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    When inhaling and lying down, the chest hurts. There is a friction noise of the outer shell of the heart – the pericardium. Further, fluid accumulates in the lungs, making breathing difficult. Glomerulonephritis paints the urine the color of Pepsi-Cola. A significant increase in the kidneys is a sign of Pasternatsky’s symptom. This symptom is accompanied by pain and an increase in red blood cells in the urine.

    Urine is one of the main indicators of AKI. Depending on the volume of urine excreted, the period of the disease can be determined. There are 4 periods of the course of the disease.

  • Starting with exposure to a damaging factor, no more than a day passes before the first clinical signs of kidney damage appear.
  • Some variants of the disease may be accompanied by a period of decreased urine volume, within 2 weeks.
  • Elimination of the damaging factor, restores the functioning of the damaged kidney. This period is manifested by polyuria and lasts 2 weeks. An increase in the volume of urine excreted, increases the risk of dehydration, with inadequate fluid intake.
  • A timely diagnosis and timely treatment lead to a recovery period. Complete recovery of kidney function lasts 4 months.
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    Diagnosis is based on:

    • Anamnesis.
    • Physical examination.
    • Laboratory examination.
    • Instrumental research.

    The main purpose of making a diagnosis is to determine the etiology of the disease. Depending on the stage of AKI, appropriate treatment is prescribed, which is aimed at eliminating reversible causes. The main role in establishing the causes is the taking of anamnesis. For this it turns out:

    • Past kidney damage, information from biochemical blood tests (creatinine, urea) and general urine analysis.
    • Surgical interventions, course and complications after surgery before the development of AKI.
    • The diseases that led to the development of AKI are also symptoms of these diseases. Information about back pain, discoloration of urine, difficulty urinating. Recent appointments with a gynecologist, urologist and ancologist.
    • Data on conservative treatment (polychemotherapy, antibiotics, analgesics), treatment with folk remedies or contact with toxic substances, in the coming months, before the development of kidney damage.
    • Obtaining additional information about the patient, identifying or excluding the causes of acute renal injury.

    Physical examination includes:

    • To identify oliguria, anuria, polyuria or nocturia, the volume of urine excreted is assessed.
    • Examination of mucous membranes for pallor, yellowness, or blue discoloration.
    • Assessment of the skin for swelling, rashes, or bleeding
    • Measurement of body temperature
    • The state of the nervous system
    • Assessment of the state of the organs of the cardiovascular system, abdominal cavity, kidneys, according to physical data. (Percussion, palpation, auscultation)

    Laboratory diagnosis of acute kidney injury includes:

  • General blood analysis.
  • Blood test for creatinine, sodium, urea, phosphorus and calcium levels.
  • General and biochemical analysis of urine.
  • If an autoimmune disease is suspected, immunological tests for complements are performed.

    For a more accurate diagnosis, the following tools are used:

    • Ultrasound of the kidneys.
    • Doppler ultrasonography of renal vessels.
    • Ultrasound of the small pelvis with postrenal kidney injury.
    • Computed tomography of the kidneys and small pelvis.

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    AKI treatment falls into the following categories:

  • Non-drug
  • Medication
  • Surgical intervention
  • Dialysis

    Non-drug treatment requires bed rest and a specific diet. The diet limits the intake of fluids and sodium, in the form of table salt. The daily rate of fluid depends on the volume of excreted urine + 300 ml of water. If edema appears, it is worth limiting salt to 0,3 grams per day. The consumed proteins of animal origin are reduced to 0,6-0,7 g/kg of body weight. For the first two days, bed rest is carried out at home, then in common wards.

    With drug treatment, a list of drugs is introduced to replenish and normalize body systems:

    • Calcium antagonist, for removing excess of these elements from the body.
    • 20% glucose paired with insulin to normalize blood potassium.
    • sodium bicarbonate
    • To replenish blood volume, in case of blood loss, 5% dextrose and a weak solution of sodium chloride are prescribed.
    • For high blood pressure and edema, intravenous injection of furosemide is used. A perfuser is used to remove nephrotoxic drugs.
    • When the patient’s life is threatened, due to a decrease in the heart rate, dopamine is administered during the day. To prevent repeated incidents, blood pressure should be measured for two days.
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    Surgical methods of treatment are aimed at eliminating the violation of the outflow of urine from the body. Surgical intervention takes place with the direct participation of a urologist. To drain urine, a catheter is inserted into the bladder.

    If the effect is insufficient, it is possible to remove the prostate gland. High obstruction of the urethra requires the imposition of external drainage – nephrostomy. This measure leads to the restoration of the volume of excreted urine and normalization of renal filtration. If the previous methods were not successful, then an operation is assigned.

    Renal replacement therapy is used under the following conditions:

  • Ineffectiveness of drug treatment.
  • Encephalopathy.
  • Excessive fluid in the body.
  • Excessive amounts of potassium.

    The main goal of dialysis therapy is complete restoration of kidney function within 3-7 weeks. Not all hospitals have an “artificial kidney” due to the high cost of this apparatus. Peritoneal dialysis (PD) may be an alternative.

    The procedure is simple and does not require a highly qualified specialist. A catheter is inserted into the patient’s abdominal cavity, 5-10 cm below the navel. Then 2 liters of dialysis solution are injected. The main complications of peritoneal dialysis are inflammation of the abdominal cavity and an opening in the intestine. PD is ideal for patients with unstable blood flow in the vessels (hemodynamics).

    The effectiveness of the treatment is checked according to the following criteria:

  • Conclusion from an acute condition.
  • Elimination of edema and cramps.
  • Normalization of the alkaline-salt balance.
  • Normal diuresis.
  • Renal function restoration.
  • Normalization of pressure.
  • Normal blood creatinine and urea levels.

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  • Tatyana Jakowenko

    Editor-in-chief of the Detonic online magazine, cardiologist Yakovenko-Plahotnaya Tatyana. Author of more than 950 scientific articles, including in foreign medical journals. He has been working as a cardiologist in a clinical hospital for over 12 years. He owns modern methods of diagnosis and treatment of cardiovascular diseases and implements them in his professional activities. For example, it uses methods of resuscitation of the heart, decoding of ECG, functional tests, cyclic ergometry and knows echocardiography very well.

    For 10 years, she has been an active participant in numerous medical symposia and workshops for doctors - families, therapists and cardiologists. He has many publications on a healthy lifestyle, diagnosis and treatment of heart and vascular diseases.

    He regularly monitors new publications of European and American cardiology journals, writes scientific articles, prepares reports at scientific conferences and participates in European cardiology congresses.