What are the causes and symptoms of Acute Kidney Injury (AKI) or Acute Renal Failure (ARF)?

From the Guidelines

Acute Kidney Injury (AKI) is a sudden decline in kidney function that develops over hours to days, and its causes can be categorized into prerenal, renal, or postrenal, with treatment depending on identifying and addressing the underlying cause while providing supportive care. The definition of AKI is based on an increase in creatinine by 0.3 mg/dL within 48 hours or an increase in serum creatinine to 1.5 times baseline (within prior 7 days) or urine volume 0.5 mL/kg/hr for 6 hours 1. AKI is common, affecting up to 20% of hospital inpatients and between 30% to 60% of critically ill patients, with a rising incidence worldwide 1.

Causes of AKI

• Prerenal factors include impaired blood flow from any cause including hypotension, hypovolemia, decreased cardiac output, or renal artery occlusion
• Renal causes include any disease that damages renal parenchyma, such as vasculitis, acute tubular necrosis, glomerulonephritis, interstitial nephritis, renal infection or infiltration, drugs, and toxins
• Postrenal AKI results from ureteral, bladder, or urethral obstruction

Symptoms of AKI

• Oliguria, which reflects decreased glomerular filtration rate (GFR)
• Changes in urine output may be physiologic, thus urine volume measurement is less important than measurement of serum creatinine in the diagnosis of AKI
• Electrolyte abnormalities, particularly hyperkalemia (potassium >5.5 mEq/L)
• Signs of uremia, refractory hyperkalemia, volume overload, or severe acidosis may require dialysis

Management of AKI

• Initial management involves ensuring adequate hydration with intravenous fluids like normal saline at 10-20 ml/kg if the patient is hypovolemic, while avoiding fluid overload in those who are euvolemic
• Nephrotoxic medications such as NSAIDs, aminoglycosides, and certain contrast agents should be immediately discontinued
• Electrolyte abnormalities require prompt treatment, and severe cases may require dialysis
• Continuous monitoring of urine output, daily weights, and regular blood tests for creatinine, BUN, and electrolytes is essential, as recommended by the Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guideline for acute kidney injury 1.

Prevention and Treatment

• The cause of AKI should be investigated as soon as possible, to prevent AKI progression, and management should be immediately started according to the initial stage, as suggested by the European Association for the Study of the Liver (EASL) clinical practice guidelines for the management of patients with decompensated cirrhosis 1
• The Canadian Society of Nephrology commentary on the 2012 KDIGO clinical practice guideline for acute kidney injury also emphasizes the importance of developing clinical practice guidelines for patients with AKI 1.

In summary, the management of AKI requires a comprehensive approach that includes identifying and addressing the underlying cause, providing supportive care, and preventing further kidney damage, with the goal of improving patient outcomes and reducing morbidity and mortality.

From the Research

Causes of Acute Kidney Injury (AKI) or Acute Renal Failure (ARF)

• Prerenal conditions account for 60 to 70 percent of cases, including dehydration, blood loss, and decreased blood flow to the kidneys 2
• Intrarenal causes, such as kidney damage or disease, can also lead to AKI or ARF
• Postrenal causes, including urinary outflow obstruction, can also contribute to the development of AKI or ARF 3, 2
• The use of certain medications, such as nephrotoxic drugs, can increase the risk of AKI or ARF 4, 2
• Radiocontrast media procedures and coronary angiography can also increase the risk of AKI or ARF 4, 2

Symptoms of Acute Kidney Injury (AKI) or Acute Renal Failure (ARF)

• Oliguria, defined as urine output <500 ml/day, occurs in about 2/3 of cases 5
• Electrolyte imbalances, fluid balance disturbances, and uremic solute accumulation can occur 3, 5
• Acid-base disturbances and uremic complications can also develop 5, 6
• Hemodynamic compromise and metabolic derangements can be present in critically ill patients with AKI or ARF 6

Prevention and Management of Acute Kidney Injury (AKI) or Acute Renal Failure (ARF)

• Prompt resuscitation of the circulation and adequate hydration are recommended to prevent AKI or ARF 4
• Avoidance of high-molecular-weight hydroxy-ethyl starch (HES) preparations and maintenance of adequate blood pressure using vasopressors in vasodilatory shock are also recommended 4
• Specific vasodilators, sodium bicarbonate, and periprocedural hemofiltration may be used in certain situations to prevent AKI or ARF 4
• Correction of fluid and electrolyte levels, avoidance of nephrotoxins, and kidney replacement therapy may be necessary to manage AKI or ARF 3, 2