Acute Kidney Injury
Acute kidney injury (AKI), previously known as acute renal failure, is a sudden decline in kidney function occurring within seven days. This condition is characterised by an increase in serum creatinine or a decrease in urine output, or both. AKI is primarily categorised into prerenal, intrinsic renal, and postrenal causes.
Signs and Symptoms
The symptoms of AKI are typically dominated by the underlying cause and the disturbances in kidney function. Common symptoms include fatigue, loss of appetite, headache, nausea, and vomiting, all due to the accumulation of urea and other nitrogen-containing substances in the bloodstream. High potassium levels can lead to severe and life-threatening abnormal heart rhythms. Pain in the flanks, thirst, and evidence of fluid depletion may also be observed. Physical examinations may reveal additional clues such as a rash in interstitial nephritis or a palpable bladder in obstructive nephropathy.
Causes
Prerenal
Prerenal causes of AKI are due to decreased blood flow to the kidneys, resulting in a reduced glomerular filtration rate (GFR). Common prerenal causes include dehydration, excessive blood loss, heart failure, and certain medications like NSAIDs.
Intrinsic or Intrarenal
Intrinsic AKI results from direct damage to the kidney itself and can affect the glomeruli, tubules, or interstitium. Causes include glomerulonephritis, acute tubular necrosis, and acute interstitial nephritis. Certain medications, such as calcineurin inhibitors, can also directly damage the kidney.
Postrenal
Postrenal AKI is caused by obstructions in the urinary tract downstream of the kidney. This can result from conditions such as benign prostatic hyperplasia, kidney stones, and bladder cancer.
Diagnosis
Definition and Staging
AKI can be diagnosed based on criteria established by the Kidney Disease: Improving Global Outcomes (KDIGO) in 2012, which include an increase in serum creatinine by ≥0.3 mg/dL within 48 hours, an increase in serum creatinine to ≥1.5 times baseline within the prior 7 days, or urine volume < 0.5 mL/kg/h for 6 hours. The RIFLE criteria further aid in assessing the severity of AKI, ranging from Risk to End-stage kidney disease.
Evaluation
Diagnosis often involves measuring urine output and blood tests for urea and creatinine. Further testing might include urine sediment analysis, renal ultrasound, and kidney biopsy. Imaging studies such as renal ultrasonography, CT scans, and MRI are used to examine the acute changes in the kidney and identify any structural abnormalities.
Treatment
The management of AKI involves treating the underlying cause and providing supportive care. Avoiding nephrotoxic substances is very important. Monitoring of kidney function through serial serum creatinine measurements and urine output is routinely performed.
Prerenal
In prerenal AKI without fluid overload, intravenous fluids are typically administered to improve kidney function. If low blood pressure persists, vasopressors and inotropes may be given to enhance blood flow to the kidney.
Intrinsic
Treatment of intrinsic AKI depends on the specific cause. For example, AKI due to vasculitis or glomerulonephritis may respond to steroids, cyclophosphamide, and plasma exchange. Discontinuation of nephrotoxic drugs is often required.
Postrenal
Postrenal AKI necessitates relieving the obstruction, which may involve procedures such as nephrostomy or urinary catheterisation.
Renal Replacement Therapy
In some cases, renal replacement therapy like haemodialysis is required. Both intermittent and continuous renal replacement therapies are used, depending on the patient's condition and response to treatment.
Prognosis and Epidemiology
Mortality rates for AKI are high, particularly in ICU settings, with a death rate as high as 50%. AKI can lead to chronic kidney disease and end-stage kidney disease, requiring lifelong dialysis or a kidney transplant. AKI is common among hospitalised patients, affecting 3-7% of those admitted to the hospital and 25-30% of ICU patients. The incidence of AKI has increased over the past 20 years, making it one of the most expensive conditions seen in hospitals.
Self-assessment MCQs (single best answer)
What is the primary characteristic of Acute Kidney Injury (AKI)?
Which of the following is NOT a common symptom of AKI?
What is a prerenal cause of AKI?
Which medication is known to cause direct damage to the kidney, leading to intrinsic AKI?
What does postrenal AKI result from?
According to KDIGO criteria, what urine volume is indicative of AKI?
What diagnostic tool is commonly used to examine acute changes in the kidney and identify structural abnormalities?
Which treatment is typically administered for prerenal AKI without fluid overload?
When might renal replacement therapy be required in the management of AKI?
Which of the following is a potential long-term consequence of AKI?
Dentaljuce
Dentaljuce provides Enhanced Continuing Professional Development (CPD) with GDC-approved Certificates for dental professionals worldwide.
Founded in 2009 by the award-winning Masters team from the School of Dentistry at the University of Birmingham, Dentaljuce has established itself as the leading platform for online CPD.
With over 100 high-quality online courses available for a single annual membership fee, Dentaljuce offers comprehensive e-learning designed for busy dental professionals.
The courses cover a complete range of topics, from clinical skills to patient communication, and are suitable for dentists, nurses, hygienists, therapists, students, and practice managers.
Dentaljuce features Dr. Aiden, a dentally trained AI-powered personal tutor available 24/7 to assist with queries and provide guidance through complex topics, enhancing the learning experience.
Check out our range of courses, or sign up now!