What are the Three Types of AKI?

Understanding AKI: Types, Causes & Warning Signs

Acute kidney injury (AKI) is a sudden deterioration of kidney function, occurring over hours to days, leading to toxin accumulation and fluid/electrolyte imbalances. This complex condition consists of various aetiologies. Understanding classifications of AKI can help plan a treatment strategy and improve patient health. 

Classification: Three Types of AKI   

AKI occurs when there is a sudden decline in kidney function, resulting in impaired waste excretion and fluid, electrolyte, and acid–base imbalance. This condition results in toxin accumulation and an imbalance of electrolytes that disrupt the body's capability of regulating fluids. The rapid deterioration of the kidneys can develop within a few days or a few hours.   

AKI has three types, and here are the brief descriptions: 

1. Prerenal AKI: Prerenal acute kidney injury happens due to inadequate blood supply to the kidney, resulting in decreased glomerular filtration rate. Prerenal AKI is the most common type of AKI and is usually reversible if promptly treated, though prolonged untreated cases may progress to intrinsic kidney damage.   
2. Intrinsic AKI: Intrinsic AKI refers to direct injury to kidney structures, including the tubules, glomeruli, interstitium, or renal vasculature.   
3. Postrenal AKI: It is the result of obstruction or blockage in the urinary tract that hampers urine flow from the kidney to the bladder. Any obstruction from the renal pelvis to the urethra causes back pressure, reducing glomerular filtration and impairing kidney function. 

Primary Causes of Prerenal Acute Kidney Injury 

Prerenal AKI has various causes, including: 

• Reduced blood pressure 
• Excessive bleeding 
• Heart diseases like heart attacks or heart failure 
• Diarrhoea 
• Liver failure 
• Infections 
• Prolonged use of non-steroidal anti-inflammatory drugs like ibuprofen, aspirin, and naproxen 
• Anaphylaxis 
• Dehydration 
    

Key Causes of the Intrinsic AKI 

Apart from problems with connective tissues and blood vessels, there are many causes for intrinsic AKI, including: 

• Clots or injury in blood vessels 
• Inflammation in the structural units of the kidneys 
• Impact of autoimmune diseases like vasculitis and lupus 
• Cancer 
• Kidney infection 
• Certain medications, such as specific antibiotics, proton pump inhibitors, and NSAIDs, may cause intrinsic AKI, typically through interstitial nephritis or tubular toxicity 
• Excessive alcohol consumption may contribute indirectly to intrinsic AKI through dehydration, hypotension, or rhabdomyolysis 
• Blood disorders such as thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome. 
    

Causes of the Postrenal AKI 

This type of AKI has some potential causes, such as: 

• Bladder or kidney tumours 
• Kidney stones 
• Cancer in the urinary bladder, cervix or colon 
• Blood clotting in the urinary tract 
• Effect of prostate disease, including prostate cancer and prostatic hyperplasia 
• Damage to bladder function 
• Nerve system issues that control the urine flow 
    

Symptoms of AKI   

Acute kidney injury symptoms appear over days or a period. Common signs include: 

• Swelling in ankles, feet and legs due to fluid retention (oedema) 
• Decreased urinary frequency 
• Fatigue 
• Severe pain in the back or abdomen 
• Chest pain 
• Muscle cramps 
• Seizures 
• Blood in urine 
• Breathing issues 
• Dark-coloured urine 
    

Prerenal, intrinsic and postrenal are the three types of acute kidney injury. Prerenal AKI occur due to reduced blood flow in the kidney, dehydration, liver failure and heart failure. 

Conversely, intrinsics cause direct kidney damage and happen due to prolonged medication with nephrotoxic drugs and inflammation of the filtering units of the kidneys. Postrenal AKI occurs due to prostate enlargement, kidney stones and tumours. 

Disclaimer: This article is intended for general informational and educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always seek the advice of a qualified healthcare professional with any questions regarding a medical condition, symptoms, or treatment options.

Also Read:

→ What are the Treatments for Paget's Disease

→ What are the Types of Stress

→ What are the Ulcerative Colitis and Crohn’s Disease Differences

→ What Causes Alpers' Disease

→ What Damages the Abducens Nerve