Acute Kidney Injury AKI

Summary

Acute kidney injury (AKI), previously known as acute renal failure, is a sudden condition where the kidneys lose their ability to filter waste from the blood within 48 hours. This dysfunction leads to elevated levels of waste products like serum creatinine and blood urea nitrogen. AKI is categorized into three types: pre-renal (due to reduced blood flow to the kidneys), intra-renal (damage within the kidney tissue), and post-renal (obstructions after the kidney). Causes include hypovolemia, heart failure, sepsis, and obstructions like tumors or kidney stones.

Takeaways

• 💉 Acute Kidney Injury (AKI) is a clinical syndrome caused by kidney dysfunction, leading to the accumulation of waste products in the blood.
• 🩸 AKI occurs when the kidneys fail to filter blood effectively, causing a buildup of substances like creatinine and urea.
• ⏱️ AKI has a rapid onset, typically occurring within 48 hours, and manifests in elevated serum creatinine levels.
• 💪 Creatinine is a byproduct of muscle metabolism, and its levels in the blood indicate kidney function.
• 🚰 Oliguria, or reduced urine output, is a common symptom of AKI due to impaired kidney filtration.
• 🔍 AKI can be classified into three subtypes based on the location of the issue: pre-renal (before the kidneys), intra-renal (within the kidneys), and post-renal (after the kidneys).
• 🩸 Pre-renal AKI is often caused by reduced blood flow to the kidneys, due to factors like hypovolemia (low blood volume), heart failure, or systemic vasodilation.
• 🦠 Intra-renal AKI involves damage to kidney tissue, which can affect the glomerulus, tubules, or interstitial spaces, and may result from immune responses or toxins.
• 🚫 Post-renal AKI is caused by obstructions in the urinary tract, such as kidney stones, tumors, or an enlarged prostate.
• 📊 Diagnosing AKI involves measuring serum creatinine and blood urea nitrogen (BUN) levels, as well as assessing urine output to monitor kidney function.

Q & A

What is acute kidney injury (AKI)?

Acute kidney injury (AKI) is a clinical syndrome caused by the sudden dysfunction of the kidneys, leading to the accumulation of substances in the blood that are normally excreted by the kidneys, such as waste products like creatinine and urea.

How is AKI diagnosed clinically?

AKI is diagnosed by observing an elevated serum creatinine level, which indicates impaired kidney function, and a reduced urine output, a condition called oliguria.

What is serum creatinine and why is it important in AKI diagnosis?

Serum creatinine is a byproduct of muscle metabolism that is filtered out by the kidneys. Elevated levels of serum creatinine in the blood indicate reduced kidney function, making it a key marker for diagnosing AKI.

What are the three subcategories of AKI?

AKI is divided into three categories based on where the issue occurs: pre-renal (before the kidneys), intra-renal (within the kidneys), and post-renal (after the kidneys). Each subcategory has different causes.

What causes pre-renal AKI?

Pre-renal AKI is caused by reduced blood flow to the kidneys, leading to hypoperfusion. This can result from conditions like hypovolemia (low blood volume), heart failure, systemic vasodilation (as in sepsis or anaphylaxis), or afferent arteriole constriction.

How can hypovolemia lead to AKI?

Hypovolemia, or low blood volume, reduces the blood pressure and blood flow to the kidneys, impairing their ability to filter waste products, which can result in pre-renal AKI.

What are common causes of intra-renal AKI?

Intra-renal AKI occurs due to damage within the kidney itself, such as acute glomerulonephritis (inflammation of the glomerulus), acute interstitial nephritis (inflammation of the kidney tissue), or acute tubular necrosis (death of tubular cells due to ischemia).

How does post-renal AKI occur?

Post-renal AKI results from an obstruction in the urinary tract after the kidneys, such as a blockage in the ureters, bladder, or urethra, often caused by tumors, kidney stones, or prostatic hyperplasia.

What is oliguria and how is it related to AKI?

Oliguria refers to reduced urine output. It is a common clinical manifestation of AKI, indicating that the kidneys are not filtering and excreting waste products properly.

What is acute tubular necrosis (ATN) and how is it related to AKI?

Acute tubular necrosis (ATN) is a condition where the tubular cells of the kidney die due to ischemia (lack of oxygen). It often occurs as a result of prolonged pre-renal AKI that leads to insufficient blood flow to the kidney tissue.