Acute Kidney Injury Overview

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Questions and Answers

Which of the following causes are classified under glomerular causes of intrinsic AKI?

Renal artery occlusion

Urethral stricture

HUS and TTP (correct)

Bladder tumor

What is the most common cause of tubular intrinsic AKI?

Vascular occlusions

Drugs and toxins

Infiltrative diseases

Ischemia (correct)

Which of the following is NOT a characteristic sign of prerenal azotemia?

Decreased skin turgor

Tachycardia

Urinary obstruction (correct)

Dry mucous membranes

Which factor is NOT considered a risk factor for AKI outcomes?

Recent surgery Signup and view all the answers

Which of the following is considered an intrinsic cause of post-renal urinary outflow obstruction?

Blood clots Signup and view all the answers

Which disease modifier affects the outcomes of AKI?

Severity of acute kidney injury Signup and view all the answers

What is a crucial initial step in the management of AKI?

Confirm AKI status Signup and view all the answers

Which of the following indicates a urinary obstruction in the context of post-renal AKI?

Urethral stricture Signup and view all the answers

What defines acute kidney injury (AKI)?

An increase in serum creatinine concentration by ≥0.3 mg/dL within 48 hours Signup and view all the answers

Which of the following is NOT a limitation of serum creatinine in diagnosing AKI?

Specific for renal tubular lesions Signup and view all the answers

What is the criteria for classifying oliguria?

Urine output less than 400 mL/24 hours Signup and view all the answers

The global prevalence of acute kidney injury (AKI) is estimated to be:

72,100 per million population Signup and view all the answers

Which statement is true regarding the renal function required for kidney health?

Normal renal blood flow and functioning glomeruli and tubules are essential Signup and view all the answers

What percentage of general hospital admissions are related to acute kidney injury (AKI)?

5 - 10% Signup and view all the answers

Which factor increases the risk of acute kidney injury in patients with chronic kidney disease (CKD)?

Reduction of renal blood flow Signup and view all the answers

Anuria is defined as a urine output of:

Less than 100 mL/24 hours Signup and view all the answers

What is the primary distinction between acute kidney injury (AKI) and chronic renal impairment?

AKI can be reversible, while chronic renal impairment is irreversible. Signup and view all the answers

Which of the following is NOT a risk factor for acute kidney injury?

History of kidney stones Signup and view all the answers

In which stage of acute kidney injury is the urine output criterion < 0.5 ml/kg/h for a duration of ≥ 12 hours?

Stage 2 Signup and view all the answers

Which category does Acute Tubular Necrosis (ATN) fall under in the classification of AKI?

Intrinsic Signup and view all the answers

What is the urine output criterion for Stage 3 acute kidney injury?

< 0.3 ml/kg/h for ≥ 24 hours or Anuria for ≥ 12 hours Signup and view all the answers

Which of the following is considered a cause of acute kidney injury specifically in a hospital setting?

Nephrotoxic drugs Signup and view all the answers

In the classification of acute kidney injury, what is categorized under Intrinsic causes?

Acute Tubular Obstruction Signup and view all the answers

Which of the following increases the likelihood of developing acute kidney injury among older adults?

Age 65 years or over Signup and view all the answers

Study Notes

Acute Kidney Injury (AKI)

AKI is a rapid and usually reversible decline in kidney function.
It's evident by a rapid decline in glomerular filtration rate (GFR) over hours to days.
AKI can occur in patients with previously normal kidneys or those with chronic kidney disease.

Definition of AKI

AKI is a clinical syndrome defined by:
- An abrupt increase in serum creatinine by ≥0.3 mg/dL within 48 hours.
- A ≥1.5-fold increase in serum creatinine over the prior 7 days.
- Urine output <0.5 mL/kg/h for 6 hours.
Only one criterion needs to be met to diagnose AKI (per KDIGO).
Even small increases in creatinine are associated with increased mortality.

Limitations of Serum Creatinine

Serum creatinine levels are influenced by various factors:
- Extracellular volume depletion
- Decreased kidney blood flow
- Age
- Sex
- Body mass
- Nutritional status
Serum creatinine is not specific for AKI and requires differentiation from other causes, such as pre-renal or extra-renal issues.
Creatinine levels don't accurately reflect early kidney dysfunction; changes are not always sensitive or specific.

Definitions of Terminology

Azotemia: Accumulation of nitrogenous wastes (high BUN).
Uremia: Clinical manifestation of symptomatic renal failure.
Oliguria: Urine output <400 mL/24 hours.
Anuria: Urine output <100 mL/24 hours.

Incidence and Prevalence of AKI

Dialysis-dependent AKI incidence: 7200 per million population annually.
AKI accounts for 5-10% of general hospital admissions.
AKI accounts for 20-25% of cases in patients with sepsis and ~50% with septic shock.
Estimated global prevalence of AKI: 72,100 per million population (mostly community-acquired).

Kidney Function Requirements and Categorization

Kidneys require normal renal blood flow (prerenal).
Functioning glomeruli, tubules, and interstitium (intrinsic/renal).
Clear urinary outflow tract (postrenal).
Distinguishing AKI from chronic renal impairment is essential for patient management.

Staging of AKI

Staging is based on creatinine (Cr) and urine output (UO) criteria.
Grade 1 is an increase in Cr by ≥26.5 µmol/l within 48 hours OR 50-99% increase in Cr from baseline.
UO for grade 1 <0.5 ml/kg/h for 6-12h
Additional criteria for determining AKI grades:
- Grade 2 : 100-199% rise in Cr OR >200% rise in Cr OR Cr rising ≥ 354
- UO for grade 2 : <0.5 ml/kg/h for ≥12h
- Grade 3: Initiation of RRT OR decrease in eGFR to <35 ml/min/1.73 m²
- UO for grade 3 : < 0.3 ml/kg/h for ≥ 24h OR Anuria for ≥12h

Risk Factors for AKI

eGFR <60 ml/min/1.73m2 or a prior history of AKI
Diabetes
Heart failure, liver disease
Neurological or cognitive impairment
Nephrotoxic drug use
Iodinated contrast agents (within the past week)
Symptoms or history of urological obstruction
Sepsis
Age 65 years or older

Types of AKI

Prerenal: Reduced blood flow to the kidneys.
Intrinsic: Damage to the kidney tissue itself.
- Glomerular (e.g., GN)
- Tubular (e.g., ATN)
- Interstitial (e.g., AIN)
- Vascular (e.g., vascular occlusions)
Postrenal: Blockage of urine outflow from the kidneys.

Causes of AKI in Hospitals

Acute tubular necrosis (most common)
Acute interstitial nephritis
Obstruction

Pathogenesis of Prerenal Failure

Reduced cardiac output or hypovolemia.
Regional vasoconstriction limits blood flow to non-vital organs.
Further decrease in blood flow leads to acute kidney injury.

Pathophysiology of Ischemic Acute Renal Failure

Microvascular and tubular events contribute to ischemic AKI.
Ischemic events and inflammatory mediators cause renal cell damage leading to obstruction and backleak.

Phases of AKI

1. Initiation phase: Normal urine output until kidney damage occurs.
1. Oliguria or anuria phase: Reduced urine output (100-400 mL/day or less than 100mL/day).
1. Polyuria phase: Increased urine output after a period of oliguria or anuria. Serum creatinine and urea may not immediately improve.
1. Recovery phase: Urine output and serum creatinine normalize.

Renal/Intrinsic AKI

Glomerular : PSGN, SLE, AGN, ANCA-associated, anti-GBM disease, HSP, Cryoglobulinemia, TTP, HUS. (5-15%)
Tubular : ATN (Ischemia 50%, Toxins 30%) (70-80%)
Interstitial : AIN (Drug, NSAIDs, Antibiotics, Infiltrative, Granulomatous, Infection) (8-20%)
Vascular : Vascular occlusions (2%)

Postrenal AKI

Intrinsic Obstruction : Intra-luminal (Stone, Blood clots, Papillary necrosis), Intra-mural (Urethral stricture, BPH, Ca prostate, bladder tumor, radiation fibrosis).
Extrinsic Obstruction: Pelvic malignancies, prolapsed uterus, retroperitoneal fibrosis.

Diagnostic Evaluation

Careful history taking and physical exam.
Suspect prerenal azotemia in presence of vomiting, diarrhea, glycosuria, or use of diuretics, NSAIDs, ACE inhibitors
Look for hypotension or tachycardia for signs of hypovolemia or dehydration.
Evaluate for prostatic disease, nephrolithiasis, or paraaortic malignancy for suspected postrenal AKI.

Management Principals for AKI

Treat infection aggressively.
Minimize indwelling lines.
Remove bladder catheters, if anuric.
Manage bleeding tendency. (PPI, H2 antagonists, avoid aspirin)
Transfuse blood if needed.

Optimise Nutritional Support for AKI

Maintain adequate nutrition for patient survival.
Maintain protein intake around 1 g/kg/day.
High protein intake (>1.2 g/kg/day) can worsen azotemia.

RRT (Renal Replacement Therapy)

Initiate dialysis before complications arise.
Early RRT improves mortality and recovery rates.
Specialized treatments are available for critically ill patients.

Additional factors and outcomes of AKI

AKI is associated with various risk factors, including age, ethnicity, and genetic predisposition.
AKI can lead to chronic kidney disease and adverse cardiovascular outcomes.
Early intervention for AKI significantly improves patient outcomes.

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Description

This quiz focuses on Acute Kidney Injury (AKI), a rapid decline in kidney function that can be reversible. Learn about the criteria for diagnosing AKI, its limitations, and the factors influencing serum creatinine levels. Understand how AKI impacts patients and the significance of early detection.