Acute Kidney Injury: Definition and Diagnosis

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Questions and Answers

What is a characteristic change in kidney function indicative of Acute Kidney Injury (AKI)?

Increase in blood urea nitrogen

Decrease in urine specific gravity

Increase in kidney size

Increase in serum creatinine (correct)

Which of the following criteria indicates that a patient has developed AKI?

Serum creatinine rises by ≥ 20 µmol/L within 48 hours

Urine output < 0.5 ml/kg/hr for 5 consecutive hours

Serum creatinine rises ≥ 1.5 fold within 7 days (correct)

Serum creatinine remains unchanged for 6 hours

Which type of patients is most frequently affected by Acute Kidney Injury?

Patients with respiratory conditions

Healthy individuals visiting clinics

Outpatients with chronic kidney disease

Hospitalized individuals (correct)

What is a common cause of Acute Kidney Injury?

Acute tubular necrosis Signup and view all the answers

What percentage of patients admitted to critical care settings develops Acute Kidney Injury?

Up to 60% Signup and view all the answers

Which urine output criteria indicates a potential case of Acute Kidney Injury?

Urine output < 0.5 ml/kg/hr for ≥ 6 hours Signup and view all the answers

What is a long-term consequence associated with Acute Kidney Injury?

Increase in long-term morbidity and mortality Signup and view all the answers

How is Acute Kidney Injury primarily defined?

An acute decrease in kidney function or GFR Signup and view all the answers

What would indicate that a patient has acute kidney injury based on serum creatinine levels?

An increase in serum creatinine levels over days Signup and view all the answers

What common risk factor could lead to acute kidney injury after surgery?

Hypotension during surgery Signup and view all the answers

Which laboratory test is NOT typically used to assess for acute kidney injury?

Complete blood count Signup and view all the answers

What is the primary characteristic of prerenal acute kidney injury?

Decreased blood flow to the kidneys Signup and view all the answers

What urinary output would suggest acute kidney injury in a patient post-cardiac surgery?

Less than 0.5 ml/kg/hour Signup and view all the answers

Which symptom is NOT typically associated with acute kidney injury?

Excessive thirst Signup and view all the answers

What is an important sign of intra-renal acute kidney injury?

Direct injury to the nephron tissue Signup and view all the answers

During assessment of a patient at risk for AKI, which factor is least likely to be a risk?

Normal serum creatinine levels Signup and view all the answers

What is a significant disadvantage of dialysis?

Hypotension can exacerbate AKI Signup and view all the answers

Which condition is indicated for dialysis?

Intoxications Signup and view all the answers

Which factor is a common cause of prerenal acute kidney injury (AKI)?

Hypovolemia Signup and view all the answers

What is a characteristic of postrenal AKI?

Obstruction of urinary tract Signup and view all the answers

What diagnostic criterion indicates acute kidney injury (AKI) concerning serum creatinine?

Serum creatinine rises by ≥ 26 µmol/L within 7 days Signup and view all the answers

Which type of acute kidney injury is primarily driven by ischemia or toxic substances?

Intrinsic AKI Signup and view all the answers

What can be a long-term consequence of acute kidney injury (AKI)?

Chronic kidney disease (CKD) Signup and view all the answers

In which circumstance is renal recovery less likely?

Poor venous access during dialysis Signup and view all the answers

What is the primary mechanism by which Amphotericin B causes acute tubular necrosis?

Direct toxicity to cells in the distal nephron Signup and view all the answers

Which symptom is not typically associated with interstitial nephritis?

Proteinuria Signup and view all the answers

Which of the following is a critical management step for drug-induced interstitial nephritis?

Discontinue the offending drug Signup and view all the answers

What is a primary cause of renal tubular obstruction in drug-induced obstructive nephropathy?

Intratubular precipitation of drug crystals Signup and view all the answers

Which drug is known to precipitate kidney stones due to renal tubular obstruction?

Indinavir Signup and view all the answers

What urine finding is indicative of interstitial nephritis?

Presence of white cell casts Signup and view all the answers

Which risk factor is associated with drug-induced kidney stones?

Daily dose of the drug Signup and view all the answers

In the context of obstructive nephropathy, which patient condition increases risk?

Volume depletion Signup and view all the answers

What is one method to prevent drug-induced obstructive nephropathy?

Aggressive hydration Signup and view all the answers

Which mechanism contributes to drug-induced stones related to metabolic changes?

Change in fluid balance Signup and view all the answers

Which finding would suggest the presence of drug-induced obstructive nephropathy?

Presence of drug crystals in urine Signup and view all the answers

Which class of medications is commonly implicated in drug-induced kidney injury due to hypersensitivity reactions?

Antibiotics Signup and view all the answers

Which supportive therapy is recommended for the management of interstitial nephritis?

Volume derangement correction Signup and view all the answers

Which type of acute kidney injury is characterized by injury due to nephrotoxic drugs, like Amphotericin B and Aminoglycosides?

Intrarenal AKI Signup and view all the answers

What is the expected urine finding in a patient with prerenal acute kidney injury caused by ACE inhibitors?

Low urine sodium concentration Signup and view all the answers

Which of the following factors significantly increases the risk of drug-induced prerenal AKI when using ACE inhibitors?

Renal artery stenosis (bilateral) Signup and view all the answers

What is a common laboratory finding in a patient with acute tubular necrosis due to Aminoglycosides?

High urine sodium level Signup and view all the answers

What mechanism explains the kidney injury caused by Angiotensin Converting Enzyme inhibitors?

Decreased glomerular filtration rate Signup and view all the answers

During the management of aminoglycoside-induced acute kidney injury, what is the recommended action?

Discontinue the aminoglycoside Signup and view all the answers

What is the role of hemodialysis in the management of drug-induced kidney injury?

To eliminate the drug and support kidney function Signup and view all the answers

Which of the following medications is associated with chronic interstitial nephritis?

Lithium Signup and view all the answers

What can lead to a rise in serum creatinine after starting ACE inhibitors?

25-30% increase within 2 to 7 days Signup and view all the answers

What is the effect of NSAIDs on renal autoregulation?

They reduce prostaglandin E2 production Signup and view all the answers

Which electrolyte imbalance is most likely in patients experiencing acute interstitial nephritis due to drug usage?

Hyperkalemia Signup and view all the answers

What is a preventive strategy for drug-induced kidney injury?

Therapeutic drug monitoring Signup and view all the answers

What change occurs in urine specific gravity in prerenal AKI?

Increases to >1.030 Signup and view all the answers

What is true regarding drug-induced postrenal AKI?

It can result from obstructive uropathy caused by certain drugs Signup and view all the answers

Study Notes

Acute Kidney Injury (AKI)

A common diagnosis in hospitalized patients affecting 5-10% of hospitalized patients and up to 60% of critical care patients.
Significantly increases short and long-term morbidity and mortality rates.
Caused by a variety of factors, including disease processes and drugs.

AKI: Definition

Defined as an acute decrease in kidney function (GFR) over hours, days, or weeks.
Characterized by waste product accumulation and volume overload.

AKI Diagnostic Criteria

- Serum creatinine rises by ≥ 26 µmol/L within 48 hours.
- Serum creatinine rises ≥ 1.5 fold from baseline within 7 days.
- Urine output is < 0.5ml/kg/hr for ≥ 6 consecutive hours.

AKI Staging

Stage 1: Serum creatinine increase ≥ 26 μmol/L within 48 hours or urine output <0.5 ml/kg/hr for ≥ 6 hours.
Stage 2: Serum creatinine increase ≥ 50 μmol/L from baseline or urine output < 0.5 ml/kg/hr for ≥ 12 hours.
Stage 3: Serum creatinine increase ≥ 354 μmol/L or commencement of renal replacement therapy (RRT) regardless of stage.

AKI Risk Factors

Pre-existing CKD
Volume depletion
Nephrotoxic agents
Urinary tract obstruction

AKI Assessment

Past medical history, including renal disease-related conditions (hypertension, diabetes).
Medication history
Patient symptoms, such as altered urinary habits, sudden weight gain, and flank pain.

AKI Assessment: Signs

Edema
Coloured or foamy urine
Orthostatic hypotension
Hypertension

AKI Assessment: Laboratory Tests

Serum creatinine
Urea/BUN (2.9-7.1 mmol/L)

Types of AKI (Prerenal, Intrarenal, Postrenal)

Prerenal: Blood supply disruption to kidney.
Intrarenal (intrinsic): Damage to kidney nephrons and interstitium.
Postrenal: Obstruction in the collecting system (ureter, bladder, urethra).

Prerenal AKI

Characterized by decreased renal blood flow.
Caused by hypovolemia, heart failure, hypotension, and sepsis.

Intrarenal AKI

Characterized by direct damage to the kidney.
Includes acute tubular necrosis (ATN), acute interstitial nephritis (AIN), and glomerulonephritis.

Postrenal AKI

Characterized by obstruction in the urinary tract.
Caused by prostate hypertrophy, kidney stones, and bladder cancer.

Drug-Induced Kidney Injury (DIKI)

Contributing factor in 19-25% of severe AKI cases.
Higher prevalence in older adults (up to 66%).

DIKI: Mechanism

Prerenal: ACE inhibitors/ARBs, NSAIDs, calcineurin inhibitors.
Intrarenal: Amphotericin B, aminoglycosides, radiographic contrast dye.
Postrenal: Acyclovir, indinavir, sulfonamide antibiotics.

Angiotensin Converting Enzyme Inhibitors (ACEi) and Angiotensin Receptor Blockers (ARBs)

High-risk patients: Those with severe atherosclerotic disease, bilateral renal artery stenosis, acute/decompensated heart failure, severe CKD, and volume depletion.
Examples: ACEi (Ramipril, Lisinopril, Perindopril), ARBs (Telmisartan, irbesartan, valsartan).

ACEi/ARBs: Mechanisms

Prevent vasoconstriction of efferent arterioles, reducing glomerular hydrostatic pressure and leading to decreased GFR.

Aminoglycosides

Mechanism: Direct nephrotoxicity to the proximal tubules.
Urine findings: Muddy brown epithelial cell casts, free epithelial cells, high urine sodium (> 40 mmol/L), FeNa >3%.

Amphotericin B

Mechanism: Direct toxicity to cells in the distal nephron, leading to cell death and impairment of renal filtration and concentration.

Amphotericin B: Risk factors

Cumulative dose
Pre-existing kidney disease
Concomitant nephrotoxic drugs
Dehydration or volume depletion.

Acute Interstitial Nephritis (AIN)

Occurs in up to 3% of AKI cases.
Presentation: Fever, rash, pyuria/hematuria, oliguria, metabolic acidosis, hyperkalemia, salt wasting.
Mechanism: Hypersensitivity reaction causing lymphocytic infiltration of the interstitium.
Implicated drugs: Penicillins, lithium.

Obstructive Nephropathy (postrenal AKI)

Caused by problems in the ureters, bladder, and urethra.
Requires involvement of both kidneys.
Types: Renal tubular obstruction, extrarenal urinary tract obstruction, nephrolithiasis.

Obstructive Nephropathy: Mechanism

Renal tubular obstruction: Intratubular precipitation of drug crystals (e.g., acyclovir) or tissue degradation products (e.g., rhabdomyolysis with statins).
Extrarenal urinary tract obstruction: Males with BPH given anticholinergic drugs.
Nephrolithiasis: Precipitation of stone-forming components into ureters (e.g., Indinavir).

Drug-Induced Stones

Occur in 1-2% of all stones.
Risk factors: Daily dose, duration of treatment, urinary excretion of drug or metabolite, solubility of drug or metabolite, concentration peaks in urine, rate of elimination, morphology of crystals.
Common causes: Sulfonamides, cephalosporins, quinolones, furanes, primidone, methotrexate, guaifenisin, allopurinol, sulfasalazine, indinavir, nelfinavir, acyclovir, triamterene.

DIKI Summary

Drugs can contribute to all three types of AKI.
Focus on prevention: Identifying high-risk patients, avoiding drug use, and discontinuing drugs as soon as possible.
Treatment is primarily supportive.
Pharmacists play a crucial role in assessing patients at risk for DIKI both in hospital and community settings.

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Description

Test your knowledge on Acute Kidney Injury (AKI), a critical condition affecting many hospitalized patients. This quiz covers the definition, diagnostic criteria, and staging of AKI. Enhance your understanding of this significant health issue.