Lecture 5 11.3 Renal Disorders Study Guide

Renal Disorders Overview

• Introduction

  • Renal disorders discussed: Evaluation of kidney function, acute kidney injury (AKI), drug-induced kidney injury.

  • Emphasis on class participation through Turning Point questions (Session ID: AKI 2025).

• Importance of Kidney Function

  • Essential for waste elimination from body to prevent toxicity.

  • Kidney function integral to medication adjustment.

  • Guidelines for class identification: 3 identifiers required for patient verification.

• Key Laboratory Values

  • Memorization of lab values critical for NAPLEX and exams.

  • Variability in normal ranges across institutions acknowledged, e.g., Creatinine (0.6 to 1.2 mg/dL).

Evaluation of Kidney Function

• Markers for Kidney Function

  • Blood urea nitrogen (BUN): Indicates waste filtration; varies with hydration status.

  • Elevated in dehydration due to increased urea reabsorption.

  • Creatinine: Muscle breakdown product; typically the best available kidney function marker.

  • Normal levels indicate kidney function but depend on muscle mass.

  • Higher muscle mass correlates with higher serum creatinine levels.

  • No reabsorption occurs in normal conditions; some 10% comes from tubular secretion.

  • Cystatin C: Newer renal marker not affected by muscle mass.

  • Ideal as a combination marker with creatinine for more accurate evaluation.

• Estimating GFR (Glomerular Filtration Rate)

  • Normal GFR is ~120 mL/min; declines in renal insufficiency (

  • Correlation of GFR with blood markers: Increased BUN and serum creatinine with declining GFR.

  • Adjustments required in consideration of muscle mass, age, and nutritional status.

  • Introduction of newer equations like CKD-EPI without race as a factor.

    • Cockcroft-Gault equation still prevalent but requires serum creatinine at steady state.

• Weight Considerations for Equations

  • Ideal body weight used generally; actual weight adjustments based on clinical scenarios for precision.

  • Adjusted body weight calculated when actual weight exceeds ideal by 30% or more.

Acute Kidney Injury (AKI)

• Definition and Incidence

  • Sudden decrease in renal function leading to changes in creatinine, BUN, and urine output.

  • High incidence in hospitalized patients: 3-18.3% in non-critically ill; 30-60% in ICU settings.

• Symptoms and Diagnosis

  • Often asymptomatic until significant Deterioration; leading indicators:

  • Drop in urine output precedes rise in serum creatinine.

  • Diagnostic criteria for AKI include:

  • Increase in serum creatinine by 0.3 mg/dL within 48 hours,

    • or a 1.5-fold increase within 7 days,

    • or urine output drop.

• Phases of Renal Injury:

  • Pre-renal: Etiology before the kidneys resulting in decreased perfusion (dehydration, shock).

  • Common medications affecting blood flow: NSAIDs, ACE inhibitors, ARBs.

  • Intrinsic renal: Damage to renal tubules themselves; acute tubular necrosis common.

  • Post-renal: Obstruction of urinary flow from kidneys, e.g., stones.

• Markers for AKI

  • BUN/creatinine ratios >20:1 indicative of pre-renal causes.

  • Fluid resuscitation and medication management are key supportive therapies.

• Novel Biomarkers for Early Detection

  • Measurements such as Timp-2 and IGFBP7 can predict AKI risk, though not widely utilized in practice.

• Management Strategies:

  • Fluids as first-line management; monitor intake/output.

  • Adjust medication dosing based on kidney function status.

  • Avoid nephrotoxic medications where possible.

  • Renal replacement therapy (dialysis) as a last resort for severe cases.

Pharmacologic Considerations

• Drug Dosing Adjustments in AKI

  • Based on estimated GFR; medications given after dialysis may require readjustment.

• Nephrotoxic Agents to Avoid

  • Common nephrotoxic drugs include NSAIDs, certain antibiotics (e.g., aminoglycosides), ACE inhibitors, ARBs under particular conditions.

• Case Management in AKI

  • Insulin for glucose management in diabetic patients with AKI; targets for therapy established.

• Pharmacological Correction Strategies

  • Use of loop diuretics for fluid overload without use to prevent AKI directly.

• Patient Profiles in Management

  • Considerations differ significantly for populations including pediatrics and transplant patients.

Chronic Kidney Disease (CKD)

• Definition and Stages

  • CKD defined by abnormal kidney function/structure persisting for 3+ months.

  • Classified by cause (most common: diabetes and hypertension) and stages based on GFR (1 through 5).

  • Importance of albuminuria in assessing kidney damage.

• Clinical Presentation of CKD

  • Symptoms emerge in later stages; weight gain, edema, fatigue, anemia, itching, and alterations in urine output.

• Laboratory Evaluations

  • Elevated levels of creatinine, BUN, potassium; low GFR indicative of renal impairment.

• Management of CKD

  • Aims to slow progression of disease, typically through lifestyle modifications and pharmacologic interventions such as ACE inhibitors, ARBs, SGLT2 inhibitors, and tighter blood glucose control.

• Preventative Strategies

  • Urged lifestyle changes (diet, exercise, smoking cessation) alongside pharmacotherapy.

  • Specific targets established for blood pressure (<120 systolic) and HbA1c levels (targeting 7% for diabetics).

• Clinical Implications

  • Emphasis on prevention, recognition of renal decline early in course, and active monitoring of biomarkers.

• Summary Considerations for CKD

  • The integral role of managing co-morbid chronic conditions to prevent deterioration of kidney function.

  • Coordination with care across specialties and attentive patient education.