Detailed Exam Study Notes on Diagnostics & Kidney Function

Diagnostic Goals

  • Understand the purpose of lab tests and how they relate to specific diagnoses.
    • Focus on common conditions and associated diagnostic tests.
  • Example: For suspected urinary tract infection (UTI), a urinalysis is typically ordered.

Key Diagnostic Tests

  • Urinalysis: Commonly performed to assess for conditions like UTIs.
    • Look for components like pH, nitrites, leukocyte esterase, and presence of bacteria.
    • A high pH (e.g., above 8) may indicate a poor specimen quality, prompting a repeat sample.
    • Nitrites: Certain bacteria (like E. Coli) convert nitrates to nitrites.
    • Presence indicates potential infection; absence does not rule out an infection.
    • Leukocyte Esterase: Indicates the presence of white blood cells in urine, suggesting infection.
    • Consider epithelial cells; high counts may indicate non-sterile sampling.

Understanding Kidney Function

  • Kidney Function Tests
    • BUN (Blood Urea Nitrogen): Elevated levels indicate impaired kidney function or liver issues.
    • Creatinine: More closely reflects kidney function; may rise with muscle breakdown.
    • Normal BUN to creatinine ratio: 20:1.
    • A ratio >20:1 suggests dehydration, while <5 suggests potential liver disease.

Kidney Physiology

  • Kidneys regulate fluid balance, electrolytes, and waste elimination.
    • Filtration Rate: Normal production should exceed 30 mL/hour to avoid concentration of waste products.
    • Antidiuretic Hormone (ADH) plays a role in fluid retention, impacting blood pressure management.
  • Loss of kidney function may cause symptoms like hypertension and anemia due to impaired erythropoietin secretion.

Patient Considerations

  • Older adults: increased risk of decreased kidney function and sensitivity to ADH.
    • Lead to more frequent urination, increased risk for dehydration, and difficulties in mobility affecting bathroom access.
  • Common medications affecting kidney function: NSAIDs, certain antibiotics, chemotherapeutics.
    • Be aware of side effects like urinary retention or incontinence from drugs (e.g., anticholinergics).

Common Conditions Impacting the Urinary System

  • Incontinence: Often due to childbirth, hormonal changes in females, or prostate enlargement in males.
  • Kidney Stones: May cause hematuria and mimic UTI symptoms.
  • Urinary Retention: Check for obstructions (e.g., impacted stool, tumors).

Assessment Techniques

  • Inspection: Check for abnormalities around the meatus.
  • Palpation: Rarely palpate the kidneys; however, may detect bladder distention.
  • Percussion: CVA (costovertebral angle) tenderness can indicate kidney issues.
  • Auscultation: Listen for abnormalities in kidney perfusion or active bowel sounds.

Other Diagnostic Tools

  • Culture and Sensitivity (C&S): Determines bacterial presence and effective antibiotics.
    • Important for treatment decisions in symptomatic patients, even if counts are below 100,000.
  • Imaging Tests:
    • CT Scan: Most effective for diagnosing kidney stones.
    • Ultrasound: Useful for visualizing any obstructions or fluid retention.
  • Biopsy: Can assess for renal function issues or pathologies.

Patient Interview Components

  • Gather health history: kidney disease, BPH, infections or surgeries impacting the genitourinary system.
  • Medication list: Check for nephrotoxicity risks, including OTC medications.
  • Evaluate fluid intake, activity level, and other contributing health factors.
    • Consider the patient's understanding of their medications and health needs.