What is the role of normal saline (0.9% NaCl) in preserving a kidney biopsy specimen?

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Last updated: November 3, 2026 • View editorial policy

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Role of Normal Saline in Kidney Biopsy Specimen Handling

Normal saline serves multiple critical functions in kidney biopsy handling: it is used to wash specimens off the biopsy needle, examine tissue under microscopy for adequacy assessment, and transport specimens when moistened on gauze or filter paper—but must be used at room temperature, as ice-cold saline causes osmotic injury artifacts. 1

Specific Applications of Normal Saline

1. Specimen Removal and Washing

  • Normal saline can be used to gently wash the biopsy sample off the needle, avoiding mechanical trauma 1
  • This is preferable to using forceps, which cause crush artifacts
  • An 18-gauge needle or wooden stick (toothpick) should be used for gentle handling

2. Microscopic Examination for Adequacy

  • The tissue is placed on a glass slide with normal saline and examined with or without a coverslip to assess specimen adequacy using either a dissecting or standard light microscope 1
  • This allows identification of cortex (containing glomeruli) versus medulla before processing

3. Transport Medium

  • Specimens can be transported on physiologic saline-moistened gauze or filter paper carefully folded over the tissue when sending to pathology 1
  • Alternative transport options include tissue culture medium

Critical Pitfalls to Avoid

Temperature-Related Artifacts

  • Never place specimens in ice-cold saline—this causes significant osmotic injury and ultrastructural artifacts 1
  • Room temperature saline is essential to prevent cellular damage
  • Recent research confirms that saline can induce ultrastructural artifacts including podocyte swelling, mesangial protuberance, and mitochondrial swelling even at room temperature with prolonged exposure 2

Osmotic Injury Prevention

  • Do not place tissue on gauze soaked with water (hypotonic)—this causes osmotic injury 1
  • Do not place on dry gauze—this causes desiccation artifacts
  • Only physiologic (0.9%) saline should be used, not water

Handling Precautions

  • Avoid freezing the entire sample
  • Avoid pulling or stretching tissue during removal
  • Never use forceps directly on the specimen

Alternative Considerations

Recent research suggests that hypoelectrolytic isoosmotic solutions (HISI) may prevent saline-induced artifacts better than normal saline when specimens are macerated for extended periods 2. However, this is not yet incorporated into standard practice guidelines, and the 2004 Renal Pathology Society guidelines remain the authoritative reference for routine clinical practice.

Practical Algorithm for Saline Use

  1. At time of biopsy: Use room-temperature normal saline to wash specimen off needle if needed
  2. For adequacy assessment: Place tissue on glass slide with normal saline for microscopic examination
  3. For transport:
    • If immediate processing: Place on saline-moistened gauze/filter paper
    • If delayed processing: Consider tissue culture medium as alternative
    • Ensure room temperature throughout
  4. Avoid: Ice-cold saline, water-soaked gauze, dry gauze, freezing

The evidence consistently emphasizes that while normal saline is acceptable and widely used, proper temperature control and minimal exposure time are essential to prevent artifacts that could compromise diagnostic accuracy.

References

1
Guideline

practice guidelines for the renal biopsy.

Modern Pathology, 2004

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.