What is the ICD‑10 code for bilateral renal cortical hypodensities, with the largest lesion in the right upper pole measuring 3.7 cm?

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ICD-10 Code for Bilateral Renal Cortical Hypodensities

The appropriate ICD-10 code for bilateral renal cortical hypodensities measuring 3.7 cm is N28.1 (Cyst of kidney, acquired) if these represent simple cysts, or Q61.9 (Cystic kidney disease, unspecified) if polycystic kidney disease is suspected based on bilateral distribution.

Coding Approach Based on Clinical Context

The selection of the correct ICD-10 code depends on the underlying etiology of the bilateral renal cortical hypodensities:

For Simple Renal Cysts

  • N28.1 is the primary code when imaging findings are consistent with acquired simple renal cysts 1
  • This applies when hypodensities demonstrate typical cystic characteristics on CT (homogeneous, well-defined, fluid density <20 HU) 2
  • Simple cysts are sporadic and acquired, representing the most common cause of bilateral renal hypodensities 1

For Polycystic Kidney Disease

  • Q61.9 (Cystic kidney disease, unspecified) should be used when bilateral distribution suggests inherited cystic disease 1
  • More specific codes include:
    • Q61.2 for Autosomal Dominant Polycystic Kidney Disease (ADPKD) if family history or genetic testing confirms diagnosis 1
    • Q61.19 for Autosomal Recessive Polycystic Kidney Disease (ARPKD) if clinically indicated 1

For Complex or Indeterminate Lesions

  • D30.0 (Benign neoplasm of kidney) may be appropriate if the hypodensities show atypical features requiring further characterization 1
  • R93.4 (Abnormal findings on diagnostic imaging of urinary organs) can be used when the nature of the hypodensities remains unclear pending additional workup 1

Key Diagnostic Considerations

Imaging characteristics determine coding accuracy:

  • Hypodensities measuring <20 HU on unenhanced CT are consistent with simple cysts 1, 2
  • Lesions with soft tissue density (>30 HU) after contrast require different coding and further evaluation 2
  • Bilateral distribution with multiple lesions (>5 cysts) suggests polycystic disease rather than simple cysts 1

The 3.7 cm size is clinically significant:

  • This measurement exceeds the typical size threshold for simple observation 1
  • Larger cysts may require classification using Bosniak criteria if complex features are present 1

Common Coding Pitfalls

  • Avoid using R93.4 as a definitive diagnosis when specific cystic disease can be identified from imaging and clinical context 1
  • Do not use tumor codes (C64.x) without histologic confirmation, even for solid-appearing hypodensities 1
  • Distinguish between acquired cysts (N28.1) and congenital cystic disease (Q61.x) based on bilateral distribution pattern and number of lesions 1

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

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Professional Medical Disclaimer

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.

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