What is the typical size of a Foley (French) catheter used in adults?

Typical Foley Catheter Size for Adults

In adults, the typical size of a Foley catheter is 14-16 French (Fr), with 16 Fr being the most commonly used standard size for routine catheterization. 1

Foley Catheter Size Selection Guidelines

Standard Adult Sizing

• 14-16 Fr is the standard size range for most adult urinary catheterization needs 1
• 12 Fr catheters may be used when minimizing urethral trauma is a priority 2
• 18 Fr catheters provide optimal flow characteristics with diminishing returns in flow rates seen with larger sizes 3

Special Considerations

• For urethral catheter drainage following bladder injury repair, standard sizing (14-16 Fr) is sufficient without need for suprapubic catheterization 1
• When performing retrograde urethrography, a 12 Fr Foley catheter is recommended for contrast administration 1
• For patients with artificial urinary sphincters, catheter size selection should be based on cuff size to prevent trauma:
  • 3.5-4.0 cm cuffs: Use 12-14 Fr catheters 2
  • 4.5 cm cuffs: Use 12-18 Fr catheters 2
  • 5.0 cm or larger cuffs: Can safely accommodate up to 22 Fr catheters 2

Clinical Considerations for Size Selection

Factors Affecting Size Choice

• Patient anatomy and condition (gender, age, urethral strictures) 1
• Purpose of catheterization (short vs. long-term) 1
• Risk of catheter blockage (presence of debris, hematuria) 4
• Duration of anticipated use 1

Risks of Inappropriate Sizing

• Oversized catheters (>18 Fr) increase risk of:
  • Urethral trauma and erosion 5
  • Bladder perforation, especially in neuropathic bladders 4
  • Patient discomfort 1
• Undersized catheters may lead to:
  • Inadequate drainage 3
  • Increased risk of bypassing (leakage around catheter) 4

Practical Recommendations

• For routine adult catheterization, start with a 16 Fr catheter 1
• For patients at risk of urethral trauma, use smaller sizes (12-14 Fr) 2
• For patients with hematuria or debris, consider 18 Fr, but avoid exceeding this size unless specifically indicated 3
• Beyond 18 Fr, there are diminishing returns in flow improvement (only 19% improvement when upsizing from 18 Fr to 20 Fr) 3
• The smallest appropriate catheter size should be selected to minimize trauma while maintaining adequate drainage 1

Pediatric Considerations

• Neonatal long lines down to 28G are available for specialized use 1
• Non-tunneled 4.5 Fr triple-lumen CVCs are available for neonates 1
• Tunneled Broviac catheters for long-term use are available down to 2.7 Fr 1

Remember that while larger catheters may provide better drainage, the risk of urethral trauma increases with catheter size. The goal is to select the smallest size that will adequately serve the clinical purpose.