Is a 0.7 cm non-obstructing stone in the right renal lower calyx with a density of 700 Hounsfield Units (HU) indicated for Extracorporeal Shock Wave Lithotripsy (ESWL)?

Management of a 0.7 cm Non-Obstructing Lower Caliceal Renal Stone with 700 HU Density

For a 0.7 cm non-obstructing lower caliceal stone with a density of 700 HU, Extracorporeal Shock Wave Lithotripsy (ESWL) is an appropriate first-line treatment option. 1, 2

Treatment Decision Factors

Stone Characteristics Supporting ESWL:

• Size: At 0.7 cm (<10 mm), this stone falls within the size range where ESWL is recommended as a first-line option 1, 2
• Location: While lower pole location reduces ESWL efficacy compared to other locations, for stones ≤10 mm, ESWL remains a viable first-line option 1
• Density: At 700 HU, this stone has a density that is within the acceptable range for ESWL treatment 3
• Non-obstructing nature: The absence of obstruction is favorable for ESWL treatment 1

Evidence-Based Treatment Algorithm:

1. For lower pole stones ≤10 mm: Both ESWL and URS (Ureteroscopy) are recommended first-line options 1, 2

   • Stone-free rates for ESWL in this scenario are acceptable 1
   • The AUA/Endourological Society guidelines specifically support either ESWL or URS for symptomatic lower pole renal stones ≤10 mm (Strong Recommendation; Evidence Strength: Grade B) 1

2. Stone density considerations:

   • While 700 HU is moderately dense, it remains below the critical threshold of 970 HU identified by research as a cutoff above which ESWL success rates significantly decrease 3
   • For stones <970 HU, the stone-free rate with ESWL has been reported at 96% 3

Procedural Considerations for ESWL

• Pre-procedure preparation:

  • Routine stenting should not be performed before ESWL 1
  • Adequate imaging (typically non-contrast CT) should be available to guide treatment 1

• Post-procedure management:

  • Consider prescribing α-blockers after ESWL to facilitate passage of stone fragments 1, 2
  • Follow-up imaging is necessary to confirm stone clearance 2

Alternative Treatment Option

If ESWL is not preferred or fails, URS should be considered as the alternative first-line treatment:

• URS offers a higher stone-free rate in a single procedure compared to ESWL 1
• URS is less affected by stone composition and density 1
• URS may be particularly beneficial if the patient has unfavorable factors for ESWL success (e.g., steep infundibular-pelvic angle, long lower pole calyx) 2

Important Caveats

• ESWL limitations: Success rates for ESWL are influenced by:

  • Stone composition (cystine stones respond poorly to ESWL) 1
  • Patient factors such as obesity and skin-to-stone distance 1
  • Collecting system anatomy 1

• Treatment failure: If initial ESWL fails, an endoscopic approach (URS) is recommended 1

• Contraindications to consider: ESWL may be contraindicated in patients with:

  • Pregnancy
  • Uncontrolled coagulopathy
  • Uncontrolled urinary tract infection
  • Anatomical obstruction distal to the stone 1

In summary, for this 0.7 cm non-obstructing lower caliceal stone with 700 HU density, ESWL is an appropriate first-line treatment with good expected outcomes based on the stone's characteristics.