Is Extracorporeal Shock Wave Lithotripsy (ESWL) indicated for a 9mm obstructive stone at the proximal ureter/pelviureteric junction causing mild left hydronephrosis with a maximum attenuation value of approximately 1230 Hounsfield Units (HU)?

Management of a 9mm Proximal Ureteral Stone with ESWL

For a 9mm obstructive stone at the proximal ureter/pelviureteric junction causing mild left hydronephrosis with a maximum attenuation value of 1230 HU, ESWL is an appropriate first-line treatment option along with ureteroscopy (URS), though URS may offer higher stone-free rates in a single procedure.

Stone Characteristics and Treatment Options

The stone in question has several important characteristics that influence treatment decisions:

• Size: 9mm (falls within the ≤10mm category)
• Location: Proximal ureter/pelviureteric junction
• Density: 1230 HU (relatively high density)
• Effect: Causing mild left hydronephrosis (indicating obstruction)

According to the AUA/ES guidelines, for proximal ureteral stones ≤10mm, both SWL and URS are recommended as first-line treatment options 1. The 2007 AUA guideline specifically notes that SWL stone-free results are approximately 82% in the proximal ureter 1.

Comparative Effectiveness

When comparing the two main treatment options:

1. ESWL:

   • Advantages:
     • Less invasive
     • Can be performed with minimal anesthesia (IV sedation)
     • Better patient-reported quality of life measures
   • Disadvantages:
     • May require additional procedures (0.62 procedures per patient for proximal ureteral stones) 1
     • Lower stone-free rates for higher density stones (>1000 HU)

2. URS:

   • Advantages:
     • Higher single-procedure stone-free rates
     • Less affected by stone density
   • Disadvantages:
     • More invasive
     • Higher risk of complications
     • Typically requires general anesthesia

Stone Density Considerations

The stone's high density (1230 HU) is an important factor. Higher stone density can reduce the effectiveness of ESWL. The AUA/ES guidelines note that "the success of SWL is dependent on a variety of factors, including obesity, skin-to-stone distance, collecting system anatomy, stone composition and stone density/attenuation" 1. Patients selected for SWL should generally have favorable parameters to maximize stone-free rates.

Treatment Algorithm

1. If patient prefers minimal invasiveness and can accept possibility of needing a second procedure:

   • Proceed with ESWL
   • Consider using an escalating voltage treatment strategy (starting at lower voltage and gradually increasing) which has shown better stone comminution and potentially less renal injury 2
   • No routine pre-stenting is recommended 1
   • Consider α-blockers after ESWL to facilitate passage of stone fragments 3

2. If patient prioritizes single-procedure success or has unfavorable factors for ESWL:

   • Proceed with URS
   • Use laser lithotripsy for optimal fragmentation
   • Consider a safety wire during the procedure 1
   • Routine stenting is not necessary but may be considered based on procedural findings 1

Follow-up and Complications

• Follow-up imaging is essential to confirm stone clearance
• Monitor for complications such as:
  • Steinstrasse (stone street) formation
  • Renal hematoma (rare but serious complication)
  • Transient increase in creatinine levels

Important Caveats

• If the patient has a bleeding diathesis or is on anticoagulation therapy that cannot be discontinued, URS would be preferred over ESWL 3
• If initial ESWL fails, an endoscopic approach (URS) is recommended 3
• For patients with solitary kidneys or at high risk for complications, consider pre-stenting before ESWL 4

While both ESWL and URS are viable options for this 9mm proximal ureteral stone, the high density (1230 HU) may slightly favor URS for a higher single-procedure success rate, though ESWL remains an appropriate choice with good expected outcomes.