Examqo › Examqo library › Urology › Stones, obstruction and endourology · IMLE
Active stone treatment: SWL, URS and PCNL
The stone treatment is chosen by size, site, density and anatomy — an uncomplicated ureteral stone up to 10 mm gets a trial of medical expulsive therapy (MET), a renal stone up to 2 cm is treated with SWL or flexible ureteroscopy (RIRS), and a renal stone over 2 cm is treated with PCNL.
Why it matters in the exam
Exam questions are built on a case with a stone of a given size and site, and the correct answer is the first treatment the guideline recommends. A stone up to 5 mm usually passes on its own; a distal ureteral stone over 5 mm and up to 10 mm gets an alpha-blocker (tamsulosin 0.4 mg once daily) for up to 4 to 6 weeks, provided there is no infection, no uncontrolled pain and no loss of renal function. Ureteroscopy (URS) is the preferred active treatment for most ureteral stones, and SWL is an alternative for an upper ureteral stone up to 10 mm.
SWL success drops when stone density is above 1000 Hounsfield units, when the skin-to-stone distance is over 10 cm, with cystine stones, and with a lower-pole stone with a steep infundibulopelvic angle, an infundibulum narrower than 5 mm or a calyx longer than 10 mm. Contraindications to SWL: pregnancy, a bleeding disorder or anticoagulants that were not stopped, an untreated urinary infection, obstruction below the stone and an arterial aneurysm close to the stone. After SWL a "stone street" (Steinstrasse) may form — a column of fragments that blocks the ureter.
Uric acid stones are radiolucent and can be dissolved by alkalinising the urine with potassium citrate to a pH of 7.0 to 7.2. Before any active treatment a urine culture is mandatory and infection must be treated. In pregnancy — ultrasound first, and if drainage is needed: a JJ stent or a nephrostomy; ureteroscopy is possible, SWL is forbidden. In PCNL an access above the 12th rib carries a risk of pleural injury.
Key points
- Uncomplicated ureteral stone up to 10 mm — MET with an alpha-blocker.
- URS is the preferred active treatment for most ureteral stones.
- Kidney up to 2 cm — SWL or RIRS; over 2 cm — PCNL.
- Predicted SWL failure: over 1000 HU, skin-to-stone distance over 10 cm, cystine.
- Infection with obstruction — drain first, fragment later.
Summary table
| Situation | First treatment | Alternative | Note |
|---|---|---|---|
| Distal ureteral stone 5 to 10 mm, uncomplicated | MET with tamsulosin | URS | Follow-up for up to 4 to 6 weeks |
| Ureteral stone that needs removal | URS | SWL for an upper stone up to 10 mm | URS gives more stone-free results in one session |
| Renal stone up to 2 cm | SWL or RIRS | PCNL | Lower pole with unfavourable anatomy — RIRS or PCNL |
| Renal stone over 2 cm or staghorn | PCNL | Staged RIRS | Access through a posterior calyx |
| Uric acid stone | Dissolution with potassium citrate | URS | Urine pH 7.0 to 7.2 |
| Pregnancy | Drainage with a stent or nephrostomy | URS | SWL and standard CT are avoided |
A free exam question
מהם התנאים הדרושים ליצירת אבני חומצה אורית? (the question as examined, in Hebrew)
- א. שתן חומצי, היפראורצמיה, נפח שתן גבוה
- ב. שתן חומצי, היפראוריקוזוריה, נפח שתן נמוך
- ג. שתן בסיסי, היפראורצמיה, נפח שתן נמוך
- ד. שתן בסיסי, היפראוריקוזוריה, נפח שתן נמוך
In the full version for subscribers
- A simple algorithm
- Memory aid
- Exam traps
- 5 review cards
- Enough for IMLE
The full version is open to subscribers of: Urology, Medical licensing exam (IMLE), General surgery, Emergency medicine.
Subscriber? Read the full topic Plans and prices 25 free questions
Sources
- EAU Guidelines on Urolithiasis, 2025 edition — Disease management: active removal of renal and ureteral stones
- AUA/Endourological Society Guideline: Surgical Management of Stones, 2016 — Ureteral and renal stone index patients
- Campbell-Walsh-Wein Urology, 12th edition (2020) — Surgical Management of Upper Urinary Tract Calculi
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.