# URS Basics > Ureteroscopy basics for NEET-SS Urology: rigid and flexible URS, RIRS, holmium laser dusting, access sheaths, stent decisions and sepsis prevention. - Canonical URL: https://prepelephant.com/topics/neet-ss/urology/urs-basics - Exam / course: NEET-SS · Subject: Urology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "URS Basics", PrepElephant, https://prepelephant.com/topics/neet-ss/urology/urs-basics ## Direct answer Rigid ureteroscopes serve the distal and mid ureter; the flexible scope climbs into the proximal ureter and the intrarenal collecting system, which is the essence of retrograde intrarenal surgery (RIRS). Ureteroscopy delivers the highest stone-free rate of any modality for ureteric stones — around 90 per cent for distal stones under 10 mm, against roughly 70 per cent for ESWL — and the holmium laser fragments every composition, including the cystine and brushite stones that defeat shock waves. A sterile pre-operative urine culture is non-negotiable because post-ureteroscopy sepsis runs at 2 to 5 per cent, and a ureteric access sheath keeps irrigation flowing, vision clear and intrarenal pressure low — the practical defence against that sepsis. ## What you must remember - **Scope–site matching:** rigid semirigid ureteroscopes for distal and mid ureteric stones; flexible ureteroscopes for proximal ureteric and intrarenal stones (RIRS). - **Laser strategy:** dusting uses low energy at high frequency (roughly 0.2–0.5 J at 40–80 Hz) to powder the stone in situ; fragmentation uses higher energy at low frequency (1–1.5 J at 10–20 Hz) with basket retrieval. - **Access sheath benefits:** repeated scope passage without ureteric trauma, continuous irrigation outflow, better vision and lower intrarenal pressure — the last is what protects against pyelovenous backflow and sepsis. - **Culture discipline:** treat or cover any positive pre-operative culture; a colonised system instrumented under pressure is the classic source of post-operative urosepsis. - **Stent decisions:** stent for injury, residual fragments, obstruction or infection; uncomplicated complete clearance can go stentless, sparing the patient stent symptoms. - **Complication ladder:** mucosal abrasion and false passage are common and usually harmless; perforation needs stenting; avulsion is the catastrophic rarity that mandates open reconstruction. Unlike ESWL, laser ureteroscopy can proceed with caution even on anticoagulated patients. ## Walking one distal ureteric stone through theatre A 42-year-old has a 9 mm stone at the right vesicoureteric junction after a failed fortnight of expulsive therapy, urine culture sterile. Under anaesthesia, a safety guidewire is passed cystoscopically — the wire stays in for the whole case, because every rescue manoeuvre depends on it. The 9.5 Fr semirigid scope follows to the stone, and the laser is set for dusting at 0.4 J and 50 Hz, delivered only on a clearly visualised stone with minimal irrigation. Larger fragments are basketed; dust is left to pass. The ureter is inspected on withdrawal — a small mucosal tear without extravasation needs nothing more. Stent or not? Complete clearance, sterile urine, uncomplicated mucosa: stentless is defensible and spares him the frequency and flank twinge of a stent. Had there been perforation, residual fragments or infection, a DJ stent for one to two weeks would close the case. The post-operative script: expect pink urine for 48 hours, return for fever — the sentence that catches early sepsis. ## The traps that separate a pass from a rank The forgotten stent: a patient defaults on follow-up, returns months later, and the stent is encrusted — removal now needs laser fragmentation around it or even cystolitholapaxy; every department has a register story, and a viva answer that mentions a stent-removal register sounds like a consultant. The dusting-versus-retrieval reflex: hard, large or infection-prone stones favour dusting to shorten time; small stones in wide ureters basket out cleanly. Pressure and sepsis: the candidate who blames "operative time" alone for post-operative fever misses that irrigation pressure against an obstructed, colonised system is the mechanism. And scope economics, increasingly real in Indian departments: flexible ureteroscopes are expensive and fragile, so case selection and careful passage are resource decisions as much as surgical ones. ## Frequently asked questions ### Why is ureteroscopy preferred over ESWL for distal ureteric stones? Distal stones under 10 mm clear in about 90 per cent of ureteroscopic procedures versus roughly 70 per cent after ESWL, with immediate clearance and no dependence on fragment passage. ESWL remains valid for patients who prefer non-invasive treatment. ### What is RIRS? Retrograde intrarenal surgery — flexible ureteroscopy reaching the renal collecting system through the natural urethral and ureteric route, typically through an access sheath, with holmium laser dusting of intrarenal stones, most useful for stones under 2 cm. ### How do dusting and fragmentation laser settings differ? Dusting uses low energy at high frequency (about 0.2–0.5 J, 40–80 Hz) to reduce the stone to passable powder in situ; fragmentation uses high energy at low frequency (1–1.5 J, 10–20 Hz) to break the stone into basket-retrievable pieces. ### Is a stent mandatory after every ureteroscopy? No. Uncomplicated procedures with complete clearance and an uninjured ureter can be managed stentless. Stents are placed for perforation, significant residual burden, obstruction or infection. ### Can ureteroscopy be performed during pregnancy? Yes — it is the definitive treatment when a pregnant patient needs stone intervention, using ultrasound guidance or minimal shielded fluoroscopy, while ESWL is absolutely contraindicated in pregnancy. ### How is post-ureteroscopy sepsis prevented? Sterilise or cover the urine before surgery based on culture, minimise irrigation pressure and operative time, use an access sheath for outflow, and stent an obstructed or infected system rather than clearing it in one sitting.