Endourology and Stone Disease
Core concepts
Master stone composition (calcium oxalate, calcium phosphate, uric acid, struvite, cystine), metabolic evaluation, and procedure selection by size and location. Ureteral stones <10 mm often pass; distal stones <10 mm may be observed with medical expulsive therapy. Ureteroscopy is first-line for many ureteral and renal stones; SWL for suitable renal stones <2 cm; PCNL for large (>2 cm) or complex renal stones. Understand staghorn management, obstruction with infection (emergent decompression), and prevention (hydration, thiazide for hypercalciuria, allopurinol for hyperuricosuria, alkalinization for uric acid and cystine).
Traps
A febrile obstructed stone is an emergency: decompress (stent or nephrostomy) and treat infection before definitive stone surgery. Do not give medical expulsive therapy for large or proximal stones. Struvite stones require complete removal because infection drives recurrence. Cystine stones need high fluid intake and alkalinization to pH >7.
Worked rule of thumb
Stone >10 mm or any obstructing stone with fever: intervene promptly. For a 6 mm distal ureteral stone with controlled pain, observe with NSAIDs and hydration, counsel on follow-up.
Exam strategy
Match procedure to size/location and always screen for infection and obstruction.