A 38-year-old man presents to the emergency department with acute right flank pain radiating to the groin. He has nausea and is writhing in discomfort. Vital signs: BP 140/90 mmHg, HR 98/min, RR 20/min, temperature 37.2°C. Urinalysis shows haematuria (3+) and crystals. Non-contrast CT abdomen (gold standard) reveals a 6 mm radiopaque stone in the right ureter at the pelvic brim. What is the most appropriate immediate management?