Urinary Stone Disease
Stones are among the commonest urologic problems — exceeded only by infections — and they recur, which makes stone disease as much about metabolic prevention as about removing the stone in front of you.
The big picture
Stones are among the commonest urologic problems — exceeded only by infections — and they recur, which makes stone disease as much about metabolic prevention as about removing the stone in front of you. The two questions that organise everything are: what is the stone made of (because each type has its own cause, radiographic behaviour, and prevention) and does this stone need treatment now or will it pass? Answer those and you can manage both the acute colic and the lifelong recurrence risk.
The framework: know the five stone types (calcium oxalate, calcium phosphate, struvite, uric acid, cystine) — each by its frequency, cause, radio-opacity, and prevention — then the acute decision (pass vs intervene) and the metabolic workup.
Mechanism pathway
Tap any step to see why it happens.
Ureter — course & three narrowings
The ureter — course & the three constrictions
The ureter is ~30 cm long and follows a smooth S-curve from the renal pelvis to the bladder. It has three natural narrowings — the classic sites where stones impact: ① the UPJ, ② where it crosses the iliac vessels, and ③ the ureterovesical junction (the narrowest).
Diagnostic algorithm
Each step answers one question. Tap to expand.
Board traps
Calcium oxalate is the most common stone; calcium stones are radio-opaque.
Struvite = infection stone (urease-producing bacteria, alkaline urine) = staghorn; cure needs complete removal.
Uric acid stones are radiolucent on plain film, low HU on CT, form in acid urine — and can be dissolved by alkalinisation.
Cystine stones are genetic (cystinuria), hexagonal crystals, recur frequently.
≤5 mm ≈ 40–50% pass; >6 mm much less — size guides whether to wait.
Calcium stones + nephrocalcinosis + hypercalcaemia → suspect hyperparathyroidism.
Obstruction + infection = emergency → drain (stent/nephrostomy).
Chemolysis works mainly for uric acid stones — alkalinise to urine pH ~6.5–7.0 (potassium citrate), monitored by dipstick; don't overshoot >7.0–7.5 (calcium phosphate risk).
Calcium and struvite stones don't dissolve with oral chemolysis.
Plain X-ray misses uric acid (radiolucent); CT sees nearly all stones and HU predicts composition (low = uric acid) and SWL success.
MET for distal stones <10 mm (best 5–10 mm), for ~4–6 weeks, then intervene — the limit protects the kidney from irreversible obstructive damage; infection/pain/falling function ends the trial early.
Comprehensive 24-hour workup is for high-risk/recurrent stone formers — a single random-diet collection suffices; recheck after treatment.