Urolithiasis
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Direct answer
Urolithiasis presents as renal colic — sudden severe loin-to-groin pain with nausea and vomiting, in a patient who writhes rather than lies still — often with haematuria. Non-contrast CT of the KUB region is the gold standard investigation, with ultrasound the usual first test in young patients and in pregnancy. Non-steroidal anti-inflammatory drugs such as diclofenac are the first-line analgesia, most stones under 5 mm pass spontaneously, and the definitive options are extracorporeal shock wave lithotripsy, ureteroscopy and percutaneous nephrolithotomy, the last reserved for large and staghorn calculi.
What you must remember
- Stone types: calcium oxalate, the commonest, is radio-opaque; struvite stones from urease-producing organisms such as Proteus grow into staghorns; uric acid stones are radiolucent on plain films but visible on CT; cystine stones affect children with cystinuria.
- The pain radiates from loin to groin as the stone descends, with strangury and referral to the tip of the external genitalia when the stone sits at the vesicoureteric junction.
- Non-contrast CT KUB is the gold standard; ultrasound is first in children, young women and pregnancy and screens for hydronephrosis.
- Non-steroidal anti-inflammatory drugs such as diclofenac give the best colic relief, superior or equal to opioids with fewer adverse effects; alpha-blocker expulsive therapy with tamsulosin is adjunctive for selected distal stones.
- Fever with an obstructed stone is an emergency — obstructed pyonephrosis — needing urgent stent or nephrostomy decompression with antibiotics.
- Treatment thresholds: observation for most stones under 5 mm; shock wave lithotripsy for selected renal stones roughly under 2 cm; ureteroscopy with laser for ureteric stones; percutaneous nephrolithotomy for staghorn and large stones, which must be treated even when silent.
- Recurrent, bilateral or childhood stone formers need metabolic evaluation including calcium, uric acid and parathyroid hormone; universal prevention is 2.5 to 3 litres of fluid daily with reduced salt and animal protein.
Common confusion
Renal colic is confused with other sudden loins: the colic patient is restless and rolls about, whereas the peritonitic or pancreatitis patient lies still, and ruptured aortic aneurysm in an older patient can mimic stone pain perfectly. Radiology confusion persists over uric acid stones — radiolucent on a plain film but fully visible on CT — and over the first analgesic answer: pethidine is the classic wrong option, diclofenac the right one. Finally, a staghorn calculus is never left alone regardless of symptoms.
Exam-focused takeaway
FMGE urolithiasis questions hinge on the sequence: writhing loin-to-groin pain with haematuria goes to non-contrast CT KUB; analgesia is a non-steroidal anti-inflammatory first; the stone under 5 mm is observed; the obstructed system with fever is drained urgently. Learn the stone-type pairs — struvite with infection, uric acid with radiolucency, cystine with children — and the modality pairs — lithotripsy for selected renal stones, ureteroscopy for the ureter, percutaneous access for staghorns. Hyperparathyroidism behind recurrent calcium stones is the classic endocrine coda.
Frequently asked questions
What is the gold standard investigation for urolithiasis?
Non-contrast CT of the kidneys, ureters and bladder, which sizes and locates every stone including radiolucent uric acid calculi.
Which analgesic is first-line for renal colic?
A non-steroidal anti-inflammatory drug such as diclofenac, superior or at least equivalent to opioids with fewer adverse effects.
Which stones grow into staghorn calculi?
Struvite infection stones formed in alkaline urine by urease-producing organisms such as Proteus, treated by percutaneous nephrolithotomy.
When is an obstructed stone an emergency?
When fever or sepsis accompanies it, indicating an infected obstructed system requiring urgent stent or nephrostomy decompression.
Which stones are radiolucent on plain X-ray?
Uric acid stones, though they are clearly seen on non-contrast CT; cystine stones are faintly opaque.
Which metabolic cause underlies recurrent calcium stones?
Primary hyperparathyroidism, screened by serum calcium and parathyroid hormone in recurrent and bilateral stone formers.