SAQ 95 – Urology – renal colic and ureteric calculi
Model Answer
Question 1. renal colic and ureteric calculi.
a. Aims of imaging
- Confirm ureterolithiasis.
- Identify stone site.
- Identify stone number.
- Measure stone size and likelihood of spontaneous passage.
- Detect obstruction or complications such as hydronephrosis, hydroureter, perinephric stranding, or renal oedema.
- Determine whether the stone is visible on plain KUB for lower-radiation follow-up.
- Exclude important alternative diagnoses such as ruptured AAA, diverticulitis, or pyelonephritis.
b. Calculus types and features
| Type | Features |
|---|---|
| Calcium oxalate/phosphate | Most common stone type; usually radio-opaque; often idiopathic or associated with hypercalciuria; prevention includes high urine output and sometimes thiazides. |
| Struvite/triple phosphate | More common in women; associated with urease-splitting organisms and alkaline urine; may grow rapidly and form staghorn calculi. |
| Uric acid/urate | About 10% of stones; radiolucent on KUB; associated with urine pH below 6 and sometimes gravel passage; prevention may include allopurinol and high urine output. |
| Cystine | Rare; associated with autosomal recessive cystinuria; consider in young patients or recurrent stones; can cause renal impairment. |
c. Medical expulsive therapy
- Alpha-blockers such as tamsulosin may help selected distal 5-10 mm stones, although evidence is mixed.
- Calcium channel blockers or phosphodiesterase-5 inhibitors have been proposed to reduce ureteric spasm, but data are conflicting.
- Urinary alkalinisation may assist dissolution of uric acid stones.
- Medical therapy is adjunctive; ensure analgesia, safety-netting, follow-up, and urology involvement when indicated.
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