AKT · Renal & urology/Infection & obstruction

Urinary tract calculi

Stone formation in the renal tract (calcium oxalate commonest; also urate, struvite, cystine)

Overview

Stones in the renal tract causing renal/ureteric colic — sudden severe loin-to-groin pain with a restless patient unable to get comfortable. Most are calcium oxalate. Non-contrast CT KUB is the diagnostic gold standard. Management depends on stone size and site (NICE NG118), and the emergency is an obstructed, infected system requiring decompression.

Recognise

Sudden severe colicky loin-to-groin pain, unable to lie still (vs peritonitis where they lie still), nausea/vomiting; visible or non-visible haematuria
CT KUB: the stone and any hydronephrosis; staghorn calculi (struvite, Proteus/urease-producers) fill the collecting system
Stone types: calcium oxalate (commonest, radio-opaque), urate (radiolucent — gout/high cell turnover), struvite (infection), cystine (hereditary)

Red flags

Obstruction + infection (fever/systemic upset) → EMERGENCY decompression (nephrostomy/stent) + antibiotics — the can't-miss
Bilateral obstructing stones or a single functioning kidney obstructed → AKI/anuria → urgent urology

Differentials & how to tell them apart

Pyelonephritisfever + loin pain + systemic upset; but exclude an obstructing infected stone

Ruptured AAAolder arteriopath with 'renal colic' — never miss a leaking AAA; cross-ref cardiovascular

Biliary colic / appendicitis / gynae (ectopic)site/examination/pregnancy test differ

Staghorn calculus filling the renal collecting system (abdominal X-ray)
Nevit Dilmen / CC BY-SA 3.0 — Wikimedia Commons

Investigations

Non-contrast CT KUB (gold standard — stone, size, site, hydronephrosis); urine dip (haematuria, infection), MSU; U&Es (renal function), calcium/urate; stone analysis; ultrasound (pregnancy/children to avoid radiation).

Management

NSAID analgesia; <5 mm pass spontaneously / alpha-blocker; size/site-based removal (SWL/URS/PCNL)

1Confirm with CT KUB and give an NSAID for analgesia. Small stones (<5 mm) usually pass — watchful waiting ± an alpha-blocker (medical expulsive therapy) for distal ureteric stones <10 mm.Gate: An obstructed AND infected system (fever/systemic upset) → EMERGENCY decompression (nephrostomy/stent) + antibiotics; and never accept 'renal colic' in an older arteriopath without excluding a ruptured AAA.
2Active removal by size/site (NG118): ureteric 20 mm or staghorn → PCNL. Investigate/prevent recurrence (hydration, stone analysis, metabolic work-up).

Analgesia: NSAID (e.g. IM/PR diclofenac) first-line ± antiemetic — NSAID is first-line for renal colic (opioid if contraindicated)

Watchful waiting / medical expulsive therapy (alpha-blocker, e.g. tamsulosin) — stones <5 mm usually pass spontaneously; alpha-blocker aids passage of distal ureteric stones <10 mm

Active removal by size/site (NG118) — ureteric 20 mm / staghorn → percutaneous nephrolithotomy (PCNL)

Emergency decompression for obstructed + infected system — nephrostomy or stent + antibiotics — before definitive stone treatment

Key points

Loin-to-groin colic + restless patient + haematuria = stone → CT KUB, NSAID analgesia. <5 mm pass; alpha-blocker for distal ureteric <10 mm; SWL/URS/PCNL by size. EMERGENCY = obstructed + infected (pyonephrosis) → decompress + antibiotics. And exclude a ruptured AAA in older patients.

Monitor & prognosis

Pain/stone passage, renal function, infection; recurrence prevention.

Most small stones pass; recurrence is common — prevention matters.

Source: NICE NG118 (renal & ureteric stones)