Reasoning GP · Algorithm · 1-page summary
Renal colic in adults
For: adults with suspected renal or ureteric colic in primary care or urgent care. Not for: children (ultrasound first-line, specialist-led). Pregnancy goes straight to block 2.
Core rule: a stone with fever, rigors or systemic illness is an infected obstructed kidney until proven otherwise — it needs emergency drainage, not antibiotics alone, and fever may be absent. Exclude AAA and ectopic pregnancy before calling it colic.
0Stop — call 999 now — before any further work-up
- Infected obstruction: colic with fever, rigors, systemic illness, hypotension, tachycardia, confusion, oliguria/anuria or AKI (fever may be absent) → 999 for IV antibiotics and decompression.
- High-risk sepsis (NG253): systolic ≤90 (or >40 below baseline), HR >130, RR ≥25, SpO₂ <92% on air, new altered mental state, no urine for 18 hours, mottled or ashen skin, non-blanching rash → 999
- AAA mimic: sudden severe abdominal, back or flank pain with collapse or syncope, a pulsatile mass, known aneurysm or haemodynamic instability → 999. Do not delay for an ultrasound.
- Bilateral or solitary-kidney obstruction, or anuria, if unstable, septic or rapidly deteriorating → 999. Never manage these conservatively; do not delay transfer for more imaging.
1Triage — where does this patient go?
| Finding | Action |
|---|---|
| Block 0 feature | 999 |
| Stable obstruction | Solitary kidney, bilateral obstruction or AKI → Same-day urology |
| Not coping | Pain not controlled by home analgesia, persistent vomiting or cannot keep fluids down → Same-day A&E |
| Will not pass | Stone unlikely to pass or pain not tolerated → Urology: surgery ≤48 h (NG118) |
| Uncomplicated | Pain controlled, drinking, no fever, AKI or high-risk kidney → primary care with CT ≤24 h and review |
2Screen — one row is enough
- Pregnant with severe or persistent pain, obstruction, infection or renal impairment → Same-day obstetrics / urology. Ultrasound, not CT; no routine NSAIDs; tamsulosin only on specialist advice.
- Woman of childbearing age: urine pregnancy test before any imaging — ectopic can mimic colic exactly.
- Diabetes or immunosuppression with fever or systemic illness → Same-day hospital (emphysematous pyelonephritis).
- Cannot pass urine with haematuria (clot retention) → Same-day urology
- Visible haematuria persisting after stone passage, aged ≥45, unexplained → MSU, then Suspected cancer pathway (NG12); younger → urology.
3Assess
☐ Temperature, pulse, BP, RR, SpO₂ ☐ Aorta, loins, abdomen (peritonism), testes and hernial orifices ☐ Urine dip; MSU if infection suspected ☐ Pregnancy test ☐ U&E/eGFR and serum calcium in all; FBC, CRP if infection suspected
Imaging: low-dose non-contrast CT within 24 hours (NG118); ultrasound in pregnancy. Dipstick blood neither confirms nor excludes a stone. Not in primary care: contrast CT, IVU; plain KUB is not a sole test.
4Classify — only if the screen is negative
- Ureteric colic — sudden severe loin-to-groin pain, waxing and waning, cannot keep still, nausea → CT ≤24 h.
- Small distal ureteric stone — most likely to pass → primary care with review. Larger or proximal → urology, guided by the CT report.
- Pyelonephritis — fever-dominant, loin tenderness, no severe colic. Possible obstruction → block 0.
- Peritonism or localised RIF pain, patient lying still → not colic: think appendicitis or peritonitis.
- Uncertain — say so. Exclude AAA, ectopic and torsion; name who reviews and when.
5Treat today — doses: NICE/SPC, BNF, local formulary
- NSAID first-line, any route (e.g. diclofenac, max 150 mg/day), lowest dose, shortest time. Avoid in AKI or renal impairment, dehydration or vomiting, peptic ulcer or GI bleed, heart failure, IHD, PAD, cerebrovascular disease, uncontrolled hypertension, pregnancy.
- NSAID unsuitable or not enough → urgent care or hospital for IV paracetamol; opioid only if both fail. Oral paracetamol + codeine is not equivalent.
- Consider tamsulosin 400 micrograms daily (off-label) for a confirmed distal ureteric stone <10 mm. Not with infection, hypotension, or obstruction with renal impairment.
- Anti-emetic short-term (metoclopramide max 5 days, or ondansetron); cannot keep fluids down → assessment. Normal hydration only; strain the urine.
6Refer routinely — and prevent
- Not passed at the 4-week review, pain persists or renal function worsens → Urgent urology
- Recurrent or high-risk (bilateral, young-onset, family history, cystine, uric-acid or struvite, staghorn, solitary kidney, CKD) → urology or stone service for metabolic assessment.
- Stone retrieved → stone analysis. After recovery: 2.5–3 L of water a day; normal dietary calcium; less salt and animal protein.
7Never reassure by
- No fever — infected obstruction can be apyrexial at first.
- A dipstick with no blood.
- "Known stones" in an older patient with vascular risk — feel the aorta.
- Calling it colic in a woman before a pregnancy test.
- A well patient this morning — they can be septic by evening.
- Blaming persistent visible haematuria on the stone.
8Safety-net — say it, then document it
999 “Call 999 if you get a fever, shivering or shaking chills — with or without pain — before the stone has passed, if you collapse or feel faint, or if you cannot pass any urine.” Same day: “Contact us today if vomiting stops you keeping down painkillers or fluids, the pain is severe and not controlled, or you pass blood clots.”
Follow-up: review at 48–72 hours (pain, fluids, MSU result, U&E) and at 4 weeks (has the stone passed?). Strain the urine and bring the stone in.
✓Safe to leave primary care only if — all five, documented
No fever, rigors, sepsis, AAA or AKI
Not pregnant (test done); no solitary kidney or bilateral obstruction
Pain controlled; able to drink
CT within 24 h and 48–72 h review booked
Safety-net given; strainer advised
Summary of the full Reasoning GP renal colic algorithm, which holds the detail, stone types, prevention and evidence. Sources: NICE NG118, QS195, NG253, NG12 (updated April 2026); EAU Urolithiasis 2024; BAUS 2023; GIRFT/BAUS 2023; MHRA. Clinical reference — follow local emergency-transfer policies and check doses: NICE/SPC, BNF.