EM SAQs · Renal colic and nephrolithiasis
Renal colic — analgesia, imaging and the infected obstructed system
An ACEM-style SAQ on uncomplicated renal colic management versus recognition of the infected obstructed kidney.
On this page
Study tools
Target exams
ACEMFRCEMABEM
Prompt
A 48-year-old man presents with sudden severe left flank pain radiating to the groin, writhing on the trolley, vomiting, afebrile, with microscopic haematuria. Outline (a) your differential with the features that distinguish the lethal mimics (3 marks), (b) first-line investigations and imaging choice with rationale (3 marks), (c) immediate ED analgesia and adjuncts with drug, dose and route (2 marks), and (d) the features that make this a urological emergency rather than dischargeable colic (2 marks).
Model answer
Reveal model answerShowHide
(a) Differential and lethal mimics
- Ureteric colic — sudden colicky loin-to-groin pain, writhing, nausea, ± haematuria.
- AAA leak/rupture (older, vasculopath) — may mimic colic; syncope, pulsatile mass, shock; examine the aorta.
- Testicular torsion — examine genitalia in every male; high-riding tender testis.
- Ectopic pregnancy — β-hCG in every reproductive-age woman.
- Also: appendicitis, pyelonephritis (fever-dominant, constant pain), mesenteric ischaemia, biliary colic, zoster.[1]
(b) Investigations and imaging
- UA (± culture), U&E/creatinine, FBC, CRP, lactate if unwell; β-hCG if applicable.
- Adult first-line: non-contrast CT KUB (extremely-high sensitivity and specificity) — size, site, hydronephrosis, and alternate causes of the pain.[3]
- Ultrasound first in pregnancy, children, recurrent known formers.
(c) Analgesia
- First-line diclofenac 75 mg IM (or 100 mg PR) — NSAID blocks PGE2-mediated spasm; Holdgate: NSAID ≥ opioid efficacy.[1][4]
- Refractory: morphine ~5 mg IV titrated (or fentanyl).
- Antiemetic: metoclopramide 10 mg IV or ondansetron 4 mg IV.
- Fluids only if dehydrated — forced diuresis does not pass stones.
(d) Urological emergency features
- Fever/sepsis with obstruction (pyonephrosis) — urgent stent or PCN + IV antibiotics; drainage is definitive.
- Anuria/solitary or bilateral obstructing stones; uncontrolled pain; significant AKI.
- These patients are not for simple discharge with a stone filter.[1]
References3ShowHide
- [1]Holdgate A, Pollock T. Systematic review of the relative efficacy of non-steroidal anti-inflammatory drugs and opioids for acute renal colic. BMJ (Clinical research ed.), 2004.PMID 15178585
- [3]Ali A, Akram F, Hussain S, et al. Non-Contrast Enhanced Multi-Slice CT-KUB In Renal Colic: Spectrum Of Abnormalities. Journal of Ayub Medical College, Abbottabad : JAMC, 2019.PMID 31535518
- [4]Yaowalaorng J, Kunthasook W, Lokeskrawee T, et al. Superior efficacy of intramuscular diclofenac compared to intravenous tramadol for acute renal colic in northern Thai patients: A randomised double-blind, sham-controlled trial. Emerg Med Australas, 2025.PMID 39763427