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This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
Key points
- Renal colic classically causes severe colicky flank pain radiating to groin, restlessness, nausea/vomiting, and microscopic or gross hematuria
- Fever, sepsis, anuria, solitary kidney, bilateral obstruction, pregnancy, uncontrolled pain/vomiting, or AKI makes stone disease urgent/high-risk
- Infected obstructing stone requires urgent decompression — antibiotics alone are not enough
- Non-contrast low-dose CT is most sensitive for stones; ultrasound is favoured first in pregnancy, children, and selected radiation-sparing pathways
- NSAIDs are first-line analgesia when safe; avoid them in significant renal impairment, dehydration, GI bleed risk, or late pregnancy
Approach to the Presentation
Flank pain can arise from kidney, ureter, vascular, gastrointestinal, gynaecological, musculoskeletal, or neurological disease. The presentation overlaps with the MCC acute abdominal pain objective because renal colic is a common lower/retroperitoneal abdominal pain mimic. In practice, the first decision is whether the patient is unstable, septic, pregnant, obstructed, has a solitary kidney, or has renal impairment. Those features determine urgent imaging and urology involvement.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Infected obstructing ureteric stone | must-not-miss | Flank colic with fever, rigors, pyuria, hypotension, AKI, or sepsis; may deteriorate rapidly | Urgent CT/ultrasound showing obstruction + infection markers; urology for decompression |
| Abdominal aortic aneurysm / dissection | must-not-miss | Older patient, vascular risk, severe back/flank/abdominal pain, syncope, hypotension, pulsatile mass | Bedside ultrasound if unstable; CTA if stable |
| Ectopic pregnancy / ovarian torsion | must-not-miss | Reproductive-age patient with pelvic/flank pain, missed period, bleeding, adnexal tenderness, vomiting | Pregnancy test + transvaginal ultrasound; urgent gynaecology |
| Acute pyelonephritis | must-not-miss | Fever, flank pain, CVA tenderness, dysuria/frequency, systemic symptoms | Urinalysis/culture; imaging if complicated or poor response |
| Uncomplicated ureteric stone | common | Colicky flank-to-groin pain, restlessness, nausea/vomiting, hematuria, afebrile | Low-dose non-contrast CT KUB; ultrasound in selected groups |
| Musculoskeletal back/flank pain | common | Reproducible with movement/palpation, no urinary symptoms, no hematuria, normal vitals | Clinical diagnosis after red flags excluded |
| Appendicitis/diverticulitis/cholecystitis | less common | Localized abdominal signs, anorexia, fever, bowel symptoms; retrocecal appendix can mimic flank pain | Abdominal exam, labs, CT/ultrasound based on location |
| Herpes zoster | less common | Dermatomal burning pain preceding vesicular rash | Clinical rash distribution |
| Renal infarction | rare | Acute severe flank pain, AF/embolism risk, elevated LDH, hematuria, minimal urinary symptoms | Contrast CT angiography; LDH supports diagnosis |
Red Flags & Key History
Symptoms
Fever, rigors, hypotension, confusion — infected obstruction or pyelonephritis
Anuria, solitary kidney, known bilateral stones, renal transplant, or rising creatinine
Syncope, hypotension, tearing back pain — AAA/dissection
Pregnancy possibility, pelvic pain, vaginal bleeding — ectopic pregnancy/ovarian pathology
Uncontrolled pain or vomiting — admission/urgent management consideration
Restlessness and inability to get comfortable — typical renal colic
Signs
CVA tenderness with fever
Peritonism or guarding
Pulsatile abdominal mass or shock
Testicular tenderness/swelling in males — referred pain or scrotal pathology
Normal abdominal exam with colicky pain and hematuria — supports uncomplicated stone
Approach to Investigation
First-line
Urinalysis ± microscopyHematuria supports stone but absence does not exclude it; leukocytes/nitrites suggest infection
Creatinine/eGFR, electrolytes, CBCAssess AKI, infection, and imaging/NSAID safety
Pregnancy test where relevantMandatory before radiation or assuming renal colic in reproductive-age patients
Urine cultureIf fever, pyuria, nitrites, pregnancy, recurrent infection, or complicated features
Second-line
Low-dose non-contrast CT KUBHighest sensitivity/specificity for ureteric stones; identifies size/location and alternative diagnoses
Renal ultrasoundHydronephrosis, obstruction, pregnancy/paediatric use, recurrent stone radiation-sparing strategy
CT angiography / abdominal imagingIf AAA, dissection, renal infarction, or surgical abdomen considered
Specialist
Urgent urologyInfected obstruction, solitary kidney, bilateral obstruction, anuria, AKI, uncontrolled symptoms, large proximal stone, or failure of conservative management
Stone analysis/metabolic evaluationRecurrent stones, bilateral stones, young age, nephrocalcinosis, solitary kidney, or high-risk occupations
Management Principles
Canadian Urological Association guideline: Management of ureteral calculi1
Uncomplicated renal colic
- Analgesia: NSAID first-line when safe; add opioid/antiemetic if needed
- Hydration to euvolaemia — do not force excessive IV fluids solely to push the stone
- Discharge only if afebrile, pain controlled, able to tolerate fluids, renal function safe, and follow-up arranged
2
Facilitate passage and follow-up
- Stone size and location guide likelihood of spontaneous passage
- Alpha-blocker medical expulsive therapy may be considered for selected distal ureteric stones
- Arrange follow-up imaging/assessment to confirm passage or resolution of obstruction
3
Infected or high-risk obstruction
- Immediate broad-spectrum antibiotics, cultures, IV fluids, sepsis care
- Urgent decompression with ureteric stent or percutaneous nephrostomy
- Definitive stone treatment is delayed until infection is controlled
Complications & Pitfalls
- Infected obstruction: The critical miss; antibiotics without drainage may fail.
- No hematuria trap: Some stones have no hematuria.
- Pregnancy trap: Always check pregnancy status before CT/radiation decisions.
- AAA mimic: Older patients with flank/back pain need vascular consideration.
- NSAID harm: NSAIDs are excellent for renal colic but unsafe in selected AKI, dehydration, GI bleed, anticoagulation, and late pregnancy settings.
MCCQE1 Exam Tips
- 1Renal colic patients are restless; peritonitis patients often lie still
- 2Fever + stone = infected obstruction; next best step is antibiotics plus urgent decompression
- 3Non-contrast CT KUB is the usual best test in non-pregnant adults when diagnosis is uncertain or risk is high
- 4Ultrasound first in pregnancy and often in children
- 5NSAIDs reduce ureteric smooth muscle spasm and are first-line if safe
- 6Do not force fluids to “flush” the stone; maintain euvolaemia
- 7Always exclude ectopic pregnancy in reproductive-age patients with flank/pelvic pain
Put your reading into practice
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