Flank pain / renal colic
A streamlined, differential-led presentation for rapid clinical review.
Twenty-second review
- Flank pain may arise from ureteric obstruction and spasm, renal infection, musculoskeletal injury, or vascular and abdominal disease.
- Fever with obstruction, anuria, shock, pregnancy, pulsatile mass, single kidney, or uncontrolled pain and vomiting is high risk.
- Keep musculoskeletal pain or shingles in the differential; overlapping or concurrent illness remains possible.
- For flank pain / renal colic, trends and combinations of findings are more informative than one isolated vital sign.
Compare the clinical patterns
The repeated material is grouped inside each possibility. Open only the condition you need.
Infected obstructionTime-sensitive high-risk possibility
HPI
Clarify sudden onset; unilateral; radiation to groin.
Signs & symptoms
Fever, shock, vascular risk, or pregnancy-related symptoms.
Focused exam
Assess hydration, edema, lung sounds, bladder or flank tenderness, urine appearance, and dialysis access when relevant; Obtain a 12-lead ECG when electrolyte disturbance is plausible.
Brief pathophysiology
Infected obstruction may cause flank pain / renal colic through a time-sensitive process capable of rapid physiological deterioration.
What the trend may show
Uncomplicated renal colic often has normal physiology apart from pain-related sympathetic changes. Fever, hypotension, or persistent tachycardia raises concern for infected obstruction or another diagnosis.
Temperature (°C)
Usually normalFever with obstruction is a high-risk finding.
Heart rate (bpm)
May rise with painPersistent tachycardia after analgesia or rest warrants reassessment.
Blood pressure (mmHg)
May rise with painHypotension is not expected in uncomplicated renal colic.
Respiratory rate (breaths/min)
May rise with painPersistent tachypnea suggests systemic illness or another cause.
Front-load in the triage report
- Infected obstruction: Fever, shock, vascular risk, or pregnancy-related symptoms.
- Sudden onset.
- Unilateral?
AAATime-sensitive high-risk possibility
HPI
Clarify unilateral; radiation to groin; hematuria.
Signs & symptoms
Fever, shock, vascular risk, or pregnancy-related symptoms.
Focused exam
Obtain a 12-lead ECG when electrolyte disturbance is plausible; Assess flank and abdominal tenderness, percussion discomfort, urine symptoms, hydration, skin, vascular signs, and pregnancy possibility.
Brief pathophysiology
AAA may cause flank pain / renal colic through a time-sensitive process capable of rapid physiological deterioration.
What the trend may show
Aortic catastrophe has no single required vital pattern. Measure pressure and pulses carefully; shock or a new inter-arm difference raises concern but may be absent.
Blood pressure (mmHg)
May be high or lowHypertension may coexist; hypotension suggests rupture, tamponade, or malperfusion.
Heart rate (bpm)
VariablePain may raise rate, while medications or reflexes can blunt it.
Pulse pressure (mmHg)
Compare pulses / armsA calculated pulse pressure is less specific than pulse deficits and appropriate bilateral BP assessment.
MAP (mmHg)
Trend perfusionA falling MAP supports hemodynamic deterioration.
Front-load in the triage report
- AAA: Fever, shock, vascular risk, or pregnancy-related symptoms.
- Unilateral?
- Radiation to groin.
Ectopic pregnancyTime-sensitive high-risk possibility
HPI
Clarify radiation to groin; hematuria; prior stones/similar.
Signs & symptoms
Fever, shock, vascular risk, or pregnancy-related symptoms.
Focused exam
Obtain a 12-lead ECG when electrolyte disturbance is plausible; Assess flank and abdominal tenderness, percussion discomfort, urine symptoms, hydration, skin, vascular signs, and pregnancy possibility.
Brief pathophysiology
Ectopic pregnancy may cause flank pain / renal colic through a time-sensitive process capable of rapid physiological deterioration.
What the trend may show
Hemorrhage is a trend diagnosis: tachycardia and narrowing pulse pressure may precede hypotension. Age, pregnancy, medications, and pacing can blunt expected responses.
Heart rate (bpm)
Often risesTachycardia is a common compensatory response but may be absent.
Pulse pressure (mmHg)
May narrowNarrowing pulse pressure can reflect reduced stroke volume.
Blood pressure (mmHg)
May fall lateA normal pressure does not exclude significant compensated hemorrhage.
MAP (mmHg)
May fallA falling trend supports worsening perfusion; interpret with mental status and skin signs.
Front-load in the triage report
- Ectopic pregnancy: Fever, shock, vascular risk, or pregnancy-related symptoms.
- Radiation to groin.
- Hematuria.
Renal colicCommon presentation pattern
HPI
Clarify sudden onset; unilateral; radiation to groin.
Signs & symptoms
Colicky flank-to-groin pain, hematuria, and restlessness may support a ureteric stone.
Focused exam
Assess hydration, edema, lung sounds, bladder or flank tenderness, urine appearance, and dialysis access when relevant; Obtain a 12-lead ECG when electrolyte disturbance is plausible.
Brief pathophysiology
Renal colic may explain the presenting symptoms through a common clinical mechanism, while serial assessment checks for complications or an alternate cause.
What the trend may show
Uncomplicated renal colic often has normal physiology apart from pain-related sympathetic changes. Fever, hypotension, or persistent tachycardia raises concern for infected obstruction or another diagnosis.
Temperature (°C)
Usually normalFever with obstruction is a high-risk finding.
Heart rate (bpm)
May rise with painPersistent tachycardia after analgesia or rest warrants reassessment.
Blood pressure (mmHg)
May rise with painHypotension is not expected in uncomplicated renal colic.
Respiratory rate (breaths/min)
May rise with painPersistent tachypnea suggests systemic illness or another cause.
Front-load in the triage report
- Colicky flank-to-groin pain, hematuria, and restlessness may support a ureteric stone.
- Sudden onset.
- Unilateral?
Musculoskeletal painImportant alternative presentation
HPI
Clarify sudden onset; unilateral; radiation to groin.
Signs & symptoms
Movement-related pain or dermatomal skin change can mimic renal disease.
Focused exam
Assess hydration, edema, lung sounds, bladder or flank tenderness, urine appearance, and dialysis access when relevant; Obtain a 12-lead ECG when electrolyte disturbance is plausible.
Brief pathophysiology
Musculoskeletal pain can resemble flank pain / renal colic through overlapping symptoms or referred physiology despite a different primary mechanism.
What the trend may show
Isolated musculoskeletal injury often leaves central vital signs near baseline. Persistent abnormality should prompt reassessment for hemorrhage, thoracic injury, infection, or a medical cause.
Heart rate (bpm)
May rise with painTachycardia can reflect pain or distress; trend after treatment.
Blood pressure (mmHg)
May rise with painHypotension is not expected in an isolated minor injury.
Respiratory rate (breaths/min)
May rise with painPersistent tachypnea suggests more than a minor isolated injury.
Oxygen saturation (SpO₂)
Usually preservedDesaturation suggests thoracic injury or concurrent disease.
Front-load in the triage report
- Movement-related pain or dermatomal skin change can mimic renal disease.
- Sudden onset.
- Unilateral?
ShinglesImportant alternative presentation
HPI
Clarify unilateral; radiation to groin; hematuria.
Signs & symptoms
Movement-related pain or dermatomal skin change can mimic renal disease.
Focused exam
Obtain a 12-lead ECG when electrolyte disturbance is plausible; Assess flank and abdominal tenderness, percussion discomfort, urine symptoms, hydration, skin, vascular signs, and pregnancy possibility.
Brief pathophysiology
Shingles can resemble flank pain / renal colic through overlapping symptoms or referred physiology despite a different primary mechanism.
What the trend may show
Uncomplicated renal colic often has normal physiology apart from pain-related sympathetic changes. Fever, hypotension, or persistent tachycardia raises concern for infected obstruction or another diagnosis.
Temperature (°C)
Usually normalFever with obstruction is a high-risk finding.
Heart rate (bpm)
May rise with painPersistent tachycardia after analgesia or rest warrants reassessment.
Blood pressure (mmHg)
May rise with painHypotension is not expected in uncomplicated renal colic.
Respiratory rate (breaths/min)
May rise with painPersistent tachypnea suggests systemic illness or another cause.
Front-load in the triage report
- Movement-related pain or dermatomal skin change can mimic renal disease.
- Unilateral?
- Radiation to groin.
Findings that should escalate concern
- Fever with obstruction, anuria, shock, pregnancy, pulsatile mass, single kidney, or uncontrolled pain and vomiting is high risk.
- Infected obstruction, AAA, or ectopic pregnancy: Fever, shock, vascular risk, or pregnancy-related symptoms.
Medication recognition
Continue the clinical pathway
Clinical and academic sources
Curated clinical guidance and peer-reviewed evidence supporting this presentation. Current BCEHS guidance, medical direction, and local policy remain authoritative for practice.
BCEHS Handbook — specific CPGs
Supporting clinical and academic evidence
- CEDIS Presenting Complaint List updateCanadian Association of Emergency Physicians
Presenting-complaint terminology and categorization context. It does not establish a prehospital “top 100” ranking.
- Acute kidney injury: prevention, detection and managementNational Institute for Health and Care Excellence
Clinical guidance for recognizing renal risk, oliguria, obstruction, electrolyte complications, and deterioration.
- EAU Guidelines on Diagnosis and Conservative Management of UrolithiasisEuropean Urology · 2016
Renal-colic diagnosis, analgesia, obstructed infection, renal risk, and urgent urologic features.