Investigation for Renal Colic

Initial Diagnostic Approach

The American College of Radiology recommends non-contrast CT of the abdomen and pelvis as the gold-standard investigation for suspected renal colic, providing superior sensitivity and specificity for stone detection, stone size, location, and degree of obstruction compared to all other modalities 1, 2
Non-contrast CT abdomen and pelvis should be performed as the primary investigation for patients presenting with acute flank pain radiating to the groin, suspected renal colic, and hematuria 1, 2
CT identifies stones with near-perfect accuracy, detects alternative diagnoses, and provides critical information about stone size, location, density, and degree of hydronephrosis 1, 2
Ultrasound with color Doppler of kidneys and bladder should be considered as first-line imaging in specific populations, such as pregnant patients, young patients requiring multiple imaging studies, and those with contraindications to CT 1, 3
Ultrasound can identify hydronephrosis, measure resistive indices, assess ureteral jets, and detect stones with 50-68% sensitivity 1, 2

The British Medical Journal recommends assessing for urological emergencies requiring immediate intervention, such as fever with obstruction, signs of sepsis, or intractable pain unresponsive to analgesia 4, 3, 5
Documenting vital signs to exclude shock and systemic infection is crucial 4
Performing urinalysis for hematuria supports diagnosis but absence does not exclude stones 4, 6

The British Medical Journal recommends intramuscular diclofenac as the first-line analgesia to provide rapid pain relief (Grade A recommendation) 4
NSAIDs are superior to opioids for renal colic pain and reduce smooth muscle spasm 4

Patients suitable for home management should receive fast-track imaging within 7 days of symptom onset, with urology outpatient assessment within 7-14 days if stone is confirmed 4, 3
Immediate urology consultation is required for evidence of urinary tract infection with obstruction, intractable pain despite analgesia, moderate-to-severe hydronephrosis, or stone >10mm unlikely to pass spontaneously 3, 5
Medical expulsive therapy should be offered for stones <10mm with controlled symptoms, but stones should pass within 28 days or intervention is indicated 3, 5

The American College of Radiology warns against assuming absence of hydronephrosis on ultrasound rules out significant stones, as negative predictive value is only 65% 3
The American College of Radiology also warns against relying solely on ultrasound for treatment decisions when CT is available, as ultrasound has only 54% sensitivity and significantly overestimates stone size 3
Delaying drainage if infection is present with obstruction constitutes a urological emergency requiring percutaneous nephrostomy within hours 6
Assuming all small stones will pass spontaneously is incorrect, as presence of moderate-to-severe hydronephrosis indicates higher risk of passage failure even with stones <5mm 1, 5