What is the best investigation and management approach for a patient presenting with renal colic, potentially with a history of kidney stones?

Investigation for Renal Colic

Non-contrast CT of the abdomen and pelvis (CT KUB) is 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

Initial Diagnostic Approach

First-Line Imaging: Non-Contrast CT

• 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 (appendicitis, cholecystitis, abdominal aortic aneurysm), and provides critical information about stone size, location, density (Hounsfield units), and degree of hydronephrosis 1, 2
• Low-dose CT protocols should be utilized when available, reducing radiation exposure from 14.5 mSv to approximately 2.1 mSv while maintaining diagnostic adequacy in 90% of cases 3

Alternative Imaging: Ultrasound with Color Doppler

• Ultrasound with color Doppler of kidneys and bladder should be considered as first-line imaging in specific populations: pregnant patients (appropriateness rating 8), young patients requiring multiple imaging studies, and those with contraindications to CT 1, 4, 5
• Ultrasound can identify hydronephrosis, measure resistive indices (elevated unilaterally in obstruction), assess ureteral jets (absent or asymmetric suggests obstruction), and detect stones with 50-68% sensitivity 1, 5
• Critical limitation: Moderate-to-severe hydronephrosis on ultrasound has 94.4% specificity for symptomatic stone but ultrasound significantly overestimates stone size in the 0-10mm range and has only 54% sensitivity for stone detection 1, 4

Adjunctive Imaging: KUB Radiography

• Plain radiography (KUB) combined with ultrasound improves stone detection from 50% to 68% for stones requiring urological intervention, but should not be used alone 1
• KUB has limited sensitivity (53-62%) and specificity (67-69%) for ureteral calculi, though 90% of stones are radio-opaque (calcium oxalate, calcium phosphate, struvite) 1

Clinical Assessment Priorities

Immediate Evaluation (Within 30 Minutes)

• Assess for urological emergencies requiring immediate intervention: fever with obstruction (infected obstructed kidney/pyonephrosis), signs of sepsis, or intractable pain unresponsive to analgesia 1, 4, 6
• Document vital signs (pulse, blood pressure, temperature) to exclude shock and systemic infection 1
• Perform urinalysis for hematuria (supports diagnosis but absence does not exclude stones—25% of ureteral injuries lack hematuria) 1, 7

High-Risk Populations Requiring Special Consideration

• Patients over 60 years: Consider leaking abdominal aortic aneurysm as alternative diagnosis 1
• Women with delayed menses: Consider ectopic pregnancy 1
• Patients with solitary kidney: Measure serum creatinine urgently as obstruction threatens remaining renal function 4

Pain Management

First-Line Analgesia

• Intramuscular diclofenac (NSAID) should be administered within 30 minutes of assessment to provide rapid pain relief (Grade A recommendation) 1
• NSAIDs are superior to opioids for renal colic pain and reduce smooth muscle spasm 1

Alternative Analgesia

• Ketorolac IV is an alternative NSAID but carries significant warnings: contraindicated in advanced renal impairment (elevated serum creatinine), increased bleeding risk (avoid perioperatively), and dose-dependent GI bleeding risk especially in elderly patients receiving >60mg/day 8
• For patients with NSAID contraindications (history of inflammatory bowel disease, coagulation disorders, aspirin triad/asthma with nasal polyps), consider narcotic analgesics instead 8

Failure of Initial Analgesia

• If pain persists after 1 hour despite adequate analgesia, immediately admit to hospital without further consultation in primary care 1

Follow-Up and Monitoring Strategy

Outpatient Management Criteria

• 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 1, 4
• Primary care physician should contact patient by phone 1 hour after initial assessment to confirm adequate pain control 1
• Advise patients to maintain high fluid intake and strain urine to capture passed stones for analysis 1, 9

Indications for Urgent Urological Intervention

• Immediate urology consultation is required for: evidence of urinary tract infection with obstruction (urological emergency requiring decompression within hours), intractable pain despite analgesia, moderate-to-severe hydronephrosis (97% sensitivity for requiring intervention), or stone >10mm unlikely to pass spontaneously 4, 6
• Medical expulsive therapy (alpha-blockers) should be offered for stones <10mm with controlled symptoms, but stones should pass within 28 days or intervention is indicated 4, 6
• Periodic imaging is necessary to monitor stone position and hydronephrosis during conservative management 4, 6

Common Pitfalls to Avoid

• Do not assume absence of hydronephrosis on ultrasound rules out significant stones—negative predictive value is only 65% 4
• Do not rely solely on ultrasound for treatment decisions when CT is available, as ultrasound has only 54% sensitivity and significantly overestimates stone size 4
• Do not delay drainage if infection is present with obstruction—this constitutes a urological emergency requiring percutaneous nephrostomy within hours, with patient survival of 92% with drainage versus 60% with medical therapy alone 7
• Do not assume all small stones will pass spontaneously—presence of moderate-to-severe hydronephrosis indicates higher risk of passage failure even with stones <5mm 1, 6