Causes and Management of Colic Pain
Primary Causes of Colic Pain
Colic pain is most commonly caused by urinary tract obstruction from kidney stones (renal colic), which triggers a surge in prostaglandin release leading to arterial vasodilation, increased vascular permeability, ureteric edema, and spasms. 1
Renal Colic Etiology
- Stone obstruction causes progressive passage along the ureter, producing characteristic referred and migratory pain patterns unique to this condition 1
- Over 80% of patients with acute renal colic test positive for hematuria 2
- Pain results from increased hydrostatic pressure in the urinary system above the obstruction 3
Other Causes to Consider
- In patients over 60 years: leaking abdominal aortic aneurysm must be excluded 2
- In women with delayed menses: ectopic pregnancy must be ruled out 2
- Infantile colic (in infants): proposed mechanisms include alterations in fecal microflora, cow's milk protein intolerance, gastrointestinal immaturity, increased serotonin secretion, and poor feeding technique 4
Diagnostic Approach
Clinical Presentation
- Abrupt onset of severe unilateral flank pain radiating into the groin or genitals is the hallmark diagnostic feature 2
- Assessment must occur within 30 minutes of presentation 2
Physical Examination
- Examine the abdomen to establish maximal tenderness site and exclude peritonitis 2
- Assess vital signs (pulse, blood pressure, temperature) to exclude shock and systemic infection 2
- Patients with shock or fever require immediate hospital admission 2
Diagnostic Testing
- Urinalysis supports diagnosis when hematuria is present (though not always practical as patients may be unable to void) 2
- All patients require imaging to identify the calculus and determine management 2
- Fast-track renal imaging should occur within 7 days of onset 2
- Spiral CT urography is superseding ultrasound and intravenous urography 2
Management Algorithm
Immediate Analgesia (First-Line)
Intramuscular diclofenac 75 mg is the preferred first-line treatment, providing rapid pain relief within 30 minutes. 2, 5
- The intramuscular route is preferred because oral and rectal administration are unreliable 2, 5
- Pain control should be maintained for at least 6 hours 2, 5
Alternative Analgesia
- For patients with NSAID contraindications or allergies: use an opiate combined with an antiemetic (morphine sulfate and cyclizine) 2, 5
Follow-Up Assessment
- Telephone follow-up at 1 hour after initial assessment to evaluate analgesic response 2, 5
- If pain is not alleviated within 60 minutes, arrange immediate hospital admission by telephone without requiring a second visit 2, 5
Hospital Admission Criteria
Immediate admission is required for:
- Failure of analgesia after 1 hour 2, 5
- Abrupt recurrence of severe pain 5, 6
- Shock or fever (risk of sepsis) 2, 6
- Patients over 60 years (to exclude AAA) 6
- Women with delayed menses (to exclude ectopic pregnancy) 6
Conservative Management
- Patients should maintain higher fluid intake 2, 5
- Attempt to sieve/strain urine to catch any passed stones 2, 5
- For analgesic refractory colic pain, extended observation (8-12 hours) under full parenteral analgesia may be appropriate in selected patients, with 41.6% successfully managed conservatively 7
Specialist Referral
- Urology outpatient assessment within 7-14 days if calculus is identified on imaging 2
- Recurrent or extensive nephrolithiasis requires urologist referral 6
- Patients with solitary kidney, bilateral obstructing stones, or stones >10mm require urologist referral 6
Critical Pitfalls to Avoid
- Never delay analgesia while waiting for diagnostic tests 5
- Avoid issuing limited quantities of oral or rectal analgesics for recurrent pain due to drug misuse potential 2, 5
- Do not assume all flank pain is renal colic—always exclude life-threatening alternatives (AAA, ectopic pregnancy) 2, 6
- Intensive hydration is not currently recommended for acute management 3
- History of previous renal colic increases risk of conservative management failure (OR 3.98) 7