Treatment of Heavy Flank Pain
Administer intramuscular diclofenac 75 mg immediately to achieve pain relief within 30 minutes, and if analgesia fails after 1 hour, admit the patient to hospital without further consultation. 1
Immediate Assessment and Triage
Timing is critical: Patients with acute flank pain require medical assessment within 30 minutes of presentation. 1 If you cannot see the patient within this timeframe, activate paramedical services to provide analgesia and transport to the emergency department. 1
Key diagnostic features to establish:
- Abrupt onset of severe unilateral flank pain radiating to groin or genitals indicates renal colic 1, 2
- Pain independent of body position suggests stone disease, while pain after prolonged static positioning suggests musculoskeletal origin 2
- Check vital signs immediately—shock or fever mandates immediate hospital admission 1, 2
Critical red flags requiring urgent evaluation:
- Age >60 years: consider leaking abdominal aortic aneurysm 1, 2
- Women with delayed menses: rule out ectopic pregnancy 1, 2
- Fever, chills, or signs of systemic infection 2
- Hemodynamic instability 2
Analgesia Protocol
First-line treatment: Intramuscular diclofenac 75 mg is the preferred route and agent. 1 Oral and rectal routes are unreliable, and intravenous administration is impractical in most settings. 1
Pain control goals:
- Achieve relief within 30 minutes of administration 1
- Maintain acceptable pain control for 6 hours or longer 1
Failure protocol: If analgesia fails after 1 hour, immediately admit the patient to hospital by phone without bringing them back for further consultation. 1 This is non-negotiable.
Diagnostic Workup
Urinalysis considerations:
- Hematuria (present in >80% of cases) supports the diagnosis 1
- However, absence of hematuria does NOT exclude stone disease—over 20% of confirmed stones have negative urinalysis 3
- Urinalysis may be impractical if patient cannot void on demand 1
Physical examination must include:
- Abdominal examination to establish maximal tenderness and exclude peritonitis 1
- Vital signs assessment (pulse, blood pressure, temperature) to exclude shock and infection 1
Imaging strategy:
- Non-contrast CT abdomen/pelvis is the gold standard with 98-100% sensitivity and specificity for stones 2, 4
- CT identifies extraurinary causes in approximately one-third of patients 2, 4
- Ultrasound is first-line for pregnant patients to avoid radiation 2
- Ultrasound has up to 100% sensitivity for hydronephrosis but may miss stones directly 2
Follow-Up and Monitoring
Immediate follow-up: Telephone the patient 1 hour after initial assessment and analgesia administration. 1, 2
Patient instructions:
- Maintain high fluid intake 1, 2
- Strain all urine through tea strainer or gauze to catch stones for analysis 1, 2
- Contact you immediately if pain worsens or new symptoms develop 1
Imaging timeline for outpatient management:
- Fast-track radiology within 7 days of symptom onset 1, 2
- Urgent urology appointment within 7 days if imaging shows stone requiring intervention 1, 2
Stone size determines management:
- Stones <5 mm typically pass spontaneously 2
- Stones >5 mm or causing complete obstruction may require endoscopic removal 2, 3
Common Pitfalls to Avoid
Do not assume all flank pain is renal: The positional nature of symptoms is key—musculoskeletal pain worsens with position changes, while renal colic is independent of position. 2
Do not delay imaging in young women: Consider gynecologic causes (ectopic pregnancy, ovarian torsion) that require urgent intervention. 2
Do not rely solely on hematuria: Clinical picture may have evolved, and absence of blood does not exclude significant pathology. 3
Do not miss alternative diagnoses: CT identifies non-urinary causes in one-third of patients, including right colonic diverticulitis, inflammatory bowel disease, renal cell carcinoma, and Page kidney (subcapsular hematoma causing hypertension). 2, 5, 6
Contrast-enhanced CT may obscure stones: Use non-contrast CT as initial study. 3