What is the appropriate evaluation and management for an adult patient with no significant medical history presenting with right flank pain?

Right Flank Pain: Evaluation and Management

Immediate Imaging Recommendation

Non-contrast CT of the abdomen and pelvis is the imaging study of choice for evaluating right flank pain in adults, with 98-100% sensitivity and specificity for detecting urinary stones and identifying alternative diagnoses in approximately one-third of patients. 1, 2, 3

Initial Clinical Assessment

Focus your history and physical examination on these specific discriminating features:

• Pain characteristics: Sudden onset, colicky wave-like pain independent of body position radiating to groin/genitals suggests renal colic, while pain worsened by movement or position suggests musculoskeletal origin 1, 4
• Associated symptoms: Nausea (71% sensitive for stones), hematuria (even microscopic shifts probability toward stone disease), fever/chills (suggests infection requiring urgent intervention) 1, 5
• Prior stone history: 59% sensitive and 66% specific for current stone disease 5
• Vital signs: Check for hemodynamic instability, fever, or signs of sepsis which mandate immediate hospital admission 1
• Urinalysis: Perform immediately, but recognize that over 20% of confirmed stones have negative urinalysis 1

Diagnostic Imaging Strategy

First-Line Imaging

Order non-contrast CT abdomen/pelvis immediately for definitive diagnosis. This modality:

• Detects stones regardless of size, location, or composition with 98-100% accuracy 1, 2
• Identifies extraurinary causes (right colonic diverticulitis, appendicitis, bowel obstruction) in one-third of patients 1, 4
• Requires no contrast agent and takes only 5 minutes to perform 2
• Provides critical management information: stones <5mm typically pass spontaneously, while larger stones or complete obstruction require urologic intervention 1

Alternative Imaging Considerations

• Ultrasound: Use as first-line only if radiation exposure is a concern (pregnancy, young patients with recurrent presentations). Sensitivity reaches 96% when combining pyeloureteral dilatation, direct stone visualization, and absent ureteral ejaculation 1, 2. However, absence of hydronephrosis makes stones >5mm less likely 1
• Plain radiography (KUB): Inadequate—only 72% sensitive for large stones and 29% for any size stone 1

Immediate Management

Pain Control

• Administer rapid analgesia within 30 minutes: Diclofenac intramuscular injection is preferred 1
• Reassess pain within 1 hour: Failure of analgesia mandates immediate hospital admission 1

Red Flags Requiring Urgent Hospital Admission

Admit immediately if any of the following are present:

• Fever, chills, or signs of systemic infection (suggests obstructive pyelonephritis/pyonephrosis requiring emergent decompression) 6, 1
• Hemodynamic instability or shock 1
• Inability to urinate or decreased urine output 1
• Failure of pain control after 1 hour 1
• Solitary kidney with obstruction 6

Disposition Based on Imaging Results

If Stone Disease Confirmed

Stones <5mm:

• Discharge with outpatient management 1
• Instruct high fluid intake and strain urine to catch stones 1
• Telephone follow-up 1 hour after discharge 1
• Fast-track radiology follow-up within 7 days 1
• Urgent urology appointment within 7-14 days if stone requires intervention 1

Stones >5mm or complete obstruction:

• Urgent urology referral for consideration of intervention (retrograde stenting or percutaneous nephrostomy) 6, 1

If Infected Hydronephrosis/Pyonephrosis

Emergent urinary decompression is lifesaving and takes priority over antibiotics alone 6. Options include:

• Percutaneous nephrostomy (PCN): 92% survival rate versus 60% with medical therapy alone 6
• Retrograde ureteral stenting: Alternative first-line option depending on local expertise 6
• Administer preprocedural antibiotics (third-generation cephalosporin preferred over fluoroquinolones) 6

If Non-Urinary Pathology Identified

Direct treatment at specific diagnosis:

• Right colonic diverticulitis: 8% of right flank pain cases 6, 1
• Appendicitis: Consider especially with fever and leukocytosis 4
• Bowel obstruction: 3% of cases 6
• Gynecologic causes in women: Benign adnexal masses, pelvic congestion syndrome, ectopic pregnancy (check pregnancy test in all women of childbearing age) 1, 4

When non-appendiceal CT diagnosis is made, 41% require hospitalization and 22% undergo surgical/interventional procedures 1.

Critical Pitfalls to Avoid

• Do not assume negative urinalysis excludes stone disease—over 20% of confirmed stones have no hematuria 1
• Do not miss ectopic pregnancy in women with delayed menses—always check pregnancy test 1
• Do not delay imaging in young females—consider gynecologic causes requiring urgent intervention 1
• Do not assume all flank pain is kidney-related—positional nature distinguishes musculoskeletal from renal causes 1
• Do not treat infected obstruction with antibiotics alone—decompression is essential and lifesaving 6