What is the diagnosis and management for a patient with significant left flank pain, worsening with food, located in the low rib cage/kidney region, with no history of injury?

Differential Diagnosis and Management of Left Flank Pain Worsening with Food

Order CT abdomen and pelvis with IV contrast immediately to establish the diagnosis, as clinical examination alone has misdiagnosis rates of 34-68% and this imaging modality has 98% diagnostic accuracy. 1

Initial Diagnostic Approach

The location (low rib cage/kidney region) and pain worsening with food creates diagnostic uncertainty that warrants imaging rather than clinical diagnosis alone. 2

Key differential diagnoses to consider:

• Acute diverticulitis - Most common cause of left lower quadrant/flank pain in adults, though pain worsening with food is atypical 1
• Renal pathology (nephrolithiasis, pyelonephritis) - Classic location for kidney stones or infection, though pain worsening with food is unusual 3
• Musculoskeletal causes - Slipping rib syndrome or painful rib syndrome can present with pain in the low rib cage region that may be affected by movement/positioning during eating 4, 5
• Splenic pathology - Left-sided location warrants consideration 1

Critical Physical Examination Findings

Perform these specific maneuvers before imaging:

• Palpate the costal margin systematically - Reproduction of pain with firm palpation of the lower ribs suggests painful rib syndrome or slipping rib syndrome 4, 5
• Hooking maneuver - Hook fingers under the lower rib margin and pull anteriorly; reproduction of pain confirms slipping rib syndrome 5, 6
• Assess for peritoneal signs - Rebound tenderness, guarding, or rigidity indicate complicated intra-abdominal pathology requiring urgent intervention 1
• Costovertebral angle tenderness - Suggests renal pathology 3

Imaging Strategy

CT abdomen and pelvis with IV contrast is rated 8/9 (usually appropriate) by the American College of Radiology and should be ordered for most patients with this presentation. 1

Benefits of CT with IV contrast: 1

• Detects complications (abscess, perforation, obstruction)
• Identifies alternative diagnoses
• Guides treatment decisions
• Reduces hospital admissions by >50%

Alternative imaging if CT contraindicated: 2

• Ultrasound with graded compression (operator-dependent, limited in obesity)
• MRI if ultrasound inconclusive

Management Based on Findings

If Diverticulitis Confirmed on CT:

Uncomplicated diverticulitis (no abscess/perforation): 2, 1

• Immunocompetent patients: Conservative management WITHOUT antibiotics - bowel rest, hydration, pain control
• Immunocompromised or elderly patients: Antibiotics for maximum 7 days (Ertapenem 1g q24h or Eravacycline 1 mg/kg q12h) 1

Complicated diverticulitis: 1

• Small abscess (<4 cm): Antibiotics alone for 7 days
• Large abscess (≥4 cm): Percutaneous drainage PLUS antibiotics for 4 days
• Perforation with peritonitis: Emergency surgical consultation

If Renal Pathology Confirmed:

• Nephrolithiasis: Hydration, analgesia, urology referral for stones >5mm or persistent symptoms 3
• Pyelonephritis: Antibiotics, hydration, admission if severe 3

If Musculoskeletal (Positive Hooking Maneuver):

• Reassurance that diagnosis is benign 4, 5
• NSAIDs and avoiding aggravating postures 5, 6
• Physical therapy or osteopathic manipulation 5
• Intercostal nerve blocks for refractory cases 5
• Surgery only for debilitating, refractory pain 5

Red Flags Requiring Emergency Evaluation

Send immediately to emergency department if any of the following present: 1

• Fever
• Inability to pass gas or stool
• Severe abdominal tenderness with guarding
• Vomiting
• Bloody stools
• Signs of shock (hypotension, tachycardia, altered mental status)
• Progressively worsening pain over several days

Critical Pitfalls to Avoid

• Do not rely on clinical examination alone - The classic triad of left lower quadrant pain, fever, and leukocytosis is present in only 25% of diverticulitis cases 1
• Do not assume pain worsening with food excludes diverticulitis - While atypical, diverticulitis can present with varied symptoms 2
• Do not miss musculoskeletal causes - 33% of patients with painful rib syndrome are referred repeatedly for unnecessary investigations, including non-curative cholecystectomies 4
• Do not order routine colonoscopy after CT-confirmed uncomplicated diverticulitis - Only indicated for age-appropriate screening not yet performed, abnormal lymph nodes, or uncertain diagnosis 1

Laboratory Studies to Order

• Complete blood count with differential - Left shift >75% suggests bacterial infection 1
• C-reactive protein - CRP >50 mg/L supports diverticulitis; CRP >170 mg/L predicts severe disease with 87.5% sensitivity 1
• Urinalysis - To evaluate for renal pathology 3