Left-Side Abdominal & Back Pain: Causes, Red Flags & Diagnosis

Left Upper Quadrant / Flank Pain: Differential Diagnosis

Pain radiating from left abdomen to back suggests several distinct etiologies:

Common Causes

Gastrointestinal

• Diverticulitis: LLQ pain, fever, leukocytosis. CT confirms.
• Pancreatitis: Epigastric → back, nausea/vomiting, elevated lipase. Alcohol, gallstones, HTG.
• Splenic Flexure Syndrome: Trapped gas at colonic bend → distension, sharp pain. Benign.
• Gastric pathology: Ulcer, cancer (refer to back).

Renal/Urologic

• Nephrolithiasis: Colicky flank → groin, hematuria. CT stone protocol.
• Pyelonephritis: Flank pain, fever, pyuria, bacteriuria.

Gynecologic (Women)

• Ovarian cyst: Usually asymptomatic; rupture/torsion → acute pain.
• Ectopic pregnancy: +β-hCG, vaginal bleeding, unilateral pain. Emergency.
• Endometriosis: Cyclic pain, dyspareunia, infertility.

Vascular

• Abdominal Aortic Aneurysm (AAA): Pulsatile mass, back pain. Rupture = catastrophe. Screen men 65–75 who smoked.
• Renal artery stenosis / dissection.

Other

• Herpes Zoster (Shingles): Dermatomal pain → rash. Can precede rash by days.
• Musculoskeletal: Costochondritis, rib fracture, thoracic radiculopathy.

Red Flags → Immediate Evaluation

• Severe, tearing pain.
• Hemodynamic instability.
• Fever + flank pain.
• Pregnancy + pain/bleeding.
• Known AAA.

Diagnostic Approach

History, exam → targeted labs (CBC, BMP, lipase, UA, β-hCG) → imaging (US, CT) based on suspicion.