Differential Diagnosis for Left Sided Flank Pain

Single Most Likely Diagnosis

• Nephrolithiasis (Kidney Stones): This is often the most common cause of flank pain, especially if the pain is severe and radiates to the groin. The left side is slightly more common due to anatomical reasons.

Other Likely Diagnoses

• Pyelonephritis: An infection of the kidney, which can cause flank pain, fever, and other urinary symptoms.
• Musculoskeletal Strain: Overuse or injury to the muscles in the flank area can cause significant pain.
• Diverticulitis: Inflammation of a diverticulum in the colon, which can cause left-sided flank pain if the diverticulum is located in the sigmoid colon.

Do Not Miss Diagnoses

• Abdominal Aortic Aneurysm: Although less common, a ruptured AAA can present with severe flank pain and is a medical emergency.
• Pulmonary Embolism: Can cause referred pain to the flank area, especially if the embolism is large and affects the lower lobes of the lung.
• Ectopic Pregnancy: In women of childbearing age, ectopic pregnancy can cause severe flank pain and is a life-threatening condition if not promptly diagnosed.

Rare Diagnoses

• Pheochromocytoma: A rare tumor of the adrenal gland that can cause episodic flank pain, hypertension, and other symptoms.
• Renal Cell Carcinoma: A type of kidney cancer that can cause flank pain, although it is typically a more chronic and less severe pain.
• Splenic Infarct: Can cause severe left-sided flank pain due to the location of the spleen, often associated with other symptoms like fever and left upper quadrant abdominal pain.