Differential Diagnosis for Right Flank Pain

Single Most Likely Diagnosis

• Musculoskeletal strain: Given the absence of dysuria, changes in urine, fever, and the non-colicky nature of the pain, musculoskeletal strain is a plausible cause. The pain being 3/10 and persistent for 5 days could be consistent with a strain or overuse injury in the flank area.

Other Likely Diagnoses

• Pyelonephritis or kidney infection without typical urinary symptoms: Although the patient denies dysuria or changes in urine, some kidney infections can present atypically, especially in certain populations like the elderly or those with diabetes. The absence of fever does not rule out this diagnosis entirely.
• Nephrolithiasis (kidney stones) with minimal symptoms: While the pain is described as not colicky, some patients with kidney stones may experience a more constant, dull pain rather than the classic severe, colicky pain. The lack of other urinary symptoms does not exclude this diagnosis.
• Costochondritis: Inflammation of the cartilage that connects the ribs to the breastbone can cause flank pain if the lower ribs are involved. This condition can cause persistent pain that worsens with movement or deep breathing.

Do Not Miss Diagnoses

• Appendicitis (especially if the appendix is retrocecal): Although the pain is on the right flank, appendicitis can sometimes present with pain in this area, especially if the appendix is located behind the cecum (retrocecal). Missing this diagnosis can lead to severe consequences, including perforation.
• Pulmonary embolism: While less common, a pulmonary embolism can cause flank pain if the embolism affects the upper parts of the lung. This is a life-threatening condition that requires immediate attention.
• AAA (Abdominal Aortic Aneurysm): An expanding or ruptured AAA can cause flank pain. This is a medical emergency that requires immediate intervention.

Rare Diagnoses

• Pheochromocytoma: A rare tumor of the adrenal gland that can cause episodic or persistent pain, among other symptoms like hypertension.
• Renal cell carcinoma: A type of kidney cancer that can cause flank pain, although it is typically associated with other symptoms like hematuria (blood in the urine).
• Epididymitis or orchitis: Inflammation of the epididymis or testis can cause pain that might radiate to the flank area, though these conditions are usually associated with scrotal pain and swelling.