Differential Diagnosis for Flank Pain

The patient presents with flank pain, no costovertebral angle (CVA) tenderness, no dysuria or change in urination, no constitutional signs, no history of trauma, and a slight increase in pain when breathing in. Based on these symptoms, the following differential diagnoses are considered:

• Single Most Likely Diagnosis

  • Musculoskeletal strain: Given the absence of CVA tenderness, urinary symptoms, and the exacerbation of pain with breathing, a musculoskeletal strain (e.g., from overuse or minor injury not recalled as significant trauma) is a plausible explanation. The pain's characteristics and the lack of systemic symptoms support this diagnosis.

• Other Likely Diagnoses

  • Pulmonary issues (e.g., pneumonia, pleurisy): The increase in pain with deep breathing suggests a possible pulmonary origin, such as pneumonia or pleurisy, especially if the pain is referred to the flank area.
  • Gastrointestinal issues (e.g., pancreatitis, gastritis): Although less common, certain gastrointestinal conditions can cause flank pain, especially if the pain is referred from the upper abdominal area.

• Do Not Miss Diagnoses

  • Pulmonary embolism: Although less likely given the description, pulmonary embolism can cause sudden onset of flank or chest pain that worsens with breathing. It's a critical diagnosis not to miss due to its high mortality rate if untreated.
  • Aortic dissection: This is a life-threatening condition that can cause severe, tearing pain that may be referred to the flank area. The absence of trauma does not rule out this diagnosis, as it can occur spontaneously in susceptible individuals (e.g., those with hypertension or aortic aneurysm).
  • Kidney stone or pyelonephritis without typical urinary symptoms: Occasionally, kidney stones or pyelonephritis can present atypically without the usual symptoms of dysuria or changes in urination, making them important not to miss.

• Rare Diagnoses

  • Tumor (e.g., renal cell carcinoma): Although rare, tumors can cause flank pain. The absence of systemic symptoms (e.g., weight loss, fever) makes this less likely, but it remains a consideration, especially if other diagnoses are ruled out.
  • Inflammatory conditions (e.g., retroperitoneal fibrosis): These are rare conditions that can cause flank pain among other symptoms. They are less likely given the acute presentation but should be considered if common diagnoses are excluded.