Differential Diagnosis for Sharp Left Lower Back Pain/Flank Pain

• Single most likely diagnosis
  • Pulmonary embolism (PE) with referred pain: The patient is already on a heparin drip for a known PE, and sharp pain in the lower back or flank area can be a referred pain from a pulmonary issue, especially when it worsens with breathing.
• Other Likely diagnoses
  • Musculoskeletal strain: Given the patient's recent history and possible immobility due to being on a heparin drip, musculoskeletal strain could be a cause of the pain, especially if the pain is not exacerbated by palpation.
  • Nephrolithiasis (kidney stones): Although the pain from kidney stones typically is more severe and radiates, it could be considered, especially if the patient has a history of stones or if the pain is accompanied by other urinary symptoms.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Aortic dissection: This is a life-threatening condition that could present with sudden, severe back pain that may radiate to the flank area. It's crucial to consider this diagnosis, especially in patients with risk factors for aortic disease.
  • Pneumothorax: Given the patient's history of PE and the fact that they are on anticoagulation, a pneumothorax could be a complication that presents with sharp chest or back pain, worsened by breathing.
  • Hemorrhage (e.g., retroperitoneal hemorrhage): Anticoagulation therapy increases the risk of bleeding, and a retroperitoneal hemorrhage could present with flank or back pain.
• Rare diagnoses
  • Pancreatitis: Although less likely, pancreatitis could cause severe back pain, especially if it radiates to the back. However, it would typically be accompanied by other symptoms like abdominal pain and elevated pancreatic enzymes.
  • Spinal infection or osteomyelitis: Infection of the spine could cause back pain, but it would likely be accompanied by fever, elevated white blood cell count, and possibly neurological deficits.
  • Tumor: A tumor in the kidney, pancreas, or spine could cause back or flank pain, but this would be less likely without other symptoms or a known history of cancer.