Differential Diagnosis for Mid Back Pain with Deep Breathing

The patient presents with mid back pain that worsens with deep breathing, which could be indicative of several conditions. Given the patient's history and recent test findings, the differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis
  • Musculoskeletal strain or costochondritis: The patient's recent 9-hour car ride could have led to musculoskeletal strain, and the pain with deep breathing could be related to costochondritis, especially given the lack of relief with ibuprofen and the absence of significant findings on lung and mediastinum imaging.
• Other Likely Diagnoses
  • Pulmonary embolism (less likely given the normal mediastinum and hila, and the absence of pleural effusion or pneumothorax, but still a consideration): Although the lungs appear mostly normal, the presence of a small pulmonary nodule and the patient's symptoms could raise suspicion for a pulmonary embolism, especially if there are other risk factors not mentioned.
  • Intercostal muscle strain: Given the patient's history of a long car ride, strain on the intercostal muscles could lead to pain that worsens with deep breathing.
  • Degenerative spinal disease: The patient has known degenerative changes in the spine, which could contribute to mid back pain, although the pain's relation to deep breathing is less typical for this condition.
• Do Not Miss Diagnoses
  • Pulmonary embolism: As mentioned, despite the low likelihood based on imaging, pulmonary embolism is a critical diagnosis that must be considered due to its high mortality rate if missed.
  • Aortic dissection: Although less likely given the lack of specific symptoms like tearing chest pain, aortic dissection is a life-threatening condition that requires immediate attention.
  • Pneumonia or other infectious processes: Despite the normal lung findings, pneumonia or other infections could present atypically, especially in older adults, and are crucial to diagnose promptly.
• Rare Diagnoses
  • Pancoast tumor: Given the presence of a small pulmonary nodule, although unlikely, a Pancoast tumor (a type of lung cancer located at the top of the lung) could cause mid back pain and should be considered, especially with further workup of the nodule.
  • Osteoporotic vertebral fracture: Although the patient's known spinal issues are degenerative, osteoporotic fractures could occur, especially with minor trauma like a long car ride, and might present with pain worsened by breathing due to movement of the fracture fragments.

Each of these diagnoses requires careful consideration of the patient's symptoms, history, and imaging findings. Further diagnostic workup, including potentially an MRI for the hepatic lesion and further evaluation of the pulmonary nodule, along with a thorough clinical examination, is necessary to determine the cause of the patient's mid back pain.