Differential Diagnosis for Pain in Mid Back Left when Lying Down

Single Most Likely Diagnosis

• Musculoskeletal strain: This is often the most common cause of mid-back pain, especially when it worsens with specific positions such as lying down. The strain could be due to overuse, poor posture, or direct injury to the muscles or ligaments in the mid-back region.

Other Likely Diagnoses

• Costochondritis: Inflammation of the cartilage that connects the ribs to the sternum can cause sharp pains in the chest or back, which might worsen when lying down due to increased pressure on the affected areas.
• Scoliosis or kyphosis: Abnormal curvatures of the spine can lead to uneven distribution of weight and strain on the muscles and joints of the back, potentially causing pain that is exacerbated by lying down.
• Herniated disk or spinal stenosis: Although more commonly associated with lower back pain, issues like herniated disks or spinal stenosis in the thoracic spine can cause mid-back pain, especially if there is nerve compression involved.

Do Not Miss Diagnoses

• Pulmonary embolism: While less common, a pulmonary embolism can cause sudden, severe chest pain that might radiate to the back and could worsen with deep breathing or certain positions, including lying down. This is a medical emergency.
• Aortic dissection: A tear in the aorta's inner layer can cause severe, tearing chest pain that radiates to the back. The pain can be constant and might worsen with movement or certain positions.
• Pneumonia or pleurisy: Infections like pneumonia or inflammation of the pleura (pleurisy) can cause sharp pains in the chest or back that worsen with deep breathing or coughing and might be affected by position.

Rare Diagnoses

• Pancreatitis: Inflammation of the pancreas can cause severe abdominal pain that radiates to the back. While the pain is typically more abdominal, it can be felt in the mid-back, especially if the pancreas's tail is involved.
• Splenic infarction or rupture: Issues with the spleen, such as an infarction (death of splenic tissue due to lack of blood supply) or rupture, can cause severe left upper quadrant abdominal pain that might radiate to the left mid-back.
• Tumors: Both benign and malignant tumors in the thoracic spine, lungs, or other nearby structures can cause mid-back pain, especially if they compress nerves, invade bone, or cause other structural issues.