Differential Diagnosis for Left Side Lower Back Pain

The patient presents with left side lower back pain that is sharp, non-radiating, and exacerbated by movement, with relief upon rest. The pain is reported to range from 3 to 8 on a 1-10 pain scale and is partially managed with ibuprofen and Tylenol. Given these symptoms, the following differential diagnoses are considered:

• Single Most Likely Diagnosis

  • Musculoskeletal strain or sprain: Despite the patient's denial of any musculoskeletal injury or trauma, the nature of the pain (sharp, exacerbated by movement, and relieved by rest) and its location (lower back) suggests a musculoskeletal origin. The effectiveness of ibuprofen and Tylenol further supports this diagnosis, as these medications are commonly used to treat pain and inflammation associated with musculoskeletal injuries.

• Other Likely Diagnoses

  • Kidney stones or nephrolithiasis: Although the patient was treated for a UTI and expected the pain to resolve, kidney stones could cause persistent pain, especially if they are not passed or if there is an underlying issue like a ureteral obstruction. The pain from kidney stones can be sharp and severe.
  • Degenerative disc disease or herniated disc: These conditions can cause lower back pain that worsens with movement and improves with rest. The pain can be sharp and localized to one side of the lower back.
  • Osteoarthritis of the lumbar spine: This condition can lead to lower back pain that is exacerbated by movement and relieved by rest. The pain can be sharp and is often localized to the lower back.

• Do Not Miss Diagnoses

  • Abdominal aortic aneurysm (AAA): Although less common, an AAA can present with lower back pain, especially if it is expanding or leaking. This condition is a medical emergency and requires immediate attention.
  • Pyelonephritis or kidney infection: Despite recent treatment for a UTI, if the infection has ascended to the kidneys, it could cause persistent or worsening pain. This condition requires prompt medical evaluation and treatment.
  • Spinal epidural abscess: A rare but serious condition that can cause back pain, fever, and neurological deficits. It is essential to consider this diagnosis, especially if there are signs of infection or neurological compromise.

• Rare Diagnoses

  • Psoas abscess: An abscess in the psoas muscle can cause lower back pain that is exacerbated by movement. This condition is rare but can be serious and requires medical attention.
  • Spinal tumors: Both benign and malignant tumors can cause lower back pain. These are less common causes of back pain but are important to consider, especially if the pain is persistent and unexplained.
  • Referred pain from intra-abdominal pathology (e.g., pancreatic cancer, spleen disorders): In some cases, intra-abdominal diseases can refer pain to the lower back. These conditions are less common but should be considered in the differential diagnosis, especially if other symptoms are present.