Differential Diagnosis for Left Lower Back Pain Radiating to the Front of the Abdomen

Single Most Likely Diagnosis

• Musculoskeletal Strain: Given the patient's symptoms of left lower back pain radiating to the front of the abdomen, worsened by movement, and tenderness, musculoskeletal strain is the most likely diagnosis. The use of heat/ice for relief and the absence of severe urinary symptoms also support this diagnosis.

Other Likely Diagnoses

• Lumbar Disc Herniation: The radiation of pain to the abdomen could be indicative of a lumbar disc herniation, particularly if the herniation is affecting nerves that innervate both the back and abdominal regions.
• Kidney Stone: Although the patient denies any urinary symptoms other than frequency, which he considers normal, a small kidney stone could potentially cause pain that radiates from the back to the abdomen without significant urinary symptoms.
• Pyelonephritis or Kidney Infection: Infection of the kidney could cause flank pain that radiates to the abdomen, though typically, it would be accompanied by more pronounced urinary symptoms such as dysuria, fever, or hematuria.

Do Not Miss Diagnoses

• Abdominal Aortic Aneurysm (AAA): Although less likely given the patient's age is not specified and the absence of a pulsatile abdominal mass on examination (not mentioned), AAA is a critical diagnosis to consider due to its high mortality rate if ruptured. Back pain radiating to the abdomen could be a presentation of a leaking or ruptured AAA.
• Pancreatitis: Acute pancreatitis can cause severe back pain that radiates to the abdomen. The absence of gastrointestinal symptoms does not rule out pancreatitis, as it can present atypically.
• Pulmonary Embolism: In rare cases, a pulmonary embolism can cause referred pain to the back and abdomen, especially if the embolism is large and affects the lower lobes of the lungs.

Rare Diagnoses

• Retroperitoneal Hematoma or Tumor: These conditions can cause back pain that radiates to the abdomen but are less common and would typically have additional symptoms or findings on imaging.
• Inflammatory Arthropathies (e.g., Ankylosing Spondylitis): While these conditions can cause back pain, the acute onset and radiation to the abdomen are less typical presentations.
• Referred Pain from Gastrointestinal Sources (e.g., Duodenal Ulcer): Certain gastrointestinal issues can cause referred pain to the back, but this would usually be accompanied by more prominent gastrointestinal symptoms.