Differential Diagnosis for Abdominal Muscle Pain in a 66-year-old

Given the scenario of a 66-year-old patient with abdominal muscle pain, normal PSA, and no neurogenic bladder, the differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis
  • Musculoskeletal Strain: This is a common condition in older adults due to decreased muscle mass and strength, which can lead to strain or injury of the abdominal muscles. The absence of systemic symptoms or specific organ-related symptoms makes this a plausible initial consideration.
• Other Likely Diagnoses
  • Diverticulitis: Although more commonly associated with left lower quadrant pain, diverticulitis can cause generalized abdominal pain and is prevalent in the elderly population.
  • Gastroesophageal Reflux Disease (GERD): Can cause referred pain to the abdominal area, especially if there's an element of gastritis or esophagitis involved.
  • Peptic Ulcer Disease: Gastric or duodenal ulcers can cause abdominal pain, and while the pain is typically more localized, it can radiate or be referred to the abdominal muscles.
• Do Not Miss Diagnoses
  • Abdominal Aortic Aneurysm (AAA): Although AAA typically presents with back or flank pain, it can cause abdominal pain and is a critical diagnosis to consider due to its high mortality rate if ruptured.
  • Mesenteric Ischemia: This condition can present with severe abdominal pain out of proportion to physical examination findings and is a medical emergency.
  • Pancreatitis: Can cause severe abdominal pain that may be referred to the muscles, especially if there's associated inflammation of the pancreatic capsule.
• Rare Diagnoses
  • Amyloidosis: A condition characterized by the deposition of amyloid proteins in various tissues, which can lead to muscle pain among other symptoms.
  • Polymyalgia Rheumatica (PMR): An inflammatory condition that affects the muscles, leading to pain and stiffness, primarily in the shoulders, hips, and thighs, but can also involve abdominal muscles.
  • Sarcoidosis: A systemic disease that can affect any organ, including muscles, leading to pain and inflammation.

Each of these diagnoses requires careful consideration of the patient's full clinical picture, including history, physical examination, and diagnostic tests, to accurately determine the cause of abdominal muscle pain.