Differential Diagnosis for Elevated Amylase in a 72-Year-Old Patient

Given the patient's presentation with elevated amylase levels, normal liver function tests, normal lipase levels, and no abdominal pain or jaundice, along with a normal CT scan, the differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis
  • Salivary Gland Pathology: The elevation of amylase without corresponding elevation in lipase and without abdominal pain suggests a non-pancreatic source of amylase. Salivary gland diseases, such as parotitis or salivary gland tumors, can cause elevated amylase levels. The patient's age and lack of other symptoms make this a plausible explanation.
• Other Likely Diagnoses
  • Macroamylasemia: A condition where amylase is bound to immunoglobulins, leading to elevated serum amylase levels without any symptoms of pancreatitis. This condition is more common in older adults and can be a cause of asymptomatic hyperamylasemia.
  • Renal Failure: Although not directly indicated by the information provided, renal failure can cause elevated amylase levels due to decreased clearance. However, this would typically be associated with other signs of renal dysfunction.
• Do Not Miss Diagnoses
  • Pancreatic Cancer: Although the CT scan is normal, pancreatic cancer can sometimes present with elevated amylase levels, especially if the tumor involves the pancreatic duct. Given the potential severity of this diagnosis, it should not be missed, even if the likelihood seems low based on the normal imaging.
  • Obstructive Jaundice: Despite the absence of jaundice, any condition causing obstruction of the pancreatic duct or common bile duct could potentially lead to elevated amylase levels. This includes stones, strictures, or tumors.
• Rare Diagnoses
  • Pulmonary Disease: Certain pulmonary conditions, such as pneumonia or lung cancer, can rarely cause elevated amylase levels due to the presence of amylase in some lung tissues.
  • Gastrointestinal Diseases: Some gastrointestinal conditions, like intestinal obstruction or ischemia, can also lead to elevated amylase levels, although these would typically be associated with significant abdominal symptoms.

Further Testing

• Salivary Gland Imaging: To evaluate for salivary gland pathology, consider ultrasound or MRI of the salivary glands.
• Serum Protein Electrophoresis: To diagnose macroamylasemia, serum protein electrophoresis can be performed to look for abnormal protein bindings.
• Renal Function Tests: Assessing renal function through serum creatinine and estimated glomerular filtration rate (eGFR) can help determine if renal failure is contributing to elevated amylase levels.
• Repeat Imaging or Endoscopic Ultrasound: If there's a high suspicion for pancreatic pathology despite a normal CT scan, consider repeat imaging with MRI or perform an endoscopic ultrasound for a more detailed evaluation of the pancreas.
• Tumor Markers: For pancreatic cancer, consider checking tumor markers like CA 19-9, although these are not definitive diagnostic tools.