Autoimmune Pancreatitis

Diagnosis

Autoimmune pancreatitis (AIP) can be particularly challenging to diagnose because it closely resembles pancreatic cancer. There is no single test or characteristic feature that physicians can use to identify AIP. Pancreatic disease specialists at Mayo Clinic are leading the effort to standardize diagnostic guidelines for autoimmune pancreatitis so that the disorder can be correctly identified and unnecessary surgery avoided.

Imaging tests

At Mayo Clinic, imaging of the pancreas and other organs is usually the first step in diagnosing autoimmune pancreatitis. Mayo Clinic radiologists have extensive experience evaluating autoimmune pancreatitis using advanced technologies, such as dual-phase helical CT scans, which produce superior images of the pancreas, bile ducts and liver. Because AIP is often misdiagnosed, it is essential to have images read by radiologists with expertise in pancreas disorders.

Blood tests

A common feature of autoimmune pancreatitis is elevated blood levels of an antibody called IgG4. If your doctor suspects that you have autoimmune pancreatitis, you're likely to have a blood test to check your IgG4 levels. Yet a positive test doesn't always mean that you have AIP. Studies conducted at Mayo Clinic have shown that a small number of patients who don't have autoimmune pancreatitis, including some with pancreatic cancer, also have high blood levels of IgG4 antibodies.

Endoscopic core biopsy

At Mayo Clinic, pathologists analyze a sample of pancreatic tissue in the laboratory to help confirm a diagnosis of AIP. Autoimmune pancreatitis has a distinctive appearance that is easily seen under a microscope. The challenge is obtaining a sample of whole tissue large enough for accurate analysis. Mayo Clinic endoscopists consistently remove adequate tissue samples using a minimally invasive procedure called endoscopic core biopsy. Mayo Clinic is one of the few medical centers in the world performing core biopsies of the pancreas.

Steroid trial

Because autoimmune pancreatitis is the only pancreatic disorder known to respond to corticosteroids, physicians at Mayo Clinic sometimes use a trial course of this drug to confirm a diagnosis. If your symptoms improve — for instance, your IgG4 level drops or a mass in your pancreas shrinks — you are considered to have AIP. Your doctor is most likely to use a steroid trial if you have an elevated IgG4 level but inconclusive imaging and biopsy results. Before starting corticosteroids, your doctor will thoroughly investigate and rule out other possible causes for a high level of IgG4 antibodies.