Getting the right diagnosis

Imaging helps spot silent organ involvement and guides safe biopsies to confirm IgG4‑RD.

Imaging in IgG4‑related disease: CT, MRI, and PET, and what they reveal

In the diagnostic evaluation of suspected IgG4‑related disease (IgG4‑RD), cross‑sectional imaging is an essential tool to help physicians understand the extent of organ involvement and help make a diagnosis.

Images from CT, MRI, and PET scans help your care team screen your body for indications of inflammation or other irregularities. These images alone are usually not enough to make the diagnosis, but they point to the right places to look for further evidence and, when needed, can guide clinicians about which organs (and where) to biopsy safely. Imaging can also help to find “silent” disease before it causes harm.¹

Types of imaging tests used

Doctors use different imaging tools to diagnose IgG4-RD and map which organs are affected. They choose CT, MRI, or PET based on the body parts that need a closer look.

Computed tomography (CT) uses low‑dose X‑rays and often a special dye (contrast) to make sharp images of organs and blood vessels. CT is fast and excellent for the chest, abdomen, and pelvis, common areas affected by IgG4‑RD.²

Magnetic resonance imaging (MRI) uses magnets (no radiation) to show soft tissues like the pancreas, kidneys, meninges, and orbits around the eyes in great detail.¹

Positron emission tomography (PET, often PET/CT) highlights areas with active inflammation by using a tiny amount of glucose tracer that “lights up” active cells because they are metabolically active. PET is helpful when we need a whole‑body map of disease extent, when we need to know if an organ or organs have active disease, to identify areas of subclinical disease, and sometimes to find the best biopsy ta rget. ^2,3

Key idea: No single test is perfect. Your team looks at your story, your physical examination, your blood tests, and your images together, and sometimes confirms the image with a biopsy. ^1,2

What the images tend to show (and why)

Tumefactive lesions are “lumps” made of inflammation and scar‑like tissue. In IgG4‑RD they often grow slowly and can look like cancer, but they are not cancer.

Patterns repeat across organs. Doctors look for certain combinations: a mass‑like area, nearby lymph nodes, and sometimes tissue sheathing around vessels or tubes. On PET scans these areas usually “glow” when active.

Let’s tour the most common regions and what we look for:

Head and neck

Salivary and lacrimal glands: Often bilateral swelling. CT, MRI or ultrasound all show enlarged, smooth glands. PET may be active when the disease is “on.”

Orbits and nerves: The tissues around the eyes and the extra‑ocular muscles can swell; the infraorbital nerve may look thick. This can cause “proptosis” (eye bulging) or double vision. CT and MRI show these findings clearly.

Sinuses and skull base: Long-standing sinusitis can be related. CT and MRI can also show pachymeningitis, a thickened brain covering that enhances with contrast.

Chest

Lungs: CT may show multiple nodules along the airways and under the pleura, masses within the lungs, lymph node enlargement in the middle of the chest, and many other findings. Doctors first rule out infection, other causes of inflammation such as ANCA-associated vasculitis or sarcoidosis, and cancer. Biopsy is key when the picture is unclear.

Abdomen

Pancreas and bile ducts: Autoimmune pancreatitis can appear as a swollen pancreas or bile-duct narrowing, leading to jaundice. CT scanning is usually the first diagnostic procedure. An MRCP (magnetic resonance cholangiopancreatography, a variant of an MRI) can view these structures with great detail.

Kidneys: Tubulointerstitial nephritis appears on CT/MRI as patches that take up contrast differently and are sometimes mistaken for renal cysts or as inflammatory changes around the rim of the kidneys.

Vessels and retroperitoneum

Aorta and branches: Imaging may show a soft‑tissue “sheath” around large arteries (periaortitis).

Coronary arteries: A coronary CT angiogram can identify vasculitis (inflammation in blood vessels) affecting the coronary arteries, sometimes leading to inflammation in or a round the arteries, to arterial narrowing, and to aneurysm development.

Retroperitoneal fibrosis: A soft‑tissue band can wrap around the ureters and cause blockage. CT/MRI track its size and response to treatment.

How imaging guides biopsy and treatment

Imaging often points to the safest, most informative biopsy site, for example, an accessible lymph node rather than a deep organ. PET/CT is especially useful when several areas are active. After treatment begins, repeat imaging shows whether inflammation is quieter, unchanged, or progressing.

A gentle caution: Imaging alone cannot prove IgG4‑RD. Pathology—the microscope view—confirms the diagnosis following clinico‑pathologic correlation by showing a dense lymphoplasmacytic infiltrate, storiform fibrosis, and sometimes obliterative phlebitis, often with many IgG4‑positive plasma cells.¹

What to expect on scan day

› CT: Usually quick. You may receive IV contrast. Tell the team about any kidney issues or past contrast reactions.

› MRI: Takes longer and can be noisy. Ear protection and calming techniques help. Let the team know if you have claustrophobia or metal implants.

› PET/CT: You’ll rest after the tracer injection to let it circulate, then lie still for imaging. Avoid heavy exercise the day before.

Your team will combine the images with your symptoms and lab tests to decide the next step. Sometimes that means observation, sometimes medicines, and occasionally procedures l ike stents if a duct or ureter is blocked.

Summary

Imaging gives your physicians the map needed to understand how the disease affects you. CT, MRI, and PET help your physicians find silent inflammation, choose the best biopsy site, and track response to therapy. Because IgG4‑RD can look like many other conditions, these images are always interpreted alongside your story, your labs, and—when needed—a tissue biopsy.

References

1. Stone JH, Zen Y, Deshpande V. IgG4‑Related Disease. N Engl J Med. 2012;366:539–551. URL: https://www.nejm.org/doi/full/10.1056/NEJMra1104650

2. Lang D, Zwerina J, Pieringer H. IgG4‑related disease: current challenges and future prospects. Ther Clin Risk Manag. 2016;12:189–199.  URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC4760655/

3. Peyronel F, Della‑Torre E, Maritati F, et al. IgG4‑related disease and other fibro‑inflammatory conditions. Nat Rev Rheumatol. 2025;21:275–290. URL: https://doi.org/10.1038/s41584-025-01240-x

4. Zhang J, Chen H, Ma Y, et al. Characterizing IgG4‑related disease with 18F‑FDG PET/CT. Eur J Nucl Med Mol Imaging. 2014;41:1624–1634. URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC4089015/