Physiologic uptake: Meaning in a Radiology Report

Also written as: physiological uptake, physiologic activity, normal biodistribution, physiologic distribution

Physiologic uptake is tracer seen where it normally collects on a PET or nuclear medicine scan. It is expected and not a sign of disease.

What it means

Tracers do not only go to problem areas. Each one also collects in healthy organs that use it or clear it from the body. With FDG, the brain is normally bright and the heart often is. The kidneys and bladder light up as tracer leaves in urine. Bowel, recently used muscles and brown fat (a heat-making fat) can also take it up. Other tracers have their own normal patterns.

When it matters

Physiologic uptake is normal and needs no action. Radiologists mention it to show they recognized it and did not mistake it for disease. Now and then it can hide or mimic a small problem nearby, for example in the bowel or bladder. Then extra images, another type of scan, or simple steps before a repeat, such as keeping warm to calm brown fat, may help.

Questions to ask your doctor

Was all the uptake on my scan physiologic, or was anything unexpected?
Could normal uptake be hiding anything in the area being checked?
Is there anything I can do before a future scan to reduce it?

General information, not medical advice. What a finding means for you depends on your symptoms, your history and the images themselves, so talk your results through with a doctor.