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Unusual Shoulder Brightness on Ultrasound May Signal Diabetes

How bright the deltoid muscle appears on ultrasound may help radiologists predict whether a person has type 2 diabetes.

Jill Sakai, Contributor
Monday, November 19, 2018


Images of the shoulder showing reversal of the rotator cuff to deltoid gradient. Image A displays the normal gradient of the deltoid muscle to the supraspinatus tendon. Image B shows reversal of the normal gradient in a type 2 diabetic patient. D: Deltoid, S: Supraspinatus, H: Humerus

Radiological Society of North America


Ultrasound is often used to diagnose causes of shoulder pain. But how bright the deltoid muscle appears in these images may also highlight whether a patient has diabetes, shows a study that will be presented Nov. 25 at the Radiological Society of North America annual meeting in Chicago.

Undiagnosed diabetes and pre-diabetes -- a condition that can develop into diabetes if not addressed with lifestyle changes -- affect millions of Americans, many of whom are unaware of their condition, according to the U.S. Centers for Disease Control and Prevention. The ability to identify and alert affected patients could allow earlier interventions, reduced medical costs and better health outcomes.

Radiologists at Henry Ford Hospital in Detroit, Michigan, noticed that shoulder muscles looked unusually bright on ultrasound in patients who reported being diabetic or pre-diabetic. To test their observations, they compiled a study sample of 137 shoulder ultrasounds from patients with type 2 diabetes or pre-diabetes and 49 shoulder ultrasounds from obese patients without diabetes. Two other radiologists were asked to classify the blinded images as normal, suspected diabetes or definite diabetes.

When both radiologists diagnosed “definite diabetes,” they were correct 89 percent of the time. They also classified all 13 pre-diabetic patients as either “suspected” or “definite” diabetes. The results show that shoulder muscle brightness on ultrasound may be a useful signal to predict the disease or its early signs.

The researchers are still investigating the link between shoulder muscle brightness and diabetes, but it may be related to glycogen, a molecule that stores sugar in the body. Ultrasounds of athletes have shown that muscles appear brighter after exercising, when glycogen levels are low. Insulin resistance is known to disrupt glycogen synthesis, so low glycogen levels may lead diabetics’ muscles to appear brighter on ultrasound.