A protein in urine could be used as a simple way to diagnose appendicitis, the most common emergency in childhood, U.S. researchers said on Tuesday.

A team at Children's Hospital Boston said a protein called leucine-rich alpha-2-glycoprotein or LRG was found in high concentrations in children with acute appendicitis, they reported in the Annals of Emergency Medicine.

Several teams have been searching for a so-called biomarker that could be used by emergency physicians to confirm appendicitis, which can be difficult to diagnose with modern imaging technology.

Some studies estimate 3 to 30 percent of emergency appendectomies done on children in the United States are unnecessary.

For their study, the team used a research tool called mass spectrometry to search concentrations of various proteins that could be detected in the urine of children in the emergency department being evaluated for suspected appendicitis.

They found that the protein LRG was strongly elevated in children with diseased appendices — even those that looked normal on ultrasound or computed tomography scans.

They said the findings could lead to a simple urine test for appendicitis in children, though more study would be needed to confirm the same biomarkers are at play in adults.

They added the research methods they used might help find diagnostic biomarkers for other diseases.