Serious cases of a disorder of the large intestine are surging among Americans younger than 50, researchers say.

Analyzing data on more than 5.2 million adults hospitalized for diverticulitis from 2005 to 2020, they found that the proportion of patients under age 50 admitted with serious complications increased from 18.5% to 28.2%.

Furthermore, patients under age 50 who were hospitalized for diverticulitis were more likely to require invasive procedures, with 29% higher odds of needing surgery to remove part of the colon and 58% higher odds of requiring insertion of a catheter to drain infected fluid, compared to their older counterparts, the researchers reported in Diseases of the Colon and Rectum.

Diverticulitis occurs when food particles, bacteria, and other debris accumulate in small pouches that have formed on weak areas on the wall of the colon, leading to abdominal pain, bloating, bleeding, constipation and diarrhea. In complicated cases, patients may develop abscesses and holes in the colon.

Until now, diverticulitis has been considered more common among older adults. It affects fewer than 20% of people by age 40, increases to 35% to 40% by age 50, and reaches about 60% by age 60, according to U.S. data. In the oldest age groups, the prevalence can exceed 70%.

"We're seeing a significant shift in who is being hospitalized for severe diverticulitis," study leader Shineui Kim of the David Geffen School of Medicine at UCLA said in a statement.

The findings point to a growing public health concern for younger Americans, with this population having experienced similar increases in colorectal cancer diagnoses, the researchers said.

Treatments have improved, they noted, with the proportion of younger patients requiring surgical removal of part of the colon decreasing from 34.7% to 20.3% during the study period.

The researchers said the potential causes of the rising burden of early-onset diverticulitis require further research.