INDIANAPOLIS — Fourteen-year-old Shelbi Anderson wanted to begin her freshman year at Highland High School today.

Instead, she’s recuperating at home from ulcerative colitis surgery to remove an abscess a week ago. She left Indianapolis-based Riley Hospital for Children on Friday and may have to be homeschooled.

Shelbi said she’s worried about acquiring another infection, but she yearns for the outside.

“I just want to see my friends,” she said.

Ulcerative colitis or UC is an immune inflammatory condition that causes white blood cells to attack the large bowel or colon.

“Your white cells in the body overreact and, in the process, injure the bowel,” said Indiana University gastroenterologist Michael Chiorean. “It’s like your bowel is an innocent bystander.”

Shelbi began bleeding from the rectum when she was 9 years old. Her pediatrician thought it was caused by a tear from a softball game. However, a month passed and the bleeding recurred. Shelbi was referred to Riley Hospital, where she was diagnosed with UC. Chiorean said a combination of genetics, bacteria and one’s immunity creates the disease.

Chiorean said the advent of disease can be benign, suffering from minimal cramps, diarrhea and bleeding and possibly mature to be life threatening.

“The bowel can basically explode and you can die of a bacterial infection,” Chiorean explained.

Chiorean said Shelbi’s diagnosis at 9 is unusual.

“By having it so early, it can change in character a lot (so her symptoms can be from UC or Crohn’s disease),” he said. “It can be UC or Crohn’s disease, a similar condition that can affect the entire gastrointestinal system from esophagus to anus. With UC and Crohn’s, about two people per 1,000 in the United States are affected.”

Onset usually occurs in 20- to 30-year-olds, Chiorean said.

Early on, Shelbi picked up weight as a side effect for using Prednisone, one of the most common steroids. More recently she has taken Colazal, another type of anti-inflammatory medication safer than Prednisone, said Chiorean. Her dosages have increased as she became more immune to the medications, said Laura Anderson, Shelbi’s mother.

Since diagnosis, Shelbi’s has had an annual colonoscopy and an occasional flare-up, but excruciating stomach pains increased last school year as an eighth-grader at East Side Middle School. Frequent tardiness, absences and lower grades followed.

About a couple of months ago, Shelbi had her large colon eviscerated. Her second surgery was to remove blockage of the small colon in July.