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NEW YORK (Reuters Health) - Summertime sees the greatest number of patients hospitalized for a common and sometimes painful digestive problem called diverticulitis, a new study finds.
The results are puzzling researchers already stumped by this disease.
"It's been a mystery for a number of years," said study author Dr. Rocco Ricciardi, adding that nobody knows for sure what triggers the problem.
In diverticulitis, tiny pouches bulge out from the lower intestine and become inflamed, which can cause fever and stomachache.
Nearly 300,000 people are hospitalized for it every year in the U.S.
Ricciardi, a colon surgeon at the Lahey Clinic in Burlington, Massachusetts, had noticed that more of his patients seemed to have flare-ups during the summer.
He and his colleagues searched through the medical records of about 1,000 hospitals nationwide -- or about one out of every five U.S. hospitals.
They found 370,000 admissions for diverticulitis over a 9-year period, averaging out to about five out of every 1,000 hospitalizations.
Combining the 9 years, the researchers found that the largest number of diverticulitis patients -- almost 30,000 -- came in during the month of August.
That was 25 percent higher than admissions during February, which were about 24,000.
"I thought that was a fairly large difference," Ricciardi told Reuters Health.
For each of the 9 years, the pattern kept repeating: peaks in hospitalizations during the summer months, lulls during the winter, and intermediate numbers of admissions during the spring and fall.
The researchers tried to determine what might contribute to the pattern, but sex, age, race, and geographic region of the country made no difference.
"It's there whether you live in a warm environment or a cold one. There's something about the summer," Ricciardi said.
Dr. Robert Madoff, chief of the Division of Colon and Rectal Surgery at the University of Minnesota, said he was surprised by the findings.
"It raises more questions than it answers," he told Reuters Health.
"I think it absolutely warrants more investigation to help clarify what diverticulitis is and what causes it," said Madoff, who was not involved in the study.
Ricciardi's research is published in this month's issue of the Archives of Surgery. He received no additional funding outside of his salary at the Lahey Clinic.
Ricciardi said the summer flare-ups could be related to seasonal variations in how much water people drink, or the types of medications they take, but he doesn't know the real reasons.
He and his colleagues are working on a follow-up study to see what factors could be responsible.
The study looked only at hospitalizations, and not whether the same seasonality happens in outpatient doctor visits.
Many people self-treat their diverticulitis at home as well, by managing the fever and pain.
Diverticulitis can be treated by eating more fiber, taking antibiotics, or by surgically removing part of the colon. It's difficult to prevent because doctors don't know the cause.
"I would say this is just the tip of the iceberg," Ricciardi said. "The vast majority of patients with diverticulitis don't come to the hospital...so we don't know what's happening with most people with diverticulitis."
SOURCE: bit.ly/f1XIZx, Archives of Surgery, March, 2011.