SAN DIEGO – A new study has found that people with diverticulosis actually have a low risk of progression to diverticulitis – far lower than the rates of 10%-25% commonly cited in the medical literature.
The actual rate seems to be at most six cases of progression from diverticulosis to diverticulitis for each 1,000 person years of follow-up. And if a stricter definition of diverticulitis is used, the rate for progression is even lower, 1.5 episodes for every 1,000 person-years, Dr. Kamyar Shahedi said at the meeting.
The newly derived rate came from a careful review of more than 2,000 people who were identified with diverticulosis in the VA Greater Los Angeles Healthcare System and followed for as long as 16 years.
The analysis also showed that the risk for developing diverticulitis subsequent to diagnosis of diverticulosis fell markedly with age, dropping by an average of 24% for each added decade of life from the time diverticulosis was first identified, said Dr. Shahedi, a gastroenterologist at the University of California, Los Angeles.
The highest cumulative hazard that people in the study faced for developing diverticulitis was if their diverticulosis was identified when they were in their 40s. The next highest rate of progression occurred among people first identified with diverticulosis in their 50s, and so on, with the lowest risk faced by people first found to have diverticulosis in their 70s.
Dr. Shahedi and his associates suspected that the age-related dimension to the risk for progression may have stemmed from a bias linked to the indication for the colonoscopy that found the diverticulosis, but after adjustment for the colonoscopy indication, younger age remained a significant, independent risk factor for more rapid progression. "Future research should try to explain how and why age affects risk," he said.
Diverticulosis is the most common finding during colonoscopy. Results from a recent review of U.S. adults who underwent colonoscopy during 2001-2005 showed that the procedures identified about 45% with diverticulosis (Gastroenterology 2009;136:741-54).
Citations for a 10%-25% rate of progression of diverticulosis to diverticulitis appear widely in the literature, such as in 1999 diverticulitis guidelines published by the American College of Gastroenterology (Am. J. Gastroenterol. 1999;94:3110-21).
But in the 1999 ACG guidelines, the citation for the 10%-25% rate is a 1975 textbook, and when Dr. Shahedi checked the book he found that the original data behind this rate came out in the 1930s, 1940s, and 1950s. "Few recent studies" have calculated a more contemporary progression rate, and the studies that have been done were small, Dr. Shahedi said.
His study involved a manual chart review of all people in the VA Greater Los Angeles Health Care system identified with diverticulosis during 1996-2011. This system includes 14 community clinics and 1 inpatient medical center and serves about 3 million people.
The manual review excluded people with a prior diagnosis of diverticulosis, and identified 2,222 newly diagnosed cases. The records for these incident diverticulosis cases then underwent further careful review to flag the people who subsequently developed diverticulitis.
The researchers used four different criteria for identifying progression to diverticulitis: a chart diagnosis that included no objective evidence of progression, a diagnosis supported by objective data but without radiographic documentation, a diagnosis supported by imaging, and a diagnosis supported by a surgical specimen.
The review identified 95 of the 2,222 people (4.3%) who progressed to diverticulitis by any of these four criteria, and 23 people (1% of the 2,222) among these 95 whose progression to diverticulitis included documentation by at least one of the two strictest criteria, either radiographic or surgical evidence. The median time to progression to diverticulitis documented by any of the four criteria was 7.1 years.
The 2,222 people with diverticulosis were all veterans, their average age was 67 years, about 98% were men, and their average body mass index was 28.5 kg/m2. About 40% of the group was white, 10% African American, 8% Hispanic, and the rest were of other ethnic groups. Dr. Shahedi noted that the study was limited by examining a VA population that largely included men, it was a retrospective study, and all the people included came from a single health care system.
Dr. Shahedi said that he had no disclosures.