New diverticulosis data challenge long-held beliefs

The primary outcome was a new IBS diagnosis after the index diverticulitis attack (for cases) or enrollment date (for controls). Ultimately, Dr. Cohen found 24 cases of newly diagnosed IBS during the study period: 20 among diverticulitis cases, and 4 among controls. That translated to a hazard ratio of 4.7 among cases compared with controls, even after adjustment for age, sex, ethnicity, race, inpatient versus outpatient status, and comorbidity score (95% CI, 1.6 –14.0; P = .006).

Dr. Cohen offered several possible explanations for the association between diverticulitis and new diagnosis of IBS.

"Inflammation may alter gastrointestinal reflexes, amplify visceral sensitivity, render the bowel more susceptible to negative effects of microbiota, and alter motility in IBS," she said.

"Another putative mechanism of chronic diverticular disease involves shifts in intestinal microbiota leading to chronic inflammation, similar to theoretical models of IBS," Dr. Cohen said.

"Future research should identify demographic and clinical predictors of post-diverticulitis irritable bowel syndrome and evaluate its incidence in prospective studies to better determine whether the link is causal or merely associative," she concluded.

Finally, a fourth study could help researchers reduce the risk of the painful inflammatory condition: Among diverticulosis patients, higher levels of serum vitamin D were associated significantly with a lower risk of diverticulitis.

In her analysis, also published in the December issue of Clinical Gastroenterology and Hepatology, Dr. Lillias H. Maguire and colleagues identified 9,116 diverticulosis patients and 922 diverticulitis patients from the Partners Healthcare Research Patient Data Registry (doi:10.1016/j.cgh.2013.07.035). All patients had at least one prediagnostic serum vitamin D level on record between 1993 and 2012.

Dr. Maguire of Massachusetts General Hospital, Boston, found that patients with uncomplicated diverticulosis had mean levels of 29.1 ng/mL, versus 25.3 ng/mL among the diverticulitis patients (P less than .0001).

A sensitivity analysis that compared the mean prediagnostic values between cases and controls who had more than one reported vitamin D level yielded similarly significant results: The mean vitamin D level of uncomplicated diverticulosis was 33.0 ng/mL, compared with 28.1 ng/mL for acute diverticulitis patients (P less than .0001), 28.8 ng/mL for complicated diverticulitis patients (P = .002), 23.9 ng/mL for surgical diverticulitis cases (P less than .0001), and 25.5 ng/mL for recurrent diverticulitis patients (P less than .0001).

Indeed, "Compared with patients with acute diverticulitis without other sequelae, patients in the subgroups who developed abscess, required surgery, or had recurrent attacks were observed to have lower prediagnostic levels of vitamin D."

These differences between diverticulitis subgroups did not reach significance except in the cohort of patients who required surgery, who had the lowest levels of all.

"Taken together with prior studies showing an inverse association of 25(OH)D and risk of colonic cancer and inflammatory bowel disease, these results highlight the potential importance of vitamin D in the maintenance of colonic health," the investigators wrote.

"Additional studies in cohorts with more detailed information on potential confounders of this association are warranted," they added.

Dr. Peery, whose study looked at fiber intake among diverticulosis patients, and her collaborators reported having no disclosures, and stated that they received funding from the National Institutes of Health.

Dr. Shahedi, who assessed the incidence of diverticulitis, disclosed that three coinvestigators are employees of Shire Pharmaceuticals, which sponsored their study. Other investigators disclosed ties to Amgen and Ironwood Pharmaceuticals.

Dr. Cohen’s coinvestigators, who studied the prevalence of IBS following diverticulitis, disclosed ties to Ironwood Pharmaceuticals, Prometheus, Takeda Pharmaceuticals, Amgen, Ritter Pharmaceuticals, and Shire. Two investigators were employees of Shire, which funded the research.

Finally, the coinvestigators of Dr. Maguire, who looked at vitamin D levels, reported ties to Shire, Bayer Health, Pfizer, Millennium Pharmaceuticals, and Pozen. They were funded by grants from the American College of Gastroenterology as well as the National Institutes of Health.