NEW YORK (Reuters Health) - The necessary, albeit unpleasant, purging to clear the bowel before colonoscopy is quite likely to be inadequate in people who are obese, a study conducted by researchers at Washington University School of Medicine shows.

A poorly cleansed bowel can interfere with the view through the colonoscope, and potentially cause cancers to be missed.

To investigate whether obesity might be associated with inadequate bowel cleansing before these procedures, Dr. Brian B. Borg and colleagues analyzed data from all 1588 colonoscopies done at their center over a 4-month period. A bowel preparation score was assigned based on various factors, including how complete the patient felt the cleansing had been and the adequacy of the examination.

More than one-fourth of all the subjects had an inadequate examination, the authors report in the journal Clinical Gastroenterology and Hepatology.

A body mass index above the normal range (above 25) was associated with a higher likelihood of an inadequate bowel-prep score.

After adjusting for other factors, obese individuals (BMI over 30) were 35 percent more likely to have an inadequate bowel preparation.

"Our results suggest that the obese patient should at least be subject to more precise instructions and possibly a more aggressive bowel preparation regimen; these general principles might even apply to the overweight patient," the researchers advise.

"A longer period of liquid diet before colonoscopy and repeat daily laxative regimens leading up to the actual bowel preparation might need to be considered," they add.

SOURCE: Clinical Gastroenterology and Hepatology, June 2009.