Study: Colonoscopy Bowel Prep Vital for Polyp Diagnosis

PHOENIX — New research emphasizes the importance of adequate bowel preparation prior to colonoscopy, and highlights the remarkable effectiveness of colonoscopies in detecting and removing pre-cancerous polyps. Adequate bowel prep is particularly useful for diagnosis of tiny, flat, potentially pre-cancerous growths in the colon known as sessile serrated adenomas.

Dr. Brindusa Truta and Francisco Ramirez of the Carl T. Hayden VA Medical Center in Phoenix analyzed data of 21,600 colonoscopies performed at their institution from January 1998 to December 2007. They presented their findings this week at the annual meeting of the AmericanCollege of Gastroenterologists.

Researchers analyzed findings from 280 patients who underwent more than one colonoscopy in the last ten years, and had at least one positive fecal occult blood test (FOBT). Twenty two percent (57 patients) of these patients had a ‘cleared’ exam, but underwent repeat colonoscopy after receiving a positive FOBT result. Researchers found 5 percent of patients had colon cancer, 33 percent had adenomatous polyps, and 26 percent of patients with adenomas had advanced neoplasia.

The average time interval between the first colonoscopy and the repeat colonoscopy for a positive FOBT was 39 months. Poor quality bowel preparation at the initial colonoscopy was associated with more missed cancers and undetected polyps.

According to Truta, “A positive fecal occult blood test after a ‘cleared’ colonoscopy should trigger a repeat colonoscopy, especially if a suboptimal bowel preparation was encountered at the initial exam.”

In a separate study, Dr. Suryakanth Gurudu and his colleagues at Mayo Clinic in Scottsdale, Ariz. examined medical records from the Clinic’s pathology database of patients who had sessile serrated adenomas removed with colonoscopy between 2005 and 2007.

Sessile serrated adenomas are a sub-class of tiny, flat pre-cancerous polyps, often found on the right side of the colon. “While small polyps are generally considered less dangerous than large polyps, not all small polyps are innocent,” said Gurudu.

Of the 5,991 patients who were found to have polyps, sessile serrated adenomas comprised 2.9 percent of all polyps removed. The sessile serrated adenomas were small and 42 percent were less than or equal to 5 mm in size, while 69 percent were less than or equal to 9 mm in size. Ninety-seven percent of polyps were removed by colonoscopy and 2.7 percent required surgical excision.

According to Gurudu, “Many of these polyps due to their size and shape might have gone undetected or not reported on an x-ray exam of the colon known as CT colonography. The effectiveness of cancer prevention comes from removing all precancerous lesions with colonoscopy, regardless of size.”

Source: American College of Gastroenterology