Positive FOBT

I am a 42 year-old woman who has had bright red blood in my stool off and on for several years.  My grandfather had colon cancer and my father has had several sessile polyps removed (my grandfather was over 60 when diagnosed, my father in his late fifties).  I had a colonoscopy in 2001 which showed only internal hemorrhoids, and another colonoscopy in November 2005 that showed internal hemorrhoids and one small benign inflammatory polyp.  My prep for both colonoscopies was described as excellent, and nothing worrying was found.  Because of my family history, I've been instructed to have a colonoscopy every five years, which I intend to do.  

Since my last colonoscopy, I still have occasional bright red blood in my stool, especially when constipated.  Yesterday during a routine visit to my gastroenterologist, the Hemoccult test came back positive.  My gastro suggests repeating three Hemoccult tests, and doing another colonoscopy if any of them are positive "in case anything was missed last time."  What are the chances of a false positive Hemoccult test?  I have read that blackberries, walnuts, and other raw fruits and vegetables (which I eat a lot of) can affect the test.  I also took aspirin and ibuprofen three days last week.  Can those medications cause enough bleeding to create a positive FOBT result?  Also, does a single positive Hemoccult test warrant another colonoscopy?  Finally, if the three Hemoccult tests are negative, can I feel comfortable skipping a colonoscopy?  Both previous tests were done by top gastros at teaching hospitals, and I thought the results were good for at least five years.  The prospect of a third colonoscopy in seven years doesn't make me happy.  Thank you for your help.          

[Kevin Pho, MD]

The colonoscopy is the most comprehensive test looking for sources of lower GI bleeding.

I agree with the approach your GI physician is taking now.  If there are hemorrhoids or an anal fissure, this may escape detection by the colonoscopy.   It may be possible that ASA or NSAIDs may exacerbate these lesions.

I cannot give specific recommendations regarding whether you should repeat the colonoscopy.  However, if one wants to be absolutely certain, repeating another one would be the most comprehensive approach.

Followup with your personal physician is essential.

This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.

Kevin, M.D.
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