DEAR Fiona,
        I have had a handful of cases of streaky blood in the stools of
very well nourished breastfeeding babies. I have to admit that I have not
seen it in artificially fed babies,...but largely my patients breastfeed!!
Anyway, each time it happens, I usually cover myself by talking to a peds
GI (this reassures the parents too) each time, and never ever did a peds GI
specialist suggest weaning! The most common explanation is that the
lymphoid tissue just beneath the intestinal mucosa (peyer's patches)
sometimes become hypertrophied (enlarged), and erode into the lining of the
mucosa, causing a limited amount of bleeding.  I have found that by
decreasing mom's dairy (cow) intake, it may help,but generally this is a
self-limiting problem. It seems to last about 3-5 days.  Again, I must
stress that I am not a peds gastroenterologist, and therefore each
situation I feel more comfortable reviewing with a specialist, as there can
be other pathology, such as a meckels diverticulum, a polyp, an infection,
etc...  I would suggest that the parents push the FP for a full explanation
as to why breastfeeding causes blood in the stool...and if he/she cannot
provide it, its the FP's responsibility to seek more information for the
patient!
                                        Anne Eglash, MD