Complicated issue...sometimes the surgeon takes too much.....
The liver synthesizes and conjugates bile salts that are necessary for proper fat digestion and for the uptake of vitamins A and D. After fat stimulates their release into the duodenum, bile salts are actively reabsorbed by the distal ileum and returned to the liver by the enterohepatic circulation to be used again. After ileal resection, length-dependent alterations in bile metabolism can lead to a multitude of intestinal events that may result in diarrhea. Even though considerable amounts of bile salts are lost in the colon, the liver can synthesize and maintain the salt pool after resection of up to 100 cm of ileum. If ileal resection is greater than 100 cm, hepatic bile salt synthesis cannot match the losses. In this case, micelle formation in the jejunum decreases, and fat malabsorption leads to steatorrhea (fecal fat of more than 20 g per day) and diarrhea. Hydroxylated fatty acids directly decrease colonic absorptive capacity, cause active secretion of electrolytes and water, and form soaps, which are cathartic.[48]
Vitamin B12 is excreted exclusively into the bile. It is highly conserved by active uptake at the terminal ileum and is returned to the liver by the enterohepatic circulation. Body stores of vitamin B12 may last three to six years in complete malabsorption and six to 30 years in partial malabsorption.[48] Loss of the distal ileum can impair vitamin B12 absorption. A loss of 50 cm of terminal ileum appears to be the critical margin for sufficient vitamin B12 absorption. Substitution of vitamin B12 should be prescribed to patients who lose more than 50 cm of terminal ileum beginning several years after surgery.
Following removal of the ileocecal valve, the absorptive processes in some patients may be affected due to the development of high concentrations of bacteria in the ileum. Severe diarrhea may occur as a result of fat malabsorption or irritation of unreabsorbed bile salts on the colonic mucosa.[38] Diarrhea also may occur when major portions of the large bowel are removed. In this case, a significant amount bicarbonate can be found in the fecal fluid, since alkaline ileal contents drain into a shortened large bowel segment, which may result in acidosis and dehydration
But lets just hope its a situation you can resolve with diet.
Here's a good article from Moffitt
www.moffitt.org/moffittapps/ccj//v3n6/a4.html
Pat