Stools can conceivably, and acceptably, come in a lot of shades of brown, and even black and green, but a white stool is not normal and requires action, according to gastoenterologist Dr. Picco at mayoclinic.com (see References).
If your stool is white it means, according to Picco, that it is lacking bile, which is digestive fluid produced by the liver and stored in the gall bladder. A lack of bile indicates the possibility of a problem in the biliary tract or liver. Healthy stool is brown and gets it color from the bile that is excreted from the liver during the digestive process and enters the small intestine. If the liver isn't producing bile or if it is but the bile is prevented or obstructed from leaving the liver, your stool will be white.
There are medications that can turn your bowel movement white, including anti-diarrheal medications and big doses of Kaopectate or Pepto-Bismol. Some anti-fungal medicines, antibiotics and antacids can also have this effect on the color of your stool.
Medical conditions that can cause stool to turn light colored or white include narrowing of bile ducts, gallstones, tumors, cysts, errors of metabolism, a liver infection such as hepatitis or biliary cirrhosis, and intestinal and bile duct congenital abnormalities.
Bile Duct Obstruction
A bile-duct obstruction can be caused by a number of conditions, including gallstones, inflamed bile ducts, injury to the gallbladder from surgery, enlarged lymph nodes in the porta hepatis, cysts in the bile duct, tumors in the pancreas or bile ducts and tumors that have spread to the biliary system. An individual might be at risk for this occurring if he has a weakened immune system, which can cause blockage via infection, injury to the abdomen, biliary cancer, biliary surgery, pancreatic cancer, pancreatitis or a history of gallstones, according to nlm.nih.gov (See References).
Other Problems Related to Bile Duct Obstruction
In addition to turning your stool white, a blocked bile duct can produce jaundice and turn your skin yellow because of the accumulation of bilirubin in the blood.
If you are having digestive issues, this can turn your stool a pale color, according to Wrongdiagnosis.com (See References). The digestive system consists of the tube that goes from the mouth to the rectum and that houses the esophagus, stomach and intestines as well as the organs that are connected to the tube, which include the liver and pancreas. If you have a duodenal, fecal incontinence, Whipple disease, dysentery or esophageal achalasia, there is a chance that your stool may be pale in color.