The liver produces bile, which is an emulsifier that helps to break down globules of fat in the intestinal tract. Bile is stored in the gall bladder, a small pouch-like organ that is tucked beneath the liver, and is released into the digestive tract via the common bile duct when it is needed. In some cases the body produces an excess of bile, and the bile builds up and crystallizes into gallstones.
If one or more gallstones become lodged in the common bile duct, this causes a condition known as acute cholecystitis. Acute cholecystitis is generally characterized by nausea, fever, and pain. Many individuals cannot tolerate food, making the impact of this condition on digestion moot; however for those who can eat, another symptom soon becomes apparent: pale or clay-colored loose stools. Without bile to break down the fats, the larger fat globules tend to pass through undigested, causing loose stools. Since the flow of bile is obstructed by the blockage, fecal matter does not develop its characteristic yellow or brown color, which originates from the bile pigments, so stools are very pale in color.
Treatment involves putting the person on a low-fat diet and either removing the bile duct blockage or removing the gallbladder and duct entirely.