Light stool color is from the lack of bile (which gives the stool a normal brown color). As I understand diarrhea is occasional, that could be explained by a dense bile (biliary sludge) or a gallstone lodged within the bile duct. A stone may also come from the pancreas.
At this point you need to know, if his bile ducts are blocked. This can be found by a HIDA scan, where they inject a contrast into his vein, and then they monitor distribution of contrast in liver, gallbladder and biliary tree.
They will probably start with ultrasound of abdominal organs, but remember, if ultrasond will be negative, this means nothing, there are other investigations which are more accurate, HIDA scan is the first of them.
Thank you for your reply
the colour varys and can be quite powdery and light in colour sometimes very pale and sometimes a normal colour. He does get abdominal cramp usually low down to the right. There doesn't seem to be an exact time of day where it gets worse.
Raised enzymes may be liver enzymes or pancreatic enzymes, what points to liver, pancreatic, gallbladder, or bile duct disease.
What is the color of his stool? Has he abdominal pain and where exactly, and when (after meals, at night...)? This comming and going diarrhea would speak for bile ducts or gallbladder disease, but can you tell more symptoms, if there aare any?