moncap,
Cholangitis, actually called ascending cholangitis, is an infection that occurs where the tiny bile duct that now replaces the common bile duct is sewn direction into the intestine.
When caught early, your Dad should take note of how his body signals infection (headache, low grade fever, tingly skin perhaps), antibiotics usually help. Often patients will be on a low dose of prophylactic antibiotic or, on their doctors orders, keep antibiotic available for when an infection comes on.
In my case I have found that mucus producing foods like dairy and coffee tend to increase my chance of infection.
Hope this helps.
-Peter