I have had this result for the past several years and I just did a Liver-Flush and got out lots of mucus and brown sludge and no stones. One reason could be that you have organisms growing in the bile system and since there is little or no pain it is probably what is called a near infection, an overgrowth. In me this situation causes a lot of digestive disturbances and poor bile production from the partially blocked bile ducts and the bacteria eating the bile. If I eat too much carbs these organisms overgrow in the small intestine and cause lots of gas/bloating.
It may be that the only way to treat this effectively would be to use Antibiotics . I plan to see a gastroerologist to discuss this problem in the near future. In the meantime I'm eating lots of apples hoping to liquify some of the sludge, using Pau d'arco to control the Candida as I think they are growing in my gallbladder, using Clark's Iodine solution and doing more parasite herbs in case there are some causing congestion in my upper intestine.
Have you been tested for Celiac Disease as that was my underlying problem?