Shelley's right. I had a so-called sluggish gallbladder and had it taken out last November. I'd been sick for 8 weeks with right-sided pain under my rib cage.
The first thing that your DH should ask for is a gallbladder scan. If it comes back with elevated numbers, that's an indication that it's gallbladder disease. You don't normally have gallstones with a sludgy gallbladder, just general right-sided absominal pain and serious problems eating certain foods, like spicy stuff and fatty foods. They both just about killed me with indigestion.
Far as I know surgery is about the only option. I feel fine now.