Most people think gallstones are hard like rocks. Actually they are more like undercooked potatoes. They are firm to the touch but crush easily. Gallbladder sludge is like potato soup. The same stuff makes up sludge that makes up gallstones, it's just, soupier. (Does that make sense?) Hope this helps
He may have a urinary tract infection or a kidney stone. If he takes a hot bath or shower and the pain moves to his back and becomes more intense it's definately his kidneys.