I often encounter patients complaining why my gallstones often attack at night. After waking up with pain at night after sleeping, they go to the hospital without pain and find it very strange and unbelievable. And some patients with gallstones go to the hospital after waking up with pain at night, but the pain persists without relief. Why is this? First, we need to know how gallbladder stones cause pain. Our gallbladder is shaped like a pear, with a large bottom and small mouth. When stones are embedded in the neck of the gallbladder, it causes pain. (Some textbooks suggest that the cause of pain is obstruction of the gallbladder duct caused by the stone, which increases the pressure in the gallbladder and prevents the bile from draining through the neck of the gallbladder and the gallbladder duct. The authors believe that the sudden pain may be due to the nerves in the gallbladder wall being continuously stimulated by the compression of the gallbladder wall caused by the stone embedded in the gallbladder neck or the gallbladder duct, because the size of the gallbladder and the gallbladder wall are basically normal in patients with pain relief on ultrasound.) When we are standing or sitting, the base of the gallbladder (pocket) is in the lowest position and stones are not embedded. When we lie down, the neck of the gallbladder (small mouth) is in the lowest position, and due to gravity, the stone gradually rolls down and causes sudden and severe pain if it is embedded in the neck of the gallbladder or the gallbladder duct (patients often wake up with pain during sleep}. This is the reason why gallbladder stones are painful at night. When we stand or sit again, the neck of gallbladder is high, if the stone is loose and not embedded, the pain will be relieved or disappear, if the stone is still stuck in the neck of gallbladder and cannot move, the pain will persist, followed by inflammation and enlargement of gallbladder.