Patients often suffer from painful gallbladder stone attacks, which occur in the middle of the night and are experienced by many patients. Even if the pain is not severe, there is often a vague feeling of discomfort in the right upper abdomen (gallbladder area) during the night. Why do most attacks occur at night? 1. Gallbladder stones are embedded in the narrow neck of the gallbladder (or gallbladder duct). The gallbladder is shaped like a duck pear, with a large bottom and small neck. When the patient sleeps on his back, the bottom of the gallbladder is facing upward, and the stones in the gallbladder will easily roll to the neck of the gallbladder (or gallbladder duct) due to gravity and get stuck there, affecting the discharge of bile from the gallbladder. In order to empty its bile, the gallbladder has to strengthen its contraction, and then the patient will feel a burst of pain. 2. The gallbladder and common bile duct are innervated by the sympathetic and vagus nerves. The sympathetic and vagus nerves act antagonistically to each other, with the sympathetic nerve weakening the smooth muscle movement of the digestive tract and the vagus nerve acting in the opposite way. At night, especially after sleep, the excitability of the vagus nerve gradually increases and reaches the peak of the day, and the excitability of the sympathetic nerve decreases, so that the pain is also triggered by violent contraction of the smooth muscle of the gallbladder.