There are three main causes of abdominal pain due to constipation: First, because of long-term constipation, food residues and stool remain in the intestinal canal for a long time, resulting in excessive absorption of water in the stool and food residues by the intestine, resulting in dry stool, which is not easily discharged, reflexively enhancing colon peristalsis and producing spasm and severe abdominal pain. Secondly, because of the prolonged accumulation of stool and food residues in the intestinal tract, some foods will produce a lot of gas in the intestinal canal, causing the intestinal canal to swell and pulling the sensory nerves causing severe pain. Finally, because the stool cannot be excreted for a long time, it can lead to complete or incomplete intestinal obstruction and cause severe pain.