Sudden constipation can be caused by cancer, but more commonly it is caused by a benign disease. Constipation is when the stool is dry and significantly less frequent, with only one bowel movement in 3 days or more. There are various causes of constipation, and benign digestive diseases such as various gastritis, enteritis, and intestinal polyps are the most common causes of constipation. Excessive consumption of fried, barbecued and other foods that are easily inflamed can also lead to constipation. Eating too little and not enough activity can also cause constipation, and there are also drugs that can cause constipation. Of course, malignant tumors in the gastrointestinal tract can also cause constipation, especially in patients with intestinal cancer, because the malignant tumors block the intestinal tract, causing the stool to stay in the large intestine for too long and the water is excessively absorbed, causing the stool to be dry and unstable. In addition, constipation caused by cancer is usually accompanied by other symptoms, such as blood in the stool, vomiting blood, abdominal pain and so on. In conclusion, although cancer can cause constipation, if constipation occurs suddenly, do not consider it to be caused by cancer first. You should consider those common diseases and multiple diseases in combination with other symptoms.