The main causes of bloating in the abdomen and wanting to have a bowel movement but not having one are constipation, bowel cancer and menstruation. 1. Constipation: constipated patients may drink too little water, which makes it difficult to pass stools. Long time accumulation of feces in intestines may increase gas-producing bacteria in the intestines, and the gas-producing bacteria will release a lot of gas when decomposing feces, which will cause abdominal distension and bloating under the dual action of feces and gas, and also stimulate anus, which will produce a sense of defecation, but because of the reduced peristaltic function of intestines, the patient is unable to pass stools. 2. Bowel cancer: Bowel cancer patient’s tumor presses the intestine, and the abdomen can produce a feeling of falling pain. It will also make the brain center mistakenly think that there is stool in the intestines, which will lead to the feeling of defecation, but it cannot be pulled out. 3. Menstruation: during menstruation, the endometrium is shedding, the pelvis is congested, and there will be a feeling of abdominal distension. In addition, the congested pelvis can compress the intestines and make the anus swell, which will produce the urge to poop, but there is not enough content in the intestines, so you can’t poop out. People who always feel bloated and want to have a bowel movement but don’t have one should go to the hospital in time to clarify the cause, so as not to miss the best time for treatment.