Lying down and feeling hardness in the left abdomen may be related to accumulation of fecal matter, intestinal obstruction, intestinal malignant tumors and other causes, which need further differential diagnosis. 1. Accumulation of feces: when a large amount of feces accumulates in the intestines, it can increase the pressure in the intestines, and the hardness of the left abdomen can be felt when lying down. 2. Intestinal obstruction: if the sigmoid colon is twisted, because the proximal intestinal contents can not continue to be discharged, the pressure in the intestinal tube increases, and the left side of the abdomen can be touched when lying down and there will be a hard feeling. 3. Malignant tumor of intestinal tract: If the tumor of malignant tumor of colon is too big, it can lead to the accumulation of intestinal contents in the area above the tumor, which can increase the pressure in the intestinal tract above the tumor, and it will feel hard when you touch it when you lie down. It is recommended that people who feel hardness in the left abdomen when lying down should go to regular hospitals in time to clarify the cause of the disease and standardize the treatment under the guidance of doctors.