Constant pain in the lower left abdomen and inability to pass stool may be functional constipation, colitis or colonic obstruction, which need to be analyzed specifically. 1. Functional constipation: irregular work and rest, work pressure or irregular diet may lead to functional constipation, may appear in the lower left abdomen persistent pain can not pull the symptoms, may also be accompanied by nausea, increased exhaust, etc., fecal imaging, gastrointestinal x-ray and other tests can assist in the definitive diagnosis. 2. Colitis: bacterial, fungal and other pathogenic infection, immune response or other physical and chemical factors can lead to colitis, clinical manifestations include abdominal pain, constipation, urgency and heaviness (discomfort in the lower abdomen, wanting to defecate very much, and a sense of incomplete defecation after defecation), mucus-pus-blood stools, fatigue, emaciation, and so on, colonoscopy, barium enema and other tests can assist in the definitive diagnosis. 3. Colonic obstruction: Tumor, intestinal torsion and other causes can lead to colonic obstruction, clinical manifestations include abdominal pain, abdominal distension, nausea, vomiting, stopping defecation and elimination of gas, etc. Abdominal X-ray film, colonoscopy and other examinations can assist in making a clear diagnosis. Persistent pain in the left lower abdomen and inability to pass stool may also be caused by other reasons, and it is recommended to consult the hospital in time to make a clear diagnosis and avoid delaying the condition.