What causes left abdominal pain upon waking up in the morning?

Left abdominal pain upon waking in the morning can be caused by various factors, mainly including: 1. Non-disease factors: such as physiological responses (normal intestinal peristalsis before defecation), cold stimulation (abdominal cooling during the night leading to smooth muscle spasm), and muscle strain (excessive abdominal muscle tension due to improper sleeping posture). 2. Digestive system diseases: such as gastritis (often accompanied by gastric mucosal swelling and congestion), gastric ulcer (upper left abdominal pain, particularly evident after meals or on an empty stomach), and colitis (mild pain in the lower left or lower abdomen accompanied by diarrhea and bloating). 3. Other diseases: such as gynecological conditions (left adnexitis, ovarian cysts, etc.), and constipation (stool accumulation in the rectum or sigmoid colon). 4. Other factors: such as strenuous exercise, high mental stress, and dietary irritation may also cause left abdominal pain.