Irritable Bowel Syndrome (IBS): This condition is characterized by abdominal pain associated with bowel movements, changes in bowel habits, and no visible signs of damage or disease in the digestive tract. The pain often improves with defecation, which aligns with the symptoms described.

Constipation: Hard stools or difficulty passing stools can cause abdominal pain that may worsen before defecation due to the body's effort to pass the stool.
Hemorrhoids: These can cause pain, especially if they are thrombosed, and the pain may be exacerbated by the act of defecation or the feeling of needing to defecate.
Anal Fissure: A small tear in the lining of the anus can cause sharp pain during and after defecation, which might start before the act if the individual anticipates pain.

Intestinal Obstruction: Although less common, an obstruction in the intestines can cause severe abdominal pain that may occur at any time, including before defecation, due to the buildup of intestinal contents.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause chronic abdominal pain, changes in bowel habits, and potentially severe complications if not treated.
Appendicitis: While the pain typically starts near the navel and then moves to the lower right abdomen, in some cases, the pain can be more diffuse or related to bowel movements, especially if the appendix is located in an unusual position.

Colorectal Cancer: Abdominal pain related to bowel movements can be a symptom, though it's more commonly associated with other signs like weight loss, changes in bowel habits, and blood in the stool.
Diverticulitis: Inflammation of the diverticula in the digestive tract can cause abdominal pain, usually on the lower left side, which might worsen with bowel movements.
Gastrointestinal Neuroendocrine Tumors: These rare tumors can cause a variety of symptoms, including abdominal pain related to eating or bowel movements, depending on their location and secretion of hormones.