Constipation: Given the colicky nature of the pain that improves and then worsens after eating, constipation is a plausible cause, especially if the patient has not had a bowel movement recently or if the stools are hard. The fact that stools are formed supports this diagnosis, as it indicates the patient is not experiencing diarrhea but could be having difficulty passing stools.

Intestinal Obstruction: Although less common, intestinal obstruction can occur post-operatively, especially after a laparoscopic procedure like cholecystectomy. The colicky pain, especially after eating, could suggest an obstruction. However, the fact that the patient has passed formed stools makes this less likely.
Adhesions: Post-operative adhesions can cause bowel obstruction or intermittent bowel obstruction, leading to colicky abdominal pain. The history of recent surgery makes this a consideration.
Gastroenteritis: An infection of the stomach and intestines could cause severe abdominal cramping, though the presence of formed stools and the specific timing related to eating might make this less likely.

Bowel Ischemia or Infarction: Although rare, bowel ischemia can occur post-operatively due to various reasons, including embolism, thrombosis, or venous thrombosis. It is critical to consider this diagnosis due to its high mortality rate if not promptly treated.
Hernia (Incisional or Internal): A hernia could cause intestinal obstruction, which might present with colicky pain, especially if it involves the bowel. Given the recent abdominal surgery, this is a critical diagnosis not to miss.
Appendicitis: Although the patient's surgery was for cholecystectomy, appendicitis can occur at any age and might present atypically in the elderly. The location and nature of the pain could suggest appendicitis, especially if the appendix is located in a retrocecal position.

Diverticulitis: While more common in the sigmoid colon, diverticulitis can occur in any part of the colon and could present with severe abdominal pain. However, it's less likely given the colicky nature and the recent post-operative status.
Inflammatory Bowel Disease (IBD) Flare: Although IBD (Crohn's disease or ulcerative colitis) can present at any age, a new diagnosis in a 75-year-old post-operative patient would be uncommon. The colicky pain and formed stools might not typically suggest IBD, but it remains a consideration in the differential diagnosis.