Diverticulitis: This condition is characterized by inflammation of the diverticula in the digestive tract, often presenting with abdominal pain, fever, and changes in bowel habits such as constipation. The symptoms can be intermittent and may worsen over time if not treated.

Irritable Bowel Syndrome (IBS): Although IBS does not typically cause fever, some patients may experience intermittent abdominal pain and changes in bowel habits, including constipation. The absence of systemic symptoms like fever might make this less likely, but it remains a consideration.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause abdominal pain, fever, and alterations in bowel habits. While they are more common in younger populations, they can occur at any age.
Gastroesophageal Reflux Disease (GERD): Although GERD primarily causes heartburn and regurgitation, some patients may experience abdominal pain and discomfort. However, fever and constipation are not typical symptoms.

Appendicitis: Although less common in older adults, appendicitis can present atypically with vague abdominal pain, fever, and changes in bowel habits. Missing this diagnosis can lead to severe consequences, including perforation and peritonitis.
Ovarian Torsion: This is a surgical emergency that can cause severe abdominal pain and fever. While it's more common in younger women, it should not be overlooked in any female patient with acute abdominal pain.
Bowel Obstruction: This condition can cause abdominal pain, fever, and significant changes in bowel habits, including constipation. It requires prompt diagnosis and treatment to prevent complications.

Neuroendocrine Tumors: These tumors can cause a variety of symptoms, including abdominal pain, changes in bowel habits, and systemic symptoms like fever, due to the production of various hormones.
Abdominal Lymphoma: Lymphoma involving the abdomen can cause fever, abdominal pain, and changes in bowel habits. It is a rare consideration but should be kept in mind, especially in the context of unexplained symptoms.
Endometriosis: Although endometriosis is more common in younger women, it can occur in postmenopausal women, especially those on hormone replacement therapy. It can cause abdominal pain and changes in bowel habits, but fever is less commonly associated with this condition.