What condition is most likely diagnosed in the 56-year-old postmenopausal woman with left lower abdominal pain and nausea?

In a 56-year-old postmenopausal woman presenting with left lower abdominal pain and nausea, acute diverticulitis is the most likely diagnosis due to the clinical scenario presented. Postmenopausal women are at an increased risk for diverticular disease, particularly as they age. Diverticulitis occurs when diverticula, small pouches that can form in the intestinal wall, become inflamed or infected.

The left lower quadrant pain is particularly suggestive, as the sigmoid colon, which is most commonly affected by diverticulitis, is located on the left side of the abdomen. The presence of nausea further supports the diagnosis, as it can be associated with inflammation of the gastrointestinal tract.

Additionally, acute diverticulitis often presents with localized tenderness in the affected area, fever, and changes in bowel habits, making it important to consider in this demographic. Other conditions, such as appendicitis, are less likely in a woman who is postmenopausal and typically presents with pain in the right lower quadrant. Ovarian cyst rupture can cause significant pain but is usually accompanied by specific gynecological symptoms, and pelvic inflammatory disease is more commonly seen in premenopausal women and often accompanied by other signs of infection.