Which condition is characterized by lower abdominal pain, diarrhea-predominant, alternating diarrhea/constipation, and nausea?

The symptoms described—lower abdominal pain, diarrhea predominantly, alternating diarrhea and constipation, and nausea—are classic features of Irritable Bowel Syndrome (IBS). This functional gastrointestinal disorder is characterized by a combination of symptoms that typically include abdominal discomfort associated with alterations in bowel habits, such as diarrhea and constipation.

In IBS, the exact cause is not fully understood, but it is believed to involve a combination of heightened sensitivity of the gastrointestinal tract and abnormalities in gut motility. The alternating patterns of bowel movements are particularly distinctive, as IBS can manifest with periods of diarrhea and periods of constipation, contributing to the variability of symptoms. Furthermore, nausea can occur in IBS due to gut-brain interactions and is often exacerbated by stress or dietary factors.

In contrast, conditions like Diverticulitis, Ulcerative Colitis, and Crohn's disease typically involve different presentations. For example, Diverticulitis often presents with localized pain in the lower left quadrant and may involve fever and a more acute onset of symptoms related to inflammation of diverticula. Ulcerative Colitis is characterized predominantly by bloody diarrhea and continuous inflammation of the colon, while Crohn's disease can lead to a more patchy distribution of inflammation and can also feature abdominal pain,