A 26-year-old man has severe right-sided abdominal pain with nausea. What condition is most suspicious in this case?

In a case of severe right-sided abdominal pain accompanied by nausea in a 26-year-old man, acute appendicitis is highly suspicious due to the classic presentation of the condition. Acute appendicitis typically manifests with pain that begins around the umbilical area and then shifts to the right lower quadrant, where the appendix is located. This shift in pain is a key indicator of appendicitis, distinguishing it from other abdominal conditions.

Alongside the pain, nausea is often reported, further supporting the diagnosis as the body responds to the inflammation. The acute onset and the location of the pain are critical factors that lead to the consideration of appendicitis over other potential causes. While gallbladder disease can also present with right-sided abdominal pain, it typically occurs in the context of eating fatty meals and is often associated with findings such as jaundice or biliary colic. Hepatitis and gastritis generally produce more diffuse discomfort and are less likely to present with the classic pain pattern seen in appendicitis.

Given these clinical features, acute appendicitis remains the most appropriate suspicion in this scenario.