Which symptom is most indicative of a vaso-occlusive crisis in a patient with sickle cell anemia?

A vaso-occlusive crisis in sickle cell anemia occurs when sickle-shaped red blood cells obstruct blood flow in small vessels, leading to ischemia and pain due to tissue hypoxia. Acute abdominal pain is a common manifestation of this crisis as the obstruction can occur in the mesenteric vessels, resulting in decreased blood supply to the intestines and abdominal organs. This pain can vary in intensity and may be accompanied by other symptoms such as nausea and vomiting.

The other options do not align with the typical presentation of a vaso-occlusive crisis. Increased hemoglobin levels typically indicate a well-oxygenated state, which would not occur during a vaso-occlusive crisis. Skin discoloration might occur in certain cases of vaso-occlusion due to poor blood flow, but it is not characteristic, nor is it the primary symptom. Increased appetite is generally not associated with vaso-occlusive episodes, as patients usually experience pain and discomfort that can affect their desire to eat. Therefore, acute abdominal pain is the most indicative symptom associated with a vaso-occlusive crisis in sickle cell anemia.