How is appendicitis diagnosed? is nausea & rebound pain always present?

No: It's the big picture. "a three-legged dog is still a dog." nausea usually but not always; rebound pain only if the peritoneum's involved.

No.: Appendicitis can present in a lot of different ways...Nausea may not always be present (but usually is), more common is a complete lack of appetite. Rebound pain is associated with later presentations of appendicitis and may not be present early in the disease. Appendicitis is diagnosed by ct scan, and occasionally by surgery.

Physical exam: Draw a line between the right hip bone jutting forward and the belly button. Divide it into 3rds. The spot 1/3rd of the way from the hip bone is mcburney's point. If fingertip pressure on this spot causes exquisite pain, then this is appendicitis until proven otherwise. Rebound implies a surgical abdomen and more immediacy. If symptoms are not convincing, wait and repeat the exam later.

Never say always : Nothing is 100%. Symptoms often depend upon the anatomical position of the appendix, the degree of inflammation and its acuteness, and how much the peritoneum is irritated. Nausea and rebound tenderness are very common but not confined to appendicitis. You can see appendicitis without either.