According to a recent 4-year study...

... just 7 emergency general surgery procedure groups accounted for 80.0% of procedures, 80.3% of deaths, 78.9% of complications, and 80.2% of inpatient costs nationwide. These seven procedure groups included:

• partial colectomy (removal of part of the colon)
• small-bowel resection
• cholecystectomy (gall bladder removal)
• operative management of peptic ulcer disease
• lysis of peritoneal adhesions (removal of abdominal adhesions)
• appendectomy
• laparotomy (procedures involving an incision in the abdomin)

Source: "Use of National Burden to Define Operative Emergency General Surgery," JAMA Surgery, April 27, 2016, http://archsurg.jamanetwork.com/article.aspx?articleid=2516780