[Principles of surgical indications: aids in decision making].

Several types of clinical studies provide important decision aids for surgical indications. They include quantitative data on outcomes and utility analysis, graphic illustration of the various possibilities for decisions by decision trees, controlled clinical trials with data used in decision trees and--if these trials fail for several reasons--carefully conducted and documented prospective and retrospective trials. Items for defining the term "surgical indication" were illustrated by constructing a decision tree for treatment of chronic duodenal ulcer.