Many people find the Official Coding Guidelines for ICD-10-PCS dense, confusing, and repetitive. Guidelines may be listed in the Introduction, in the ICD-10-PCS Official Guidelines for Coding and Reporting, or in an appendix. Some of the sections on ancillary services include no guidelines at all. Many of the guidelines seem to raise as many questions as they answer. The approaches use terms such as percutaneous endoscopy rather than more familiar terms such as laparoscopy or arthroscopy. Another point of confusion is the terms used for the values used to build a code. What is a contractibility modulation device or a hemodynamic device? This publication addresses these problems. This book is an expanded version of the 2019 ICD-10-PCS book, with more detailed description of each character used in the codes for each body system and a summary of 2019 changes. It also includes: Description of general PCS guidelines; Guidelines and examples for specific body systems in the Medical and Surgical section; Decision trees to help select the appropriate root operation and approach; and a dictionary of terms used in PCS.