Embryology for Urologists

Introduction

The embryology of the genito-urinary tract is fascinating and is an integral part of our daily practice. As practitioners of our “art” we generally do not think of the underlying embryological development until we see a problem. In fact, as clinicians and surgeons in both our adult and pediatric practice, we often, if not daily, hear about, see in consultation, care for, or operate on patients with problems that have an embryological anomalous basis. Unfortunately, most of us were glad when “embryology” was behind us and while we generally know how to correct the problem we do not really recall how or why it occurred.

The purpose of this chapter is to present a short, practical, in-the-trenches guide to the embryology we deal with as urologists. It is in no way intended to replace the very interesting and more detailed explanations of these embryological events as described in the several excellent embryology textbooks available to us. (See references.) It is however a succinct presentation of the basic embryological knowledge that you might need to better understand the patients’ problem, further evaluate, direct therapy, and explain to your patient why the problem occurred and why and how it may or may not need treatment. It is also intended to be a fun and easy way to review the underlying cause

of the many problems we see on a daily or regular basis.

This chapter is based and modeled after the annual lecture presentation given at the annual Basic Science and Review courses sponsored by the AUA and EUA. Many of the pictures used in that lecture presentation come from Netter’s medical illustrations in Ciba’s book two and six. In addition to the pictures presented in this text, the reader is encouraged to review those illustrations to provide a visual description of the embryology presented. Finally, I should note that while we address each individual area of embryological development separately (kidneys, ureters, bladder, etc.) as well as their more common associated anomalies, the reader must visualize and recognize that the ongoing development is bilateral and overlapping.

Incidence of Congenital

Anomalies

Congenital anomalies of the genito-urinary tract are common and an estimated 10% occur in the population in general. If other systems are congenitally abnormal, the incidence of the genito-urinary tract being involved increases to 30%, and if one genito-urinary anomaly exists, there is a 75% chance that a coexisting