Introduction

The urinary system has a complex embryological development, and the function is performed by multiple different embryonic structures at different stages of development. The kidneys are mesodermal in origin, and are sequentially formed through pronephros into metanephros, which forms the adult kidneys which ascend from the pelvis into their anatomical location in the abdomen. Aberrations in this development leads to anatomical abnormalities and variants, which range from incidental findings to lethal congenital conditions, described elsewhere in the book.

Development of kidneys

The intraembryonic mesoderm has three parts: paraxial mesoderm, lateral plate mesoderm and intermediate mesoderm. There is bulging of intermediate mesoderm on posterior abdominal wall known as urogenital ridge. This urogenital ridge is divided into two parts:

The kidney in the human develops from cranial to caudal through the three stages (Fig. 10.5.1):