Descending Colon

The descending colon is about 10 in. (25 cm) long and lies in the left upper and lower quadrants. It extends downward from the left colic flexure, to the pelvic brim, where it becomes continuous with the sigmoid colon. The peritoneum covers the front and the sides and binds it to the posterior abdominal wall.

Relations:

• Anteriorly: Coils of small intestine, the greater omentum, and the anterior abdominal wall
• Posteriorly: The lateral border of the left kidney, the origin of the transversus abdominis muscle, the quadratus lumborum, the iliac crest, the iliacus, and the left psoas. The iliohypogastric and the ilioinguinal nerves, the lateral cutaneous nerve of the thigh, and the femoral nerve also lie posteriorly.