Opposite the ascending colon, the descending colon is found on the left side of the abdominal cavity. It extends downward from the left colic flexure toward the iliac crest. Upon reaching the left iliac fossa, it further continues as the sigmoid colon.

The descending colon begins as a continuation of the transverse colon and is about 9.84 to 11.81 inches (25 - 30 cm) long. It is smaller in diameter than the ascending colon. Also, it is situated more deeply and has more pronounced epiploic appendices.

The descending colon is located retroperitoneally, and the peritoneum covers its anterior and lateral surfaces. The descending colon is typically immobile. However, around 33% of individuals can have a short descending mesocolon, and in that case, it can be slightly mobile.

Posterior to the descending colon is the renal fascia, as well as the quadratus lumborum muscle, transversus abdominis muscle, iliacus muscle, and psoas major muscle. Several neurovascular structures are also located posterior to the descending colon, including the subcostal arteries, subcostal veins and subcostal nerves, fourth lumbar artery, iliohypogastric nerve, ilioinguinal nerve, lateral femoral cutaneous nerve, femoral nerve, and genitofemoral nerve. Anteriorly, the descending colon is related to the greater omentum and the loops of the jejunum.

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Descending colon