In human foetus, the mesenteries that carry vascular and neural supply to the alimentary tube play an important role in its development and anatomical location within the abdominal cavity. The mesenteric attachments of the small bowel, transverse colon and sigmoid allow them to be intraperitoneally mobile structures. In contrast, the ascending and descending colon lose their mesenteries by fusion with the parietal peritoneum and become fixed in retroperitoneal position along the posterolateral walls of the abdomen. In about 2%–4% of individuals, this process is disrupted, causing a complete or partial retention of their congenital mesocolon. The ascending or descending colon will then remain intraperitoneally mobile, affecting the normal visceral anatomy and causing potential complications. This article reviews the spectrum of radiological manifestations and clinical consequences of these anomalies.