[Human ontogeny of the left colon. Fetal stage].

Foetal evolution of bowel is the result of unequal growth of its segments and abdominal constraint of pressure. Caecum and appendix on the cranial and right side of intestine torsion differentiate colic anlage. Left colon observations in 20 foetus reveal a dorsal peritoneal fusion between 12 and 17 weeks: Progressive growth of left colon and meso, without dorsal fixation, beyond left kidney and subrenal gland. First mesocolon fixation at the left kidney. A tunnel persist between this fusion and the primitive mesocolon root. Radial advance of peritoneal fusion up to sigmoid mesocolon, with disappearance of the tunnel. Peritoneal fusion confirmed by histology.