This article continues to discuss the patent and potential spaces of the abdominal region. The spaces of the infracolic region, along with their related structures, boundaries and contents, as well as some clinical notes will be reviewed.
Infracolic Compartment of the Abdominal Cavity
The infracolic compartment is located caudal to the transverse mesocolon. The oblique root of the mesentery of the small intestines further divides the compartment into a left and right infracolic compartment. The smaller right infracolic space is a triangular region whose base is the transverse mesocolon, right border is the medial wall of the ascending colon and left border is the lateral part of the root of the small intestinal mesentery. The apex of the space continues inferiorly towards the ileocecal junction and may contain the vermiform appendix. Also traveling behind the peritoneum of the right infracolic space are the right colic and ileocolic branches of the superior mesenteric artery and their corresponding veins. The right gonadal vessels and the right ureter also pass through the space. The larger left infracolic compartment is more quadrilateral in shape. It is bordered superiorly by the transverse mesocolon, laterally by the medial wall of the descending colon, inferolaterally by the superior part of the sigmoid mesocolon and medially by the medial part of the root of the small intestinal mesentery. Inferomedially, the left infracolic space communicates with the pelvic cavity. The distal half of the right ureter, the left ureter and gonadal vessels, the inferomedial part of the left kidney, as well as the common iliac and inferior mesenteric vessels traverse this space, posterior to its peritoneal sheath. Jejunoileal loops of small intestines occupy the infracolic space.
There are paracolic gutters adjacent to the infracolic compartments that are clinically significant. On the right hand side, the right lateral paracolic gutter is found lateral to the ascending colon and medial to the lateral part of the anterior abdominal wall. It extends from the right colic (hepatic) flexure, surrounds the cecum and enters the pelvic cavity. A right medial paracolic gutter has also been described in cases where the ascending colon has a mesentery; it is limited inferiorly by the ilium and its mesentery. Similar to the right, the left lateral paracolic gutter extends from the left colic (splenic) flexure adjacent to the lateral wall of the descending colon and medial to the left lateral part of the anterior abdominal wall, to its termination at the at the sigmoid mesocolon’s lateral edge. Unlike the right lateral paracolic gutter, the left lateral paracolic gutter is limited superiorly by the phrenicocolic ligament (phrenico = relating to the diaphragm). Therefore the left lateral paracolic gutter does not communicate with the supracolic compartment, but the right lateral paracolic gutter does.
There are numerous peritoneal folds around the duodenum that create potential spaces within the peritoneal cavity. These spaces have been classified as duodenal recesses. There are four duodenal recesses:
- The superior duodenal recess lies at the termination of the pars ascendens (fourth part) of the duodenum, anterior to the L2 vertebra. The inferior mesenteric vein and left colic branch of the inferior mesenteric artery are located lateral to the caudal opening of the space.
- The inferior duodenal recess is usually found in association with the superior duodenal recess, anterior to L3 vertebra. It is located lateral to the proximal part of pars ascendens of the duodenum and its opening is located cranially and medial to the inferior mesenteric vein and right colic artery.
- The paraduodenal recess is more prominent paediatric structure located behind the free border of the inferior mesenteric vein and the left colic artery. Commonly associated with the superior and inferior duodenal recesses, it rests posterior to falciform paraduodenal fold with its opening towards the right, opposite to the pars ascendens of the duodenum.
- Finally, there is an inconstant retroduodenal recess that is larger than the previously mentioned spaces with its opening pointing to the left and inferiorly. When present, it extends behind the pars horizontalis and pars ascendens of the duodenum, anterior to the abdominal aorta. Its superior limit approaches the duodenojejunal flexure and it is bounded laterally by duodenuparietal folds.
Similar phenomena of peritoneal folds occur around the caecum as previously described around the duodenum. There are three paracaecal recesses to be discussed in this article:
- The superior ileocecal recess is another space that is more prominent in paediatric patients. The posterior limit of the fold is formed by the mesentery of the ilium with the posterior caecal and appendicular branches of the ileocolic artery. Inferiorly, it is bounded by the terminal ilium and anteriorly by the caecal fold along with the anterior caecal artery.
- The inferior ileocecal recess is formed beneath the bloodless fold of Treves (ileocecal fold). Posterior to the space is the proximal part of the mesentery of the appendix along with the appendicular artery. The medial border is formed by part of the terminal ileum while its lateral limit is the proximal part of the vermiform appendix and the medial surface of the cecum.
- Lastly, the retrocecal (retrocolic) recess is found posterior to the caecum and may extend as far as the proximal ascending colon. Caecal folds on either side of the space form its lateral and medial limits. On occasions when the vermiform appendix is in a retrocecal position, it would be found in this space.
The intersigmoidal recess is a space formed between and inferior to the Λ-shaped (capital lambda shaped) sigmoid mesocolon above the left sacroiliac joint at the brim of the pelvis. Travelling through this recess are the left common iliac artery and vein and the left ureter.