The anterior pararenal space is the portion of the retroperitoneum that lies between the posterior surface of the parietal peritoneum and the anterior reflection of the renal fascia.

Gross anatomy

It contains the retroperitoneal portion of the duodenum (distal D1 to D3), the pancreas, and retroperitoneal segments of the ascending and descending colon. It also contains the roots of the small bowel mesentery and transverse mesocolon ¹.

It should be noted that earlier versions of Gray's Anatomy had incorrectly stated the anterior pararenal space to include "the second part...and the fourth part of the duodenum" ², and subsequently this has been extensively incorrectly quoted in the literature. This has been updated as of the 42^nd edition as "the second and third portions of the duodenum" ¹, however, it is widely agreed that the distal portion of the first part is retroperitoneal, which would also logically be included within the space.

Boundaries

• medially: there is continuity with the contralateral anterior pararenal space although in most cases, fluid will lateralize to the side of the pathology

• laterally: the compartment is limited as the lateroconal fascia and parietal peritoneum merge

• superiorly: fluid may extend to the dome of the diaphragm immediately posterior to the esophagus and phrenicoesophageal ligament

• inferiorly: fluid may extend to the iliac fossa, from there into the pelvis and potentially to the rectus sheath, around the round ligament or ductus deferens and even into the femoral sheath

Radiographic features

There is a paucity of fat within the compartment and therefore, it is difficult to identify on CT or MRI in patients with no additional pathology.

When fluid collects within the anterior pararenal space it becomes easier to identify on CT or MRI. Additionally, because the renal fascia is bilaminated, fluid in the compartment can dissect between the anterior and posterior fascia and sit behind the kidney.

Additionally, fluid can dissect along ligaments and mesenteries to lie in the subperitoneal space, e.g. gastrosplenic ligament, transverse mesocolon and greater omentum.