anterior pararenal space

The

anatomical compartments and their connections as demonstrated by ectopic air. Duodenal perforation complicating ERCP in a 60-year-old man. Contrast-enhanced CT scan at the level of right renal hilum (a, b) and iliac crest (c) shows the retroperitoneal and interfascial planes. a Anterior pararenal space (APS) is limited by posterior parietal peritoneum and anterior renal fascia, with midline continuity; posterior pararenal space (PPS) between posterior renal fascia and transversalis layer of endoabdominal fascia; perirenal space (PS) between anterior and posterior renal fascias. Renal and lateroconal fasciae are laminated, defining potential spaces: the retromesenteric (RMP), the retrorenal (RRP) and lateroconal planes (LP) that all communicate at fascial trifurcation. b Axial image focused on fascial trifurcation. Ectopic gas is seen extending through the retromesenteric plane (RMP), retrorenal plane (RRP) and lateroconal plane (LP), and meeting at the fascial trifurcation (red star). Posterior pararenal space (PPS) anteriorly continues as a fat stripe in the properitoneal space (PP). c Inferior extension of the interfascial plane, delineated by ectopic gas/air. The retromesenteric and the retrorenal planes approximate one another as the fat cone of perirenal fat diminishes inferiorly, resulting in the combined interfascial plane (CIP); it continues in the pelvis along the anterolateral margins of the psoas muscle contiguous with the pelvic retroperitoneal perivesical and presacral spaces

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The

anatomical compartments and their connections as demonstrated by ectopic air. Emphysematous necrotising pancreatitis in a 64-year-old woman. Contrast-enhanced axial CT scan demonstrates a mottled collection of gas bubbles mainly involving the body and tail of the pancreas; inflammatory changes in the surrounding fat are seen. Gas spread is depicted along the retromesenteric plane and along properitoneal space (red star). RMP retromesenteric plane, APS anterior pararenal space, PP properitoneal space

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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 perirenal fascia.

Gross anatomy

It contains the duodenum (D2 & D4), pancreas and retroperitoneal segments of the ascending and descending colon. It also contains the roots of the small bowel mesentery and transverse mesocolon.

Boundaries

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