Course and splitting of the retroperitoneal fascia
The retroperitoneal fascia begins at the level of the posterior axillary line. In this zone, the parietal peritoneum and the endoabdominal fascia (fascia endoabdominalis) fuse firmly, forming the so-called fascial junction.
Heading medially, at the lateral contour of the kidney, the fascia divides into two laminae:
- Prerenal fascia (fascia prerenalis) — covers the renal adipose capsule anteriorly.
- Retrorenal fascia (fascia retrorenalis) — a well-defined layer passing posterior to the kidney.
Both laminae play a key role in organ fixation and limiting the pathways of infection spread.
Features of the prerenal and retrorenal fasciae
Each of the laminae has its own specific topography and fixation points.
The prerenal fascia forms an isolated sheath for the adrenal gland in its upper part. On the left, it attaches to the tissues surrounding the celiac trunk and superior mesenteric artery, and on the right, to the sheath of the inferior vena cava. A crucial feature: below the origin of the superior mesenteric artery, this lamina continuously crosses to the opposite side, while sending laminae to the aorta and inferior vena cava. Descending inferiorly, it transforms into the fascia preureterica and thins out at the level of the III–V lumbar vertebrae, merging with the parietal peritoneum.
The retrorenal fascia fuses superiorly with the prerenal fascia and attaches to the sheaths of the crura of the diaphragm. Medially, it blends into the sheaths of the major vessels and firmly, intimately fuses with the fascia of the psoas major muscle (m. psoas major). Inferiorly, it continues as the retroureteric fascia (fascia retroureterica).
Retroperitoneal tissue proper
This is the first layer of adipose tissue located immediately posterior to the fascia retrorenalis. Its boundaries are clearly delineated:
- Anteriorly: retrorenal fascia.
- Posteriorly: endoabdominal fascia covering the muscles of the posterior abdominal wall.
- Superiorly: the space is blindly closed at the level of the 12th rib (the site of fusion of the fascia endoabdominalis with the diaphragm).
- Inferiorly: the adipose tissue descends freely into the pelvic cavity.
- Medially: bounded by the zone of fusion between the retrorenal fascia and the sheaths of the vessels and iliopsoas muscle.
- Laterally: the space is closed at the posterior axillary line, therefore this layer does not extend into the preperitoneal tissue.
The tissue itself consists of large fat lobules permeated by delicate connective tissue septa running in different planes. Such loose reticular structure is of clinical significance: it allows the unimpeded introduction of gas (oxygen) for X-ray diagnostics — pneumoretroperitoneum.
Paranephric body (renal adipose capsule)
The second layer of adipose tissue is the paranephric body (paranephron, or capsula adiposa renis). It is enclosed between the laminae of the retroperitoneal fascia (prerenal and retrorenal) and completely envelops the kidney.
Topographically, the paranephron is divided into three parts:
- Superior — the fascial and adipose sheath of the adrenal gland. Clinically important: it is completely isolated from the adipose tissue of the kidney itself.
- Middle — the renal adipose capsule proper.
- Inferior — the fascial and adipose sheath of the ureter.
Unlike the adrenal gland, the fascial and adipose spaces of the kidney and ureter communicate freely with each other, which determines the pathways of fluid spread and inflammatory processes (e.g., in paranephritis).
Briefly: answers to topical questions
What layers of adipose tissue are distinguished in the retroperitoneal space?
Three layers of adipose tissue are distinguished in the retroperitoneal space.
- Retroperitoneal tissue proper (textus cellulosus retroperitonealis) — the first layer, located immediately posterior to the retrorenal fascia.
- Perirenal adipose tissue (paranephron) — the second layer, representing the adipose capsule enclosing the kidney on all sides.
- Paracolic adipose tissue (paracolon) — the third layer, located posterior to the ascending and descending parts of the colon.
Which organs are located retroperitoneally?
The following organs are located in the retroperitoneal space or have extraperitoneal parts:
- Kidneys (renes) — located in the upper part of the retroperitoneal space within their own adipose capsule.
- Adrenal glands (glandulae suprarenales) — located above the upper poles of the kidneys and enclosed in fascial capsules.
- Ureters (ureter) — surrounded by periureteric adipose tissue extending along the ureter.
- Ascending and descending colon (colon ascendens, colon descendens) — their extraperitoneal parts are covered by retrocolic fascia.
Which nerve plexuses are located in the retroperitoneal space?
Autonomic nerve plexuses with ganglia are located in the retroperitoneal space.
- Celiac plexus (plexus celiacus) — the largest autonomic plexus in the retroperitoneal space; located on the anterior surface of the aorta on either side of the celiac trunk.
- Suprarenal plexuses — occupy a position between the celiac plexus and the adrenal glands.
To avoid confusing the adipose layers from outside to inside, remember: first comes the "Retroperitoneal tissue proper", and then, deeper, around the kidney — the "Paranephron".
Class and exam questions
Does the proper retroperitoneal tissue actually continue into the proper peritoneal preperitoneal tissue on the lateral abdominal wall?
No, it does not. At the level of the posterior axillary line, the parietal peritoneum firmly fuses with the endoabdominal fascia, forming an impassable barrier.
Does the adrenal tissue communicate with the renal adipose capsule?
No, the superior part of the paranephron, which forms the sheath for the adrenal gland, is completely isolated from the renal adipose tissue.
How does the pre-renal fascia behave medially?
Inferior to the origin of the superior mesenteric artery, it crosses to the opposite side as a single continuous lamina, participating in the formation of the sheaths of the aorta and inferior vena cava.
Where can pus from the paranephron spread?
Since the fascial and adipose sheaths of the kidney and ureter communicate, the process can descend unhindered along the course of the ureter down into the pelvic adipose tissue.
What else to study on this topic
- Topography of the retroperitoneal space on a horizontal section (Stromberg's diagram)
- Sagittal section of the retroperitoneal space and its relationship with the diaphragm
- Paracolic adipose tissue (paracolon) and Toldt's fascia
- Sheaths of the major vessels (aorta and inferior vena cava)
- Connection of the retroperitoneal adipose tissue with the fascial spaces of the pelvis
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