The Three Extraperitoneal Compartments and Perirenal Fasciae

Detailed evaluation shows that the extraperitoneal region, rather than being composed of amorphous "straggling mesenchyme," is distinctly demarcated by well-defined fascial planes. Figure 8-1a is an enlarged horizontal cross-section through the flank at the lower pole of the kidney. Central to the division of the extra-peritoneal region are the conspicuous anterior and posterior layers of renal fascia. (The posterior renal fascia was first described by Zuckerkandl21 [Fig. 8-2] and the anterior renal fascia subsequently by Gerota22 [Fig. 83], but the two layers have since been known collectively as Gerota's fascia.23)

The renal fascia is a dense, collagenous, elastic connective tissue sheath that envelops the kidney and peri-renal fat. Its two layers fuse behind the ascending or descending colon to form the single lateroconal fascia, which then continues around the flank to blend with the peritoneal reflection forming the paracolic gutter. Figure 8-1b illustrates these important fascial relationships by computed tomography. In this way, I have defined precisely three individual extraperitoneal compartments. Their major fascial marginations are illustrated in Figure 8-1c.

1. The anterior pararenal space extends from the posterior parietal peritoneum to the anterior renal fascia. Significantly, it is confined laterally by the lateroconal fascia.

2. The perirenal space encompasses the kidney and its investing fat. A conspicuous anatomic feature is the peri-renal fat, which is most abundant behind and somewhat

Extraperitoneum Pararenal Fascia

Fig. 8—1. Extraperitoneal anatomy of the flank.

(a) Transverse cross section. The anterior and posterior renal fasciae (black arrows) envelop the kidney (K) and perirenal fat. From their line of fusion, the lateroconal fascia (white arrows) continues behind the descending colon (C) to the parietal peritoneum (black arrowheads). The posterior pararenal fat (p) is continuous with the flank fat (f) deep to the transversalis fascia (white arrowheads). PM = psoas muscle.

(b) Computed tomography demonstrates the anterior and posterior renal fasciae and the lateroconal fascia, which demarcate the extraperitoneal fat. Note their relationships to the kidney (K) and descending colon (C).

(c) The three extraperitoneal spaces: 1 = the anterior pararenal space; 2 = the perirenal space; 3 = the posterior pararenal space; QL = quadratus lumborum muscle. As evident in the cross-section at the level of the lower renal pole in a, this depicts an acute angle between the anterior and posterior renal fasciae at their junction lateral to the kidney. At this level, the junction is indeed more posteriorly located compared with the level of the renal hilus.20 Imaging studies, as in b, generally show the leaves and their junction smoothly curved and parallel to the renal contour.20

(Modified from Meyers.9)

Fig. 8—1. Extraperitoneal anatomy of the flank.

(a) Transverse cross section. The anterior and posterior renal fasciae (black arrows) envelop the kidney (K) and perirenal fat. From their line of fusion, the lateroconal fascia (white arrows) continues behind the descending colon (C) to the parietal peritoneum (black arrowheads). The posterior pararenal fat (p) is continuous with the flank fat (f) deep to the transversalis fascia (white arrowheads). PM = psoas muscle.

(b) Computed tomography demonstrates the anterior and posterior renal fasciae and the lateroconal fascia, which demarcate the extraperitoneal fat. Note their relationships to the kidney (K) and descending colon (C).

(c) The three extraperitoneal spaces: 1 = the anterior pararenal space; 2 = the perirenal space; 3 = the posterior pararenal space; QL = quadratus lumborum muscle. As evident in the cross-section at the level of the lower renal pole in a, this depicts an acute angle between the anterior and posterior renal fasciae at their junction lateral to the kidney. At this level, the junction is indeed more posteriorly located compared with the level of the renal hilus.20 Imaging studies, as in b, generally show the leaves and their junction smoothly curved and parallel to the renal contour.20

(Modified from Meyers.9)

Otto Zuckerkandl

Fig. 8-2. Emil Zuckerkandl (1849-1910), at the age of 25.

The Austrian Zuckerkandl was the favorite pupil of the eminent Professor of Anatomy Josef Hyrtl in Vienna, and he subsequently became Professor of Anatomy in Graz and Vienna. He was a universal and productive anatomist, especially active in the field of otorhinology. Among his many publications, of special interest are his descriptions of collections of chromaffin tissue near the origin of the inferior mesenteric artery in 1901, called the organ of Zuckerkandl and the posterior renal fascia in 1883, sometimes called the fascia of Zuckerkandl. (Courtesy of the Institut für Geschichte der Medizin der Universität Wien, Museum Josephinum, Vienna.)

Fig. 8-2. Emil Zuckerkandl (1849-1910), at the age of 25.

The Austrian Zuckerkandl was the favorite pupil of the eminent Professor of Anatomy Josef Hyrtl in Vienna, and he subsequently became Professor of Anatomy in Graz and Vienna. He was a universal and productive anatomist, especially active in the field of otorhinology. Among his many publications, of special interest are his descriptions of collections of chromaffin tissue near the origin of the inferior mesenteric artery in 1901, called the organ of Zuckerkandl and the posterior renal fascia in 1883, sometimes called the fascia of Zuckerkandl. (Courtesy of the Institut für Geschichte der Medizin der Universität Wien, Museum Josephinum, Vienna.)

Organ Zuckerkandl Pheo

Fig. 8-3. Dimitrie Gerota (1867-1939).

Gerota received his medical education in Bucharest and published his classic article in 1895 on the fixation of the kidneys and the presence of the anterior renal fascia, sometimes selectively called Gerota'sfascia. In 1898, he wrote the book The Röntgen Rays or the X-rays. He initiated academic radiologic education in Romania but was obliged to abandon radiology because of radiodermatitis and epithelioma of the hand, which required amputation. From 1913 onward, he continued as Professor of Anatomy in Bucharest and owner and principal of the leading private hospital at that time, The Gerota Sanitorium. (Courtesy of Prof. dr Nicolae Marcu, University of Bucharest.)

Fig. 8-3. Dimitrie Gerota (1867-1939).

Gerota received his medical education in Bucharest and published his classic article in 1895 on the fixation of the kidneys and the presence of the anterior renal fascia, sometimes selectively called Gerota'sfascia. In 1898, he wrote the book The Röntgen Rays or the X-rays. He initiated academic radiologic education in Romania but was obliged to abandon radiology because of radiodermatitis and epithelioma of the hand, which required amputation. From 1913 onward, he continued as Professor of Anatomy in Bucharest and owner and principal of the leading private hospital at that time, The Gerota Sanitorium. (Courtesy of Prof. dr Nicolae Marcu, University of Bucharest.)

lateral to the lower pole of the kidney. This becomes of practical importance in the diagnosis of coalescent per-irenal abscesses and hematomas.

3. The posterior pararenal space extends from the posterior renal fascia to the transversalis fascia. It consists of a thin layer of fat, and its most notable feature is that it continues uninterruptedly external to the lateroconal fascia as the properitoneal fat of the abdominal wall. It is important to recognize that it is the posterior pararenal fat, as it courses laterally external to the lateroconal fascia and deep to the transversalis fascia, that is radiologically visualized as the "flank stripe" (Figs. 8-4 and 8-5).

Figure 8-6a is a horizontal diagram illustrating the major relationships and components of the three extra-peritoneal compartments.

The anterior pararenal space includes the ascending and descending colon, the duodenal loop, and the pancreas. In other words, the extraperitoneal portions of the alimentary tract reside within this compartment. While the space is potentially continuous across the midline, fluid volumes even under pressure typically reach only the midline (Fig. 8-7) or shortly beyond (Fig. 8-8). Clinically, moreover, I have observed that collections of fluid or gas are generally confined to their side of origin. A notable exception includes pancreatic extravasations, probably for two reasons: (a) the pancreas itself straddles

Perirenal Fascia

The blood is seen as a prominent soft-tissue mass displacing the intact flank stripe medially (arrows). These features localize the hematoma to be superficial to the transversalis fascia and therefore subcutaneous in position.

Flank Stripe Sign

Fig. 8—4. Flank stripe highlighted by air postlaparoscopy.

Following laparoscopy, air inadvertently entering the anterior abdominal wall is seen as it courses around the flank extraperitoneally (arrows). Here, it lies deep to the transversalis fascia, within the flank extension of the posterior pararenal fat.

the midline and (b) liberated pancreatic enzymes, particularly trypsin, dissect the fascial planes and permit freer dissemination. Ventrally, the anterior pararenal space is anatomically continuous with the roots of the small bowel mesentery and transverse mesocolon.24,43

The perirenal spaces generally have no continuity across the midline. Medially, the posterior fascial layer fuses

with the psoas or quadratus lumborum fascia, and the anterior renal fascia blends into the dense mass of connective tissue surrounding the great vessels in the root of the mesentery and behind the pancreas and duode-num44 (Fig. 8-9). Originally, Gerota22 claimed bilateral continuity of the perirenal compartments deep to the anterior renal fasciae. When pressure markedly increases

The blood is seen as a prominent soft-tissue mass displacing the intact flank stripe medially (arrows). These features localize the hematoma to be superficial to the transversalis fascia and therefore subcutaneous in position.

within the perirenal space acutely, rupture occurs in the hilar region, the anterior renal fascia first giving way and then perhaps the peritoneum.27 Most precise dissections and injection experiments and meticulous CT observations have shown that the two perirenal spaces have no actual or direct communications generally throughout most of their courses.8,9,12,17 At the level of the renal hilum, CT seems to confirm the work of Martin,26 namely, that the anterior and posterior ipsilateral fasciae occasionally fuse and blend with the hilar vessels, preventing communications between both perirenal spaces across the midline17 (Fig. 8-10). Lower, however, at the levels of L3 to L5, there is evidence that indicates potential communication across the midline27-29 (Figs. 811 through 8-13). Contralateral extension of fluid, when the disease process originates in the kidney, is impeded by fibrous septa and by the narrowness of the potentially communicating channel.27,30 Indeed, recent

Extraperitoneal

Fig. 8—6. The three extraperitoneal compartments.

(a) and (b) Striped areas = anterior pararenal space; stippled areas space; IVC = inferior vena cava. (Reproduced from Meyers.8)

Posterior Pararenal Space

= perirenal space; cross-hatched areas = posterior pararenal

Retromesenteric Plane Hemorrhage

Fig. 8—7. Hemorrhage in anterior pararenal space extending to midline.

Owing to complications in a nephrostomy procedure, extravasation has occurred not only within the perirenal space but also of considerable volume within the anterior pararenal space (APS), where it spreads to the third portion of the duodenum (D) in the midline but not to the contralateral side.

(Courtesy of Michiel Feldberg, M.D., University of Utrecht, The Netherlands.)

Fig. 8—7. Hemorrhage in anterior pararenal space extending to midline.

Owing to complications in a nephrostomy procedure, extravasation has occurred not only within the perirenal space but also of considerable volume within the anterior pararenal space (APS), where it spreads to the third portion of the duodenum (D) in the midline but not to the contralateral side.

(Courtesy of Michiel Feldberg, M.D., University of Utrecht, The Netherlands.)

Pararenal Perirenal

Fig. 8—8. In vivo opacification of right anterior pararenal space.

This occurred from extravasation of contrast medium from a ruptured pseudocyst in the head of the pancreas during ERCP. Note that there is extension in this plane across the midline. Laterally, the extravasate is in relationship to the posterior hepatic flexure (phf) and angle of the liver (l). a = aorta; v = inferior vena cava.

Fig. 8—9. Midline termination of the anterior renal fascia.

CT shows thickened anterior renal fascia (arrows) blending into tissues near the midline around the renal pedicle in relationship to the superior mesenteric artery (SMA). There is no evidence of continuity across the midline. Ao = aorta; P = pancreas; C = inferior vena cava.

Fig. 8-10. Medial fascial closure of the perirenal space.

CT demonstrates accentuated renal fascial planes fusing medially around the renal pedicle (arrows). (Courtesy of Michiel Feldberg, M.D., University of Utrecht, The Netherlands.)

Fascial PlanesAnterior Midline Mesenteric

v^bc FA fcE

W

t ■

Pvi

W m

1*

K' T3

Fig. 8-11. Midline continuity of the anterior renal fascia.

At the level of the lower renal poles, the anterior renal fascia is identified to be continuous across the midline (arrows), anterior to the ureters (U), inferior vena cava (C), and aorta (A). (Reproduced from Pistolesi GF, Procacci C, Tonegutti N, et al: Analyse des différents espaces des régions extrapéritonéales. Radiologie J CEPUR 1990; 10:195-204.)

Anterior Midline Mesenteric

Fig. 8-12. Midline continuity of the anterior renal fascia.

At a level 6-cm caudal to the renal vessels, reactive thickening allows clear identification of the anterior renal fascia as continuous across the midline (arrows). In this patient with lymphoma, the fascia is seen between retroperitoneal nodal masses (N) and mesenteric adenopathy (M), both of low attenuation. It extends posterior to the ascending (ac) and descending colon (dc), which are displaced medially by intraperitoneal fluid. (Courtesy of Michael Oliphant, M.D., Crouse Hospital, Syracuse, NY.)

Perirenal Aorta

Fig. 8—13. Potential midline communication of perirenal spaces.

CT scan of prone cadaver at the level of the lower renal pole following injection of 200 mL of contrast medium into the right perirenal space (closed arrow) shows narrow channel to the midline (open arrow) anterior to the inferior vena cava (C) and aorta (Ao). (Reproduced from Mindell et al.29)

Fig. 8—13. Potential midline communication of perirenal spaces.

CT scan of prone cadaver at the level of the lower renal pole following injection of 200 mL of contrast medium into the right perirenal space (closed arrow) shows narrow channel to the midline (open arrow) anterior to the inferior vena cava (C) and aorta (Ao). (Reproduced from Mindell et al.29)

clinical investigations strongly suggest that such infrequently encountered midline communications are actually within the retromesenteric plane. Dissection of fluids within this anatomic plane of the anterior pararenal space, based on embryologic fascial fusions,31-33 has received renewed appreciation.34,35 At levels just inferior to the origin of the superior mesenteric artery, fluid can track anterior to the aorta, inferior vena cava, and left renal vein and posterior to the root of the mesentery. This is the characteristic location in which retroperito-neal collections cross the midline.

It has been recently reported that the anterior renal fascia may be deficient over the upper portion of the right kidney and adrenal gland so that the superior aspect of the perirenal space is open toward the bare area of the liver36-38 (Fig. 8-14). Whether this is a variation in extent and attachments or actual rupture through the fascia creating a communication remains to be further determined. These anatomic relationships may be of considerable clinical significance. In the occasional circumstance of a hepatic injury involving the posterior segment of the right lobe of the liver with the capsular extent of laceration limited to the bare area, retroperi-

toneal rather than intraperitoneal bleeding may oc-cur39,40 (Fig. 8-15). Thus, the classic peritoneal findings may be absent, and peritoneal lavage may not show intraabdominal blood. Rupture of amoebic liver abscess into the retroperitoneum along this precise anatomic route has also been documented.41

The posterior pararenal space is demarcated on each side of the body by the fusion of the transversalis fascia medially with the muscle fascia. It is therefore limited by and parallels the margin of the psoas muscle. The space is open laterally toward the flank and inferiorly toward the pelvis (Fig. 8-16). Bilaterally they are potentially in communication only via the properitoneal fat of the anterior abdominal wall deep to the transversalis fascia. As opposed to the other two extraperitoneal spaces, the posterior pararenal spaces contain no organs.

Figure 8-17 displays several anatomic features particularly relevant to clinical imaging and an understanding of disease processes.

Figure 8-6b is a sagittal view of a few more anatomic features that have particular diagnostic significance:

1. The lines of fusion of the anterior and posterior renal fascial layers are unique and contribute distinctly to the spread and confinement of extraperitoneal effusions. The perirenal space on each side narrows as it extends inferiorly, resembling an inverted cone. (For this reason, the single layer of fascia extending laterally from the cone of renal fascia has been designated as the latero-conal fascia.) Inferiorly, the layers fuse weakly or blend with the iliac fascia; as they narrow medially, they also blend loosely with the periureteric connective tissue. Investigators differ regarding patency of the apex of the cone. Some describe a multilaminar fusion,42 whereas others have documented ready communication toward the iliac fossa.29 However, it has been consistently observed clinically that infections and other effusions arising in the kidney or perirenal tissues are confined to the perirenal space. It may also be postulated that there is early inflammatory sealing of the potential outlet or that acute distention of the cone results in a self-sealing mechanism. Superiorly, the two layers are firmly fixed to each other above the adrenal glands to the diaphragmatic fascia.13 (Fig. 8-18).

2. At the level of the iliac crest, below the cone of renal fascia, the anterior and posterior pararenal spaces are in potential communication.

3. At this same level, the lateroconal fascia disappears as a distinct boundary so that the anterior pararenal space communicates laterally with the properitoneal fat of the flank stripe.

4. Superiorly, posterior pararenal fat continues as a thin subdiaphragmatic layer of extraperitoneal fat.

Flank Stripe Radiology

Fig. 8—14. Communication between the right perirenal space and the bare area of the liver.

(a) Occult right renal cell carcinoma (not shown) results in massive perirenal hemorrhage (H).

(b) At a higher level, the blood has risen to the site of the bare area of the liver (arrows) and encircles the inferior vena cava (C).

Morisons Pouch Seen

Fig. 8—15. Traumatic laceration of bare area of liver with communication to periadrenal tissues.

(a) CT shows that simple hepatic laceration involving the bare area is associated with hemorrhage, which is presumably subcapsular. No free fluid was seen in Morison's pouch or in the pelvis.

(b) At a level 2 cm inferiorly, a hematoma (arrow) surrounds and obscures the right adrenal gland. This had resolved at follow-up CT performed 6 days later.

(Reproduced from Patten et al.39)

Fig. 8—15. Traumatic laceration of bare area of liver with communication to periadrenal tissues.

(a) CT shows that simple hepatic laceration involving the bare area is associated with hemorrhage, which is presumably subcapsular. No free fluid was seen in Morison's pouch or in the pelvis.

(b) At a level 2 cm inferiorly, a hematoma (arrow) surrounds and obscures the right adrenal gland. This had resolved at follow-up CT performed 6 days later.

(Reproduced from Patten et al.39)

Liver Subcapsular Hematoma

Fig. 8—16. Anterolateral extension of posterior pararenal space and its communication to extraperitoneal spaces in the pelvis.

(a) CT scan of prone cadaver after injection of 100 mL of contrast medium into the left posterior pararenal space (small arrow) documents its anterolateral extension around the flank within the properitoneal fat (large arrow).

(b) CT scan of prone cadaver after injection of 300 mL of contrast medium into the left posterior pararenal space shows its connection with infrarenal space (small arrow) and its extension anterolaterally (large arrow) en route to prevesical space.

(Reproduced from Mindell et al.29)

Fig. 8—16. Anterolateral extension of posterior pararenal space and its communication to extraperitoneal spaces in the pelvis.

(a) CT scan of prone cadaver after injection of 100 mL of contrast medium into the left posterior pararenal space (small arrow) documents its anterolateral extension around the flank within the properitoneal fat (large arrow).

(b) CT scan of prone cadaver after injection of 300 mL of contrast medium into the left posterior pararenal space shows its connection with infrarenal space (small arrow) and its extension anterolaterally (large arrow) en route to prevesical space.

(Reproduced from Mindell et al.29)

At the level of the renal hilum, the posterior renal fascia terminates at the midportion of the psoas muscle. Further down it withdraws toward the quadratus lum-borum muscle (Fig. 8-19), only to fuse again with the posterolateral margin of the psoas muscle at the level of the inferior apex of the cone.17,25,26,45

The normal thickness of the fascial planes is 1-2 mm. On CT, the posterior renal fascia is normally seen far more often than the anterior. A fascia that is focally thickened or greater than 2-3 mm in width is usually abnormal19,46 (Figs. 8-20 and 8-21). Renal fascial thickening may be caused by edema, hyperemia, fibrosis, or lipolysis.47 It has been reported in a large variety ofpath-

ologic conditions,46,48,49 including inflammatory, malignant, and traumatic processes, and it is further nonspecific in not allowing diagnostic localization to a primary extraperitoneal site since it may be related to disease in the kidney, perirenal space, or pararenal compart-ments,7,8,11,19,50 or even intraperitoneal structures.51

Rarely, the appearance of thickened fascia may be simulated on CT supine scans by intraperitoneal fluid within posterior peritoneal recesses, particularly on the left.17,52,53 Fluid layering in a deep left paracolic gutter may mimic thickening of the lateroconal fascia and a portion of the posterior renal fascia. As the fluid continues superiorly into the inferior extension of the splenorenal recess, and perhaps to some degree medially within the unusual variant of a retropancreatic recess, the appearance of a thickened anterior renal fascia may result (Fig. 8-22). In those cases where distinction from intrinsic involvement of the anterior pararenal space

may be difficult. I have noted that two further findings may be of value; (a) intraperitoneal fluid would be expected to shift position on decubitus or prone CT scans; and (b) although there is some variability in the peritoneal fixation of the descending colon54,55 (Figs. 8-23 and 8-24) evidence of involvement of the extraperito-neal attachment of the descending colon indicates fluid in the anterior pararenal space (Fig. 8-25).

The posterior renal fascia has been shown by dissection studies to be divided into two laminae at a variable point from the kidney.20 The thinner anterior leaf extends anteriorly to be continuous with the anterior renal fascia. The thicker posterior lamina becomes the

Anatomic Compartments Abdomen

Fig. 8—17. Transverse anatomic cross-sections.

Connective tissues of spaces as well as mesenteries and fasciae are stained by dye permeation. (This figure also appears in the color insert.)

(a) Level of uncinate process of pancreas and renal arteries.

(b) Level of third portion of duodenum and the infrarenal abdominal aorta. These stained sections demonstrate particularly relevant features:

1. Anatomically, the anterior pararenal space is potentially continuous across the midline.

2. The perirenal spaces at these levels share no bilateral continuity; there is midline termination of the anterior renal fascia.

3. The anterior pararenal space ventrally is anatomically continuous with the roots of the small bowel mesentery and similarly of the transverse mesocolon. Lesions of the perirenal contents, including the kidneys and adrenals, are provided anatomic continuity along their major vessels to the aorta and inferior vena cava and thereby to the small bowel mesentery and transverse mesocolon. Extraperitoneal and intraperitoneal structures constitute the continuum designated as the subperitoneal space. This is fully discussed in Chapter 13.

4. Rupture of an abdominal aortic aneurysm can be anticipated as likely occurring into the perirenal space or dissecting into the posterior pararenal space or psoas muscle on the left. Anatomic considerations include the point of rupture both on the circumference of the aorta and on the cephalocaudal level. Other factors include the acuity, force, and volume of the rupture and preexisting adhesions.

(Reprinted with permission from Han M-C, Kim C-W: Sectional Human Anatomy, 2nd ed. Ilchokak, Seoul, Korea, 1989.)

Extraperitoneum Pararenal Fascia

AC = Ascending colon APS = Anterior pararenal space ARF = Anterior renal fascia Ao = Aorta Ca = Cartilage Co = Colon

D2 = Second portion of duodenum D3 = Third portion of duodenum D4 = Fourth portion of duodenum DC = Descending colon EO = External oblique muscle IO = Internal oblique muscle IVC = Inferior vena cava IE = Ileum

IlC = Iliocostalis muscle Je = Jejunum

L1-2 = L1-2 intervertebral disc

L2 = L2 vertebral body

L3 = L3 vertebral body

LC = Left diaphragmatic crus

LCoF = Lateroconal fascia

LK = Left kidney

LRA = Left renal artery

LRV = Left renal vein

LgD = Longissimus dorsi muscle

LtD = Latissimus dorsi muscle

MeF = Mesenteric fat

Mf = Multifidus muscle

PF = Perirenal fat

PP = Parietal peritoneum

PPE = Posterior pararenal fat

PRE = Posterior renal fascia

PeC = Peritoneal cavity

Ps = Psoas muscle

OL = Quadratus lumborum muscle

RC = Right diaphragmatic crus

RCx = Renal cortex

RK = Right kidney

RL = Right lobe of liver

RP = Renal pelvis

RRA = Right renal artery

RRV = Right renal vein

ReA = Rectus abdominis muscle

SMA = Superior mesenteric vein

TA = Transversus abdominis muscle

TC = Transverse colon

UnP = Uncinate process of pancreas, head

Ur = Ureter

Fig. 8—18. Attachment of adrenal gland to renal fascia superiorly.

The distinction of an adrenal mass from an upper renal pole mass can be readily made on erect films. Highlighted by retroperitoneal pneumography, the upright position allows the kidney (K) to fall, but the adrenal gland (A) harboring a pheochromocytoma remains fixed by its fascial attachment. (Reproduced from Meyers.13)

Lateroconal Fascia

lateroconal fascia. Figures 8-26 through 8-29 clearly display these laminae in four different patients. A potential space between the two laminae is thus anatomically continuous with the anterior pararenal space20 (Fig. 8-30). The laminated, potentially expansile fascial planes of the extraperitoneal tissues provide pathways of

spread.

On plain films of the abdomen, the lateroconal fascia sometimes appears as a thin line lateral to the kidney (Fig. 8-31). It is more commonly seen on the right, where it projects inferior to the hepatic angle. Characteristically, it is slightly angled medially as it extends in-feriorly. The lateral fusion of the renal fascial layers at the level of the lateroconal fascia demarcates the peri-renal fat medially from the posterior pararenal fat laterally as it extends into the flank stripe. These fascial layers are more frequently visualized in nephrotomog-raphy. In the past, this fascial line has been mistaken for the peritoneal reflection itself, leading to considerable confusion in the radiologic localization of disease processes. Its significance lies in the fact that it is truly an extraperitoneal structure that provides a boundary.

Variations in the origin of the lateroconal fascia may explain the uncommon occurrence of retrorenal colon (Fig. 8-32) or extension of ascitic fluid.56-58 The site of blending of the lateroconal fascia with the perirenal fascia varies from patient to patient as well as from side to side and from cephalad to caudad, and ranges from a location anterior to a location posterior to the kidney.20 It has been pointed out that abundant perirenal fat is much more common in men than in women and that a lack of this adipose tissue may contribute to the colon lying lateral to, or even behind, the kidney.59 Recognition of retrorenal colon may have practical applications when an invasive renal procedure is contemplated.

Kunin has called attention to three groups ofbridging connective tissue septa that may divide the perirenal space into relatively discrete compartments. These include fibrous lamellae that connect the renal capsule to the perirenal fascia and some that connect the anterior and posterior renal fasciae, but the most commonly visible in well-fatted patients is the posterior renorenal bridging septum.60 This is attached only to the renal capsule and runs parallel to the surface of the kidney. It is variable in extent somewhere between the postero-medial and posterolateral margins (Figs. 8-33 and 8-34). The septa may course over a considerable distance (Fig. 8-35) and may thicken in response to the same stimuli that cause thickening and increased visibility of the text continues on page 353

Fascia Van Zuckerkandl

Fig. 8—19. Medial insertion of posterior renal fascia.

Anatomic cross-section (a) and CT (b) below midlevel of left kidney (K) show termination of the posterior renal fascia in relationship to the quadratus lumborum muscle (arrow). The quadratus lumborum has variable width and thus the medial extent of the posterior pararenal space varies from patient to patient.20 PM = psoas muscle; C = descending colon; ARF = anterior renal fascia; LCF = lateroconal fascia; PRF = posterior renal fascia; 1 = anterior pararenal space; 2 = perirenal space; 3 = posterior pararenal space.

Posterior Pararenal Space Mass

Fig. 8—20. Localized thickening of the renal fascia

(arrow) at the site of a pyelonephritic cortical scar. (Courtesy of Roger Parienty, M.D., Neuilly, France.)

Right Quadratus Lumborum Scan
Fig. 8-21. Thickening of the renal fascia (arrows) in conjunction with an infected right renal cyst. An uninvolved simple renal cyst is present on the left. (Courtesy of Roger Parienty, M.D., Neuilly, France.)

Fig. 8—22. Thickened fascia simulated by intraperitoneal fluid.

In this cirrhotic patient with portal hypertension and widespread varices, ascitic fluid (A) occasions the appearance of thickening of the anterior renal fascia, lateroconal fascia, and a segment of the posterior renal fascia (arrows).

Lateroconal FasciaPeritoneal Reflection Colon
Fig. 8—23. The peritoneal reflection over the descending colon (arrows) is shown on this CT study by intraperitoneal contrast medium. The bare area of the descending colon (DC) is contiguous with the adipose tissue of the anterior pararenal space ventral to the left kidney (K).

Fig. 8—24. Partial peritonealization of the descending colon.

CT shows the descending colon (DC) in this case is partially peritonealized, secondary to incomplete posterior fusion of the descending mesocolon, allowing posterior extension of the left paracolic gutter (asterisk).

Left Paracolic Gutter

Fig. 8—25. Involvement of descending colon's extraperitoneal bare area.

In a case of thickened renal fascia secondary to acute pancreatitis, CT demonstrates inflammatory involvement of the extraperitoneal fat related to the bare area of the descending colon (C). This localizes the process to the anterior pararenal space and distinguishes the changes from intraperitoneal fluid.

Extraperitoneal FatParacolic Fascia

Fig. 8—26. In vivo identification of the two layers of the posterior renal fascia.

CT demonstrates an enlarged left kidney, secondary to acute pyelonephritis, abutting the posterior renal fascia and the presence of a double line of the posterior renal fascia (arrows). The inner line adjacent to the kidney is thickened, and the potential space between the two leaves of the posterior renal fascia is now seen. (Courtesy of Michael Oliphant, M.D., Syracuse, NY.)

Fig. 8—26. In vivo identification of the two layers of the posterior renal fascia.

CT demonstrates an enlarged left kidney, secondary to acute pyelonephritis, abutting the posterior renal fascia and the presence of a double line of the posterior renal fascia (arrows). The inner line adjacent to the kidney is thickened, and the potential space between the two leaves of the posterior renal fascia is now seen. (Courtesy of Michael Oliphant, M.D., Syracuse, NY.)

Lateroconal Fascia

Fig. 8-27. In vivo identification of the two laminae of the posterior renal fascia.

CT demonstrates continuity of the inner layer with the anterior renal fascia (open arrowheads) and of the outer layer with the lateroconal fascia (closed arrowheads). The anterior pararenal space thus extends between the two laminae. (Courtesy ofJay P. Heiken, M.D., Mallinckrodt Institute of Radiology, St. Louis, MO.)

Fascia Lateroconal

Fig. 8—28. In vivo identification of the two laminae of the posterior renal fascia.

CT demonstrates the inner layer of the posterior renal fascia merging with the anterior renal fascia (open arrowheads) and the outer layer continuing as the lateroconal fascia (closed arrowheads). Mural thickening with luminal narrowing of the descending colon (DC) in this instance is due to ischemic colitis.

Fig. 8—28. In vivo identification of the two laminae of the posterior renal fascia.

CT demonstrates the inner layer of the posterior renal fascia merging with the anterior renal fascia (open arrowheads) and the outer layer continuing as the lateroconal fascia (closed arrowheads). Mural thickening with luminal narrowing of the descending colon (DC) in this instance is due to ischemic colitis.

Fig. 8—29. Two layers of the posterior renal fascia

(arrows) shown discretely by magnetic resonance imaging.

2069 SpacePosterior Pararenal Fascia
Fig. 8—30. Anatomic continuity of the anterior pararenal space between the two leaves of the posterior renal fascia, as described by Raptopoulos et al. K = kidney; C = descending colon; PM = psoas muscle; QL = quadratus lumborum muscle.

Fig. 8—31. Plain film demonstration of the edge of the lateroconal fascia (arrows).

This projects as a thin density inferior to the angle of the liver (L) and lateral to the kidney (K). This demarcates the extraperitoneal adipose tissue into the perirenal fat medially and posterior pararenal fat laterally, extending into the flank fat.

(Reproduced from Meyers et al.12)

Perirenal FatRetrorenal Colon

Fig. 8-32. Retrorenal colon.

The transverse colon and hepatic flexure are insinuated deeply lateral and posterior to the right kidney. This is explained by the variable origin of the lateroconal fascia.

(Courtesy of Jay P. Heiken, M.D., Mallinckrodt Institute of Radiology, St. Louis, MO.)

Deflected Septum

Fig. 8—33. Deflection of the posterior renorenal septum.

A large renal cyst (Cy) displaces the adjacent renorenal bridging septum (arrowheads) outward to the renal fascia

(Courtesy of Michiel Feldberg, M.D., University of Utrecht, The Netherlands.)

Fig. 8—33. Deflection of the posterior renorenal septum.

A large renal cyst (Cy) displaces the adjacent renorenal bridging septum (arrowheads) outward to the renal fascia

(Courtesy of Michiel Feldberg, M.D., University of Utrecht, The Netherlands.)

anterior and posterior renal fasciae61,62 (Figs. 8-36 and 8-37). Venous collaterals in the perirenal fat secondary to renal vein occlusion46,63 or simply the hypervascularity associated with a neoplasm46 should be distinguished from thickened bridging renal septa.

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Essentials of Human Physiology

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Responses

  • Kerry Christie
    Where is lateral conal fascia of right kidney?
    7 years ago
  • michael
    What is zukercandle fascia?
    3 years ago
  • tobias
    Which muscle of the body are found at the interface three dynamic compatment?
    2 years ago
  • Siiri
    What is difference.between perirenal fascia and renal fascia?
    2 years ago

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