retroperitoneo anatomía

Correlative anatomy and

computed tomography:

A module on the pancreas and posterior

abdominal wall

Carl J. Zylak, M.D.

w. Pallie, MB.

An appreciation of the retroperitoneum stems from an under-

standing ofits layered nature.

Several texts have appeared which seek to correlate computed tomo- Introduction

graphic images with cross-sectional human anatomy. In general, they relate

CT scans to cadaveric anatomy as represented by various old anatomic at-

lases. Accordingly, they are of limited value in the interpretation of living

anatomy as recorded by clinical computed tomography. To facilitate the

interpretation of CT scans, this exhibit presents the following:

1 . Schematic drawings illustrating the basic morphologic concept of

the layered retroperitoneum.

2. Normal CT images with interpretation of the anatomy.

3. Abnormal CT images with interpretation of the pathology.

An appreciation of the retroperitoneum stems from an understanding

of its layered nature. Considered from posterior to anterior, one may

distinguish:

1 . A musculoaponeurotic plane, embracing the quadratus lumborum

and psoas muscles, the diaphragmatic crura and associated liga-

mentous fascia.

2. The posterior pararenal space, which continues anteriorly into the

properitoneal fat, the extraperitoneal fat of the anterior abdominal

wall.

3. The perirenal space which is contained by the renal fascias.

4. The anterior pararenal space which is limited anteriorly by the

posterior peritoneum, and which is continuous across the midline.

It lies immediately anterior to the perirenal space.

From the Departments of Radiology and Anatomy, McMaster University and Medical

Centre, Hamilton, Ontario.

Volume 1, Number 1 May 1981 RadioGraphics 61

FASCIA TRANSVERSAHS

ontenor (A

middle M) ] Laminaeposter or

Zylak, Pallie

62 RadioGraphics May 1981 Volume 1, Number 1

Correlative Anatomy and Computed Tomography

Normal anatomy, posterior abdominal wall:

LIGAMENTS AND MUSCLES

Figure lACoronal schematic. Heavy black

lines indicate the median arcuate

ligament across the crura of the

diaphragm (dotted lines), the

medial arcuate ligament over the

psoas muscle, and the lateral arcu-

ate ligament over the quadratus

lumborum muscle.

Figure lB

Cross-sectional schematic demon-

strating the fascial relationships of

the right and left crura of the dia-

phragm, the psoas muscle, the

quadratus lumborum muscle and

the sacrospinalis muscle.

B

(P

FAT

Key: #{174}= aorta; Ab-R rectus aixlominis muscle; ALL anterior longitudinal ligament;CRL = left diaphragmatic crus; CRR right diaphragmatic crus; EO external oblique

muscle; 10 = internal oblique muscle; MLD latissimus dorsi muscle; MSPI serratus

posterior inferior muscle; Ps psoas muscle; QL quadratus lumborum muscle; SSp sa-

crospinalis muscle; TD thoracic duct; TR transverse abdominis muscle; VA azygos

vein.

B


Zylak, PallieCorrelative Anatomy and Computed Tomography

Normal anatomy, retroperitoneum:

KIDNEYS

Figure 2A

Coronal schematic showing position of

kidneys, adrenals and the aorta relative

to the muscles and ligaments of the pos-

tenor abdominal wall.

Figure 2BCross-sectional schematic showing the

perirenal fat (stippled) enclosed by the

anterior and posterior layers of renal

fascia. The posterior renal fat (hatched)

is continuous laterally with the flank fat

and the extraperitoneal fat of the ab-

dominal wall. The transversalis fascia

(black line) lies external to the extra

peritoneal fat.

Figure 2C

Coronal schematic. The renal fascia

blends with the adjacent fascias in all

directions.

Figure 2D

Parasagittal schematic showing the re-

lationships of the perirenal (stippled) and

posterior pararenal (hatched) spaces.

A

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Zylak, Pallie

RadioGraphics May 1981 Volume 1, Number 164



INFERIOR VENA CAVA, RENAL VEINS, KIDNEYS, URETERS

Figure 3A

Coronal schematic with the inferior vena

cava, the renal veins and the ureters

added.

Figure 3B

Cross-sectional schematic. The perirenal fat

(stippled) is enclosed by the anterior and

posterior layers of the renal fascia both of

which lie anterior to the posterior pararenal

space (hatched). In the midline region, the

aorta, the inferior vena cava and the hilar

structures of the kidneys with their sur-

rounding fascias effectively shut off the

perirenal spaces.

Figure 3C

A radiograph of a cadaver cross section

showing the conspicuous fat in the perirenal

space and its delimitation by fascial tissue

in the midline area.

B

A

B




VASCULAR RELATIONSHIPS

Key: A = aorta; IMV = inferior mesenteric vein; IVC= inferior vena cava; PV = portal vein; RV(L) = leftrenal vein; SA = splenic artery; SMA = superiormesenteric artery; SMV = superior mesenteric vein;

SV = splenic vein.

Figure 4A

Coronal schematic of the retroper-

itoneum showing vascular rela-

tionships as well as the position of

the spleen. The inferior mesenteric

vein joins the splenic vein which in

turn is joined by the superior mes-

enteric vein to form the portal vein

which crosses to the right. The left

renal vein lies posterior to the su-

perior mesenteric vessels; the

splenic vein crosses anterior to the

superior mesenteric artery.

Figure 4B

Cross-sectional schematic

again demonstrating vascular

relationships. The portal vein

lies anterior to the plane of the

aorta and the vena cava.

C D

Zylak, Pallie




DUODENUM, PANCREAS

Figure 5ACoronal schematic showing the relation-

ships of the duodenum and pancreas. The

uncinate process of the pancreas hooks

behind the superior mesenteric vessels

which lie anterior to the horizontal (third)

portion of the duodenum. The hepatic

artery is shown above the duodenum.

Figure 5B

Cross-sectional schematic. The anterior

pararenal compartment (stippled) contains

the pancreas, duodenum and, imbedded

posteriorly, the aorta, inferior vena cava,

duodenojejunal flexure and the ascending

and descending colon. On each side, ex-

tensions of this space in the flanks, merge

with the extraperitoneal fat layers.

Figure 5C

Parasaggital schematic showing the rela-

tionship of the three spaces: the anterior

pararenal (stippled), the perirenal (finely

stippled), and the posterior pararenal

(hatched). (1)

Figure 5D

Saggital section demonstrating peripan-

creatic (anterior pararenal compartment)

spaces connecting with the mesenteries of

the transverse colon and the small

bowel.

Key: A = aorta; C colon; CA ascending colon;CD = descending colon; CT transverse colon; D

= duodenum; D2 second portion of duodenum;

HA = hepatic artery; IVC inferior vena cava; J= Jejunum; KL = left kidney; KR = right kidney;

P = pancreas; St = stomach.

SUBEOSTAL PLANE




PANCREATIC TOPOGRAPHY

Figure 6

PANCREATIC MEASUREMENTS, VARIATIONS IN POSITION

PM CT SCAN ULTRASOUND

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Zylak, Pallie

RadioGraphics May 1981 Volume 1, Number 1

Figure 7

Sagittal, coronal and cross-

sectional schematic dem-

onstrating the relationships,

positional variation and

measurements of the pan-

creas.



Figure 8A

Schematic representa-

tion of the anatomic re-

lationships of structures

about the biliary and

pancreatic ducts.

Figure 8B

Endoscopic retrograde

choledochopancreato -

gram

illustrating relationships

shown in Figure 8A.

Key: D2 = second portion of

duodenum; GB = gallbladder;HA = hepatic artery; Pd =

pancreatic duct; PV = portalvein.

68

STRUCTURES RELATED TO DUCTS

SUBCOSTAL PLANE (L3) PLANE OF L2 (INFERIOR)

Key: A = aorta; CA = ascending colon; CD descending colon; DII second portion of

duodenum; GB - gallbladder; IVC inferior vena cava; K(R) & K(L) right and left kidneys;PS = psoas muscle; SMA = superior mesenteric artery; SMV superior mesenteric vein; UP

= uncinate process of pancreas.


Zylak, Pallie


Normal cross-sectional (CT) anatomy:

B

Figures 9A & B

This scan lies caudad to the pancreas, cutting

through the plane of the horizontal (third)

portion of the duodenum. Posteriorly lie the

aorta, inferior vena cava, kidneys and ureters,

in the perirenal space. Anteriorly lie the su-

perior mesenteric vessels (not identified), the

jejunum and transverse colon. The ascending

and descending portions of the colon flank the

inferior poles of the kidneys

B

Figures 1OA & B

This scan lies immediately cephalad to the

subcostal plane (L2). The uncinate process of

the pancreas is defined in the midline by the

superior mesenteric vessels anteriorly and the

aorta posteriorly. Anterior to these lie the

transverse colon (in the midline), the liver and

gallbladder (on the right), and loops of opaci-

fied small bowel (on the left).

PLANE OF L2 (SUPERIOR) TRANSPYLORIC PLANE (Li.)

Figures hA & B

B

Key (pages 70 and 71): A aorta; B body of pancreas; C colon; CRR right crus of di-

aphragm; D duodenum; Dl first portion of duodenum; D2 second portion of duo-

(lenum; GB = gallbladder; H head of pancreas; IVC inferior vena cava; J jejunum;

Zylak, Pallie




B

Scan at the level of L2. Two veins, the left renal

and splenic, cross the midline separated by the

superior mesenteric vessels. Anterior to the

right kidney lies the duodenum, the head of

the pancreas, the inferior vena cava, and the

right crus of the diaphragm.

Figures 12A & B

Scan through transverse pyloric plane (L12).

The head of the pancreas is shown in relation

to the duodenum. The pancreas continues to

cross the midline anterior to the aorta and su-

perior mesenteric vessels. The left hypochon-

drium contains loops of jejunum, splenic

flexure and the lower end of the spleen.

PLANE OF Li (INFERIOR) PLANE OF Li (SUPERIOR)

LCF = splenic flexure; LO lesser omentum; L(R) right lobe of liver; L(RL) right and

left lobes of liver; RK & L(K) right and left kidneys; RVL left renal vein; S or St

stomach; SM superior mesenteric vessels; Sp spleen; SV splenic vein; T tail of pan-

creas; TO = tuber omentale of pancreas.


Zylak, Pallie



Figures 13A & B

The neck of the pancreas crosses the superior

mesenteric vessels in the midline. The body of

the pancreas is related to the stmoach anteri-

orly with the lesser sac interposed between

them. Jejunum and omental fat occupy the left

hypochondrium.

Figures 14A & B

This scan cuts the lesser curvature of the

stomach (upper L1). The lesser omentum abuts

on the tuber omentale of the body of the pan-

creas. The pancreas is well defined by pen-

pancreatic fat and the tail of the pancreas

points to the splenic hilum.

Zylak, Pallie


Pathology, anterior pararenal space:

CALCIFIC PANCREATITIS

Figures i5A & B

A survey radiograph (A) illustrates pancreatic calcifi-

cation and topography for comparison with CT scans

of the same patient. In the scans which have been made

at successively higher (more cranial) levels, note the

anatomic relationships of the pancreas. The head lies medial to the second portion of the duodenum (B).

The pancreas is opacified by calcifications.

PSEUDOCYSTS OF PANCREAS

L I

A pseudocyst in the head of the pancreas is identified by endoscopic retrograde choledochopancreatography

(A). On the most caudal CT scan (B) the same cyst is indicated by an arrow.


Zylak, Pallie


The neck and body lie anterior to the superior mesentenic artery (arrow) (C). The stomach lies anterior

to the pancreas. The tail of the pancreas abuts on the splenic hilum (D).

Figures 16C & DCT scans of the same patient exposed at higher levels (C and D) demonstrate additional cysts (arrows)

in the body and tail of the pancreas.


Zylak, Pallie


Pathology, anterior pararenal space:

PHLEGMONOUS PANCREATITIS

The inferior aspect of the right perirenal space containing fat (arrows) is recorded in scan A. At the same

level, an inflammatory mass (M) is seen surrounding the right renal cone laterally and anteriorly. In a

more cranial scan (B) the right kidney and penirenal fat appear normal, indicating no involvement of the

penirenal space.

Figures 18A & B

A survey radiograph (A) shows the stomach to be displaced infeniorly and laterally by a large mass. On

the most caudal of the CT scans (B) fluid is evident medial to the liver (arrows) with a much larger collection

(C) medial to this, located in the lesser omentum. The pancreatic head is probably enlarged with loss ofpenipancreatic fat planes.


Figures i7C & D

At a yet higher level (C) the inflammatory mass (M) is seen to extend across the midline and to distend

the anterior pararenal space. Dot like opacities adjacent to the lateral margin of the stomach in scan D,

are vessels which may represent varices.

Zylak, Pallie


Zylak, Pallie


Pathology, anterior pararenal space:AORTIC ANEU

Figure l9A Figure i9B

The most caudal scan of this patient, demonstrates In a more cranial section, the aneurysm is readily ap-

calcification in the aorta (A) which is only slightly di- parent. The lucent crescent represents thrombus.

lated.

LYMPHOMA

Figures 20A & B

In CT scan A, large nodal masses (M) displace the aorta (cursor) to the right and obliterate the paravascular

fat planes. In a more cranial scan (B) a large right retrocrural lymph node (arrow) displaces the crus.


Zylak, Pallie


Figure i9C Figure i9D

In a yet more cranial scan, the aneurysm is seen to At the level of the superior mesentenic artery (arrow),

bulge from the right side of the aorta which contains the aneurysm is no longer evident.

calcification. Renal cysts are present on the left.

Pathology, perirenal Space:

Multiple CT scans representing successively more cranial planes show the penirenal space on the left to

be distended by an inflammatory process, which obliterates the penirenal fat and thickens the renal fascia.

The posterior paranenal and extrapenitoneal fat planes are preserved (arrow).

URINOMA

I_c,____

A delayed radiograph from the excretory urogram of

a 70-year-old male with carcinoma of the bladder

shows penirenal extravasation of contrast material

(arrow).

CT scan at the level of the lower pole of the left kidney

shows a fluid (F) collection in the penirenal space

medially. The renal fascia is clearly delineated (ar-

rows).

Zylak, Pallie



Pathology, perirenal Space:

)

A more cranial scan through the plane of the renal The scan shows fluid (F) occupying the penirenal space

pelvis shows loculated fluid (F) in the medial and cranial to the left kidney. This may account for the low

posterior parts of the penirenal space displacing the position of the left kidney in this case.

kidney anterolaterally. The compartmentalization

medially is well defined (arrow).



In the scan, fluid (F) is present in the right posterior In a scan cranial to the right kidney, craniad extension

pararenal space. This represents blood from a leaking of blood (F) in the posterior pararenal space is dem-

aortic aneurysm. Large bilateral renal cysts are onstrated.

present.

ABSCESS

Figures 25A-D

This series of CT scans shows loculated fluid collections (A) with enhancement of their margins located

in the posterior abdominal wall and encroaching on the left posterior pararenal space. Note that the per-

irenal space and propenitoneal fat plane (arrow) are not involved.


Zylak, Pallie


Pathology, posterior pararenal space:

LEAKING AORTIC ANEURYSM

ScanCrepresenting the level of the superior mesentenic artery (arrow) demonstrates fluid (F) in the right

posterior pararenal space. This is shown in more detail in the enlargement (D).


Zylak, Pallie


Zylak, Pallie


Pathology, multiple space involvement:

Figures 26A-D

This series of CT scans demonstrates involvement of the anterior paranenal space with transgression of

the renal fascia on the right. Note the obliteration of penirenal fat anterolaterally on the night as compared

to the left side. Fluid within the anterior pararenal space is shown extending into the right iliac fossa.

In Figures 1 through 8, the positions and relationships of successively

more anterior structures of the retropenitoneum are illustrated with coronal

and cross-sectional schematic drawings. These schematics emphasize the

concept of the layered retropenitoneum and clarify the spatial relations of

structures recorded in CT scans.

Examples of pathologic anatomy as recorded by computed tomography

are interpreted by reference to the normal anatomy of the three spaces of

the retropenitoneum. Pancreatitis serves as the model for understanding the

anterior pararenal space. The confinement of pathology within the penirenal

space by the renal fascia is illustrated by several examples, including that

of a uninoma. The posterior pararenal space is illustrated with clinical scans

demonstrating an abscess and leakage from an aortic aneurysm. Also included

are scans of a patient with pancreatitis, illustrating a pathologic process in-

volving multiple spaces.

SUMMARYThis exhibit has presented an approach to the understanding of the

cross-sectional anatomy of the retnopenitoneum that facilitates the task of

interpreting normal and pathologic CT scans. The normal appearance of

the individual compartments of the retroperitoneum and the appearance

of pathologic processes involving them, both individually and in combination,

have been demonstrated. Clinical CT scans illustrating the findings in


Zylak, Pallie


pancreatitis, urinoma and renal abscess, adrenal tumor, aortic aneurysm,

and lymphoma have been presented.

1. Meyers MA: Dynamic Radiology of the Abdomen. New York, Springer-Verlag, Berlin, ReferencesHeidelburg, 1976, pp 113-190

2. DeGraaff CS, Taylor KJW, Simonds BD, Rosenfield AT: Gray-scale ecography of the

pancreas: re-evaluation of normal size. Radiology 129:157-161, 19783. Kreel L: Computerized tomography of the pancreas. Computed Axial Tomography 1:

287-297, 1977

ACKNOWLEDGMENTS

Mrs. Deborah Miller for the excellent art work, the Audiovisual Depart-

ment, McMaster University and Mrs. L. MacRae for typing the manu-

script.


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retroperitoneo anatomía