3. INTRODUCTION
Retroperitoneum: A Hidden Space
• Arise outside of major retroperitoneal organs
• 0.1-0.2 % of all malignancies, 80-90% malignant
• Primary retroperitoneal masses may be categorized as solid or cystic and range from benign to aggressive
in behavior
• Awareness of specific components of masses, tumor vascularity, and specific patterns of spread helps in
further narrowing the differential diagnosis
9. Pattern of spread
Local spread
Insinuation between normal structure - Growth along the
course of normalstructures
• Lymphangioma
• Ganglioneuroma
• Lymphoma
• Retroperitoneal fibrosis
Growth along the course of normal structures
• Paraganglioma
• Ganglioneuroma
Invading type: sarcomas
Distant spread
• Liver via hematogenous route - particularly
from
• leiomyosarcoma and angiosarcoma
--- lungs (38%)
additional sites of involvement - adrenals,
muscles, subcutaneous tissue, bones, and brain.
• Lymph node metastases are distinctly
uncommon(3.5%) - rhabdomyosarcoma,
synovial, vascular, and epithelioid sarcoma
• Peritoneal spread can occur in the abdomen
with seeding to produce disseminated implants
in omentum, mesentery, and peritoneum.
10.
11.
12.
13.
14. IMAGING APPROACH IN RETROPERITONEAL NEOPLASM
• Confirm retroperitoneal and subcompartmental
location
---Anterior displacement of retroperitoneal organ
---Displacement/encasement of major vessels
---Signs
• Look for morphological markers pointing to specific
pathology
18. Hypervascular masses are often
supplied by feeding arteries that are
prominent enough to be visualized at
CT or MR imaging - important key to
understanding the origin of the mass
19. Morphological markers of
pathology
Fat Myxoid Stroma
• Myxoid stroma - T1 hypo/T2
Hyperintense and shows delayed
enhancement after injection of
contrast medium
• ganglioneuroma,schwannoma,
neurofibroma, myxoid liposarcoma,
malignant fibrohistiocytoma,
ganglioneuroblastoma and malignant
tumor of the peripheral nerve sheaths
• Lipoma
• Liposarcoma
• Teratoma
• Cystic lymphangioma
21. Common Primary Retroperitoneal
Neoplasms
• Lymphoma:
• most common malignant retroperitoneal neoplasm and most common small round cell
tumor
• infiltrative homogenous hypovascular masses around the aorta/IVC extending between
and encasing structures without compressing them
• Upliftment of the great vessels results in “floating aorta” or “CT angiogram” sign
• Abdominal lymphomas are classified into: a.solitary mass type
b.multiple nodular type and
c.diffuse type
• CT: homogenous enhancement of the enlarged lymph nodes with fewer calcifications
22.
23. SARCOMAS
• 90% of mesodermal tumors
• 40-60 years
• Notorious for presenting with large size and at advanced stages
• Lung, brain, bone and liver metastasis
• Rarely spread to nodes(exceptions - epithelioid,rhabdoma,clear cell)
a. Liposarcoma- 40%
b.Leiomyosarcoma - 30%
c.Malignant fibrous histiocytoma- 15%
24. Liposarcoma
• mesenchymal tumors arising from
adipose tissue
• Retroperitoneal liposarcomas are
classified into five groups:
well-differentiated
liposarcoma
myxoid liposarcoma
round cell liposarcoma
pleomorphic liposarcoma and
dedifferentiated liposarcoma
25. • Well differentiated - lipoma
like and thicker and nodular
enhancing septations
-soft-tissue–attenuating nodule
measuring greater than or
equal to 1 cm(differentiates if
from benign)
• Dedifferentiated ---
bimorphic mass with clear
demarcation between the
predominantly fatty tissue
and the nonfatty solid tissue,
Calcifications- 1/5th of cases
26. • Myxoid - predominantly nonfatty, with a
cystic appearance at CT and MRI due to the
extra-cellular myxoid matrix
- varying amounts of contrast material
enhancement - “pseudocystic”
27. LEIOMYOSARCOMAS
• Large soft-tissue masses - internal
heterogeneity and heterogeneous
enhancement(secondary to necrosis and
hemorrhage)
• Calcifications are not common
• Adipose tissue is absent
• Purely intravascular lesions -
heterogeneously enhancing expansile
masses.low to intermediate T1 signal
intensity and intermediate to high T2 signal
intensity.
28. Neurofibroma
Target sign on MRI - central low-
intermediate T2-signal intensity
due to fibrous tissue surrounded
by a peripheral high signal
intensity of myxoid tissue
29. Paraganglioma
• Chromaffin cell origin
• extra-adrenal paraganglion cells of sympathetic or
parasympathetic nervous systems.
• M/C site in the abdomen- organ of Zuckerkandl
located in the para-aortic region near the origin of
the inferior mesenteric artery
• Heterogeneous masses with necrosis, hemorrhage,
and/or calcifications.
• Avid contrast enhancement - hypervascular nature
especially peripheral.
• T2W - diffuse high signal intensity - “lightbulb” sign
• 20-40 yrs/elevated catecholamines/VHL,MEN,NF1
30. Teratoma
• Mature cystic teratomas (MCTs) - cystic
tumors with fat attenuation and Rokitansky’s
protuberance
• Rokitansky’s nodules - softtissue
protuberance
• Bone or teeth, if present, tend to be located
with Rokitansky’s nodule
• Do not invade the surrounding soft tissues or
bone but may gradually compress them.
32. Cystic Lymphangioma
• congenital benign tumors
• failure of the developing lymphatic
tissue to establish normal
communication with the remainder
of the lymphatic system
CT: large, thin-walled, multiseptate
cystic mass,attenuation values vary
from that of fluid to that of fat
• elongated shape and a crossing
from one retroperitoneal
compartment to an adjacent one
are characteristic of the mass
33. Mucinous Cystadenoma
• Coelomic metaplasia -
tumors arise from
invagination of the
peritoneal mesothelial
layer that undergoes
mucinous metaplasia
with cyst formation.
• CT: homogeneous,
unilocular cystic mass
34. Tailgut Cyst
• (also known as retrorectal cystic
hamar-tomas)
• uncommon congenital lesions that
arise from the embryonic hindgut
• presacral or retrorectal space
• occasional extension into the ischio-
anal fossa
• CT - well-defined unilocular or
multilocular hypoattenuating cystic
lesion with variably thick septa and
occasional calcifications
• MRI - T2 hyperintense and T1
hypointense
35. Retroperitoneal fibrosis
• Proliferation of fibroinflammatory tissue - surrounds
the infrarenal portion of the abdominal aorta, inferior
vena cava, and iliac vessels
• USG:hypoechoic or isoechoic, well-demarcated but
irregularly contoured retroperitoneal mass anterior to
the lower lumbar spine or sacral promontory
---unilateral or bilateral hydronephrosis or hydroureter
Intravenous urography - classic triad
1. Medial deviation of the middle third of the ureters
(maiden waist sign )
2. Tapering of the lumen of one or both ureters in the
lower lumbar spine or upper sacral region
3. Proximal unilateral or bilateral
hydroureteronephrosis with delayed excretion of
contrast material
36. CT: soft tissue density mass located around
the aorta and iliac arteries.
Classically - develops around the aortic
bifurcation and spreads upwards where it
can envelop the renal hila
In early or active stages - variable
enhancement .
37. Erdheim-Chester disease
• rare non-Langerhans cell histiocytosis of unknown origin
• hairy kidney sign: irregular symmetric infiltration of the
bilateral perirenal and posterior pararenal spaces
• coated aorta sign: periaortic soft tissue
• inferior vena cava and pelvic ureters are typically spared,
which are useful cross-sectional imaging findings for
differentiation of retroperitoneal Erdheim-Chester disease
from retroperitoneal fibrosis
• Bone changes are common
38. Scenario 1
• A 63-year-old woman presented with
backache, decreased appetite, and
weight loss
Diagnosis - de-differentiated retroperitoneal liposarcoma.
(The anterior rotational displacement of the kidney seen in this
patient is characteristic of retroperitoneal sarcomas)
39. Scenario 2
A 42-year-old woman presented with a headache. Her blood
pressure was 148 over 94 mm Hg, and her urine
vanillylmandelic acid (VMA) was 79 mg/24 h (reference range,
1.8–6.7 mg/24 h)
paraganglioma
40. Scenario 3
A 50-year-old man presented with vague abdominal pain, fever, and weight loss
Lymphoma
42. SUMMARY ...
• Target sign: neurofibromas and schwannoma
• Bowl of fruit sign: malignant fibrohistiocytoma, synovial sarcoma and Ewing’s sarcoma
• Whorled appearance: ganglioneuroma and neurofibroma
• Speckled enhancement: this can be found in T1- weighted images post contrast - intratumoral structures similar
to septa - leiomyosarcoma and rhabdomyosarcoma
• “floating aorta” or “CT angiogram” sign - Lymphoma
• A large nonfat-containing retroperitoneal mass with involvement of a contiguous vessel and varying internal
necrosis should raise the possibility of a leiomyosarcoma
43. REFERENCES ...
• Nishino M, Hayakawa K, Minami M, Yamamoto A, Ueda H, Takasu K. Primary
Retroperitoneal Neoplasms: CT and MR Imaging Findings with Anatomic and Pathologic
Diagnostic Clues. RadioGraphics. 2003 Jan;23(1):45–57.
• Gupta A, Manchanda A, Singh S, Singh R, Khurana N, Durgad AS. Primary
Retroperitoneal Masses: A Pictorial Essay. 2023 Aug 31;07(01):065–72.
• Tirkes T, Sandrasegaran K, Patel AA, Hollar MA, Tejada JG, Tann M, et al. Peritoneal and
Retroperitoneal Anatomy and Its Relevance for Cross-Sectional Imaging. RadioGraphics.
2012 Mar;32(2):437–51.
• Sanyal R, Remer EM. Radiology of the Retroperitoneum: Case-Based Review. American
Journal of Roentgenology. 2009 Jun;192(6_supplement):S112–7.
1. Be sure of the compartment
2. further evaluation - biopsy or surgery
The retroperitoneum extends from the diaphragm to the pelvis
It extends between the posterior parietal peritoneum anteriorly and the fascia transversalis posteriorly.
Drawing of the anatomy of the retroperitoneal spaces at the level of the kidneys. The anterior pararenal space (APRS) is located between the parietal peritoneum (PP) and the anterior renal fascia (ARF) and contains the pancreas (Pan), the ascending colon (AC), and the descending colon (DC). The posterior pararenal space (PPRS) is located between the posterior renal fascia (PRF) and the transversalis fascia (TF). The perirenal space (PRS) is located between the anterior renal fascia and the posterior renal fascia. Ao = aorta, IVC = inferior vena cava, LCF = lateroconal fascia.
facia layers are laminated so they for expansile planes The respective fascial layers can expand, giving rise to interfascial planes that allow communication across the retroperitoneal compartments. LCP = lateroconal plane, RMP = retromesenteric plane, RRP = retrorenal plane. - Retromesenteric place when zerotas facia expands,,, retro renal plane when zukerkandle splace expands, lateral conal plane when lcf expands,,, these meet up at fascial trifurcation and expands inferiorly as combined interfascil plane
Inferiorly, these form the com-bined interfascial plane, which courses anteriorly to the psoas muscle, allowing communication to the pelvis (Fig 1b) (5). Some authors (6) have proposed an additional interfascial plane, termed the subfascial plane, which is located between the posterior pararenal space and the transversalis fas-cia. Perinephric bridging septa serve as potential channels that allow disease processes to commu-nicate from the perirenal space to the interfascial planes
particularly from leiomyosarcoma and angiosarcoma, can have marked enhancement; hence, both pre- and postintravenous contrast CT of the liver should be performed as a routine in these patients.
Axial illustration of the right kidney shows the presence of bridging septa (white arrows) that allow communication from the perirenal space to the retromesenteric (shaded light blue) and retrorenal (shaded green) planes, respectively. Perirenal lymphatic vessels (thick solid black arrow), arteries (dashed black arrow), and veins (thin solid black arrow) are also shown.
diverticulitis of descending colon inflammatory process spreading to retromesentric, retrorenal and lateral conal spaceses that got expanded
y shaped i was saying sag cect contrast ct scan --- retromesentric and retrorenal plane and combiled
(a) Diagram shows the anterior (APS) and posterior (PPS) pararenal spaces, perirenal space (PS), retromesenteric plane (RMP), retrorenal plane (RRP), and lateral conal (LP) planes. (b) Axial CT image, obtained in a 76-year-old man with duodenal perforation who underwent endoscopic retrograde cholangio-pancreatography, shows a large amount of dissected retroperitoneal air outlining the retromesenteric plane (RMP)—which connects across the midline—and retrorenal plane (RRP). The anterior pararenal space (APS) is mostly free of gas. Note that it is possible for disease to extend from the posterior pararenal space (PPS), through the quadratus lumborum muscle (arrow), and into the subcutaneous space, the site of an inferior lumbar hernia as well as the Grey-Turner sign, which manifests as lateral abdominal discoloration in patients with severe pancreatitis. Extravasated air has dissected into the Morison pouch (MP), a finding indicative of abrupt accumulation of air or fluid that crosses the peritoneal and retroperitoneal spaces. (c) Axial unenhanced CT image shows bilateral lumbar hernias arising from the superior lumbar triangles (arrows)
anteriorly displaced kidney with bukkling of renal cortex without infiltration
A mass that arises from a given organ often appears embedded within in and the interface between the two may be difficult to appreciate (Fig. 10). Conversely, a mass that abuts but does not originate from a hollow structure compresses it to produce a crescentic deformity
T scan shows a huge heterogeneous mass. The lumen of the duodenum is stretched toward the mass, and the wall of the duodenum appears embedded in the mass at the contact surface (arrow). These findings represent gastrointestinal stromal tumor of the duodenum with a positive embedded organ sign.
(A) and CT scan after CM administration (B). The appearance is supported by parenchymal tokens that “envelop” the tumor. The lesion originates from the organ (renal mass).Negative beak sign: diagram (C) and CT scan after contrast medium administration (D). The tumor does not originate from the organ, which is also compressed. An acute angle forms at the contact points between the resident organ and the lesion as shown in (c) (primary retroperitoneal mass)
A large mass, particularly when arising from a small organ, may render the organ of origin undetectable (Fig 11). Conversely, absence of the invisible organ sign suggests primary retroperitoneal pathology
Phantom organ sign: diagram (E) and CT scan after CM administration (F). The tumor’s originating organ (right kidney) appears totally incorporated by the tumor and is no longer recognizable (F)
Prominent feeding artery sign, Axial CECT image of right renal cell carcinoma showing the mass being supplied by the right renal artery.
Myxoid stroma is charac-terized pathologically by a mucoid matrix that isrich in acid mucopolysaccharides
(schwannomas, neurofibromas,ganglioneuromas, ganglioneuroblastomas, malig-nant peripheral nerve sheath tumors),
Malignant paraganglioma in a 57-year-old man.(a)Abdominal CT scan shows an ill-defined, hyper-vascular tumor with a central low-attenuation focus,findings that were interpreted as a malignant tumor with centralnecrosis.
typically presents as
Mesenteric lymph nodes are more commonly involved in
tuberculosis. It is often associated with tuberculous perito_x0002_nitis, which is characterized by omental caking, smudged
mesentery, and high-density ascites.
Mesenteric lymph
nodes are not commonly involved in Hodgkin’s disease.
Axial contrast-enhanced computed tomography (CT) of the abdomen in a 55-year-old man shows a homogenously enhancing mass
lesion in the central vascular space of the retroperitoneum causing anterior and lateral displacement of the pancreas and bowel loops,
respectively. The lesion is closely abutting the liver, spleen, and bilateral kidneys. It is encasing the aorta and displacing it anteriorly giving
the “floating aorta sign” (arrows in A), celiac trunk (notched arrow in A), right renal artery (thin arrow in B). On histopathology, it was proven to be
a lymphoma of diffuse large B-cell type (DLBCL).
Axial contrast-enhanced computed tomography (CT) of the
abdomen shows a large retroperitoneal mass of fat attenuation
(arrow) displacing the right kidney. On histopathology, it proved to be
a well-differentiated liposarcoma.
(b) Axial contrast-enhanced fat-suppressed T1-weighted MR image shows a fat-containing mass (*) with thin enhancing septa (arrow).
Well-differentiated liposarcomas appear as well-defined
fat containing masses with thin septa. Calcifications
or ossifications within a liposarcoma have proved to be a sign
of poor prognosis, often indicating dedifferentiation.Welldifferentiated liposarcomas almost always undergo dedifferentiation-which is suggested by the additional presence of a
focal, nodular nonlipomatous region greater than 1 cm in
size. Calcification is an important sign of dedifferentiation
(hypoattenuating com-pared with muscle at CT, high signal intensity at T2-weighted MRI, and low signal intensity at T1-weighted MRI) (Fig 4a, 4b) (26).
(a, b) Axial T2-weighted MR images acquired without (a) and with (b) fat sup-pression reveal a hyperintense mass (* in a) without fat suppression. Lacelike signal hypointensity is seen (arrowhead in b). (c) Axial fat-suppressed contrast-enhanced T1-weighted MR image shows patchy areas of enhancement (arrow).
malignant tumor of smooth muscle cells (9), with a retroperitoneal location in 12%–69% of cases (36,37). It is the second most common primary malignant retroperito-neal sarcoma, accounting for 28% of cases
che. Axial contrast-enhanced CT scan shows well-defined, lobulated, heterogeneously enhancing lesion filling inferior vena cava with large exophytic component. Lesion is partially encasing aorta.
In this example, although the tumor is large and exophytic, it appears to be embedded in the IVC, indicating that the IVC is the site of origin (the positive embedded organ sign).
(d) Axial T2-weighted MR image with fat suppression in an 18-year-old woman with neurofibroma shows the classic target sign, as evidenced by the characteristic central area of low signal intensity surrounded by a rim of high signal intensity (arrowhead).
The organ of Zuckerkandl comprises of a small mass of chromaffin cells derived from neural crest located along the aorta, beginning cranial to the superior mesenteric artery or renal arteries and extending to the level of the aortic bifurcation or just beyond. The highest concentration is typically seen at the origin of the inferior mesenteric artery.
well-defined hetero enhancing mass is noted at the left para aortic region which shows a large area of internal necrosis.
Teratomas may be composed of mature or immature tissues
deriving from the three pluripotent germ cell layers.
Mature teratoma in a 23-year-old female. CT scan showing a retroperitoneal mass with fat components, cystic areas, and calcifications (arrow). These findings, especially the fat component, are suggestive of a germ-cell origin. Note the anterior displacement of the aorta in relation to the vertebral body-an indirect sign of retroperitoneal location (arrowhead). The diagnosis was confirmed by percutaneous biopsy.
Most cystic lymphangiomas occur in the head or neck; a retroperitoneal location is unusual
An elongated shape and a crossing from one retroperitoneal compartment to an adjacent one are characteristic of the mass (,1). Rarely, cystic lymphangiomas may have wall calcification (,1). Surgical excision is the treatment of choice (,2)
Contrast-enhanced CT scans show a lobulated cystic mass (thick arrows) with tiny mural calcifications (thin arrow in b) in the anterior pararenal space. The third portion of the duodenum is compressed by the mass.
Normal ovaries and appendix
Differentiating this mass from cystic mesothelioma, cystic lymphangioma, and nonpancreatic pseudocyst is difficult.
Retroperitoneal mucinous cystadenoma in a 56-year-old woman. Contrast-enhanced CT scan shows a homogeneously hypoattenuating mass in the right retroperitoneal space (arrow). The ascending colon is displaced anteriorly. Note the dilatation of the left ureter, which is caused by a ureteral stone.
(a) T2-weighted MR image shows a presacral multiloculated cystic mass without solid components. The tumor has high signal intensity.
Axial fat-suppressed T2-weighted (a) and sagittal fat-suppressed contrast-en-hanced T1-weighted (b) MR images show a large cystic presacral mass without internal nodularity or septa (*
other developmental cysts in the retrorectal region
retrorectal epidermoid cyst
retrorectal dermoid cyst
retrorectal neurenteric cysts
cystic sacrococcygeal teratoma
anterior sacral meningocele
Urography of RPF. Excretory urogram shows medial deviation of the middle third of the left ureter and tapering of the ureteral lumen at the L4–S1 vertebral level (arrows). Note also the delay in excretion of contrast material in the right kidney (*)
proliferation of aberrant fibroinflammatory tissue, which usually surrounds the infrarenal portion of the abdominal aorta, inferior vena cava, and iliac vessels
proliferation of aberrant fibroinflammatory tissue, which usually surrounds the infrarenal portion of the abdominal aorta, inferior vena cava, and iliac vessels
primary biliary cirrhosis, bile duct dilatation due to sclerosing cholangitis, and focal or diffuse pancreatic distortion due to sclerosing pancreatitis
RPF in a 56-year-old man. Axial CT image obtained 60 seconds after contrast material administration shows a plaque-like area of attenuation (arrow) surrounding the aorta and IVC. Peripheral infiltration encases both ureters (arrowheads) and does not separate the aorta from the spine, findings indicative of benign RPF. Note the bilateral ureteral stents.
Symmetric stranding surrounding both kidneys and extending into the renal hila and along the course of the proximal ureters with increased thickening and enhancement. No obstruction.
Axial contrast-enhanced CT scan shows large, predominantly fatty mass involving right abdomen and causing anterior rotational displacement of right kidney. Bowel is displaced anteriorly and to the left. Note multiple enhancing nodular areas of soft-tissue attenuation in largely fatty mass.
Large areas of low-density fat with an adjacent bulky nodular component seen in this example indicates the coexistence of a predominantly fatty, well-differentiated liposarcoma juxtaposed to a nonlipomatous mass,. This bimorphic appearance is seen with de-differentiated retroperitoneal liposarcomas
e. Axial contrast-enhanced CT scan shows well-defined, strongly enhancing left perihilar lesion with central hypodense area. No calcification is present. Lateral limb of left adrenal gland is seen separate from mass.
he. Coronal CT image shows lesion abutting medial cortex of kidney; intervening fat plane is maintained. Left adrenal gland is located superiorly and is separate from lesion.
Axial contrast-enhanced CT showed a well-defined, strongly enhancing, left perihilar lesion in a central hypodense area (Fig. 3A). No calcification was present. Coronal CT showed the lesion abutting the medial cortex of the kidney and an intervening fat plane (Fig. 3B). The left adrenal gland was located superiorly and was separate from the lesion.
The first step in diagnosing a primary retroperitoneal tumor is to confirm that it is arising from the retroperitoneal space.
Axial contrast-enhanced CT scan shows large homogeneous, low-attenuation, mildly enhancing mass that is encasing aorta and left renal vein. Mass has displaced pancreas and bowel loops anteriorly. Inferior vena cava is also partially encased. On left side, mass is abutting and laterally displacing kidney. Note left hydronephrosis.
che. Axial contrast-enhanced CT scan shows well-defined, lobulated, heterogeneously enhancing lesion filling inferior vena cava with large exophytic component. Lesion is partially encasing aorta.
In this example, although the tumor is large and exophytic, it appears to be embedded in the IVC, indicating that the IVC is the site of origin (the positive embedded organ sign).
