The document discusses the anatomy and imaging of the retroperitoneal spaces. It describes the locations of the different retroperitoneal spaces and fascial planes. CT and MRI are important imaging modalities for evaluating retroperitoneal pathology such as hemorrhage, fluid collections, masses and abdominal aortic aneurysms. The document also discusses approaches to characterizing and diagnosing different retroperitoneal neoplasms and infections based on imaging findings.

1. References: CT and MR imaging of whole abdomen
John R. Haaga, MD, FACR

2.  Anatomy
 Role of imaging in Localization of pathology
 Neoplasms

3.  Posterior peritoneum
 Renal (Gerota’s) fasciae
 Lateroconal fascia
 Musculoaponeurotic plane, embracing the
quadratus lumborum and psoas muscles, the
diaphragmatic crura and associated
ligamentous fascia.

6. Retroperitoneal spaces

8.  Iliopsoas compartment
- located within and immediate adjacent to
psoas muscle
- posteromedial to the posterior pararenal
space

11.  The retromesenteric, retrorenal, and lateroconal
planes are potential routes of interfascial
communication between the retroperitoneal
spaces. Retroperitoneal hemorrhage or rapidly
expanding fluid collections can spread via
these interfascial connections.

12.  Largest
 Pancreas, Duodenum, Colon
 Continuous across the midline

14.  Smallest
 Continues anterolaterally into the
properitoneal fat, the extraperitoneal fat of the
anterior abdominal wall.

21.  Plain radiograph
 USG
 CT
 MRI

22. Pancreatic calcification
 Common  Rare
- Chronic alcoholic - Idiopathic
pancreatitis - Hereditary pancreatitis
- Cystic fibrosis
- Hyperparathyroidism
- Protein malnutrition
- Cystic tumours
- Cavernous lymphangioma
- Islet cell tumours
- Haemangioma
- Pseudo cysts
- Haematoma

30.  Multidetector CT in retroperitoneal
haemorrhages, fluid collections, AAA and
masses.
 Magnetic resonance (MR) imaging has an
increasing role in evaluating soft-tissue masses
of the extraperitoneal spaces.

31.  Below the kidneys, the retroperitoneal spaces -a single
space with direct contiguity between the anterior and
posterior portions.
 Retroperitoneal hemorrhage or fluid spread from the
abdominal retroperitoneum into the extraperitoneal
pelvis along the anterior and posterior perirenal
fasciae, which combine to form the fascial plane in the
iliac fossa .
 Superiorly, the perirenal fasciae are attached to the
diaphragm.
 On the right side, the bare area of the liver is directly
connected to the anterior pararenal space.
Therefore, hepatic lacerations involving the bare area
of the liver can be a source (albeit uncommon) of
retroperitoneal hemorrhage.

32.  CT findings of duodenal injury
- duodenal wall thickening
- periduodenal fluid
- Fluid in the right anterior pararenal space
- Diminished bowel wall enhancement of the
injured segment
- extraluminal air (More specific sign of duodenal
perforation)
- extraluminal oral contrast material air (More
specific sign of duodenal perforation)
- the “sentinel clot” sign

36.  Two-thirds of blunt pancreatic injuries occur in
the pancreatic body, with the remainder
occurring with equal frequency in the
head, neck, and tail.

41.  Goals of imaging
- to identify the retroperitoneal hemorrhage, its
location and its possible source
- to assess its relative stability on the basis of the
size and presence (or absence) of active
extravasation of intravascular contrast material

42. Surgical standpoint, the retroperitoneum can be
divided into zones because hematoma location
has therapeutic implications

46.  Pelvic retroperitoneum is the most common
location of retroperitoneal
hemorrhage, frequently in association with
pelvic fractures.

47.  In the setting of trauma should raise suspicion
for
- Pancreatic injury
- Duodenal injury
- Renal collecting system injury (with urine
leakage)
- Retroperitoneal hemorrhage

48.  Primary
- Lymphoid malignancy : NHL, HL, HIV related
NHL
- Enlarged LNs in HIV
- Soft tissue masses
 Secondary
- Lymphnodes Testicular, Prostate
- Metastases UB, Cervix etc..

49.  Lymphnodes
1) Paracaval and paraortic : > 10 mm
2) Retrocural : > 7 mm
 MRI has better distinction than CT between
LNs and vessels and bowels

50.  NHL/HD
 Paraortic LN very frequent in NHL as compared to
HD
Ann Arbor staging

53.  Characterization of the Retroperitoneal Space
 Displacement of retroperitoneal organs
strongly suggests that the tumor arises in the
retroperitoneum
 Displacement of Major vessels and some of
their branches

54.  Beak Sign: a mass deforms the edge of an adjacent
organ into a “beak” shape, it is likely that the mass
arises from that organ (beak sign)

55. Embedded Organ Sign.—When a tumor compresses an
adjacent plastic organ (eg, gastrointestinal tract, inferior
vena cava) that is not the organ of origin.

56.  Phantom (Invisible) Organ Sign.—When a
large mass arises from a small organ, the organ
sometimes becomes undetectable.
 Prominent Feeding Artery Sign.—
Hypervascular masses are often supplied by
feeding arteries that are prominent enough to
be visualized at CT or MR imaging, a finding
that provides an important key to
understanding the origin of the mass.

57.  Although the MR imaging appearance of most
soft-tissue masses is nonspecific
 The presence of certain histologic components
(eg, myxoid stroma, collagen
fibers, calcification, and fat) can be suggested
by evaluating intralesion signal intensity and
enhancement patterns.
 Determination of the dominant histologic
component can help narrow the differential
diagnosis of the lesion.
 However, management changes a bit

58. Poorly differentiated liposarcoma

59.  Target Sign: a central area of low to
intermediate signal intensity surrounded by a
ring of high signal intensity on T2-weighted
images
 Corresponds to fibrous tissue centrally and
myxoid tissue peripherally and is commonly
seen in neurofibroma and schwannoma

60. Neurofibroma

61.  Bowl of Fruit Sign: A mosaic of mixed
low, intermediate, and high signal intensity on
T2- weighted images as a result of admixture of
solid components, cystic
degeneration, hemorrhage, myxoid
stroma, and fibrous tissue.
 This finding is commonly seen in malignant
fibrous histiocytoma, synovial sarcoma, and
Ewing sarcoma.

62. Malignant fibrous histiocytoma

63.  Proliferation of fibroblasts, infiltration of acute
inflammatory cells, and proliferation of
capillaries, surrounded by collagen fibers.

64.  Eitiology
- Idiopathic (70 %) - Focal inflammatory or
- Around AAAs infectious conditions
- Medications e.g. - (e.g., diverticulosis, app
methysergide, beta endicitis, extravasation
blockers, methyldopa, h from the urinary tract).
ydralazine, antibiotics, a - Previous surgery or
nd some analgesics radiation treatment.
- systemic infections - Trauma.
(e.g., tuberculosis, syphi - Retroperitoneal
lis, actinomycosis, bruce hemorrhage.
llosis, fungal infections). - Marfan's disease.
- Inflammatow bowel
disease

67.  Defined as focal area of dilatation of aortic
diameter >3 cm
 Majority are infrarenal
 2-20 %- juxtrarenal and pararenal
 Atherosclerotic/ degenerative- most common
 Other causes

69.  Inflammatory aneurysm (5-15 %)
 Results from fibrotic autoimmune reaction to
atherosclerotic plaque
 Difficult surgical management

71.  Infected aneurysms
 More prone to rupture
 Increased periaortic fat earliest sign
 Irregularly shaped