We retrospectively studied 25 patients with abdominal mass lesions and subsequently confirmed with surgical and histopathological diagnoses of retroperitoneal and intraperitoneal (IP) mass lesions.
The cases included were retroperitoneal sarcomas,
renal cell carcinoma,
suprarenal lesions,
mesenteric mass and GIST.
Approach to retroperitoneal (RP) lesions:
Step 1.
Intraabdominal or Retroperitoneal (figure 5)
Ø The retroperitoneal lesion due to its location tends to show mass effect on the adjacent retroperitoneal structures.
Ø Lateral or anterior displacement of the retroperitoneal structures or compression over the retroperitoneal structures.
Case 1 (figure 6)
A 35 year old male presented with abdominal mass.
There is displacement of the superior mesenteric vessels.
The lesion is identified as right renal mass and was pathologically proven to be a RCC.
Case 2 (figure 7)
A 42 year old male patient with a mass in the left posterior pararenal space displacing the left kidney anteromedially.
The mass was diagnosed as retroperitoneal sarcoma.
Case 3 (figure 8)
A 55 years old patient with left lower pole renal cell carcinoma showing displacement of the ascending colon anteriorly.
Case 4 (figure 9)
The pancreas is seen displaced anteriorly by the prevertebral mass in a 40 year old female patient which was diagnosed as retroperitoneal lymphoma.
Case 5 (figure 10)
The pancreatic tail mass lesion displacing the ascending colon anteriorly.
Case 6 (figure 11)
Psoas mass lesion seen displacing the aorta anteriorly.
Step 2 - Primary retroperitoneal lesions (figure 12)
Primary retroperitoneal lesions are the lesions within the retroperitoneum but outside the retroperitoneal structures.
Ø They have to be suspected if the lesion is displacing the retroperitoneal structures anteriorly
Ø According to the pattern of the spread like encasement of the aorta,
growth along the paraspinal region and along the normal structures.
Pattern of spread and Infiltration of the retroperitoneal structures
Case 7 (figure 13)
Sagittal CT image of a 35 year old male patient with retroperitoneal lymphoma demonstrating encasement and infiltration of the inferior vena cava by the mass.
Case 8 (figure 14)
Sagittal CT image of a 35 year old male patient with retroperitoneal lymphoma demonstrating encasement of the right ureter.
Case 9 (figure 15)
Retroperitoneal mass lesion seen encasing and infiltrating the left ureter causing left hydroureteronephrosis.
Floating aorta sign:
Floating aorta sign: encasement of aorta by retroperitoneal mass.
Case 10 (figure 16)
A 38 years old male patient with retroperitoneal lymphoma showing encasement of the aorta by the retroperitoneal mass.
Step 3-Retroperitoneal lesions from retroperitoneal structures.
(figure 17)
There are four different signs on MDCT which aid in identifying the origin of the lesion.
Ø Beak sign: Beak deformation of edge of adjacent organ
Ø Phantom organ sign: Obscuration of small organs by large mass.
Ø Embedded organ sign: Part of organ of origin is embedded in the mass with adjacent desmoplastic reaction .
Ø Prominent feeding artery sign: Feeding artery to the lesion arises from the organ of origin.
Beak sign
Case 11 (figure 18)
Axial CT image of left renal cell carcinoma demonstrating beak shaped deformation at the edge of the left kidney.
Case 12 (figure 19)
Beak sign demonstrated in a case of pancreatic tail mass lesion.
Case 13 (figure 20)
Sagittal CT image demonstrating beak sign in case of renal cell carcinoma.
Phantom organ sign
Case 14 (figure 21)
Axial CT image of a case of pheochromocytoma.
Left adrenal gland is not visualized.
Embedded organ sign
Case 15 (figure 22)
Axial CT image of right renal cell carcinoma showing compression of the right kidney by the mass .
The right kidney appears embedded within the mass with desmoplastic reaction at the contact surface.
Case 16 (figure 23)
Sagittal CT image of a case of left psoas abscess demonstrating embedded organ sign
Prominent feeding artery sign
Case 17 (figure 24)
Axial CT image of right renal cell carcinoma showing the mass being supplied by the right renal artery.
Case 18 (figure 25)
The retroperitoneal pancreatic mass showing its arterial supply from the celiac artery .
Step 4-Intraperitoneal lesions (figure 26)
Points aid in diagnosis of intraperitoneal lesions
Ø Identifying organ of origin
Ø Mass effect on the adjacent structures
Ø Growth within the peritoneal cavity
Ø Posterior displacement of the retroperitoneal structures.
Case 19 (figure 27)
A 42 year old patient with gastrointestinal stromal tumour with mass effect on intraperitoneal structures- spleen,
small bowel,
liver.
Case 21 (figure 28)
Coronal and Sagittal CT images of a mesenteric mass within peritoneal cavity,
anterior to aorta,
IVC and mass effect on urinary bladder and small bowel.
Case 22 (figure 29)
Axial and sagittal CT images of a mesenteric mass lesion deforming the shape of liver and causing posterior displacement of aorta and kidney.
Flowchart to approach the retroperitoneal/intraperitoneal lesions.
(figure 30)