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GM Werder,1 GA Arnold,1 SA Vartanian,1 F Sokhandon,1 SH Jafri,1 MB Amin,2 IR Francis,3 MA Amendola4
1 Department of Radiology, William Beaumont Hospital, Royal Oak, MI2 Department of Pathology, William Beaumont Hospital, Royal Oak, MI
3 Department of Radiology, University of Michigan, Ann Arbor, MI4 Department of Radiology, University of Miami, Coral Gables, FL
Infectious, Inflammatory, & Neoplastic Conditions of the Retroperitoneum
Objectives
• Describe basic retroperitoneal anatomy
• Present an organized approach to pathologic retroperitoneal processes
• Illustrate patterns of involvement, imaging features, & interpretation pitfalls in an unknown-case format
• Discuss patient management & clinical implications
Retroperitoneum• Boundaries
– Anterior: posterior parietal peritoneum– Posterior midline: anterior longitudinal ligament– Posterior off-midline: paraspinal musculature & transversalis fascia– Lateral: transversalis fascia – Superior: diaphragm– Inferior: pelvis
• Continues inferiorly as pelvic extraperitoneal space
• Contents– Genitourinary: kidneys, ureters, adrenal glands– Gastrointestinal: pancreas*, duodenum*, colon*– Vascular: aorta, inferior vena cava, portal vein– Lymphatic: cisterna chyli, thoracic duct– Neural: celiac plexus, sympathetic trunks– Quadratus lumborum, iliopsoas, & other paraspinal musculature is
technically retrofascial, but practically regarded as retroperitoneal
*pancreatic tail, 1st/4th segments of duodenum, & transverse colon are intraperitoneal
Peritoneum Lateroconal plane
Retromesenteric plane Retrorenal plane
Air in retromesenteric (blue) & retrorenal (yellow) planes in a patient with perforated viscus.
Interfascial Plane Model
A patient with hydronephrosis who underwent bilateral percutaneous nephrostomy complicated by left retroperitoneal hematoma; there is thickening & increased attenuation of the posterior pararenal space (yellow) with extension to the anterior pararenal space (blue), outlining the spared perirenal space (green).
A
Tricompartmental Model Peritoneum Perirenal space
Anterior pararenal space Posterior pararenal space
• Infectious– Nodal
– Vascular
– Musculoskeletal
• Inflammatory– Primary
– Vascular
• Neoplastic– Primary
– Neurovascular
– Metastatic/nodal
Pathologic Processes
Click BLUE subheadings to
navigate to unknown cases
Case 1: 39-year-old male with weight loss & night sweats
A B
(A) Enlarged low-attenuation lymph nodes with peripheral enhancement, characteristic of tuberculous adenitis. (B) Right psoas abscess (cold abscess); though absent here, calcification is not uncommon in tuberculous abscesses.
Sonographic (A, B) and CT (C, D) correlation of bulky hypoechoic, low-attenuation lymphadenopathy. CT-guided biopsy (E) was positive for Mycobacterium tuberculosis.
A
C
B
D
E
Case 1: Companion case
Case 2: Immunocompromised adult female with fever
A patient with Mycobacterium avium-intracellulare lymphadenopathy. As compared to tuberculous lymphadenopathy, these nodes are smaller, more
numerous, more discrete, & exhibit uniform soft tissue attenuation.
Another patient with Mycobacterium avium-intracellulare lymphadenoapathy. Axial CT (A) shows bulky retroperitoneal lymph nodes without vascular or intestinal displacement. Again, relative to tuberculous adenopathy, these nodes are smaller, more numerous, more discrete, & of uniform
soft tissue attenuation. Pathology (B) shows innumerable intracellular acid-fast bacilli.
A B
Case 2: Companion case
Case 2: Companion case #2
Although central low attenuation with peripheral enhancement is more typical of tuberculous lymphadenopathy, culture in this patient yielded Mycobacterium avium-intracellulare, illustrating the overlap in imaging appearance.
Initial CT (A) demonstrates partially calcified retroperitoneal lymph nodes. Six month follow-up CT (B) demonstrates new lytic osseous lesion & bilateral psoas abscesses, of which the
left is contiguous with the spine lesion.
A B
Case 3: 30-year-old male with AIDS, fever, chills, & abdominal pain
CT-guided biopsy (A) of a calcified left para-aortic lymph node; hematoxylin & eosin (B) shows necrotizing granulomatous inflammation & Grocott stain (C)
shows numerous fungal yeast forms, compatible with Histoplasma capsulatum.
Case 3: 30-year-old male with AIDS, fever, chills, & abdominal pain
BA C
Another patient with AIDS & similar-appearing partially calcified retroperitoneal lymphadenopathy. Methenamine silver stain of a biopsied lymph node was consistent
with extrapulmonary Pneumocystis jirovecii (formerly Pneumocystis carinii).
Case 4: Adult female with AIDS, cough, fever, chills, weight loss, & abdominal pain
• Mycobacterium tuberculosis– Lymphadenopathy most common abdominal manifestation of TB– Central low attenuation (caseation necrosis), peripheral enhancement
(inflammatory granulomatous hypervascularity), may calcify – Similar to MAC, metastases, Whipple disease, & lymphoma
• Mycobacterium avium-intracellulare (MAC)– Common in AIDS and may mimic Kaposi sarcoma or lymphoma– Tend to be smaller & uniform soft tissue attenuation compared to TB
• Histoplasmosis capsulatum– Enlarged, variable appearance: homogeneous soft-tissue density (44%),
diffuse or central low density (13%), or both (19%)– May calcify
• Pneumocystis jirovecii (formerly Pneumocystis carinii)– Extrapulmonary disease occurs in 1% & is associated with use of
aerosolized pentamidine, which suppresses pulmonary infection but has no extrapulmonary effect
– Imaging features not well documented
Infectious Lymphadenopathy
• Infectious– Nodal
• Mycobacteria, Histoplasma, Pneumocystis– Vascular
– Musculoskeletal
• Inflammatory– Primary
– Vascular
• Neoplastic– Primary
– Neurovascular
– Metastatic/nodal
Pathologic Processes
Click RED subheadings to . navigate to previous cases .
Click BLUE subheadings to navigate to unknown cases
Case 5: Adult female with signs of sepsis, but negative blood cultures & no identifiable source of infection
A B
Presentation CT (A) demonstrates periaortic soft tissue, which was interpreted as reactive lymphadenopathy secondary to occult infection; patient was discharged on
antibiotics. Follow-up CT (B) obtained 3 weeks later for recurrent sepsis demonstrates increased inflammation & left posterolateral outpouching consistent with mycotic
aneurysm. Repeat blood cultures were positive for Salmonella enteriditis.
Short-term follow up demonstrates development of eccentric saccular
mycotic aneurysm.
Hepatic flexure wall thickening & adjacent inflammation, periaortic
inflammatory change, & gas within wall of abdominal aorta, compatible with infectious aortitis secondary to
perforated colon cancer.
One-month follow-up demonstrates interval increase in size.
Postoperative changes of axillobifemoral bypass with aortic
ligation, excision of the aneurysm, & devascularization of the left kidney.
Case 5: Companion case
Axial (A) & coronal (B) CT demonstrate abdominal aortic aneurysm with surrounding inflammatory change interpreted as rupture. Patient consequently underwent urgent endovascular stent-graft repair (C).
Follow-up CT 3 weeks later (D) demonstrates progression of saccular dilatation & inflammatory change compatible with mycotic aneurysm & stent-graft infection.
A B
D
C
Case 6: Adult male with abdominal pain
A
B
DC
Case 6: Companion case
(A) Large mycotic aneurysm on digital subtraction angiography shows mural thickening/soft tissue mass on CT (B) with erosion into adjacent spine causing discitis/osteomyelitis, evident on pre- (C) & post-contrast (D) lumbar MRI.
Mycotic Aortic Aneurysm• Pathogenesis
– Inoculation• Septic embolization of vasa vasorum (e.g. endocarditis)• Hematogenous seeding of preexisting intimal defect (e.g. sepsis)• Contiguous involvement from adjacent source (e.g. Crohn’s, discitis)• Direct traumatic inoculation (e.g. stab wound, intravenous drug use)
– Negative blood cultures in 25%• When positive, most commonly Salmonella, Staphylococcus, & Streptococcus
– Acute rupture/hemorrhage in 75%– Mortality rate 67%
• Imaging features– Lobulated, eccentric, saccular aneurysm with indistinct, irregular wall– Rarely calcified (exception: syphilitic aneurysm)– Perianeurysmal edema, gas, soft tissue mass, &/or enhancement– Increased accumulation of 111Indium-labeled white blood cells
• Risk factors & demographics– IV drug use, immunodeficiency, bacterial endocarditis, vascular prostheses– Incidence: 1-2.5% of all aortic aneurysms
• Management:– Endovascular (stent-graft) or surgical (bypass) intervention– Prolonged antibiotic therapy
• Infectious– Nodal
• Mycobacteria, Histoplasma, Pneumocystis– Vascular
• Mycotic aneurysm– Musculoskeletal
• Inflammatory– Primary
– Vascular
• Neoplastic– Primary
– Neurovascular
– Metastatic/nodal
Pathologic Processes
Click RED subheadings to . navigate to previous cases .
Click BLUE subheadings to navigate to unknown cases
Case 7: Adult male with lower back pain & radiculopathy
Axial CT demonstrates marked vertebral body
destruction with contiguous bilateral psoas abscesses.
Sagittal gadolinium-enhanced MRI demonstrates vertebral body destruction
out of proportion to intervertebral disc space involvement, compatible with
tuberculous spondylitis.
Case 7: Adult male with lower back pain & radiculopathy
T1 PostcontrastT1 Postcontrast
In contrast to disc sparing as in TB infection, patchy disc enhancement in this patient is characteristic of pyogenic spondylodiscitis. Also noted is dural thickening & enhancement, as well as extension of disease into the psoas muscles. Culture was positive for Streptococcus viridans.
T1 Precontrast T1 Postcontrast
T1 Precontrast
T1 Postcontrast
Postcontrast CT
Case 8: Adult male with severe lumbar back pain
T1 Precontrast T1 PostcontrastFeatures which help distinguish tuberculous spondylitis from pyogenic spondylodiscitis:
• 3 or more contiguous segments involved
• Multiple noncontiguous “skip” lesions (yellow)
• Anterior vertebral body collapse with resultant focal kyphosis (Gibbous deformity; green)
• Disproportionate prevertebral soft tissue extending craniocaudally along anterior longitudinal ligament (blue)
• Relative intervertebral disc sparing (red)
Axial imaging of the prior patient demonstrates paraspinal cold abscesses under the anterior longitudinal ligament. CT images better depict vertebral
body destruction. Biopsy revealed necrotizing granulomatous inflammation & sequestrum, typical of tuberculous spondylitis (Pott’s disease).
T1 Precontrast T1 Postcontrast T2
Precontrast CT Postcontrast CT CT-Guided Biopsy
Oblique pelvic radiographs (A, B) reveal ill-defined margins of right sacroiliac joint (blue). Pre- (C) & post-contrast (D) T1WI demonstrates enhancement of right sacroiliac joint with extension
to right iliopsoas muscle. Blood culture positive for Enterobacter & clinical/imaging improvement on ertapenem helped confirm diagnosis of pyogenic sacroiliitis.
A
B D
C
Case 9: Adolescent male with right hip pain
Axial CT demonstrates a fluid-attenuation collection in the left psoas muscle with a thick enhancing wall, compatible with psoas abscess. Aspirate revealed Staphylococcus aureus.
Case 10: 71-year-old female on ribavirin for hepatitis C with fever, chills, & left lower abdominal quadrant pain
Case 11: Adult male with right lower abdominal quadrant pain, fever, & leukocytosis
BA
Axial CT demonstrates ruptured appendicitis with retroperitoneal air extending superiorly into right posterior
pararenal space (blue) & along lateral conal plane (red), as well as inferiorly along iliopsoas muscle into proximal thigh.
Case 11: Adult male with right lower abdominal quadrant pain, fever, & leukocytosis
Percutaneous drainage was performed (A) with complete resolution several days later (B).
BA
Musculoskeletal Infections with Retroperitoneal Extension
• Tuberculous spondylitis (Pott’s disease)– Incidence increasing secondary to immigration & AIDS– Epicenter typically anteroinferior vertebral body, with disease extension
along ligaments, sparing intervertebral discs– Contiguous vertebral segment involvement, skip lesions, & paraspinal
abscesses are characteristic
• Pyogenic spondylodiscitis– Most common causative organism Staphylococcus aureus (60%),
Enterobacter (30%), Escherichia coli, Pseudomonas, and Klebsiella• Remains true in immunocompromised populations
– Inoculation via hematogenous spread (e.g. intravenous drug use), ascending route (e.g. genitourinary manipulation), direct (e.g. postsurgical)
– In adults, epicenter is vertebral body endplate; in children, begins in disc
• Pyogenic sacroiliitis– Extremely rare & predominately affects pediatric & young adult patients– Most common organisms Staphylococcus, Streptococcus, & Salmonella
• Infectious– Nodal
• Mycobacteria, Histoplasma, Pneumocystis– Vascular
• Mycotic aneurysm– Musculoskeletal
• Pott's disease, discitis/osteomyelitis, sacroiliitis, psoas abscess
• Inflammatory– Primary
– Vascular
• Neoplastic– Primary
– Neurovascular
– Metastatic/nodal
Pathologic Processes
Click RED subheadings to . navigate to previous cases .
Click BLUE subheadings to navigate to unknown cases
Case 12: 44-year-old male with elevated angiotensin converting enzyme level
BA
(A) CT scout image shows coarse linear pulmonary parenchymal opacities & upper lung predominant peribronchovascular nodules. (B) Axial CT shows extensive retroperitoneal lymphadenopathy, biopsy of which demonstrated
non-caseating granulomatous tissue compatible with sarcoidosis.
Case 12: Companion case
(A) Axial CT through the lungs demonstrates bilateral hilar lymphadenopathy & interstitial disease. (B) Axial CT through the upper abdomen shows retrocrural & aortocaval lymphadenopathy (blue), compatible with retroperitoneal sarcoidosis.
BA
Case 13: 75-year-old male with flank pain
Axial CT demonstrates extensive soft tissue encasing the aorta from above the celiac axis to below the iliac bifurcation; ureteral involvement is resulting in hydroureteronephrosis, likely responsible for the patient’s symptoms.
Case 13: 75-year-old male with flank pain
Percutaneous biopsy performed to exclude lymphoma & metastatic adenopathy confirmed suspected diagnosis of retroperitoneal fibrosis.
Case 14: 50-year-old male with intermittent bilateral flank pain for 3 days
D
Axial & coronal CT demonstrates bilateral hydronephrosis & inflammatory soft tissue extending along the course of the left ureter (blue).
Case 14: 50-year-old male with intermittent bilateral flank pain for 3 days
Biopsy demonstrated “foamy histiocytes,” lipid-laden macrophages characteristic of Erdheim-Chester disease.
Extensive symmetric periureteral mixed attenuation tissue exhibiting both soft tissue & macroscopic fat components with resultant right-sided hydronephrosis.
Case 14: Companion case
Case 14: Companion case
Coronal reformatted images demonstrating the same findings.
Case 14: Companion case
BA C
D
(A, B) CT of the orbits shows a similar fibroproliferative process in the retrobulbar region as that seen in the retroperitoneum.
(C) Bone scintigraphy demonstrates right-sided hydronephrosis & bilateral increased tibial diaphyseal accumulation of radiotracer.
(D) Presumptive diagnosis of Erdheim-Chester disease was made & percutaneous retroperitoneal biopsy was performed; however,
pathology demonstrated fibroadipose tissue with lymphocytic infiltration rather than the lipid-laden macrophages characteristic of Erdheim-Chester, consistent with a diagnosis of fibrolipomatosis.
• Retroperitoneal sarcoidosis– Etiology: unknown– Imaging
• Chest findings present in 90% of patients with sarcoidosis• Retroperitoneal lymph node involvement rare (usually associated chest findings)• Retroperitoneal lymphadenopathy in patient with sarcoidosis remains non-specific
& must be differentiated from lymphoma or metastatic disease– Treatment: corticosteroids
• Idiopathic retroperitoneal fibrosis– Etiology: autoimmune, drug reaction (methysergide, β-blockers, hydralazine) – Imaging: vascular encasement; medial ureteral deviation/hydronephrosis– Treatment: corticosteroids
• Erdheim-Chester (“polyostotic sclerosing” or “non-LCH” histiocytosis)– Etiology: abnormal proliferation of tissue macrophages (histiocytes)– Manifestations
• Bone pain (secondary to diaphyseal sclerosis)• Urinary symptoms (secondary to retroperitoneal fibrosis)• Diabetes insipidus (secondary to pituitary involvement)• Exophthalmos (secondary to retrobulbar fibrosis)
– Treatment: corticosteroids
D
Primary Inflammatory Conditions
CT at presentation (A) demonstrates multiple low-attenuation collections within the right kidney oriented peripherally around a large central “staghorn” calculus, imaging features typical of
xanthogranulomatous pyelonephritis. Ten month follow-up CT (B) shows interval development of marked perirenal fibrofatty proliferation with neoplasm-like extension into the posterolateral
abdominal wall, compatible with retroperitoneal xanthogranulomatosis.
Case 15: Adult female with nausea & lethargy
At presentation 10 months later
A B
Case 15: Companion case
At presentation 10 months later
Two additional patients with retroperitoneal xanthogranulomatosis demonstrating characteristic extensive fibrofatty proliferation
• Pathogenesis– Rare inflammatory response to chronic renal infection characterized by
destruction & replacement of renal parenchyma with lipid-laden "foamy" macrophages (xanthoma cells) & granulomatous infiltrate
– Chronic renal infection generally secondary to obstructive process
• Classic triad of imaging findings– Diffuse renal enlargement with multiple focal low-attenuation xanthomatous
collections replacing renal parenchyma in a hydronephrotic-like distribution• Differentiate from hydronephrosis by lack of infundibular/pelvic dilatation
– Obstructing staghorn calculus (70%)– Perirenal fibrofatty proliferation
• Risk factors & demographics– 45-65 years– Female predominance– Diabetes mellitus in immunocompromised patients– Abnormal lipid metabolism
• Management: nephrectomy– Careful assessment of contralateral kidney critical
Retroperitoneal Xanthogranulomatosis
• Infectious– Nodal
• Mycobacteria, Histoplasma, Pneumocystis– Vascular
• Mycotic aneurysm– Musculoskeletal
• Pott's disease, discitis/osteomyelitis, sacroiliitis, psoas abscess
• Inflammatory– Primary
• Sarcoidosis, idiopathic fibrosis, Erdheim-Chester, xanthogranulomatosis– Vascular
• Neoplastic– Primary
– Neurovascular
– Metastatic/nodal
Pathologic Processes
Click RED subheadings to . navigate to previous cases .
Click BLUE subheadings to navigate to unknown cases
Case 16: 57-year-old female with polymyalgia rheumatica, night sweats, anemia, & elevated CRP/ESR*
A B
C
At presentation 3 years prior
Follow-up
*CRP: C-reactive protein; ESR: Erythrocyte sedimentation rate
Axial CT (A) demonstrates aortic mural thickening & enhancement (blue), not present
on examination three years prior (B), consistent with non-infectious aortitis; short-
term follow-up MRI (C) confirms findings.
Case 17: 73-year-old male with prior abdominal aortic aneurysm repair presents with gastrointestinal bleeding
Axial CT shows abnormal communication (blue) between the aorta & jejunum, consistent with aortoenteric fistula. The patient was not a surgical candidate & expired with conservative therapy.
Case 17: Companion case
Axial CT demonstrates a large aortic aneurysm with internal curvilinear hyperdensity & extensive retroperitoneal hemorrhage into the left anterior & posterior pararenal spaces,
compatible with aneurysmal rupture. The patient underwent emergent aortobifemoral bypass, but suffered a myocardial infarction in the perioperative period & subsequently
developed both renal & respiratory failure. Care was withdrawn one week later.
Case 17: Companion case #2
Axial CT demonstrates active extravasation of contrast from a ruptured infrarenal abdominal aortic aneurysm; the patient underwent
emergent aortoiliac stent graft placement & made a full recovery.
Case 18: 86-year-old anticoagulated male with back pain, shortness of breath, & supratherapeutic INR
Axial CT demonstrates blood in the right posterior pararenal space infiltrating/expanding the right iliopsoas muscle & resulting in
surrounding fat stranding, compatible with retroperitoneal hematoma.
Case 18: Companion case
Axial pre- (A) & post-contrast (B) CT in another patient with retroperitoneal hematoma demonstrates a less typical appearance.
A B
Case 18: Companion case #2
Coronal (A) & axial (B) CT in a trauma patient demonstrate a mass-like retroperitoneal
hematoma (blue) inferoposterior to the duodenum.A
B
Pathologic Processes• Infectious
– Nodal• Mycobacteria, Histoplasma, Pneumocystis
– Vascular• Mycotic aneurysm
– Musculoskeletal• Pott's disease, discitis/osteomyelitis, sacroiliitis, psoas abscess
• Inflammatory– Primary
• Sarcoidosis, idiopathic fibrosis, Erdheim-Chester, xanthogranulomatosis– Vascular
• Aortitis, ruptured aortic aneurysm, retroperitoneal hematoma
• Neoplastic– Primary
– Neurovascular
– Metastatic/nodal
Click RED subheadings to . navigate to previous cases .
Click BLUE subheadings to navigate to unknown cases
Case 19: 50-year-old female with left lower abdominal quadrant pain
CT shows a large encapsulated left retroperitoneal mass adjacent to the anterior aspect of the left kidney. Upon en bloc resection of the mass & left kidney, pathology was
consistent with a leiomyoma of renal capsular smooth muscle cell origin.
Case 20: 53-year-old female with palpable mass
Multiplanar reconstructed CT shows a large, heterogeneously enhancing retroperitoneal mass arising from the anterior aspect of the left kidney; ultrasound-guided biopsy was
positive for leiomyosarcoma.
Case 21: 57-year-old male with abdominal distension
Axial CT demonstrates a large heterogeneous retroperitoneal mass composed of adipose & soft tissue markedly displacing
all intrabdominal contents.
Upon resection of a 40 lb mass, pathology was positive for a
mixed low-grade liposarcoma with lipomatous, sclerosing, &
myxoid subtypes.
Axial CT demonstrates a large heterogeneous retroperitoneal
mass with scant areas of internal macroscopic fat.
Pathology was positive for a well-differentiated sclerosing
subtype liposarcoma.
Case 21: Companion case
Axial CT demonstrates a large heterogeneous retroperitoneal
mass with scant areas of internal macroscopic fat.
Pathology was positive for a well-differentiated sclerosing
subtype liposarcoma.
Case 21: Companion case #2
Axial CT demonstrates a large heterogeneous retroperitoneal mass composed of adipose & soft tissue.
Pathology was positive for a high-grade dedifferentiated liposarcoma.
Case 21: Companion case #3
Axial CT shows a large primarily soft
tissue density retroperitoneal
mass displacing the right kidney & all intrabdominal
contents to the left abdomen.
Pathology was consistent with a myxoid subtype
liposarcoma.
Case 22: 63-year-old male with abdominal discomfort
Axial CT demonstrates a large heterogeneously enhancing right retroperitoneal mass closely
approximated to the inferior pole of the right kidney.
Percutaneous biopsy yielded tissue compatible with primary retroperitoneal malignant fibrous histiocytoma.
Case 23: 79-year-old female with abdominal pain & shortness of breath
Axial CT demonstrates contained rupture of an aortic pseudoaneurysm
within extensive periaortic soft tissue (blue). The
patient expired & autopsy showed malignant fibrous histiocytoma encasing & invading the suprarenal aorta, celiac artery, left renal artery, & adrenal
artery, as well as involving the pancreatic head, left kidney, & left
adrenal gland.
Case 24: 3-year-old female with palpable mass
Axial CT shows a large left upper
abdominal quadrant mass with internal
fat, fluid, soft tissue, & calcium density, compatible with teratoma; upon
surgical resection, the location of the
mass was confirmed to be retroperitoneal.
• Infectious– Nodal
• Mycobacteria, Histoplasma, Pneumocystis– Vascular
• Mycotic aneurysm– Musculoskeletal
• Pott's disease, discitis/osteomyelitis, sacroiliitis, psoas abscess
• Inflammatory– Primary
• Sarcoidosis, idiopathic fibrosis, Erdheim-Chester, xanthogranulomatosis– Vascular
• Aortitis, ruptured aortic aneurysm, retroperitoneal hematoma
• Neoplastic– Primary
• Leiomyoma/-sarcoma, liposarcoma, malignant fibrous histiocytoma, teratoma– Neurovascular
– Metastatic/nodal
Pathologic Processes
Click RED subheadings to . navigate to previous cases .
Click BLUE subheadings to navigate to unknown cases
Case 25: 43-year-old male with longstanding history of neurofibromatosis
Axial CT (A) demonstrates a large heterogeneous left-sided retroperitoneal mass. Bone window (B) shows expansion of sacral neural foramina (blue). CT-guided biopsy (C)
was compatible with neurofibrosarcoma.
A
B C
CT T1 C–
T1 C+
T2
T1 C–
CT T1 C–
T1 C+
T2
T1 C–
Case 25: Companion case
A
B C
Axial CT & contrast-enhanced MRI show two round low-attenuation, low-T1/high-T2, enhancing lesions (blue) arising from the L4 & L5 nerve roots, compatible with peripheral nerve sheath tumors.
Precontrast
Postcontrast (90 sec)
Postcontrast (3 min)
Case 26: 74-year-old male with hypertension
Axial & coronal CT demonstrate a large
heterogeneously enhancing left
retroperitoneal mass that is distinct from normal adrenal glands (blue).
Percutaneous biopsy was performed &
pathology was positive for extra-adrenal
pheochromocytoma.
Case 26: Companion case
Axial & coronal CT images show a large
heterogeneously enhancing right
retroperitoneal mass with cystic areas & calcification that is
distinct from normal adrenal glands (blue).
Biopsy was positive for extra-adrenal
pheochromocytoma.
This particular mass falls in the minority of pheochromocytomas that are calcified, as
well as in the minority that are extra-adrenal.
Case 27: 41-year-old female with right flank pain
Axial CT demonstrates
Biopsy proven leiomyosarcoma of
vascular origin.
Axial CT & contrast-enhanced MRI show a combination of tumor thrombus (blue) & bland thrombus (red) involving the IVC & right renal vein. The patient
underwent transjugular biopsy, which was positive for IVC leiomyosarcoma.
CT
T2 LAVA early LAVA late
T1 precontrast T1 postcontrast
• Infectious– Nodal
• Mycobacteria, Histoplasma, Pneumocystis– Vascular
• Mycotic aneurysm– Musculoskeletal
• Pott's disease, discitis/osteomyelitis, sacroiliitis, psoas abscess
• Inflammatory– Primary
• Sarcoidosis, idiopathic fibrosis, Erdheim-Chester, xanthogranulomatosis– Vascular
• Aortitis, ruptured aortic aneurysm, retroperitoneal hematoma
• Neoplastic– Primary
• Leiomyoma/-sarcoma, liposarcoma, malignant fibrous histiocytoma, teratoma– Neurovascular
• Peripheral nerve sheath tumor, pheochromocytoma, IVC leiomyosarcoma– Metastatic/nodal
Pathologic Processes
Click RED subheadings to . navigate to previous cases .
Click BLUE subheadings to navigate to unknown cases
Case 28: 72-year-old female with new neck nodule
Axial CT shows bulky retroperitoneal lymphadenopathy (blue) that encases, but does not compress, mesenteric vasculature; this is a characteristic finding of lymphoma.
Case 28: 72-year-old female with new neck nodule
Axial CT demonstrates an infiltrating process involving the perirenal spaces
bilaterally, resembling inflammatory stranding; however, as there is no
hydronephrosis, biopsy was performed, which was positive for non-
Hodgkin’s lymphoma.
Case 29: 51-year-old female with flank pain & hematuria
Axial CT shows left renal enlargement with a mixed attenuation subcapsular collection & perinephric
fascial thickening & inflammatory stranding.
Initially thought to represent hemorrhagic
renal cell carcinoma, the left kidney & adrenal
gland were resected en bloc & pathology was
consistent with metastatic rhabdoid tumor with renal capsular, perinephric, &
lymphovascular invasion. Images also demonstrate periarterial involvement with a large renal infarct
and tumor thrombus within the renal vein.
Case 30: 35-year-old male status post orchiectomy for non-seminoma germ cell tumor, routine tumor surveillance
2005 2006
2007 2008
Serial axial CT images demonstrate a slow-growing, homogenous, low-attenuation mass in the aortocaval space at the level of the aortic bifurcation.
Case 30: 35-year-old male status post orchiectomy for non-seminoma germ cell tumor, routine tumor surveillance
CT-guided biopsy of the mass demonstrates a keratinaceous cyst, a mature teratomatous element from the patient’s known testicular tumor, compatible with growing teratoma syndrome.
• Diagnosis– Slow-growing mass post-chemotherapy for non-seminoma germ cell tumor– Typically occurs in mediastinum or retroperitoneum– Absence of tumor marker elevation (AFP, β-hCG, LDH), even in patients
who exhibit marked elevation from primary tumor– Pathology:
• Presence of benign mature teratomatous elements• Absence of immature malignant germ cells
• Pathogenesis (proposed theories)– Chemotherapy selectively kills immature malignant cells, leaving only mature
benign teratomatous elements– Chemotherapy-induced or spontaneous transformation of an immature
malignant germ cell into a benign mature teratomatous element
• Complications– Mass effect on adjacent structures– Malignant degeneration
• Management: complete surgical resection
Growing Teratoma Syndrome
• Infectious– Nodal
• Mycobacteria, Histoplasma, Pneumocystis– Vascular
• Mycotic aneurysm– Musculoskeletal
• Pott's disease, discitis/osteomyelitis, sacroiliitis, psoas abscess
• Inflammatory– Primary
• Sarcoidosis, idiopathic fibrosis, Erdheim-Chester, xanthogranulomatosis– Vascular
• Aortitis, ruptured aortic aneurysm, retroperitoneal hematoma
• Neoplastic– Primary
• Leiomyoma/-sarcoma, liposarcoma, malignant fibrous histiocytoma, teratoma– Neurovascular
• Peripheral nerve sheath tumor, pheochromocytoma, IVC leiomyosarcoma– Metastatic/nodal
• Lymphoma, metastasis, growing teratoma syndrome
Summary
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