Incidentalomas in the Abdomen

Transcription

‘INCIDENTALOMAS’ – The definition
Tumor (-oma)/Lesion found by coincidence
(incidental) without clinical symptoms or
suspicion.
Worry gives a small thing a big shadow
OBJECTIVES OF THIS TALK
To appreciate the magnitude of ‘the incidentalomas’
To help differentiate between ‘benign lesions’ from those that are significant. Identify the ideal imaging modalities / most cost effective workup for lesions needing further evaluation.
To discuss the benign incidentalomas
commonly encountered on imaging. Incidentalomas‐ Incidence
A recent study stated 37% of patients receiving whole‐body CT scan may have abnormal findings that need further evaluation.
Incidence of the incidentalomas is increasing correlating with increase in health screening programs and unnecessary imaging used in low risk patients especially in the ER
Consequences of detection Issue facing us?
NOT SIMPLE
For clinicians : Provoked in part by fear of lawsuits, additional tests are performed. All too often, these tests do not result in diagnostic certainty.. For radiologists : Caught in the same bind, are inclined to suggest additional tests and to dictate in their reports "Cannot exclude . . .,” and "Clinical correlation required," implying that a sinister cause of the finding might be discovered.
For patients: Heightens worry and yet offers little insight into the appropriate level of concern. Commonly encountered incidentalomas
“Organ of origin and significance”
Liver
Renal Adrenal Lymph nodes
CT TECHNIQUE
Regular contrast enhanced CT exam: Portal venous phase ( 70 sec post iv contrast)
Hepatic protocol: Triphasic exam including non contrast, arterial (15‐20 sec ), portal venous phase (70 sec post iv contrast).
Renal protocol: Triphasic exam includes non contrast, cortico‐medullary (20‐30 sec) and nephrographic phase (70‐140 sec post iv contrast).
Liver ‘Incidentalomas’
Benign or
Significant
Significant
UDO ( Unidentified
dark objects)
Simple Cysts, Biliary
Hamartomas, Focal
Fat, TSTC ( too small
to characterize)
Multiple TSTC in a
patient with known
cancer
UBO ( Unidentified
bright objects)
Hemangiomas, Focal
Nodular Hyperplasia
Adenomas ( > 5 cm)
UTBO (
Unidentified
transient bright
objects)
THAD/THID
(Transient hepatic
attenuation
differences/ intensity
differences)
THAD/THID
associated with mass
Maarten van Leeuwen for the Dutch Radiology Society
Simple Liver Cysts
Congenital in origin
5% incidence.
Fluid within the cyst has composition mimicking plasma. Simple Liver Cysts ‐ USG
Rounded, thin walled,
well defined, anechoic,
posterior acoustic
enhancement
Simple Liver cysts CT
well defined, low
attenuation (0-10HU),
No contrast enhancement
Simple Liver Cyst ‐ MRI
T1 weighted
T2 weighted
Post Gad T1 weighted
well defined, high SI on
T2 and no contrast
enhancement
Significant hepatic cysts
Echinococcal/Hydatid cysts‐
parasite Echinococcus granulosus. At risk population: sheep and cattle farmers. T2 - WI
Cysts have an outer layer of inflammatory tissue and an inner germinal membrane that produces daughter cysts. T2 – WI (MRCP)
T 1- WI
Echinococcal cyst : Imaging Collapsed parasitic membranes appear as twisted linear structures within the cyst – Floating membrane sign.
- WI
Rupture into biliaryT1tract or peritoneum may also T2 - WI
be visualized
Iván Pedrosa, MD, Antonio Saíz, MD et al Hydatid Disease: Radiologic and
Pathologic Features and Complications Radiographics. 2000;20:795-817. T2 - WI
Significant hepatic cysts
Adult polycystic liver disease (AD‐PCLD) – usually associated with ADPKD. Biliary hamartoma
aka von Meyenburg complex
Benign liver malformations that histologically contain cystic dilated bile ducts within 10 mm dm surrounded by abundant fibrous stroma
Imaging: Typically multiple round or irregular focal lesions of nearly uniform size (up to 15 mm) scattered throughout the liver oCT‐ hypodense, similar to cysts oUSG‐ hypoechoic or hyperechoic foci, they may have a comet tail artifact oMRI‐ hypointense on T1 and hyperintense on T2 weighted images. No contrast enhancement. Sonographic Features of Biliary Hamartomas
With Histopathologic Correlation J Ultrasound
Med 2006 25:1631
Biliary Hamartoma: Imaging
T2 - WI
Post Gad T1 - WI
T1 - WI
TSTC ‐ too small to characterize lesions <1 cm
Large series of 1500 patients who had an abdominal CT examination. TSTC lesions were found in 17% of patients. 45 pts without a known malignancy, all lesions were benign 209 pts with a known malignancy 86 had 1 TSTC: 5% malignant 74 had 2-4 TSTCs: 19% malignant 49 with >5 TSTCs: 76% malignant.
Another study of 2978 pts known malignancy
TSTCs in 12%
88% benign
12% metastases (1.4% of all patients)
The frequency and significance of small ( less than or equal to
15mm) hepatic lesions detected by CT AJR: 158, 535-539
TSTC (cont.) ‐ Conclusion
In a patient without a known malignancy, these small hypodense lesions, as a rule, should be considered as benign
In a patient with a known malignancy
Single TSTC lesion can also be assumed to be benign
Multiple TSTCs in these patients are also mostly benign, especially when they are small, sharply defined and hypodense. When to worry: Known malignancy, multiple TSTCs which appear heterogenous and with soft tissue attenuation
The primary tumor is breast cancer Prevalence and Importance of Small Hepatic Lesions Found at CT in Patients with Cancer.
Radiology. 1999;210:71-74
Small 'indeterminate' lesions on CT of the liver: a follow-up study of stability P J Robinson,,
P Arnold, and D Wilson, British Journal of Radiology (2003) 76, 866-874
Focal Fat Sparing/Infiltration
Related to regional differences or disturbances in hepatic blood flow Usual locations:
adjacent to gallbladder bed
fissure of the ligamentum teres
medial segment of the left lobe
ventral to the bifurcation of the main branch of the portal vein
the subcapsular location. Fatty liver ‐ USG
Fatty Liver ‐ CT
Fatty liver ‐ MR
T1- WI in phase
T1- WI out of phase
Focal Fat sparing ‐ USG
Differentiate from space occupying lesions
does not cause any mass effect or contour deformation of the organ. Following iv contrast intrahepatic vessels follow their normal course through the lesion without deformity. Typical location of the anomaly.
Focal Fat sparing ‐ USG
Focal Fat Sparing ‐ CT
Focal Fat infiltration‐
CT
UBO‐ Incidental bright/hypervascular lesions
Incidence ‐ Autopsy incidence of 20 % hemangioma, 3% FNH and 1% adenoma. Introduction of MDCT and MRI – Increased detection due to multiple reasons including faster scanning, improved spatial and temporal resolution, less respiratory misregistration, better contrast bolus capture and timing of arterial and venous phases, and volumetric acquisition of the entire data set in single breath‐hold. Hemangioma
Most common benign liver lesion
Slowly perfused vascular space.
Incidence : 5‐20% of the population Hemangioma ‐ USG
Well- circumscribed uniformly hyperechoic lesion.
Hemangioma ‐ CT
Non- contrast
Arterial
> 1cm peripheral, discontinuous, intense nodular enhancement during the arterial phase with progressive centripetal fill‐in on delayed phases
Venous
Giant Hemangioma ‐ CT
Arterial
Venous
Hemangioma ‐ MRI
Shows the same enhancement characteristics. Advantage of MR over CT is its higher sensitivity to contrast
< 1 cm ‐ demonstrate immediate homogenous enhancement, isodense to the aorta (flash hemangioma). T2 - WI
Arterial
Venous
Focal Nodular Hyperplasia Incidence : 2‐5% population Nonencapsulated firm nodule of normal hepatocytes with a distinct central scar and thin radiating fibrous septa containing Kupffer's cells and primitive bile ductules.
Arterial
T2- WI
Arterial
Delayed
Difficult to delineate in the portal venous phase.
Delayed phase often shows hyperattenuation of the central scar.
No calcifications, inhomogeneity or capsule should be seen in FNH
Focal Nodular Hyperplasia ‐ Imaging T1- WI
T2 -WI
FNH
Arterial
Portal
Hepatic Adenoma

Uncommon benign epithelial liver tumors Young women (20 to 44 yr)
Typically solitary
Frequently in the right hepatic lobe
Multiple lesions with prolonged oral contraceptive use, glycogen storage diseases and hepatic adenomatosis. Complications: malignant transformation, spontaneous hemorrhage, and rupture Non-contrast
Arterial

Portal
Well‐circumscribed lesion that may display low attenuation because of the presence of fat, old hemorrhage, or necrosis. Recent hemorrhage display high attenuation. Calcification is present in 5–10% of cases. Early enhancement during the arterial phase.
Significant Lesion: Adenoma
5cm.
Arterial
Portal
Tendency for spontanous hemorrhage and rupture esp. if predominantly exophytic
THED‐ Transient hepatic enhancement differences An area of bright contrast enhancement on the arterial phase images that returns to isoattenuation on the portal venous phase. DOES NOT CORRESPOND TO MASS Causes: increase in the primary arterial inflow, indirectly by means of portal hypoperfusion, flow diversion caused by an arterioportal shunt, aberrant venous drainage
THAD/THID associated with a focal lesion
THAD/THID without a focal lesion THAD without mass: Imaging Arterial
THAD without mass: Imaging Arterial
Portal
THAD with mass: Imaging THAD with mass: Imaging Characterization of hepatic lesion
Preferred modality to characterize incidentalomas is MRI
Better for lesion characterization (multiple sequences)
Minimize radiation burden.
Part 2 ‐ Renal incidentalomas
Renal lesions
Insignificant
Significant
Low
attenuation
Simple cyst,
TSTC, Small
AML
Large AML (> 4
cm)
High
attenuation
Hemorrhagic
cyst
Renal cell
carcinoma
The Simple Renal Cyst
Fifty per cent of individuals over 50 years of age have single or multiple cysts. Homogeneity, water content, and a sharp interface with adjacent renal parenchyma, with
no wall thickening, calcification, or enhancement.
T1- WI
T2 - WI
Renal cysts and ADPKD‐
The Big Question
Diagnosis of ADPKD < 30 yrs – 2 cysts (unilateral or bilateral),
30–60 yrs ‐ > 5 cysts > 60 yrs ‐ > 8 cysts bilaterally Positive family history and association with liver cysts Recommended that screening for intracranial aneurysms ‐ patients with a personal or family history of intracranial hemorrhage. Patient with ADPKD has a 5% chance of getting brain aneurysms. Renal cystic disease (ADPKD and
ARPKD) Nephrol Dial Transplant (2002)
17: 311-314
Acquired renal cystic disease
The Bosniak system of renal cysts
Type I ‐ simple cysts.
Type II ‐ minimally complicated cysts.

Thin (< 1mm) septations (few).
Hyperdense cysts.
Fine calcification in wall/septae. IGNORE
Type II F – Multiple thin septa, mild thickening of wall/septa without enhancement.
FOLLOW
Type III indeterminate ‐ may show uniform wall thickening, nodularity with enhancement, thick or irregular peripheral calcification, or a multilocular nature with multiple enhancing septa. (80‐90% malignant) EXCISE
Type IV ‐ nonuniform or enhancing thick wall, enhancing or large nodules in the wall, or clearly solid components in the cystic lesion. Practical approach to cystic renal mass : David S. Hartman, MD, Peter L. Choyke, MD
and Matthew S. Hartman, MD
How I do it: Evaluating Renal masses. Gary M. Israel, MD and Morton A. Bosniak, MD
Bosniak
Type I
Non-contrast
Arterial
Bosniak
Type II
Portal
Hemorrhagic renal cyst (Bosniak Type II)
Acquired cystic renal disease or autosomal
dominant
polycystic renal disease
Criteria described by Bosniak
•small (with a diameter of 3 cm or less)
•round, well marginated
•homogeneously hyperattenuating
•should not enhance.
Non-contrast
T1- WI
Post Gad T1-WI
T2-WI
Arterial
Hemorrhagic Cyst – Imaging Bosniak Type IIF Bosniak Type III
Bosniak Type IV
The Bosniak system of renal cysts
Type I ‐ simple cysts.
Type II ‐ minimally complicated cysts.

Thin (< 1mm) septations (few).
Hyperdense cysts.
Fine calcification in wall/septae. IGNORE
Type II F – Multiple thin septa, mild thickening of wall/septa without enhancement.
FOLLOW
Type III indeterminate ‐ may show uniform wall thickening, nodularity with enhancement, thick or irregular peripheral calcification, or a multilocular nature with multiple enhancing septa. (80‐90% malignant) EXCISE
Type IV ‐ nonuniform or enhancing thick wall, enhancing or large nodules in the wall, or clearly solid components in the cystic lesion. Practical approach to cystic renal mass : David S. Hartman, MD, Peter L. Choyke, MD
and Matthew S. Hartman, MD
How I do it: Evaluating Renal masses. Gary M. Israel, MD and Morton A. Bosniak, MD
Angiomyolipoma
Benign neoplasm composed of fat,
vascular and smooth muscle elements
Incidence - 0.3-3%, Male: female: 1: 4
Symptomatic : palpable abdominal
mass, hematuria or flank pain.
Angiomyolipoma‐ Imaging Angiomyolipoma : Significant
Part 3 : Adrenal incidentalomas
Adrenal Incidentalomas
Prevalence ranges from 1.4% to 8.7%, increasing with age
Most of these masses are benign, even in patients with a known malignancy.
Most common tumor in the adrenal gland is the adenoma.
A recent study <3 cm nononcologic patient – 99% benign
<3 cm oncologic patient – 67% benign
Imaging of Adenoma: CT
Generally small (< 3cm) Density <10 HU on a non contrast CT sensitivity of 70% and a high specificity of 98% for the diagnosis of an adenoma. Imaging of Adenoma: CT
Non-contrast
Mean: 3 HU
30% of adrenal adenomas do not contain enough intracellular lipid to have a density of less than 10 HU ‐
called lipid‐poor.
CT washout study: Attenuation values are measured on unenhanced, initial Non-contrast
Portal
Delayed
enhanced (at 60 sec) and delayed CT (at 15 min) .
Absolute & relative wash out is calculated.
Imaging of Adenoma: MRI
T1-WI in phase
Loss of signal on out of phase imaging
T1-WI out phase
Myelolipoma
Benign neoplasm composed of mature adipose tissue and a variable amount of hematopoietic elements. Incidence varies from 0.08‐0.4% at autopsy.
Most are unilateral
Large amounts of fat often are seen interspersed with higher‐attenuation myeloid tissue. May contain calcification in as many as 20% of patients which may be due to previous hemorrhage. Myelolipoma : USG and CT Imaging
Key to diagnosis is to find a true focal fat
collection in the adrenal mass.
A Last Note: Lymph nodes
Lymph Nodes : Size criteria
Upper abdominal lymph nodes: criteria for normal size
determined with CT. Radiology 1991; 180 319
Pathological Lymphadenopathy
Conclusions
Abdominal Incidentalomas are very common on imaging with an increasing incidence. Most incidentalomas can be diagnosed with certainty on imaging Clinical history may be instrumental for correct diagnosis.
Diagnosis is not the end, but the beginning of practice. ~ Martin H. Fischer