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‘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 Rounded, thin walled, well defined, low attenuation (0-10HU), No contrast enhancement Simple Liver Cyst ‐ MRI T1 weighted T2 weighted Post Gad T1 weighted Rounded, thin walled, 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 Imaging of Adenoma: CT Imaging of Adenoma: CT 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
