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Noncardiac findings on cardiac CT. Part II: Spectrum of imaging findings
Journal of Cardiovascular Computed Tomography (2009) 3, 361–371
Review Article
Noncardiac findings on cardiac CT. Part II: Spectrum of imaging findings Ronan P. Killeen, MDa, Ricardo C. Cury, MDb, Aoife McErlean, MDa, Jonathan D. Dodd, MDa,* a
Department of Radiology, St. Vincent’s University Hospital, Elm Park, Dublin 4, Ireland and bCardiovascular MR and CT Program, Baptist (Miami) Cardiac and Vascular Institute and Baptist Hospital of Miami, 8900 N Kendall Drive, Miami, FL 33146, USA KEYWORDS: Coronary angiography; Heart/radiography; Incidental findings; Lung/radiography; Prognosis; Tomography; X-ray computed
Abstract. Cardiac computed tomography (CT) has evolved into an effective imaging technique for the evaluation of coronary artery disease in selected patients. Two distinct advantages over other noninvasive cardiac imaging methods include its ability to directly evaluate the coronary arteries and to provide a unique opportunity to evaluate for alternative diagnoses by assessing the extracardiac structures, such as the lungs and mediastinum, particularly in patients presenting with the chief symptom of acute chest pain. Some centers reconstruct a small field of view (FOV) cropped around the heart but a full FOV (from skin to skin in the area irradiated) is obtainable in the raw data of every scan so that clinically relevant noncardiac findings are identifiable. Debate in the scientific community has centered on the necessity for this large FOV. A review of noncardiac structures provides the opportunity to make alternative diagnoses that may account for the patient’s presentation or to detect important but clinically silent problems such as lung cancer. Critics argue that the yield of biopsy-proven cancers is low and that the follow-up of incidental noncardiac findings is expensive, resulting in increased radiation exposure and possibly unnecessary further testing. In this 2-part review we outline the issues surrounding the concept of the noncardiac read, looking for noncardiac findings on cardiac CT. Part I focused on the pros and cons for and against the practice of identifying noncardiac findings on cardiac CT. Part II illustrates the imaging spectrum of cardiac CT appearances of benign and malignant noncardiac pathology. Ó 2009 Society of Cardiovascular Computed Tomography. All rights reserved.
Introduction Cardiac computed tomography (CT) has become accepted as a useful noninvasive technique for the evaluation of coronary artery disease in selected patients.1,2 A distinct Conflict of interest: The authors report no conflicts of interest. * Corresponding author. E-mail address: [email protected] Submitted June 14, 2009. Accepted for publication October 24, 2009.
advantage of cardiac CTover other noninvasive cardiac imaging tests is its ability to evaluate noncardiac structures to identify other sources accounting for patient’s symptoms. A full field of view (from skin to skin in the area irradiated) is obtainable in the raw data of every scan, and many centers include this so that clinically relevant noncardiac findings can be identified.3 A review of noncardiac structures provides the opportunity to make alternative diagnoses that may account for the patient’s symptoms. Alternatively, it may allow detection of important but clinically silent problems such as lung cancer.4
1934-5925/$ -see front matter Ó 2009 Society of Cardiovascular Computed Tomography. All rights reserved. doi:10.1016/j.jcct.2009.10.007
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In this 2-part review, we outline the issues surrounding the concept of the noncardiac read, looking for noncardiac findings on cardiac CT. Part I focused on the arguments for and against the practice of identifying noncardiac findings on cardiac CT. In this article, Part II, we illustrate the spectrum of cardiac CT imaging appearances of the commonest benign and malignant noncardiac diseases. We will also describe in detail the imaging characteristics of these common incidental findings, thus providing an educational resource on how their characterization should be done.
Noncardiac disease on CT: Systematic evaluation We believe, like others, that the optimal method to detecting relevant noncardiac disorders when reading cardiac CT is a systematic approach to each organ system.5,6 We apply such an approach to cardiac CT by examining those systems yielding the highest prevalence of relevant noncardiac findings. Thus, in our centers we commonly start with a review of the lung parenchyma, followed by the mediastinum/aorta, pulmonary arteries, chest wall/ pleura, and upper abdomen.
Lungs Noncalcified pulmonary nodules are by far the commonest noncardiac finding on cardiac CT that require further workup.7 In the study by Koonce et al7 of 1764 cardiac CTs, 11.5% of patients had a nodule. Onuma et al4 detected nodules in 10% of 503 cardiac CTs. The appearance of the nodule should include an assessment of size, density, location, and border.
Size The risk of malignancy increases with increasing size of the nodule. Almost all masses .3 cm are malignant (Fig. 1). In the Early Lung Cancer Action Project, in which 1000 smokers older than 55 years were screened with lowdose chest CT, the frequency with which malignancy was or could have been diagnosed when a nodule was ,5.0 mm was 0 of 378, compared with 13 of 238 when the largest nodule was 5.0–9 mm in diameter.8 Similarly, in the Mayo Clinic Lung Cancer Screening Trial, 1520 smokers underwent low-dose CT examinations, and 36 lung cancers were diagnosed (2.6% of participants, 1.4% of nodules).9 Of these, 32 (80%) were .8 mm, and only 1 was ,5 mm at the time of detection.
Figure 1 Shown is a CT from a 73-year-old man with chest pain who underwent a cardiac CT among other investigations. Axial CT reformat showed a 5.8-cm mass (arrow) in the lingula. The size of the mass and absence of air bronchograms suggests malignancy. This was biopsy-proven adenocarcinoma.
nodule is most in keeping with a calcified granuloma, most commonly from an old tuberculosis infection (Fig. 2). A predominantly fatty nodule (negative Hounsfield units) is most in keeping with a hamartoma (Fig. 3), as is popcorn calcification or more rarely a lipoid granuloma or lipoma.11 Aside from calcification and fat density, CT lung cancer screening studies have shown 3 different nodule densities: solid, partsolid, and pure ground glass.12 A solid nodule is a nodule that completely obscures the underlying lung parenchyma. Part-solid nodules contain both solid and ground-glass components and are associated with a higher malignancy rate than either solid or pure ground-glass nodules (Fig. 4A). Ground-glass opacity is defined as hazy increased opacity of the lung, with preservation of bronchial and vascular margins. Pure ground-glass nodules appear most closely associated with adenocarcinoma-bronchoalveolar carcinoma (BAC) subtype (Fig.4A). Bronchoalveolar cell carcinomas are a particular type of adenocarcinoma that are usually slower growing compared with other types of lung cancers, with a lower risk of nodal metastases and an improved prognosis. Solid BACs often have bubble-like lucencies caused by the characteristic ‘‘lepidic’’ growth of the tumor along airways, rather than frank invasion (Fig. 5). Difficulty may arise in differentiating BAC from atypical adenomatous hyperplasia, which is now considered a premalignant lesion. Some studies have attempted to differentiate the 2. Typically, BAC is larger, appears more nodular and spherical, and has accompanying bubble-like lucencies compared with atypical adenomatous hyperplasia.13,14
Density Location Certain nodule densities are associated with benign nodules. Nodule calcification, particularly in certain patterns, equates with benignity. These include diffuse, lamellar, central, or popcorn calcification.10 A centrally calcified
Multiple nodules in a cluster of .7 favors infection (Fig. 6).11 A triangular or ovoid 6- to 9-mm nodule adjacent to the pleura usually represents a small intrapulmonary
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Figure 2 Shown is a CT from a 68-year-old man with atypical chest pain. Axial CT reformat (lung windows, left) showed an incidental 7-mm nodule (arrow). On mediastinal windows (right) it was entirely calcified, consistent with a calcified granuloma.
lymph node.15 Primary lung carcinomas occur with increased frequency in the upper lobes, whereas pulmonary metastases are usually smooth walled rather than spiculated, and they are usually most numerous in the lung bases, reflecting the effect of gravity on blood flow. They are usually multiple, and of various sizes (Fig. 7). Rarely, they can be so numerous as to be miliary.
Border Most primary lung cancers have an irregular or spiculated border (Fig. 4).16 Lindell et al17 described the margin on CT in 61 cancers from the Mayo Clinic. For adenocarcinomas (25 cases) 14 (56%) had an irregular margin, for
squamous cell carcinoma (14 cases) 10 (71%) had an irregular margin, and for small cell carcinoma (7 cases) 4 (71%) had an irregular margin.
Management Incidental, small (,10 mm) noncalcified pulmonary nodules are by far the commonest noncardiac finding on cardiac CT (Fig. 8). The Fleischner Society nodule recommendations are a useful way of managing most of these nodules (Table 1).18 Furthermore, several nodule CT appearances are pathognomonic for a benign nodule and need no further follow-up. Calcification is a reliable sign of benignity, but it has to be nodule central (Fig. 2).
Figure 3 (A) Shown is a CT from a 52-year-old man with atypical chest pain (left). Axial CT reformat showed an 18-mm nodule in the left upper lobe with popcorn calcification characteristic of hamartoma. (B) Shown is a CT of a 48-year-old man with atypical chest pain. Axial CT reformat showed a 10-mm right upper lobe nodule with a focus of fat density (240 to 2120 HU) (curved arrow), pathognomonic of a hamartoma.
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Figure 4 (A) Shown is a CT from a 62-year-old with chest pain with a history of coronary artery bypass grafts who underwent cardiac CT. Part-solid/ground-glass nodule (arrow) in the left upper lobe was biopsy-proven adenocarcinoma. (B) Shown is a CT of a 58-year-old woman with chest pain. A tiny ground-glass nodule (arrow) was identified in the right middle lobe. It did not resolve on serial scanning. This was biopsy-proven bronchoalveolar cell carcinoma.
Beware of eccentric calcification in one side of a nodule, which can occur in primary lung cancers that have engulfed a granuloma. For cavitating nodules, a useful CT feature differentiating benign from malignant causes is wall thickness. Cavity walls , 5 mm are usually benign, whereas walls . 15 mm are almost always malignant (Fig. 9).
Diffuse parenchymal disease The commonest differential diagnosis for diffuse parenchymal lung disease on cardiac CT is multifocal pneumonia (Fig. 10), but note that diffuse pulmonary hemorrhage and occasionally pulmonary edema can also cause diffuse consolidation in the appropriate clinical context. The commonest
Figure 5 This 51-year-old man with breathlessness underwent a triple rule-out CT to exclude a PE and coronary artery disease. He was a life-long smoker. Axial CT reformat showed a spiculated nodule in the left upper lobe. The nodule contained air-bronchograms and was biopsy-proven bronchoalveolar carcinoma. Note the mass in the right upper lobe, biopsy of which was most consistent with a synchronous primary adenocarcinoma.
organisms in adults include Mycoplasma pneumoniae, Streptococcus pneumoniae, and Haemophilus influenzae. Idiopathic pulmonary fibrosis is the commonest fibrotic lung disease (Fig. 11). Most patients are older than 50 years and typically present with inexorably progressive dyspnea. There is an increased risk of pulmonary carcinoma (10%). Idiopathic pulmonary fibrosis carries a significant rate of morbidity and mortality, the median survival being 2–4 years (5-year survival of 30%–50%). Emphysema is frequently incidentally evident and has been reported in approximately 9% of patients undergoing cardiac CT.19 Centrilobular emphysema is the commonest subtype and is associated with cigarette smoking (Fig. 12). This form of emphysema has upper lobe predominance and most frequently affects the apical and posterior segments of the upper lobes and the superior segments of the lower
Figure 6 Shown is a CT from a 61-year-old man with breathlessness. Axial cardiac CT reformat showed multiple clustered nodules in the lingula. This was biopsy-proven cryptococcus.
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Figure 7 Shown is a CT from a 67-year-old man with atypical chest pain. Axial CT reformat showed multiple bilateral nodules of various sizes with smooth borders characteristic of pulmonary metastases. He had known squamous cell carcinoma of the vocal cord.
lobes. The CT findings include discrete loss of lung parenchyma in the center of the secondary pulmonary lobule surrounding the bronchovascular bundle. By contrast, another subtype, panacinar emphysema diffusely involves the acinus of the secondary pulmonary lobule, has a lower lobe predominance, and is associated with a-1-antitrypsin deficiency.20 If emphysema is seen on cardiac CT, be especially aware of pulmonary nodules, because this is the group that is at high-risk for lung cancer. Bronchiectasis is defined as irreversible localized or diffuse bronchial dilatation, usually resulting from chronic infection, proximal airway obstruction, or congenital bronchial abnormality.19 It is diagnosed on CT when the bronchial lumen dimension is greater than its accompanying pulmonary artery. This is termed the signet ring sign (Fig. 13). Other features include lack of tapering of bronchi and identification of
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Figure 8 This 51-year-old man with atypical chest pain and positive family history for coronary artery disease underwent cardiac CT. He was a life-long nonsmoker. Axial CT reformat showed a 3-mm (long-axis) noncalcified nodule (arrow) in the inferior lingula. This patient had a low risk of malignancy, and no follow-up was performed for this nodule.
bronchi within 1 cm of the pleural surface. It can be classified into cylindric, varicose, or cystic subtypes, depending on the severity of the airway dilation. Bronchiectasis is often accompanied by bronchial wall thickening, mucoid impaction, and small-airway abnormalities.
Mediastinum The commonest mediastinal abnormalities in the study by Koonce et al7 of 1764 cardiac CTs were aortic aneurysms (1%) and lymph node enlargement (0.7%). Thoracic aortic aneurysms are defined as a nonreversible dilation of the aorta .5 cm. Most are atherosclerotic in origin and are seen in older patients. The majority originate in the ascending aorta (50%) and are usually visible on cardiac CT (Fig. 14).20 Cardiac CT is an accurate method of diagnosis, and also provides a pre-operative evaluation of the coronary arteries.21 A
Table 1 Guidelines from the Fleischner Society for the follow-up and management of pulmonary nodules measuring ,8 mm incidentally detected on CT Nodule size*
Low-risk patient†
High-risk patient‡
% 4 mm
No follow-up neededx
.4–6 mm
Follow-up CT at 12 months; if unchanged, no further follow-upjj Initial follow-up CT at 6–12 months then 18–24 months if no change Follow-up CT at approximately 3, 9, and 24 months, dynamic contrast-enhanced CT, PET, and/or biopsy
Follow-up CT at 12 months; if unchanged, no further follow-upjj Initial follow-up CT at 6–12 months then 18–24 months if no changejj Initial follow-up CT at 3–6 months then 9–12 and 24 months if no change Same as for low-risk patient
.6–8 mm .8 mm
Guidelines are for newly detected indeterminate nodule in persons 35 years of age or older. PET, positron emission tomography. *Average of length and width. † Minimal or absent history of smoking and of other known risk factors. ‡ History of smoking or of other know risk factors. x The risk of malignancy (,1%) in this category is substantially less than that in a baseline CT scan of an asymptomatic smoker. jj Nonsolid (ground-glass) or partly solid nodules may require longer follow-up to exclude indolent adenocarcinoma.
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Figure 9 Shown is a CT from 68-year-old man with chest pain, with a history of smoking. Axial CT reformat showed a thickwalled cavitating nodule in the right lower. This was biopsyproven squamous cell carcinoma.
related entity is a penetrating atherosclerotic ulcer, which occurs when an atherosclerotic ulcer penetrates the elastic lamina.22 They may rupture (Fig. 15) or may predispose to dissection. The ulcer is detected on cardiac CT as a defect in the aortic wall that extends beyond the aortic adventia. Finally, acute intramural hematoma of the aorta refers to hemorrhage within the aortic media. It is a related form of dissection, although no flowing blood is identified in the aortic wall. It may progress to aortic dissection, is classified using standard aortic dissection classifications, and treated in a similar way. Normal lymph nodes are smooth and ovoid in outline and shape. The normal size of lymph nodes varies depending on the location in the mediastinum. A widely used approach is to consider all nodes . 10 mm in the shortest dimension as abnormal. They should not be mistaken for normal pericardial recesses, which can be surprisingly good mimickers (Fig. 16).23 Two common miss areas include the internal mammary lymph node chains (Fig. 17) and the diaphragmatic nodes, but both are important, because the
Figure 10 Shown is a CT from a 51-year-old man with chest pain. Axial CT reformat showed consolidation in the left upper lobe, with air bronchograms and cavitation (arrowheads). It was sputum-proved pneumonia from Staphyloncus aureus.
Figure 11 Shown is a CT from a 72-year-old man with atypical chest pain. Axial CT reformat showed bilateral increased reticulation and extensive small cystic airspaces (honeycombing). Fibrosis predominating in the lung bases with honeycombing are typical of idiopathic pulmonary fibrosis.
breasts drain to the internal mammary lymph nodes and the chest wall drains to the diaphragmatic nodes. Mediastinal/hilar lymph node enlargement has benign and malignant causes. Of the benign causes, reactive nodes to lung parenchymal infection are the most common. Such nodes are usually low volume and resolve once the pneumonia has been treated. Sarcoidosis is another benign cause and classically manifests as bilateral hilar lymph node
Figure 12 Shown is a CT from a 64-year-old man with chest pain. Axial CT reformat of the left upper lobe at the level of the aortic arch showed multiple focal areas of decreased attenuation without perceptible walls. Small vessels can be seen in the center of some of these areas, corresponding to the bronchovascular bundle. This pattern is typical of centrilobular emphysema.
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Figure 15 Shown is a CT from a 63-year-old woman who presented with chest pain and had a normal echocardiogram. Axial CT showed a penetrating atherosclerotic ulcer (arrow) that had ruptured, causing a resultant pseudoaneurysm.
Chest wall/pleura
Figure 13 Shown is a CT from a 63-year-old man with chest pain. Axial CT reformat of the right upper lobe showed typical ‘‘signet ring’’ appearance of an enlarged bronchial lumen with greater luminal diameter than the adjacent pulmonary artery (straight arrow). Marked airway thickening (curved arrow) and mucus plugging (arrowhead) were also present. These appearances are typical of bronchiectasis.
enlargement (Fig. 18). Calcified nodes are almost always indicative of previous remote exposure to tuberculosis or histoplasmosis. Malignant nodes will often have a low-density center, indicating central necrosis. Of the malignant causes, the most common are lymphoma (Fig. 19) and metastases.
Figure 14 Shown is a CT from 51-year-old man presenting with chest pain. Axial CT reformat showed a large ascending aortic aneurysm (6.1 cm) and normal coronary arteries. Note the difference in diameter of the ascending and descending aorta. It is important to note that measurements of aortic diameter should be made in a plane perpendicular to the long axis of the aorta to compensate for obliquity of the vessel.
The breasts are typically included within the scan range of a cardiac CT and thus must be evaluated. Breast lesions are often overlooked on cardiac CT, but such are the soft-tissue capabilities of multidetector CT that a confident diagnosis of breast pathology can often be made. In the study by Onuma et al4 0.8% of patients had incidental breast lesions identified and 0.4% subsequently proved to have breast malignancy. However, CT cannot detect microcalcifications as well as can mammography, which is a hallmark for breast malignancy. Irregular margins, irregular shape, and rim enhancement are the most highly predictive features for breast malignancy on CT (Fig. 20).24 It should not be assumed that those patients with breast lesions found incidentally on CT are within a screening group. Obviously, breast lesions found on cardiac CT cannot be ignored in the hope that the patient will be screened and the potential cancer found.
Figure 16 Shown is a CT from a 63-year-man with chest pain. The superior aortic sinus (curved arrow) is a normal pericardial recess often identified on cardiac CT and should not be mistaken for lymph node enlargement.
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Figure 17 Shown is a CT from a 48-year-old woman with a history of breast cancer and recurrent dyspnea. Axial CT reformat showed right internal mammary lymph node enlargement (straight arrow). Note the location of the right internal mammary artery (arrowhead) and the malignant right pleural effusion.
Dedicated imaging is usually required for definitive diagnosis, but it is important for the radiologist to be able to identify and characterize lesions as benign, indeterminate. or likely malignant. Pleural effusions are common abnormalities detected on cardiac CT. Transudative effusions are commonly caused by left heart failure. Exudative effusions are commonly parapneumonic, but malignancy should always be considered, especially in a patient with a known primary malignancy. Pleural effusions classically have a low Hounsfield unit value, usually between 0 and 20 HU. Differentiating effusions from ascites can be done by looking for the interface sign or the diaphragm sign. Mesothelioma usually appears as thick, nodular thickening of the pleura with marked enhancement in the clinical setting of significant asbestos exposure.
Figure 19 Shown is a CT from a 63-year-old woman with chest pain. Axial CT reformat showed extensive anterior mediastinal lymph node enlargement (straight arrow) that had invaded through the anterior chest wall (hollow arrow). Note the malignat pericardial effusion (curved arrow). This was biopsy-proven nonHodgkin lymphoma.
on coronary CT and 1 (0.4%) on a coronary bypass graft CT. PE is diagnosed on CT when there is a partial or complete filling defect within an opacified artery (Fig. 21).25 Evaluation of the lung parenchyma may show secondary effects of the PE, such as consolidation and ground-glass opacities. Pulmonary infarcts classically appear as wedgeshaped areas of consolidation in the periphery of the lung.26 Ground-glass opacities typically represent areas of pulmonary hemorrhage. Care should be taken not to overcall PE in the lower lobes, which are often not optimally opacified on dedicated coronary CT angiography.20
Pulmonary arteries Regarding pulmonary embolism (PE), in the study by Koonce et al7 of 1764 cardiac CTs, 5 (0.7%) were detected
Figure 18 Shown is a CT from a 47-year-old with chest pain and known sarcoidosis. Axial CT reformat showed bilateral symmetric hilar lymph node enlargement (arrows).
Figure 20 Shown is a CT from a 48-year-old man with chest pain. Axial CT reformat showed an infiltrating, irregular, soft-tissue mass (arrow) in the left breast (compare its appearance with the normal right-sided breast tissue). This was biopsy-proven breast carcinoma.
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Figure 21 Shown is a CT from a 41-year-old with dyspnea and chest pain. Oblique CT reformat showed extensive pulmonary emboli (straight arrows). Note CT signs of right heart strain, including flattening of the interventricular septum (curved arrow) and dilation of the right ventricle.
Secondary signs of right heart strain may be seen, including dilation of the right ventricle, straightening of the interventricular septum, and a decrease in right ventricular function on multiphasic sequences (Fig. 21).27,28 Such appearances are considered to indicate a subgroup of patients with a worse prognosis.
Upper abdomen Simple liver cysts are one of the commonest incidental cardiac CT findings, and it is estimated that approximately 5% of the general population have one (Fig. 22). Typically,
369 they have a homogenous low density appearance with a sharply circumscribed border and do not communicate with the biliary tree. They show no enhancement and no internal septations. The overwhelming majority are asymptomatic. In patients with no known malignancy the majority of incidental hepatic lesions ,15 mm in size prove to be benign. In the presence of known malignancy %50% of these lesions will be metastases. Confirmatory imaging is suggested with targeted ultrasound scanning to confirm a purely cystic benign-appearing lesion. In larger cysts (.4cm) follow-up ultrasound at three months may be prudent to ensure no change. In patients with known malignancy, longer term follow-up is suggested to ensure lesion stability.29 The differential diagnosis includes parasitic cysts, multiple cysts in polycystic liver or kidney disease, and cystic tumors. Usually, cystic tumors have thicker walls and may have heterogeneous internal content such as blood or septae. Transient hemodynamic arterial defect lesions are secondary to variant venous drainage within the liver parenchyma (Fig. 20). They are not of any pathologic significance. Hemangiomas classically show peripheral nodular filling-in on the portal venous phase of a liver CT (so-called ‘peripheral puddling’). Finally, the liver is the second most commonly involved organ from metastases, after the lungs. The commonest primary tumors are from colon, stomach, pancreas, breast, and lung. Metastases typically have poorly defined borders, are low density (but may enhance if hypervascular) and may be associated with biliary obstruction or portal vein thrombosis. Abdominal aortic aneurysms are defined as local dilatation of the aorta with an anteroposterior diameter .30 mm or .1.5 times the diameter of the proximal aorta. Measurements should be made in a plane perpendicular to the long axis of the aorta. Detection of such aneurysm is of extreme importance because the mortality rate is much
Figure 22 Shown is a CT from a 55-year-old man with chest pain (left). Axial CT reformat showed a small, homogenous, low-density sharply circumscribed lesion in the liver, confirmed on liver ultrasound scanning to represent a cyst. (Right) Shown is a CT from a 71-year-old man with chest pain. Axial CT reformat showed a transient hyperdense lesion in the right lobe of liver, subsequently diagnosed on liver magnetic resonance imaging to be a transient hemodynamic arterial defect.
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References
Figure 23 Shown is a CT from a 52-year-old woman with chest pain. Axial CT reformat showed a retrocardiac mass (straight arrow) with pockets of air within it (curved arrow), typical of a hiatus hernia.
higher for emergency surgical repair (85%–95%) than for elective repair (5%). Aneurysms .5.5 cm are usually considered for surgical or endovascular repair. Aneurysms ,5.5 cm should be followed with serial abdominal ultrasound scanning.30 Hiatus hernias are present in approximately 10% of the population (Fig. 23). The incidence increases with age, and they have been noted in %24% of patients undergoing coronary CT.19 The clinical significance of hiatus hernias noted incidentally is uncertain. When symptomatic, they may present with epigastric pain that may be relevant in patients investigated for recurrent chest pain who have normal coronary arteries. No specific follow-up is required for incidentally noted hiatus hernias.
Conclusion The evaluation of structures outside of the heart is an unavoidable responsibility of cardiac CT readers involved in these examinations. Collaboration between radiologists and cardiologists should be pursued in benefit of patient care. The prevalence of such findings is strongly influenced by the cardiac CT protocol and the patient population being studied, as discussed in part 1 of this review. If extracardiac structures are not systematically analyzed, alternative causes of patient symptoms may go undetected thereby delaying patient care, and treatable asymptomatic malignancies may be overlooked. The review of extracardiac structures by a qualified reader is of paramount importance so that correct diagnosis can be made, and an appropriate management plan can be instituted.
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19. Hansell DM, Bankier AA, MacMahon H, McLoud TC, Muller NL, Remy J: Fleischner Society: glossary of terms for thoracic imaging. Radiology. 2008;246:697–722. 20. Dodd JD, Kalva S, Pena A, Bamberg F, Shapiro MD, Abbara S, Cury RC, Brady TJ, Hoffmann U: Emergency cardiac CT for suspected acute coronary syndrome: qualitative and quantitative assessment of coronary, pulmonary, and aortic image quality. AJR Am J Roentgenol. 2008;191:870–7. 21. White CS, Kuo D, Kelemen M, Jain V, Musk A, Zaidi E, Read K, Sliker C, Prasad R: Chest pain evaluation in the emergency department: can MDCT provide a comprehensive evaluation? AJR Am J Roentgenol. 2005;185:533–40. 22. Kazerooni EA, Bree RL, Williams DM: Penetrating atherosclerotic ulcers of the descending thoracic aorta: evaluation with CT and distinction from aortic dissection. Radiology. 1992;183:759–65. 23. Truong MT, Erasmus JJ, Gladish GW, Sabloff BS, Marom EM, Madewell JE, Chasen MH, Munden RF: Anatomy of pericardial recesses on multidetector CT: implications for oncologic imaging. AJR Am J Roentgenol. 2003;181:1109–13. 24. Harish MG, Konda SD, MacMahon H, Newstead GM: Breast lesions incidentally detected with CT: what the general radiologist needs to know. Radiographics. 2007;27(Suppl 1):S37–51.
371 25. Remy-Jardin M, Pistolesi M, Goodman LR, Gefter WB, Gottschalk A, Mayo JR, Sostman HD: Management of suspected acute pulmonary embolism in the era of CT angiography: a statement from the Fleischner Society. Radiology. 2007;245:315–29. 26. Balakrishnan J, Meziane MA, Siegelman SS, Fishman EK: Pulmonary infarction: CT appearance with pathologic correlation. J Comput Assist Tomogr. 1989;13:941–5. 27. Remy-Jardin M, Delhaye D, Teisseire A, Hossein-Foucher C, Duhamel A, Remy J: MDCT of right ventricular function: impact of methodologic approach in estimation of right ventricular ejection fraction, part 2. AJR Am J Roentgenol. 2006;187:1605–9. 28. Delhaye D, Remy-Jardin M, Teisseire A, Hossein-Foucher C, Leroy S, Duhamel A, Remy J: MDCT of right ventricular function: comparison of right ventricular ejection fraction estimation and equilibrium radionuclide ventriculography, part 1. AJR Am J Roentgenol. 2006;187: 1597–604. 29. Schwartz LH, Gandras EJ, Colangelo SM, Ercolani MC, Panicek DM: Prevalence and Importance of Small Hepatic Lesions Found at CT in Patients with Cancer. Radiology. 1999;210:71–4. 30. Lederle FA, Kane RL, MacDonald R, Wilt TJ: Systematic review: repair of unruptured abdominal aortic aneurysm. Ann Intern Med. 2007;146:735.
Review Article
Noncardiac findings on cardiac CT. Part II: Spectrum of imaging findings Ronan P. Killeen, MDa, Ricardo C. Cury, MDb, Aoife McErlean, MDa, Jonathan D. Dodd, MDa,* a
Department of Radiology, St. Vincent’s University Hospital, Elm Park, Dublin 4, Ireland and bCardiovascular MR and CT Program, Baptist (Miami) Cardiac and Vascular Institute and Baptist Hospital of Miami, 8900 N Kendall Drive, Miami, FL 33146, USA KEYWORDS: Coronary angiography; Heart/radiography; Incidental findings; Lung/radiography; Prognosis; Tomography; X-ray computed
Abstract. Cardiac computed tomography (CT) has evolved into an effective imaging technique for the evaluation of coronary artery disease in selected patients. Two distinct advantages over other noninvasive cardiac imaging methods include its ability to directly evaluate the coronary arteries and to provide a unique opportunity to evaluate for alternative diagnoses by assessing the extracardiac structures, such as the lungs and mediastinum, particularly in patients presenting with the chief symptom of acute chest pain. Some centers reconstruct a small field of view (FOV) cropped around the heart but a full FOV (from skin to skin in the area irradiated) is obtainable in the raw data of every scan so that clinically relevant noncardiac findings are identifiable. Debate in the scientific community has centered on the necessity for this large FOV. A review of noncardiac structures provides the opportunity to make alternative diagnoses that may account for the patient’s presentation or to detect important but clinically silent problems such as lung cancer. Critics argue that the yield of biopsy-proven cancers is low and that the follow-up of incidental noncardiac findings is expensive, resulting in increased radiation exposure and possibly unnecessary further testing. In this 2-part review we outline the issues surrounding the concept of the noncardiac read, looking for noncardiac findings on cardiac CT. Part I focused on the pros and cons for and against the practice of identifying noncardiac findings on cardiac CT. Part II illustrates the imaging spectrum of cardiac CT appearances of benign and malignant noncardiac pathology. Ó 2009 Society of Cardiovascular Computed Tomography. All rights reserved.
Introduction Cardiac computed tomography (CT) has become accepted as a useful noninvasive technique for the evaluation of coronary artery disease in selected patients.1,2 A distinct Conflict of interest: The authors report no conflicts of interest. * Corresponding author. E-mail address: [email protected] Submitted June 14, 2009. Accepted for publication October 24, 2009.
advantage of cardiac CTover other noninvasive cardiac imaging tests is its ability to evaluate noncardiac structures to identify other sources accounting for patient’s symptoms. A full field of view (from skin to skin in the area irradiated) is obtainable in the raw data of every scan, and many centers include this so that clinically relevant noncardiac findings can be identified.3 A review of noncardiac structures provides the opportunity to make alternative diagnoses that may account for the patient’s symptoms. Alternatively, it may allow detection of important but clinically silent problems such as lung cancer.4
1934-5925/$ -see front matter Ó 2009 Society of Cardiovascular Computed Tomography. All rights reserved. doi:10.1016/j.jcct.2009.10.007
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In this 2-part review, we outline the issues surrounding the concept of the noncardiac read, looking for noncardiac findings on cardiac CT. Part I focused on the arguments for and against the practice of identifying noncardiac findings on cardiac CT. In this article, Part II, we illustrate the spectrum of cardiac CT imaging appearances of the commonest benign and malignant noncardiac diseases. We will also describe in detail the imaging characteristics of these common incidental findings, thus providing an educational resource on how their characterization should be done.
Noncardiac disease on CT: Systematic evaluation We believe, like others, that the optimal method to detecting relevant noncardiac disorders when reading cardiac CT is a systematic approach to each organ system.5,6 We apply such an approach to cardiac CT by examining those systems yielding the highest prevalence of relevant noncardiac findings. Thus, in our centers we commonly start with a review of the lung parenchyma, followed by the mediastinum/aorta, pulmonary arteries, chest wall/ pleura, and upper abdomen.
Lungs Noncalcified pulmonary nodules are by far the commonest noncardiac finding on cardiac CT that require further workup.7 In the study by Koonce et al7 of 1764 cardiac CTs, 11.5% of patients had a nodule. Onuma et al4 detected nodules in 10% of 503 cardiac CTs. The appearance of the nodule should include an assessment of size, density, location, and border.
Size The risk of malignancy increases with increasing size of the nodule. Almost all masses .3 cm are malignant (Fig. 1). In the Early Lung Cancer Action Project, in which 1000 smokers older than 55 years were screened with lowdose chest CT, the frequency with which malignancy was or could have been diagnosed when a nodule was ,5.0 mm was 0 of 378, compared with 13 of 238 when the largest nodule was 5.0–9 mm in diameter.8 Similarly, in the Mayo Clinic Lung Cancer Screening Trial, 1520 smokers underwent low-dose CT examinations, and 36 lung cancers were diagnosed (2.6% of participants, 1.4% of nodules).9 Of these, 32 (80%) were .8 mm, and only 1 was ,5 mm at the time of detection.
Figure 1 Shown is a CT from a 73-year-old man with chest pain who underwent a cardiac CT among other investigations. Axial CT reformat showed a 5.8-cm mass (arrow) in the lingula. The size of the mass and absence of air bronchograms suggests malignancy. This was biopsy-proven adenocarcinoma.
nodule is most in keeping with a calcified granuloma, most commonly from an old tuberculosis infection (Fig. 2). A predominantly fatty nodule (negative Hounsfield units) is most in keeping with a hamartoma (Fig. 3), as is popcorn calcification or more rarely a lipoid granuloma or lipoma.11 Aside from calcification and fat density, CT lung cancer screening studies have shown 3 different nodule densities: solid, partsolid, and pure ground glass.12 A solid nodule is a nodule that completely obscures the underlying lung parenchyma. Part-solid nodules contain both solid and ground-glass components and are associated with a higher malignancy rate than either solid or pure ground-glass nodules (Fig. 4A). Ground-glass opacity is defined as hazy increased opacity of the lung, with preservation of bronchial and vascular margins. Pure ground-glass nodules appear most closely associated with adenocarcinoma-bronchoalveolar carcinoma (BAC) subtype (Fig.4A). Bronchoalveolar cell carcinomas are a particular type of adenocarcinoma that are usually slower growing compared with other types of lung cancers, with a lower risk of nodal metastases and an improved prognosis. Solid BACs often have bubble-like lucencies caused by the characteristic ‘‘lepidic’’ growth of the tumor along airways, rather than frank invasion (Fig. 5). Difficulty may arise in differentiating BAC from atypical adenomatous hyperplasia, which is now considered a premalignant lesion. Some studies have attempted to differentiate the 2. Typically, BAC is larger, appears more nodular and spherical, and has accompanying bubble-like lucencies compared with atypical adenomatous hyperplasia.13,14
Density Location Certain nodule densities are associated with benign nodules. Nodule calcification, particularly in certain patterns, equates with benignity. These include diffuse, lamellar, central, or popcorn calcification.10 A centrally calcified
Multiple nodules in a cluster of .7 favors infection (Fig. 6).11 A triangular or ovoid 6- to 9-mm nodule adjacent to the pleura usually represents a small intrapulmonary
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Figure 2 Shown is a CT from a 68-year-old man with atypical chest pain. Axial CT reformat (lung windows, left) showed an incidental 7-mm nodule (arrow). On mediastinal windows (right) it was entirely calcified, consistent with a calcified granuloma.
lymph node.15 Primary lung carcinomas occur with increased frequency in the upper lobes, whereas pulmonary metastases are usually smooth walled rather than spiculated, and they are usually most numerous in the lung bases, reflecting the effect of gravity on blood flow. They are usually multiple, and of various sizes (Fig. 7). Rarely, they can be so numerous as to be miliary.
Border Most primary lung cancers have an irregular or spiculated border (Fig. 4).16 Lindell et al17 described the margin on CT in 61 cancers from the Mayo Clinic. For adenocarcinomas (25 cases) 14 (56%) had an irregular margin, for
squamous cell carcinoma (14 cases) 10 (71%) had an irregular margin, and for small cell carcinoma (7 cases) 4 (71%) had an irregular margin.
Management Incidental, small (,10 mm) noncalcified pulmonary nodules are by far the commonest noncardiac finding on cardiac CT (Fig. 8). The Fleischner Society nodule recommendations are a useful way of managing most of these nodules (Table 1).18 Furthermore, several nodule CT appearances are pathognomonic for a benign nodule and need no further follow-up. Calcification is a reliable sign of benignity, but it has to be nodule central (Fig. 2).
Figure 3 (A) Shown is a CT from a 52-year-old man with atypical chest pain (left). Axial CT reformat showed an 18-mm nodule in the left upper lobe with popcorn calcification characteristic of hamartoma. (B) Shown is a CT of a 48-year-old man with atypical chest pain. Axial CT reformat showed a 10-mm right upper lobe nodule with a focus of fat density (240 to 2120 HU) (curved arrow), pathognomonic of a hamartoma.
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Figure 4 (A) Shown is a CT from a 62-year-old with chest pain with a history of coronary artery bypass grafts who underwent cardiac CT. Part-solid/ground-glass nodule (arrow) in the left upper lobe was biopsy-proven adenocarcinoma. (B) Shown is a CT of a 58-year-old woman with chest pain. A tiny ground-glass nodule (arrow) was identified in the right middle lobe. It did not resolve on serial scanning. This was biopsy-proven bronchoalveolar cell carcinoma.
Beware of eccentric calcification in one side of a nodule, which can occur in primary lung cancers that have engulfed a granuloma. For cavitating nodules, a useful CT feature differentiating benign from malignant causes is wall thickness. Cavity walls , 5 mm are usually benign, whereas walls . 15 mm are almost always malignant (Fig. 9).
Diffuse parenchymal disease The commonest differential diagnosis for diffuse parenchymal lung disease on cardiac CT is multifocal pneumonia (Fig. 10), but note that diffuse pulmonary hemorrhage and occasionally pulmonary edema can also cause diffuse consolidation in the appropriate clinical context. The commonest
Figure 5 This 51-year-old man with breathlessness underwent a triple rule-out CT to exclude a PE and coronary artery disease. He was a life-long smoker. Axial CT reformat showed a spiculated nodule in the left upper lobe. The nodule contained air-bronchograms and was biopsy-proven bronchoalveolar carcinoma. Note the mass in the right upper lobe, biopsy of which was most consistent with a synchronous primary adenocarcinoma.
organisms in adults include Mycoplasma pneumoniae, Streptococcus pneumoniae, and Haemophilus influenzae. Idiopathic pulmonary fibrosis is the commonest fibrotic lung disease (Fig. 11). Most patients are older than 50 years and typically present with inexorably progressive dyspnea. There is an increased risk of pulmonary carcinoma (10%). Idiopathic pulmonary fibrosis carries a significant rate of morbidity and mortality, the median survival being 2–4 years (5-year survival of 30%–50%). Emphysema is frequently incidentally evident and has been reported in approximately 9% of patients undergoing cardiac CT.19 Centrilobular emphysema is the commonest subtype and is associated with cigarette smoking (Fig. 12). This form of emphysema has upper lobe predominance and most frequently affects the apical and posterior segments of the upper lobes and the superior segments of the lower
Figure 6 Shown is a CT from a 61-year-old man with breathlessness. Axial cardiac CT reformat showed multiple clustered nodules in the lingula. This was biopsy-proven cryptococcus.
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Figure 7 Shown is a CT from a 67-year-old man with atypical chest pain. Axial CT reformat showed multiple bilateral nodules of various sizes with smooth borders characteristic of pulmonary metastases. He had known squamous cell carcinoma of the vocal cord.
lobes. The CT findings include discrete loss of lung parenchyma in the center of the secondary pulmonary lobule surrounding the bronchovascular bundle. By contrast, another subtype, panacinar emphysema diffusely involves the acinus of the secondary pulmonary lobule, has a lower lobe predominance, and is associated with a-1-antitrypsin deficiency.20 If emphysema is seen on cardiac CT, be especially aware of pulmonary nodules, because this is the group that is at high-risk for lung cancer. Bronchiectasis is defined as irreversible localized or diffuse bronchial dilatation, usually resulting from chronic infection, proximal airway obstruction, or congenital bronchial abnormality.19 It is diagnosed on CT when the bronchial lumen dimension is greater than its accompanying pulmonary artery. This is termed the signet ring sign (Fig. 13). Other features include lack of tapering of bronchi and identification of
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Figure 8 This 51-year-old man with atypical chest pain and positive family history for coronary artery disease underwent cardiac CT. He was a life-long nonsmoker. Axial CT reformat showed a 3-mm (long-axis) noncalcified nodule (arrow) in the inferior lingula. This patient had a low risk of malignancy, and no follow-up was performed for this nodule.
bronchi within 1 cm of the pleural surface. It can be classified into cylindric, varicose, or cystic subtypes, depending on the severity of the airway dilation. Bronchiectasis is often accompanied by bronchial wall thickening, mucoid impaction, and small-airway abnormalities.
Mediastinum The commonest mediastinal abnormalities in the study by Koonce et al7 of 1764 cardiac CTs were aortic aneurysms (1%) and lymph node enlargement (0.7%). Thoracic aortic aneurysms are defined as a nonreversible dilation of the aorta .5 cm. Most are atherosclerotic in origin and are seen in older patients. The majority originate in the ascending aorta (50%) and are usually visible on cardiac CT (Fig. 14).20 Cardiac CT is an accurate method of diagnosis, and also provides a pre-operative evaluation of the coronary arteries.21 A
Table 1 Guidelines from the Fleischner Society for the follow-up and management of pulmonary nodules measuring ,8 mm incidentally detected on CT Nodule size*
Low-risk patient†
High-risk patient‡
% 4 mm
No follow-up neededx
.4–6 mm
Follow-up CT at 12 months; if unchanged, no further follow-upjj Initial follow-up CT at 6–12 months then 18–24 months if no change Follow-up CT at approximately 3, 9, and 24 months, dynamic contrast-enhanced CT, PET, and/or biopsy
Follow-up CT at 12 months; if unchanged, no further follow-upjj Initial follow-up CT at 6–12 months then 18–24 months if no changejj Initial follow-up CT at 3–6 months then 9–12 and 24 months if no change Same as for low-risk patient
.6–8 mm .8 mm
Guidelines are for newly detected indeterminate nodule in persons 35 years of age or older. PET, positron emission tomography. *Average of length and width. † Minimal or absent history of smoking and of other known risk factors. ‡ History of smoking or of other know risk factors. x The risk of malignancy (,1%) in this category is substantially less than that in a baseline CT scan of an asymptomatic smoker. jj Nonsolid (ground-glass) or partly solid nodules may require longer follow-up to exclude indolent adenocarcinoma.
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Figure 9 Shown is a CT from 68-year-old man with chest pain, with a history of smoking. Axial CT reformat showed a thickwalled cavitating nodule in the right lower. This was biopsyproven squamous cell carcinoma.
related entity is a penetrating atherosclerotic ulcer, which occurs when an atherosclerotic ulcer penetrates the elastic lamina.22 They may rupture (Fig. 15) or may predispose to dissection. The ulcer is detected on cardiac CT as a defect in the aortic wall that extends beyond the aortic adventia. Finally, acute intramural hematoma of the aorta refers to hemorrhage within the aortic media. It is a related form of dissection, although no flowing blood is identified in the aortic wall. It may progress to aortic dissection, is classified using standard aortic dissection classifications, and treated in a similar way. Normal lymph nodes are smooth and ovoid in outline and shape. The normal size of lymph nodes varies depending on the location in the mediastinum. A widely used approach is to consider all nodes . 10 mm in the shortest dimension as abnormal. They should not be mistaken for normal pericardial recesses, which can be surprisingly good mimickers (Fig. 16).23 Two common miss areas include the internal mammary lymph node chains (Fig. 17) and the diaphragmatic nodes, but both are important, because the
Figure 10 Shown is a CT from a 51-year-old man with chest pain. Axial CT reformat showed consolidation in the left upper lobe, with air bronchograms and cavitation (arrowheads). It was sputum-proved pneumonia from Staphyloncus aureus.
Figure 11 Shown is a CT from a 72-year-old man with atypical chest pain. Axial CT reformat showed bilateral increased reticulation and extensive small cystic airspaces (honeycombing). Fibrosis predominating in the lung bases with honeycombing are typical of idiopathic pulmonary fibrosis.
breasts drain to the internal mammary lymph nodes and the chest wall drains to the diaphragmatic nodes. Mediastinal/hilar lymph node enlargement has benign and malignant causes. Of the benign causes, reactive nodes to lung parenchymal infection are the most common. Such nodes are usually low volume and resolve once the pneumonia has been treated. Sarcoidosis is another benign cause and classically manifests as bilateral hilar lymph node
Figure 12 Shown is a CT from a 64-year-old man with chest pain. Axial CT reformat of the left upper lobe at the level of the aortic arch showed multiple focal areas of decreased attenuation without perceptible walls. Small vessels can be seen in the center of some of these areas, corresponding to the bronchovascular bundle. This pattern is typical of centrilobular emphysema.
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Figure 15 Shown is a CT from a 63-year-old woman who presented with chest pain and had a normal echocardiogram. Axial CT showed a penetrating atherosclerotic ulcer (arrow) that had ruptured, causing a resultant pseudoaneurysm.
Chest wall/pleura
Figure 13 Shown is a CT from a 63-year-old man with chest pain. Axial CT reformat of the right upper lobe showed typical ‘‘signet ring’’ appearance of an enlarged bronchial lumen with greater luminal diameter than the adjacent pulmonary artery (straight arrow). Marked airway thickening (curved arrow) and mucus plugging (arrowhead) were also present. These appearances are typical of bronchiectasis.
enlargement (Fig. 18). Calcified nodes are almost always indicative of previous remote exposure to tuberculosis or histoplasmosis. Malignant nodes will often have a low-density center, indicating central necrosis. Of the malignant causes, the most common are lymphoma (Fig. 19) and metastases.
Figure 14 Shown is a CT from 51-year-old man presenting with chest pain. Axial CT reformat showed a large ascending aortic aneurysm (6.1 cm) and normal coronary arteries. Note the difference in diameter of the ascending and descending aorta. It is important to note that measurements of aortic diameter should be made in a plane perpendicular to the long axis of the aorta to compensate for obliquity of the vessel.
The breasts are typically included within the scan range of a cardiac CT and thus must be evaluated. Breast lesions are often overlooked on cardiac CT, but such are the soft-tissue capabilities of multidetector CT that a confident diagnosis of breast pathology can often be made. In the study by Onuma et al4 0.8% of patients had incidental breast lesions identified and 0.4% subsequently proved to have breast malignancy. However, CT cannot detect microcalcifications as well as can mammography, which is a hallmark for breast malignancy. Irregular margins, irregular shape, and rim enhancement are the most highly predictive features for breast malignancy on CT (Fig. 20).24 It should not be assumed that those patients with breast lesions found incidentally on CT are within a screening group. Obviously, breast lesions found on cardiac CT cannot be ignored in the hope that the patient will be screened and the potential cancer found.
Figure 16 Shown is a CT from a 63-year-man with chest pain. The superior aortic sinus (curved arrow) is a normal pericardial recess often identified on cardiac CT and should not be mistaken for lymph node enlargement.
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Figure 17 Shown is a CT from a 48-year-old woman with a history of breast cancer and recurrent dyspnea. Axial CT reformat showed right internal mammary lymph node enlargement (straight arrow). Note the location of the right internal mammary artery (arrowhead) and the malignant right pleural effusion.
Dedicated imaging is usually required for definitive diagnosis, but it is important for the radiologist to be able to identify and characterize lesions as benign, indeterminate. or likely malignant. Pleural effusions are common abnormalities detected on cardiac CT. Transudative effusions are commonly caused by left heart failure. Exudative effusions are commonly parapneumonic, but malignancy should always be considered, especially in a patient with a known primary malignancy. Pleural effusions classically have a low Hounsfield unit value, usually between 0 and 20 HU. Differentiating effusions from ascites can be done by looking for the interface sign or the diaphragm sign. Mesothelioma usually appears as thick, nodular thickening of the pleura with marked enhancement in the clinical setting of significant asbestos exposure.
Figure 19 Shown is a CT from a 63-year-old woman with chest pain. Axial CT reformat showed extensive anterior mediastinal lymph node enlargement (straight arrow) that had invaded through the anterior chest wall (hollow arrow). Note the malignat pericardial effusion (curved arrow). This was biopsy-proven nonHodgkin lymphoma.
on coronary CT and 1 (0.4%) on a coronary bypass graft CT. PE is diagnosed on CT when there is a partial or complete filling defect within an opacified artery (Fig. 21).25 Evaluation of the lung parenchyma may show secondary effects of the PE, such as consolidation and ground-glass opacities. Pulmonary infarcts classically appear as wedgeshaped areas of consolidation in the periphery of the lung.26 Ground-glass opacities typically represent areas of pulmonary hemorrhage. Care should be taken not to overcall PE in the lower lobes, which are often not optimally opacified on dedicated coronary CT angiography.20
Pulmonary arteries Regarding pulmonary embolism (PE), in the study by Koonce et al7 of 1764 cardiac CTs, 5 (0.7%) were detected
Figure 18 Shown is a CT from a 47-year-old with chest pain and known sarcoidosis. Axial CT reformat showed bilateral symmetric hilar lymph node enlargement (arrows).
Figure 20 Shown is a CT from a 48-year-old man with chest pain. Axial CT reformat showed an infiltrating, irregular, soft-tissue mass (arrow) in the left breast (compare its appearance with the normal right-sided breast tissue). This was biopsy-proven breast carcinoma.
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Figure 21 Shown is a CT from a 41-year-old with dyspnea and chest pain. Oblique CT reformat showed extensive pulmonary emboli (straight arrows). Note CT signs of right heart strain, including flattening of the interventricular septum (curved arrow) and dilation of the right ventricle.
Secondary signs of right heart strain may be seen, including dilation of the right ventricle, straightening of the interventricular septum, and a decrease in right ventricular function on multiphasic sequences (Fig. 21).27,28 Such appearances are considered to indicate a subgroup of patients with a worse prognosis.
Upper abdomen Simple liver cysts are one of the commonest incidental cardiac CT findings, and it is estimated that approximately 5% of the general population have one (Fig. 22). Typically,
369 they have a homogenous low density appearance with a sharply circumscribed border and do not communicate with the biliary tree. They show no enhancement and no internal septations. The overwhelming majority are asymptomatic. In patients with no known malignancy the majority of incidental hepatic lesions ,15 mm in size prove to be benign. In the presence of known malignancy %50% of these lesions will be metastases. Confirmatory imaging is suggested with targeted ultrasound scanning to confirm a purely cystic benign-appearing lesion. In larger cysts (.4cm) follow-up ultrasound at three months may be prudent to ensure no change. In patients with known malignancy, longer term follow-up is suggested to ensure lesion stability.29 The differential diagnosis includes parasitic cysts, multiple cysts in polycystic liver or kidney disease, and cystic tumors. Usually, cystic tumors have thicker walls and may have heterogeneous internal content such as blood or septae. Transient hemodynamic arterial defect lesions are secondary to variant venous drainage within the liver parenchyma (Fig. 20). They are not of any pathologic significance. Hemangiomas classically show peripheral nodular filling-in on the portal venous phase of a liver CT (so-called ‘peripheral puddling’). Finally, the liver is the second most commonly involved organ from metastases, after the lungs. The commonest primary tumors are from colon, stomach, pancreas, breast, and lung. Metastases typically have poorly defined borders, are low density (but may enhance if hypervascular) and may be associated with biliary obstruction or portal vein thrombosis. Abdominal aortic aneurysms are defined as local dilatation of the aorta with an anteroposterior diameter .30 mm or .1.5 times the diameter of the proximal aorta. Measurements should be made in a plane perpendicular to the long axis of the aorta. Detection of such aneurysm is of extreme importance because the mortality rate is much
Figure 22 Shown is a CT from a 55-year-old man with chest pain (left). Axial CT reformat showed a small, homogenous, low-density sharply circumscribed lesion in the liver, confirmed on liver ultrasound scanning to represent a cyst. (Right) Shown is a CT from a 71-year-old man with chest pain. Axial CT reformat showed a transient hyperdense lesion in the right lobe of liver, subsequently diagnosed on liver magnetic resonance imaging to be a transient hemodynamic arterial defect.
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References
Figure 23 Shown is a CT from a 52-year-old woman with chest pain. Axial CT reformat showed a retrocardiac mass (straight arrow) with pockets of air within it (curved arrow), typical of a hiatus hernia.
higher for emergency surgical repair (85%–95%) than for elective repair (5%). Aneurysms .5.5 cm are usually considered for surgical or endovascular repair. Aneurysms ,5.5 cm should be followed with serial abdominal ultrasound scanning.30 Hiatus hernias are present in approximately 10% of the population (Fig. 23). The incidence increases with age, and they have been noted in %24% of patients undergoing coronary CT.19 The clinical significance of hiatus hernias noted incidentally is uncertain. When symptomatic, they may present with epigastric pain that may be relevant in patients investigated for recurrent chest pain who have normal coronary arteries. No specific follow-up is required for incidentally noted hiatus hernias.
Conclusion The evaluation of structures outside of the heart is an unavoidable responsibility of cardiac CT readers involved in these examinations. Collaboration between radiologists and cardiologists should be pursued in benefit of patient care. The prevalence of such findings is strongly influenced by the cardiac CT protocol and the patient population being studied, as discussed in part 1 of this review. If extracardiac structures are not systematically analyzed, alternative causes of patient symptoms may go undetected thereby delaying patient care, and treatable asymptomatic malignancies may be overlooked. The review of extracardiac structures by a qualified reader is of paramount importance so that correct diagnosis can be made, and an appropriate management plan can be instituted.
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