Incidental Radiological Findings by Sabine Weckbach

Author:Sabine Weckbach
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

1 Pulmonary Incidental Findings

For the assessment of pulmonary nodules, the guidelines of the Fleischner Society are well established. Their recommendations for solid and subsolid lung nodules can help the radiologist in classifying a finding as (most likely) benign and advising follow-up examinations.

1.1 Small Pulmonary Nodules

Small pulmonary nodules are very common findings. They can be detected in scans that involve the whole chest, for example, a trauma scan after a car crash, as well as in scans that only show parts of the lung parenchyma such as a contrast-enhanced CT scan of the supra-aortic arteries. The likelihood increases with the age of the patient collective, and is higher in smokers than in nonsmokers. With current modern scanners, detecting even the smallest nodules with 1–2 mm in diameter has become routine. Since only a slight percentage of incidentally detected, small pulmonary nodules will be malignant, controlling all of them several times is not feasible. Therefore, the Fleischner Society published a position paper in 2005 (MacMahon et al. 2005). This paper should provide practical guidelines for the management of incidentally detected, small pulmonary nodules. The given recommendations apply to adult patients (>35 years) without any known or suspected malignant disease and without fever. The guidelines are based on several follow-up studies evaluating the risk of having or developing lung cancer when a small pulmonary nodule is found. For this assessment, several characteristics of incidental, small pulmonary nodules need to be taken into consideration, such as nodule size, growth rate, and risk factors: the larger the nodule the more likely it is malignant, and follow-ups need to be more frequent. Growth rates of lung nodules differ between ground-glass opacities, ground-glass opacities with a solid component, and solid nodules, with solid nodules showing the shortest mean volume-doubling time. Furthermore, the relative risk for developing lung carcinoma is an important parameter, with smoking being the most important risk factor. For example, the Fleischner Society follow-up and management recommendations for incidentally detected, small pulmonary nodules say that no follow-up is needed for a nodule smaller than 4 mm in a patient with a minimal or absent history of smoking and of other known risk factors. If a nodule of the same size is found in a patient with a history of smoking or with other known risk factors, a follow-up CT after 12 months is recommended. If the nodule size is unchanged, no further scans are required. But, it needs to be considered that a ground-glass or partly solid nodule may require a longer follow-up to exclude indolent adenocarcinoma due to a longer mean volume-doubling time of nonsolid nodules (MacMahon et al. 2005). Equivalent recommendations are given for nodules with a size between 4 and 6 mm, 6 and 8 mm, and for those larger than 8 mm (for further details, please see the table “Recommendations for follow-up and management of nodules smaller than 8 mm detected incidentally at nonscreening CT” (MacMahon et al. 2005)).

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