Normal chest CT findings

Evaluation of pulmonary parenchyma and vessels

When analyzing CT scans, it is important to compare structural symmetry. For instance, in pulmonary hypoplasia, attenuation of the pulmonary vascular pattern and underdevelopment of the pulmonary vein are detected on the affected side, whereas the contralateral lung maintains a normal CT appearance.

Special attention is paid to the course of the great vessels. In congenital venolobar syndrome (scimitar syndrome), CT with 3D reconstruction demonstrates a reduced-volume right lung and a hypoplastic right pulmonary artery. The key marker of this anomaly is the aberrant pulmonary vein (resembling a scimitar), which abnormally drains blood from the right lung directly into the inferior vena cava.

Analysis of anterior mediastinal structures

Normally, the thymus is visualized in the anterior mediastinum and undergoes involution with age. In thymic pathologies, the radiological appearance changes dramatically:

• Thymolipomas: Rare benign tumors composed of normal or involuted thymic tissue and mature fat. On CT, they show predominantly fat density with fibrous septa. Due to their soft consistency, they "flow around" the diaphragm and mediastinum, sometimes mimicking lobar atelectasis or cardiomegaly.
• Thymic carcinoma: A heterogeneously enhancing mass, frequently invading adjacent structures (e.g., the lung) and metastasizing to lymph nodes.
• Neuroendocrine tumors (carcinoids): Lobulated masses with areas of central necrosis or hemorrhage. They are characterized by aggressive growth and frequently cause superior vena cava obstruction syndrome.
• Germ cell tumors: The most frequent of these is the mature teratoma. On CT, it appears as a well-circumscribed mass with thick walls, areas of fatty tissue, and internal calcifications (present in 25% of cases).

Middle and posterior mediastinum

For accurate diagnosis, it is essential to understand which structures normally predominate in each compartment.

In the middle mediastinum, congenital cysts (bronchogenic, duplication cysts) and lymphadenopathy are most frequently detected. Lymph node enlargement is usually secondary to infectious processes, particularly Mycobacterium tuberculosis infection.

In the posterior mediastinum, elements of the nervous system are localized, therefore neurogenic tumors such as ganglioneuromas and neuroblastomas predominate here.

Visualization of the esophagus and adjacent structures

When evaluating the esophagus on CT, the walls should normally not show focal thickening. Benign submucosal tumors, such as leiomyoma, appear as homogeneous soft-tissue density masses with clear contours, occasionally with punctate internal calcification.

Fibrovascular polyps originating from the upper third of the esophagus may contain areas of both fatty and soft-tissue density. Congenital foregut duplication cysts on MRI demonstrate the appearance of a typical simple cyst.

In the postoperative period (e.g., after esophagectomy), CT allows the detection of gastric graft wall defects and concomitant pneumothorax, indicating a dangerous complication—anastomotic leakage.

CT anatomy of the adrenal glands (extrathoracic findings)

During comprehensive diagnostic imaging, the adrenal glands frequently fall into the scan field. Normally, they have clear contours and a regular shape. In pathologies, their size and structure change:

• Atrophic or normal glands: Observed in secondary and tertiary adrenal insufficiency (due to decreased ACTH production by the pituitary or hypothalamus), as well as abrupt steroid withdrawal.
• Enlarged glands: Characteristic of hemorrhagic necrosis (Waterhouse-Friderichsen syndrome) or active infections (HIV, cytomegalovirus, tuberculosis).
• Atrophy: In the presence of a hormone-active adenoma of one adrenal gland (heterogeneously enhancing on contrast-enhanced CT in Cushing's syndrome), the contralateral adrenal gland often atrophies due to the suppression of ACTH secretion.

Class and exam questions

What else to study on this topic

• The role of PET/CT and bone scintigraphy in staging malignant mediastinal tumors.
• Endosonography with fine-needle aspiration (EUS-FNA) in the diagnosis of submucosal esophageal lesions.
• Radiological appearance of the adrenal glands in autoimmune adrenalitis and Addison's disease.
• Differential diagnosis of thymic lymphoid follicular hyperplasia in myasthenia gravis.
• Fluoroscopic signs of glycogen acanthosis and its association with GERD.

Other topics in the section "Diagnostic Radiology of the Abdominal Organs"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.