Last updated on April 24, 2014 at 17:35 EDT

Radiology Corner

August 9, 2008

By Slotto, James Folio, Les

Answer to last month’s radiology case (#25) and image: Cystic Fibrosis Chest X-Ray Findings: A Teaching Analog (Case # 26 appears at the end of this article)


Two patients are shown for comparison purposes. The first is a 21 year old male with long-standing cystic fibrosis who presented with an increasingly productive cough and required a PICC line for long- term antibiotic therapy. The second patient is a 53 year-old woman two days status-post medium sternotomy now with bilateral atelectasis.

Summary of Findings, Diagnosis of each case:

Case 1: Figure 1 A demonstrates several features of cystic fibrosis. Mucus plugging of the small bronchioles results in hyper- inflation of the lungs. There are multiple nodular opacities which represent the mucus plugs. Tram-tracking is visible in all lung fields, most conspicuous in the bilateral upper lungs extending laterally from the right hilum. In addition, multiple ringed shadows are scattered throughout.

The chronic pathologic mucus plugging of the bronchioles in a patient with cystic fibrosis makes them prone to repeated respiratory infections. A PICC line was placed to allow for home- based delivery of medication.

Case 2: Figure 1 B is a portable chest film on post-operative day 2 of the 53 year-old female who underwent a medial sternotomy for repair of an A-V fistula graft. Note the sternal wires, ECG leads, and surgical drain. There are diffuse, bilateral lower lung field densities. The left heart border is obscured, as are both costophrenic angles and hemidiaphragms. Of significance for this comparison is the complete air-bronchogram in the left lower lung field that extends from the hilum to the periphery, and the partial airbronchogram in the right lower lung field extending inferiorly from the hilum. see the full-text version for more detail.

Post-operative patients are prone to pulmonary issues as a result of prolonged immobilization. In patients who have chest wall surgery or upper abdomen surgery, post-operative pain can limit inspiratory effort and limit normal lung expansion. Pain and sedation can also block the normal drive and mechanism of secretion clearance by coughing [1].


The two cases presented here involve a specific diagnosis and illustrate radiographie findings commonly found in these two situations. However, tram-tracks are not exclusive to a patient with Cystic Fibrosis, nor are Air-Bronchograms specific for atelectasis. Both signs appear when an airway is more visible than usual. In the case of tram-tracking, it is the dilation and inflammation of the bronchioles that gives the characteristic parallel lines. Air- bronchograms appear when the surrounding lung parenchyma is more radiographically dense and outlines the normal patent bronchiole.

Both signs have a long differential. Tram-tracking is most commonly seen with bronchiectasis, a process of permanent dilation of the bronchioles. This is often the result of repetitive and chronic plugging of the airways, resulting in infection, inflammation, and dilation [2].

In an effort to present a clearer picture of the processes involved and the “classic” appearance of these signs, an experimental model was created using household objects and was imaged using standard plain-film and CT modalities. Figure 2 shows the experimental model setup, which involves an apple, two large sponges, and multiple straws. Figure 3(A) and 3(B) show side-by- side comparisons of both patient’s radiographic findings next to the experimental analog of the same process.

The authors would like to graciously thank the following radiologic technologists for assisting with the experimental models: Raymond Fudge, RT; Ralph Alexander, RT; and Robert Robertson, RT.

Case #26

The answer to this case will appear in the next issue of Military Medicine

History: An active duty 31 year old deployed troop presents with penetrating gun shot wound to the left chest. An AP portable chest is obtained in the deployed combat hospital in Iraq, with follow-up CT Angiogram of the chest.

What are the findings (there are multiple)? What is the differential diagnosis? Identify the bullet trajectory and think about why that is important in this case. What is your best diagnosis?


1. Uzieblo, Matthew Et al; Incidence and Significance of Lobar Atelectasis Thoracic Surgical Patients. American Surgeon, 2000, Vol. 66: 5, p476-480.

2. Mysliwiec, Vincent MD; Pina, Joseph S. MD Bronchiectasis: the ‘other’ obstructive lung disease. Post Graduate Medicine 1999; 106:1

Contributors: ENS James Slotto, MC, USN*; COL Les Folio, MC, FS, USAF*,[dagger]

* Uniformed Services University, Bethesda, MD, 20814-4799; [dagger] Walter Reed Army Medical Center; Washington, DC, 20012

The full text version is available in a downloadable PDF file on the AMSUS page of the USUHS website at: http://rad. usuhs. mil/ amsus. html

The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or reflecting the views of the Uniformed Services University of the Health Sciences or the Department of Defense. Reprint & Copyright (c) by Association of Military Surgeons of U.S., 2006.

Copyright Association of Military Surgeons of the United States Jul 2008

(c) 2008 Military Medicine. Provided by ProQuest Information and Learning. All rights Reserved.