Volume 4, Case 6
Craig T. Nakamura, MD
Kapiolani Medical Center For Women And Children
University of Hawaiʻi John A. Burns School of Medicine
This is a three-year old Korean male who presents to the emergency department with respiratory distress. Ten days ago, he had developed a cough, rhinorrhea, sore throat, and temperature of 39.4 degrees. The cough, rhinorrhea, and sore throat resolved after a three day period. However, he continued to spike fevers. Three days ago, he was seen by his primary care physician. A PPD was placed. He was then started on oral cefuroxime. He was previously exposed to a grandaunt who was treated for tuberculosis in Korea and a grandfather with a chronic cough within the household. He has had a decreased oral intake and a two kilogram weight loss over the previous two weeks.
Exam: VS T39.2, P148, RR68, BP 104/69. Oxygen saturation 90% in room air (100% on 5 liters O2 by nasal cannula). He is alert with moderate respiratory distress. HEENT Normal. No lymphadenopathy. Neck supple. Heart regular without murmurs. Moderately severe chest retractions noted. Breath sounds are decreased on the right. There is good aeration over the left lung fields. No wheezing, rhonchi, or rales are heard. There is dullness to percussion over the right base. Abdomen soft, flat, bowel sounds active, without tenderness. Extremities significant for a positive PPD. Capillary refill < 2 seconds.
Laboratory studies: CBC WBC 9.2 with 41% lymphs, 43% segs, 14% monos, 1% eos, 1% basos. Hgb. 12.6, hct. 37.2. Chemistry panel is normal.
A chest radiograph is obtained.
View chest radiograph.
If you can see vertical lines on the image (resembling stripes), these are due to an artifact of the radiographic "grid" used on the film. This grid is very fine and only visible on very close inspection. Unfortunately, the scanning process enhances the visibility of this grid. Ignore this artifact.
A PA view is shown here. His chest radiograph demonstrates a complete opacification of the right hemithorax with a shift of the mediastinal structures to the left.
This patient presents with primary tuberculosis (TB) and a pleural effusion. There are two types of pulmonary TB: primary and postprimary. In primary TB, the typical route of infection occurs by the inhalation of aerosolized (two to five micron) droplets laden with Mycobacterium tuberculosis from the cough of a person with active disease. The mycobacteria usually deposit in the middle or lower lobes, where they undergo phagocytosis and multiply intracellularly. As neutrophils arrive, tubercles are formed and the phagocytized tubercles are carried to regional lymph nodes. During this stage, there are both lymphatic and hematogenous dissemination, as the primary focus of infection becomes encapsulated and eventually calcifies. Hypersensitivity develops over a period of two to ten weeks. In the majority of cases, surviving mycobacteria remain dormant.
Postprimary TB involves the reactivation of dormant bacilli which occurs with episodes of immunosuppression, malnutrition, or debilitation, typically within two years following exposure. It occurs in 5% to 15% of cases of TB. Primary and postprimary TB differ clinically, pathologically, and radiologically.
There are five distinct radiographic presentations of primary TB:
1. Parenchymal disease
2. Atelectasis
3. Lymphadenopathy
4. Pleural effusion
5. Miliary disease
Parenchymal disease is seen as a unifocal consolidation, typically involving the right lung (there are conflicting reports as to the preference of which regions are affected within the lung). The infiltrate is multilobar in approximately 25% of the cases. These infiltrates are usually homogeneous with ill-defined borders. Lamont further subdivided the consolidations into six types: linear interstitial, segmental or lobar consolidation, confluent, collapse, emphysema, and cavitation. The most common consolidation type is linear interstitial. Air bronchograms or associated lymphadenopathy may be present. The infiltrates clear in about two-thirds of all cases. After an initial paradoxical worsening of the consolidation, resolution occurs over a period of six months to two years. In 15% of the cases, a calcified scar may persist (the Ghon focus). For evaluation of treatment efficacy, the parenchymal infiltrates should be followed every two to three months until stable or cleared.
Lobar or segmental atelectasis occurs most frequently in children under two years of age. The atelectasis is caused by either endobronchial disease or external bronchial compression due to hilar adenopathy. It usually involves the anterior segment of the upper lobe or the medial segment of the middle lobe and will persist until the node or endobronchial lesion regresses.
Hilar and mediastinal adenopathy can be seen in about 96% of children with primary TB, and is considered the radiological hallmark. The most frequently involved nodes are the hilar and right paratracheal. The involvement is usually unilateral and right-sided (bilateral in 25% to 30% of cases). Often there is an associated parenchymal infiltrate or region of atelectasis. The lateral chest radiograph is particularly beneficial in the evaluation of adenopathy and should be included in the investigation of children suspected of having TB or those in contact with adults with TB. The adenopathy with primary TB usually resolves without sequelae, although nodal calcification may occur. A nodal calcification associated with a Ghon focus is known as a Ranke complex. The adenopathy should be monitored on an annual basis until stable or resolved.
Pleural effusion, uncommon in infants and young children, can be seen in adolescents and adults. It is usually unilateral and occurs in 6% to 12% of primary TB infections. The effusion may mask underlying parenchymal disease. However, with appropriate therapy, resolution is often rapid and without sequelae.
During the hematogenous stage of primary TB, between 1% and 7% of patients will have radiographic evidence of miliary disease. Children under two years of age are most commonly affected, usually within six months of infection. When symptoms begin, the chest radiograph is typically normal. Hyperinflation may occur during the first two weeks. This can be followed by diffuse, small nodular opacities about six weeks after the onset of symptoms. Left untreated, the nodules may enlarge to about five millimeters or may coalesce and cavitate. With proper therapy, the nodules resolve within two to six months. Miliary calcification is uncommon.
View miliary TB example.
These PA and lateral chest radiograph views are taken in a 7-month old with miliary TB. There are multiple small nodules throughout the lungs bilaterally. There is a focal consolidation in the right upper lobe.
To illustrate how rapidly this can improve, examine the follow-up chest radiographs taken three weeks after anti-TB therapy is initiated.
View miliary TB follow-up.
Note the substantial clearing of the multiple small nodular densities and the clearing of the right upper lobe consolidation.
The radiologic patterns observed in postprimary TB can be divided into four categories:
1. Parenchymal disease and cavitation
2. Airway disease
3. Pleural disease
4. Other
The first manifestation of parenchymal disease is a heterogeneous poorly defined infiltrate (the exudative lesion) within the apical/posterior segments of the upper lobe or the superior segment of the lower lobe. This is thought to be secondary to a higher oxygen tension or decreased lymphatic clearance within these regions. This may progress to lobar or lung opacifications or may evolve into better-defined coarse reticular or nodular opacities (the fibroproliferative lesion). The lesion may calcify. Pleural thickening with subpleural atelectsis and fibrosis often leads to an "apical cap" in 40% of the patients. One important point is that disease activity cannot be assessed by radiologic characteristics.
Inactive disease is defined as a stable chest radiograph for six months and repeatedly negative sputum cultures. Cavitation may occur in 40% to 90% of those with parenchymal disease. The cavities are often multiple and are between one and three millimeters. They have thick and irregular walls, but can become emphysematous in nature.
Airway TB manifests as bronchial stenosis, tracheal TB, or laryngeal TB. Bronchial stenosis is the most common of the three, and occurs in 10% to 40% of cases of active TB. This complication is visualized radiographically as persistent lobar or segmental collapse, hyperinflation, or mucoid impaction. It may lead to bronchiectasis.
The pleural disease of post primary TB occurs in 6% to 18% of cases. These pleural effusions are often small (as opposed to the large effusions characteristic of primary TB) and associated with significant parenchymal disease.
Other radiographic characteristics of postprimary TB include pseudoaneurysms which are seen as an enlarging mass or a rapidly appearing consolidation. Vertebral osteomyelitis may occur as well as paraspinal and prevertebral abscesses.
References