Paratracheal Air Cysts Research Articles

Clinical significance of para-carinal air cysts in patients with pleuroparenchymal fibroelastosis: The relationship with pneumomediastinum and pneumothorax.

Para-tracheal or para-carinal air cysts (PACs) are often asymptomatic and usually detected incidentally by methods such as computed tomography. Their clinical significance is unclear in patients with pleuroparenchymal fibroelastosis (PPFE). We evaluated the clinical significance of PACs in PPFE and their relationship with pneumomediastinum or pneumothorax. In total, 50 patients had PPFE and 34 (68%) had PACs. Most PACs were para-carinal (n = 30). A para-tracheal air cyst was detected in only nine patients, which included five patients having both para-carinal and para-tracheal air cysts. Overall median survival was 24.7months. Survival was not significantly different between the patients with [PACs(+)] and without PACs (P = 0.268). A high frequency (64%) of the complication of pneumomediastinum or pneumothorax occurred in the overall population during follow-up. Pneumomediastinum/pneumothorax occurred significantly more frequently in patients with PACs(+) than in those without (76.5% vs. 37.5%; P = 0.012). PACs(+) was the only significant risk factor for pneumomediastinum/pneumothorax. Our data showed that PACs commonly occur in patients with PPFE, and most PACs were para-carinal air cysts. Additionally, PACs(+) was a significant risk factor for pneumomediastinum/pneumothorax; therefore, clinicians should be more aware of these complications during follow-up examination, particular in PACs(+) patients with PPFE.

Paratracheal air cysts; a rare cause of recurrent hemoptysis

Paratracheal air cysts (PTACs) refer to small collections of air, present at the level of the thoracic inlet, adjacent to the trachea. PTACs encompass a variety of pathological entities and are usually encountered incidentally on computed tomography (CT) of the chest. Clinically, most patients remain asymptomatic; while a minority, may be associated with cough, dyspnea and hemoptysis probably as a result of pooled secretions and secondary infections. We report one such case of recurrent hemoptysis in a 30-year-old male, as a result of a right paratracheal air cyst.

A Case of Paratracheal Air Cysts Communicating with the Thoracic Cavity

A Case of Paratracheal Air Cysts Communicating with the Thoracic Cavity

TRACHEAL DIVERTICULUM: DIAGNOSIS AND TREATMENT OPTIONS

SESSION TITLE: Wednesday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/23/2019 09:45 AM - 10:45 AM INTRODUCTION: Tracheal Diverticulum is a rare and often incidental diagnosis found on chest imaging in an asymptomatic patient with underlying lung disease. Management includes conservative and possible surgical treatment depending on age and symptoms. CASE PRESENTATION: 72 yom presents with dyspnea and chronic cough. He is a nonsmoker and has a history of asthma, chronic sinusitis and right lung lobectomy after mva. Chest CT revealed pockets of air in superior mediastinum along the right posterior tracheal wall suggestive of tracheal diverticulum. Patient was medically managed with symptomatic improvement. DISCUSSION: Tracheal diverticulum (TD) is a benign and often incidental finding on chest imaging as an out pouching of the tracheal wall. According to their location, size and histopathology TD can be classified in either congenital or acquired. Acquired TD has a wide opening, can be found at any level in the thoracic cavity and occurs as a result of herniation of the weakened tracheal wall due to increased luminal pressure in the trachea. Congenital TD is thought to represent a malformation of the supernumerary branches of the trachea and usually occurs above the carina with small neck openings. The histopathological difference between them is the presence of smooth muscle and cartilage in congenital TD while acquired TD lacks these structures. Medical management of TD include physiotherapy, mucolytic and antibiotics in some cases. When symptomatic, patients may present with cough, hemoptysis and recurrent respiratory infections due to either the compression of adjacent organs or secondary bacterial infections. In symptomatic patients (cough, hemoptysis and recurrent respiratory infections) surgical treatment and endoscopic laser cauterization have been reported to be effective and safe. There is a lack of consensus regarding indications for treatment due to the rarity of this cases CONCLUSIONS: Tracheal diverticulum (TD) is defined as a benign out-pouching of the tracheal wall due to structural weakness that can be congenital or acquired in origin. Most cases are found incidentally since majority of patients are asymptomatic. Uncomplicated TDs are usually asymptomatic and when symptoms have occurred, they usually present with non-specific symptoms like pharyngeal discomfort, cough, dyspnea, and recurrent respiratory infection. Asymptomatic TDs usually require no treatment and managed conservatively while surgical excision is indicated in cases of recurrent infections or compression of adjacent organs. Reference #1: .Lee S-Y, Joo S, Lee GD, Ham SJ, Park CH, Lee S. A Case of Symptomatic Tracheal Diverticulum and Surgical Resection as a Treatment Modality. The Korean Journal of Thoracic and Cardiovascular Surgery. 2016;49(5):405-407. https://doi.org/10.5090/kjtcs.2016.49.5.405 Reference #2: Tanaka H, Mori Y, Kurokawa K, Abe S. Paratracheal air cysts communicating with the trachea: CT findings. J Thorac Imaging. 1997;12:38–40. https://doi.org/10.1097/00005382-199701000-00005. [PubMed][Cross Ref] Reference #3: Collin JD, Batchelor T, Hughes CW. Transcervical repair of tracheal diverticulum. Ann Thorac Surg. 2014;98:1490–2. https://doi.org/10.1016/j.athoracsur.2014.02.081. [PubMed] [Cross Ref DISCLOSURES: No relevant relationships by Anastasia Novikov, source=Web Response No relevant relationships by Theo Trandafirescu, source=Web Response

Ultrasonography of Extrathyroidal Diseases Mimicking Intrinsic Thyroid Lesions.

Some localized or multisystem diseases as well as congenital anomalies occasionally involve thyroid and unusual findings will be identified during thyroid ultrasonography. Recognition of these entities will minimize unnecessary complementary examination and lead to appropriate management for patients. Therefore, we aim to review sonographic features of these extrathyroidal diseases that affect thyroid in adults. Our review derives from cases diagnosed in our hospital and published literature, with pictures accessible using as illustration. These disorders included intrathyroidal parathyroid adenoma, intrathyroidal cystic findings of nonthyroid origin, metastases to the thyroid, esophageal diverticulum, paratracheal air cysts, and ossification of anterior longitudinal ligament.

Anatomical and radiologic approach to tracheal diverticula

Tracheal diverticula (TD) are benign conditions characterized by single or multiple outpouchings from the tracheal wall. Different series which demonstrate tracheal diverticula on autopsy series, fiber optic bronchoscope examinations, and CT images are found in the literature. Treatment options for TD are surgical resection, endoscopic cauterization with laser or electrocoagulation and conservative management. Surgery is the treatment choice for young patients, while conservative treatment is recommended for elderly patients. We performed a retrospective study on 2271 patients who underwent thoracic CT examination for different reasons. Presence, number, anatomical location, level, diameter, cystic component, and accompanying variations were assessed and recorded. A total of 2271 patients were evaluated in the present study. 73 patients (38 females, 35 males) with TD were detected. The prevalence of TD was found to be 3.2%. It was found more frequently in women (52.1%) than in men (47.9%). The mean diameter of the diverticula was 4.5 mm (range 1-15 mm) in females and 5mm (1-14) in males. There was no difference between gender groups according diameter median values (p=0.811). TD was solitary in 71 (97.2%) patients and doubled (2.7%) in two patients. In conclusion our data showed a female predilection of prevalence, but no statistically significant difference between gender and other parameters (diameter, side, and level) was indicated. Patients with paratracheal air cysts that have no connection with the tracheal lumen were also analyzed in this study, and cystic group’s diameter values were found to be higher than the non-cystic group. This difference was found to be statistically significant.

Incidental Paratracheal Air Cysts on Thoracic CT and Their Association with Chronic Inflammatory Lung Disease.

Purpose. To determine the association between the progression of upper lung fibrosis and paratracheal air cysts (PACs) size. Materials and Methods. The thoracic CT images of 4573 patients were reviewed for the prevalence, size, and location of PACs and their communication with trachea. In addition, the presence of upper lung fibrosis, emphysema, and bronchiectasis was evaluated in patients with PACs and compared with a control group without PACs. Upper lung fibrosis was analyzed using a fibrosis score system. Results. The prevalence of PACs was 6.8%. Communication with tracheal lumen was demonstrated by 31.5% of patients with PACs. The prevalence of fibrosis, emphysema, and bronchiectasis in patients with PACs were 67.5%, 21.9%, and 28.3%, respectively. The prevalence of fibrosis was significantly different in the two groups by univariable and multivariable analysis (odds ratio = 2.077, P < 0.001). 140 patients with fibrosis among PAC group underwent a previous or follow-up CT; the prevalence with increase in PAC sizes was higher in patients with increase in fibrosis score than those without it (66.2% versus 17.3%, P < 0.001). Conclusions. PACs appear to be highly related to upper lung fibrosis and moderately related to bronchiectasis. In patients with fibrosis, PAC sizes tended to increase with the progression of upper lung fibrosis.

Tracheal Diverculum: A Rare Entity Diagnosed in the Context of Blunt Thoracic Trauma Report of A Case

Tracheal diverticulum (TD) is an outpouching or sac arising from the wall of the trachea. It can can be classified, based on etiology, in congenital and acquired. Congenital tracheal diverticulum is the consequence of a defect in endodermal differentiation of the membranous posterior tracheal wall and it contains all the layers of the airway wall (true diverticulum). Acquired diverticulum is the result of an abnormally increased pressure inside the airways pushing the respiratory mucosa out of a defect of the airway wall; it contains only mucosa (pseudodiverticulum). Both types are rare, accounting only for a limited percentage of the paratracheal air cysts (PTACs) from which TD should be differentiated in consideration of the similar basic pattern of “paratracheal air collection”. Diagnosis of TD is difficult because of its rarity, lack of symptomatology or specific symptomatology and low sensibility of the diagnostic tools available to date (chest CT and bronchoscopy). Apart from its intrinsic rarity, the case of TD we present here has the peculiarity of being diagnosed, differently from usual, by direct bronchoscopic visualization. The blunt thoracic trauma of which the patient was victim, gives more exemplarity to the diagnostic pathway of this entity. Indeed the detection of a para tracheal air collection on CT images could have been interpreted as a traumatic rupture of the trachea rather than a TD, leading to an unjustified surgical treatment. It was only clinical judgment combined with the use of the diagnostic imaging and bronchoscopy that conducted to the correct diagnosis.

Thoracic Esophagus Cancer Revealing a Tracheal Diverticulum

Tracheal diverticulum is rarely encountered in a clinical setting since almost all patients are asymptomatic. However, its presence may become a problem during esophageal cancer operations in terms of anesthesia and lymph node dissection of superior mediastinum lymphadenectomy. A 70-year-old man with esophageal cancer was referred to our hospital. During thoracoscopic subtotal esophagectomy, we found a cystic lesion connected to the right posterior wall of the trachea. We evaluated the preoperative computed tomography scan during surgery and made a diagnosis of tracheal diverticulum because of the presence of paratracheal air cysts, which had not been noticed preoperatively. It was resected by a linear stapler and the postoperative course of the patient was uneventful. A careful preoperative evaluation of computed tomography and operation are necessary to avoid injury of tracheal diverticulum during thoracoscopic esophagectomy for esophageal cancer revealing a tracheal diverticulum.

Paratracheal air cysts are uncommon findings in the pediatric population.

To determine the prevalence of paratracheal air cysts (PACs) in the pediatric population. The chest CT images of pediatric patients between July 2007 and December 2014 were retrospectively reviewed for the presence and imaging findings of PACs. In addition, the association between PACs and the presence of bronchiectasis and air cystic pulmonary lesions were evaluated. Among a total of 819 pediatric patients (males=527, 64.3%), the overall prevalence of PACs was 1.3% (n=11; 1.7% for infants, 0.4% for children, and 1.9% for adolescents). The presence of PACs showed no association with gender, age groups, or the presence of bronchiectasis and air cystic pulmonary lesions (P=0.56, 0.88, 0.57 and 0.89, respectively). All PACs were located at the right side of the trachea at the thoracic inlet, and the median transverse diameter was 3.7mm (range 2.0-7.0mm); one PAC showed septation, and 27.3% of PACs had communication with the trachea. In the pediatric population, the prevalence of PACs is 1.3% as detected by chest CT. Knowledge of the prevalence and imaging findings of PAC would be useful to prevent confusion with pneumomediastinum or other cystic lesions in pediatric patients.

Is There a Relationship Between Paratracheal Air Cysts and Upper Lobe Fibrosis?

The purpose of this study was to determine the characteristics of paratracheal air cysts (PACs) and their relationship with upper lobe pulmonary fibrosis. The routine thoracic computed tomography scans of 3549 patients carried out between January 2014 and April 2015 were retrospectively evaluated. The presence, location, structural characteristics (uniloculated or multiloculated), number of cysts, and anterior-posterior and transverse dimensions of the PAC and its communication with the tracheal lumen were evaluated. The presence of upper lobe fibrosis, emphysema, and bronchiectasis was also evaluated. The relationship between upper lobe fibrosis, emphysema, bronchiectasis, and the presence of paratracheal cysts was evaluated in all patients. An equal number of randomized patients with no paratracheal cysts were selected as a control group. A total of 190 PAC cases were diagnosed, with a prevalence rate of 5.35%: 146 (76.8%) of the cases were men, 44 (23.2%) were female, and the mean (SD) age was 53.79 (16.64) years (range, 12-89 years). The control group included 105 men (57.4%) and 78 women (42.6%), and the mean (SD) age was 53.87 (16.65) years (range, 13-87 years). The groups were similar in terms of age (P = 0.876), whereas the proportion of men in the PAC group was significantly higher (P < 0.001). Most of the PACs were located on the right side (n = 188, 98.9%). The incidence of fibrosis in the paratracheal cyst group was 45.8% (n = 87) compared with 19.5% (n = 37) in the control group; this difference was statistically significant (P < 0.001). The prevalence rates of emphysema in the cyst group and the control group were 29.5% (n = 56) and 11.6% (n = 22), respectively, and the difference was statistically significant (P < 0.001). When the groups were compared regarding bronchiectasis (scar and non-scar related), the rate of bronchiectasis in the paratracheal cyst group was 17.9% (n = 34), compared with 3.7% (n = 7) in the control group; this difference was statistically significant (P < 0.001). Paratracheal air cysts are relatively common, but the etiology is still unclear. We detected increased rates of cyst formation that may result from the traction effect on the tracheal wall in the presence of upper lobe fibrosis.

Paratracheal air cysts: prevalence and relevance to pulmonary emphysema and bronchiectasis using thoracic multidetector CT

We aimed to determine the prevalence of paratracheal air cysts (PTACs) and the relationship of PTACs with emphysema and bronchiectasis through retrospective analysis of multidetector computed tomography (MDCT) findings. MDCT findings of 1027 consecutive patients who underwent routine thorax examination between January 2012 and January 2013 were evaluated retrospectively for the presence of PTACs. Localization of the PTACs, as well as their size, shape, and relationship with the trachea were examined. Presence of emphysema and bronchiectasis was recorded, and bronchiectasis severity index was calculated when present. We randomly selected 80 patients who had no visible PTACs as the control group. The findings of patients with and without PTACs were compared. PTACs were determined in 82 of 1027 patients (8%), in 8.8% of females and 7.3% of males. The presence of PTACs was determined to be independent of gender (P = 0.361). Eighty-one PTACs (98.8%) were located in the right side of the trachea and 56.1% had a tracheal connection. The presence of PTACs significantly correlated with the presence and severity of bronchiectasis (P = 0.001 and P = 0.005 respectively). There was no significant relationship between the presence of PTACs and the presence of emphysema on CT images (P = 0.125). The prevalence of PTACs was determined as 8% in this study. There was significant association between PTACs and bronchiectasis.

Tracheal Diverticulum: A Unique Case with Intraoperative Morphologic Assessment.

There are rare case reports of tracheal diverticula or paratracheal air cysts. These cases, however, were reported mostly as incidental sonographic or radiologic findings without histologic confirmation. Furthermore, the handful of studies that describe this entity histopathologically report only cases in patients with prior respiratory symptoms. Here, we report a rare case of an asymptomatic 60-year-old female with no significant past medical history who presented with primary hyperparathyroidism. She was found to have an incidental right paraesophageal air-filled diverticulum with multiple thin septations on her imaging studies. She was taken to surgery and the histologic examination of the specimen revealed multiloculated cystic cavity lined by respiratory-type columnar epithelium with lymphocytic infiltrate and minor salivary glands within the surrounding stroma, rendering the diagnosis of tracheal diverticula.

An investigation into the prevalence of paratracheal air cysts revealed on multidetector computed tomography.

Paratracheal air cysts (PTACs) are frequently and incidentally found on computed tomography (CT) examinations of the chest, neck, and spine. Aetiology, pathophysiology, clinical and radiological relevance, and accompanying airway and parenchymal pathologies of PTACs are not known. A limited number of studies have discussed the association between PTACs and radiological or clinical abnormalities. Goo et al. and Kim et al. reported a relationship between emphysema and PTACs. However, Cheng et al., Buterbaugh et al., and Bae et al. found no association between emphysema and PTACs. Most patients are asymptomatic. The aim of this study was to investigate the prevalence of PTAC and the association between the PTACs and emphysema, bronchiectasis, pneumothorax, bullea, and sternotomies on multidetector CT (MDCT) examinations.

Paratracheal air cysts: Prevalence and correlation with lung diseases using multi‐detector CT

The purpose of this study was to determine the prevalence of paratracheal air cysts (PACs), their correlation with different lung diseases and their connection with the trachea by chest multi detector computed tomography (MDCT). We retrospectively reviewed chest MDCT images of 8240 consecutive patients obtained from January 2010 to December 2011 with a 16-detector multi-detector CT scanner. PACs were assessed for prevalence, location, level, size and the presence of visible communication with the trachea. MDCT diagnoses were classified as normal, primary or metastatic malignancies, chronic obstructive pulmonary disease (COPD), pneumonia and other lung diseases. We randomly selected 330 patients who had no visible PACs for the control group. We evaluated the associations between patients' demographic findings (age and sex), MDCT findings of lung and the presence of PACs. The findings of the PACs and control groups were compared. Statistical analysis used chi-squared test and Mann-Whitney U-test for evaluation. PACs were presented in 301 patients (4%); 204 men and 97 women, ranging in age from 14 to 91 years (median = 57 years). There was no significant difference in the presence of PACs by age (P > 0.05). Male subjects showed higher prevalence (P = 0.005). Fifty PACs (16.6%) showed communication with the trachea or main bronchus. Although the relation between COPD and PACs was statistically significant (P < 0.001), there was no relation between primary or metastatic malignancies, pneumonia and other lung diseases and PACs. PACs are common in MDCT and should not be misdiagnosed as pneumomediastinum. It should be kept in mind that PACs may be associated with COPD.

Paratracheal air cysts on thoracic multidetector CT: incidence, morphological characteristics and relevance to pulmonary emphysema

To determine the incidence, morphological characteristics and relevance of paratracheal air cysts (PTACs) with pulmonary emphysema, as seen on thoracic multidetector CT (MDCT). The CT images of 854 consecutive patients who underwent thoracic MDCT during a period of 2 months at our institution were reviewed. 538 of the patients were male and 316 were female. The incidence, size and shape of the PTACs and their relation to pulmonary emphysema were retrospectively analysed. Among the 854 patients, 69 (8.1%) had PTACs. 37 (6.9%) of the 538 male patients and 32 (10.1%) of the 316 female patients had PTACs. The highest prevalence of PTACs (25 patients, 11.2%) was found in those who were in the sixth decade of life. 48 (69.6%) PTACs measured 3-10 mm at the longest diameter and 33 (47.8%) were elongated on the coronal section images. 12 (17.4%) patients with PTACs had underlying gross morphological emphysema. The relationship between the presence of PTACs and the presence of emphysema and the relationship between the presence of PTACs and the severity of emphysema were not statistically significant. The size of PTACs showed an inverse relation to the severity of emphysema. The incidence of PTACs was estimated to be much higher than that of previous studies. There was a slight female predilection for PTACs, most commonly found in the sixth decade of life; PTACs mostly measured 3-10 mm and were elongated in shape. The relation of PTACs to gross morphological emphysema was low. PTACs are not correlated with the presence of emphysema on MDCT.

Chronic Cough Due to Tracheal Diverticulum

Tracheal diverticulum (TD) is a rare benign condition characterised by invaginations of the tracheal wall resulting in paratracheal air cysts. Sixty nine years old female patient admitted to our clinic with chest pain, prolonged cough for 3 months and dyspnea. She had no smoking history. Physical examination, chest X-ray and pulmonary function test results were normal. Air filled lesion with 1 cm in dimension on right paratracheal area connected to tracheal lumen was determined on thorax computed tomography. Patient was diagnosed as TD. TD is usually located on the right wall of trachea as in our patient. Majority of patients are asymptomatic, however diverticulum can retain secretions and act as reservoir for secretions predisposing recurrent infections. TD incidence may be as high as 2%, although rarely reported in clinical practice and literature. Therefore, clinicians should keep in mind TD for patients presenting with chronic cough particularly if chest radiograph and spirometry are normal.

Prevalence and characteristics of paratracheal air cysts and their association with emphysema in a general population

BackgroundTo evaluate the prevalence and characteristics of paratracheal air cysts and their association with emphysema and gender in a general population using low-dose computed tomography scanning of the chest. Materials and methodsWe retrospectively enrolled a total of 924 patients (584 women, 340 men; mean age, 59.73 years; range, 37–89 years) who had received low-dose computed tomography scanning for health examination during the period January 1, 2010 to June 30, 2010. Computed tomographic images were evaluated for the presence of paratracheal air cysts. If paratracheal air cysts were identified, the lungs were reconstructed as a three-dimensional model on a commercial workstation. An emphysema index, an objective quantification of the extent of emphysematous changes on CT imaging, was defined as the percentage area of lung with attenuation values below −950Hounsfield units. ResultsA total of 60 patients with paratracheal air cysts were included in this study (estimated prevalence, 6.5%; 12 men, 48 women; mean age, 59.85; range 45–89 years). Emphysema index differed significantly between genders (P<0.0001). The prevalence of paratracheal air cysts in men was significantly lower than that in women (P=0.005); however, the emphysema index in patients of both genders showed no evidence of emphysema. The majority (95%) of paratracheal air cysts were at the level of the seventh cervical to the second thoracic vertebrae. ConclusionThe presence of paratracheal air cysts is a common condition in general populations and should not be misdiagnosed as abnormal paratracheal free air. Paratracheal air cysts are more common in woman than in man. In our study, there is no patient with paratracheal air cysts has CT evidence of emphysema.

Paratracheal air cysts using low-dose screening chest computed tomography: clinical significance and imaging findings

The aim of this study was to evaluate the prevalence and clinical relevance of paratracheal air cysts in a general population who underwent low-dose computed tomography (LDCT). From July 2005 to March 2008, a total of 2002 persons underwent LDCT and were included in the study. We retrospectively reviewed the chest CT images and analyzed the location, level, and size of the air cysts. We checked whether the cysts had communication with the trachea. Other abnormalities of the lung were noted. We evaluated whether the presence of paratracheal air cysts is associated with abnormal pulmonary function. In all, 75 persons (3.7%) had 77 paratracheal air cysts: 76 (98.7%) at the right side and 36 (46.7%) at the level of the T2 vertebral body. The mean anteroposterior diameter of the paratracheal air cysts was 7.5 mm, and mean transverse diameter was 4.2 mm. Altogether, 26 paratracheal air cysts (33.8%) showed communication with the trachea. Only two persons had respiratory symptoms. Pulmonary function tests showed that five patients (6.7%) had an obstructive pattern. The paratracheal air cysts were mostly located at the right side of the trachea and at the thoracic inlet level. One-third had communication with the trachea. Paratracheal air cysts are not associated with respiratory symptoms or obstructive lung disease clinically or radiologically.

Subcarinal Air Cysts

The purpose of this study was to assess the computed tomographic (CT) features of subcarinal air cysts, which may be related to bronchial diverticula. Seven patients with subcarinal air cysts were retrospectively identified. The following CT features were assessed: location, size, and marginal characteristics of subcarinal air cysts; number, location, and size of communication between the air cyst and bronchi if present; presence of bronchial diverticula in any other location; presence of the pulmonary lesion; and interval change of subcarinal air cysts on follow-up CT. The air cysts were located inferior or inferoposterior to the carina. The subcarinal air cysts typically had a lobulated margin and demonstrated ductlike communications between the air cyst and bronchi. Ductlike communications arose from the posterointerior aspect of the proximal side of main bronchi and were either solitary or multiple. The larger subcarinal air cysts tended to be multiloculated. Subcarinal air cysts may be considered as part of a spectrum of conditions, which include bronchial diverticula and right paratracheal air cysts. Because of their predictable location and appearance, they should be easily distinguished from pathologic lesions such as pneumomediastinum.