CT diagnosis of granulomatous mediastinitis due to tuberculosis

EUROPEANJOURNALOF

RADIOLOGY ELSEVIER

European Journal of Radiology 23 (1996) 241 246

CT diagnosis of granulomatous mediastinitis due to tuberculosis Kernal O d e v *a, F a r u k O z e r b, S a m i C e r a n c, A y d i n K a r a b a c a k o ~ , l u a, A l a a d d i n V u r a l a aDepartment of Radiology, Sel~uk University, School of Medicine, 42080 Konya, Turkey bDepartment of Pulmonary Diseases, Seiqad¢ University, School of Medicine, 42080 Konya, Turkey cDepartment of Thoracic and Cardiovascular Surgery, Sel¢uk University, School of Medicine, 42080 Konya, Turkey Received 29 November 1995; revised 13 December 1995; accepted 5 February 1996

Keywords: Computed tomography (CT), Mediastinum; Mediastinum, Tuberculosis; Mediastinum, CT

1. Introduction Tuberculosis is an important cause of mediastinal granuloma with fibrosing mediastinitis [1,2]. Fibrosing mediastinitis is a chronic process and a late manifestation of mediastinal granuloma. Chronic granulomatous inflammation is characterized by slow progression of fibrosis and fibrocaseous granulomas which develop in the regional mediastinal lymph nodes [2,3]. Plain chest radiograph often confirms the presence of a widened mediastinum but rarely helps in defining the etiology. Cross-sectional imaging of the mediastinum by computed tomography (CT) has become the method of choice for further investigation of a mediastinal abnormality [4]. Magnetic resonance imaging (MRI), on the other hand, can show the vasocompressive effects of fibrosis without the need for intravenous contrast opacification [5]. We report two cases of chronic fibrosing mediastinitis, which is one of the late manifestations of tuberculous infection. 2. Case reports 2.1. Case 1

A 52-year-old man was first evaluated at another hospital in September 1991 with complaints of chronic coughing, dyspnea and haemoptysis. A chest radiogram showed a right superior mediastinal mass (Fig. la). Relevant medical history included a 30-year history of * Corresponding author, Tel.: +90 332 3232600; Fax: +90 332 3232641.

heavy smoking. Blood cultures were negative. He was treated with erythromycin and had a temporary improvement. However, the patient's symptoms recurred 3 weeks later. A routine chest radiogram made 2 months prior to admission had shown gross mediastinal widening without evidence of parenchymal disease (Fig. lb). The patient was admitted to our hospital for further evaluation in February 1992; his condition had got progressively worse. Clinical findings included tachypnea and tachycardia of 150/rain and a blood pressure of 160/90 mmHg. Anterio-posterior diameter of the chest was increased. Wheezing and bilateral basilar rales were present on the chest examination. On physical examination, the cutaneous veins were dilated. The signs of superior vena cava syndrome included edema of the face, neck, facial flush, cyanosis of the upper body and grossly visible dilated veins in the neck. A tuberculin skin test was positive. Several sputum cultures remained negative. Pulmonary function tests revealed a marked obstructive pattern. Superior vena cavography was performed by simultaneous bilateral cubital vein injection. Venography demonstrated almost complete obstruction of the superior vena cava (SVC) with patency and partial obstruction of the right brachiocephalic vein (Fig. lc). Enhanced CT scanning demonstrated more masses with stippled or dense calcifications in the right paratracheal, pretracheal and subcarinal regions (Figs. ld,e). Moreover, non-calcified lymph nodes were present in these regions. Obliteration of perinodal fat was present. On Jan. 1, 1992 a median sternotomy was performed through a sternal splitting incision. The mediastinal mass consisted of dense fibrous tissue. A fibrocaseous

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K. Odev et al. / European Journal o f Radiology 23 (1996) 241 246

Fig. 1 a-d.

mass was present, densely adherent to the brachiocephalic veins, superior vena cava and azygous vein. Mediastinal calcified nodes were observed to be hard and confluent. The right jugular vein and brachiocephalic veins were explored, but the SVC and azygous vein could not be explored. Venous obstruction was noted. The right atrium was anastomosed to the right brachiocephalic vein thus bypassing the obstruction. The distal end of the internal jugular vein was then anastomosed to the right atrium. Partial excision o f the mass was performed. The postoperative course was uncomplicated. Multiple biopsy specimens taken from the

masses exhibited dense fibrous tissue containing tubercle-like granulomas with many reactive giant cells. The patient was treated with corticosteroids in order to prevent further scarring and obstruction. The latest follow-up 3 years after surgical intervention has revealed a relatively asymptomatic clinical condition, although the plain chest radiograph showed some superior mediastinal widening (Fig. 10. Serial contiguous enhanced CT scans demonstrated partial patency of the superior vena cava associated with the continuation of a compression due to mediastinal calcified masses (Figs,, ld,e,g).

K. Oder et al. European Journal of Radiology 23 (1996) 241-246

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Fig. 1. Case 1. (a) The initial chest radiograph shows right superior mediastinal widening. (b) Chest radiograph obtained in 1992 shows abnormal mediastinai widening. (c) Superior vena cavogram shows severe obstruction from granulomatousmediastinitis with fibrosis. (d) Enhanced CT scan through upper mediastinum shows considerably enlarged confluent lymph nodes with calcification in the paratracheal region and severe compression of SVC. (e) The CT scan shows calcified nodes occupying precarinal and subcarinal areas. (f) Postoperative appearance of the mediastinum, 3 years after partial excision of the mass. (g) Postoperative enhanced CT scan at different levels of the mediastinum which discloses calcified mass with compression of SVC and the calcification of the hilar and mediastinal nodes.

2.2. Case 2

3. ~ o n

A 68-year-old women was admitted to our hospital for the first time on Jan 5, 1991 with a 2-year history of cough, haemoptysis and dyspnea. She had experienced mild asthmatic attacks associated with upper respiratory tract infection. On physical examination, the patient was febrile to 38.4°C. Rhonchi were noted over the right and left hemithorax. A tuberculin skin test was positive after 72 h. Pulmonary function studies suggested a moderate obstructive compression. Routine chest film demonstrated asymmetric mediastinal widening (Fig. 2a). Enhanced CT scan revealed large calcified nodes involving pretracheal, right hilar, and paratracheal areas (Figs. 2b,c). Mediastinoscopic biopsy was performed, revealing caseous appearance of the mediastinal lymph nodes. Tissue sections showed fibrocaseous granulomas.

Mediastinal granuloma is the term used for caseous or fibrocaseous nodes or masses found in the mediastinum. Fibrocaseous granulomas develop in the regional mediastinal lymph nodes as a result of the healing of the acute infection [3,6]. In many cases hilar and mediastinal adenopathy develop without evidence of parenchymal involvement. Although in the majority of cases the etiology of the granulomatous inflammation is not established completely, it is possible that histoplasmosis and tuberculosis are the most common causes [2,3,6-9]. Other described etiologies of mediastinal granulomas are sarcoidosis, silicosis, mycotic infections (e.g. actinomyces, aspergillus, nocardia, and phycomycetes) [2,7-9]. Tuberculosis is thought to be the precursor of this pathology with significantly less frequency. The

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Fig. 2. Case 2. (a) Chest radiograph reveals mediastinal widening. (b) Enhanced CT scan demonstrates amorphous mediastinal mass with calcification surrounding the paratracheal area. Moreover, compact calcification of lymph nodes in the retrosternal area is evident. (c) CT scan demonstrates enlarged calcified lymph nodes in the pretracheal, anterior mediastinum, and aortico pulmonary window areas.

disease may affect almost all mediastinal structures. Many mediastinal granulomas are asymptomatic but others may produce non-specific signs and symptoms including cough, dyspnea, wheezing, mediastinitis, superior vena cava syndrome, and tracheal or esophageal obstruction [1-3,6,8]. Inflammatory process develops almost invariably in the upper half of the mediastinum, usually anterior to and near the bifurcation of the trachea or at the lung hilum. The inflammation is usually associated with considerable fibrosis. The hallmark of a mediastinal granuloma, which distinguishes it from mediastinal adenitis, is the formation of an encapsulated fibrous

mass surrounding a core of caseating lymph nodes. The development of symptoms and signs in granulomatous mediastinitis depends on the degree of fibrotic reaction around the mediastinal lymph nodes [2,6,8,9]. The most common complications of mediastinal granuloma are fibrosing mediastinitis and obstruction of the superior vena cava. Other complications are obstruction of the innominate vein, azygous vein, esophageal compression, and tracheobronchial compression [3,6,8,9]. Radiographically, the most common manifestation of granulomatous mediastinitis is asymmetric mediastinal widening. Standard chest radiography is rarely diagnostic. The diagnostic difficulties arise when the chest film

K. Odev et al. / European Journal of Radiology 23 (1996) 241-246

shows an enlarged transverse upper mediastinal shadow [4,8,10]. Conventional chest radiograms may demonstrate a mediastinal or hilar mass containing calcifications. The calcifications in the hilar or mediastinal nodes can be seen in sarcoidosis, certain fungal infections (e.g. histoplasmosis, coccidioidomycosis), disseminated pneumocystis carinii infections, silicosis, granulomatous infection representing the healed lesioning tuberculosis, treated mediastinal lymph node metastases and primary mediastinal neoplasms [7-9,11,12]. Castleman disease and amyloidosis are other less common causes of calcified mediastinal lymph nodes [12]. Plain chest radiograph generally is not helpful in the differential diagnosis. CT scanning may be helpful to determine the presence of dense calcifications throughout masses and their location, as well as in differentiation of granulomatous lesions from other causes [12,13]. The existence of a distinct outline between the mass and surrounding mediastinal structures is considered to indicate benign disease; however, this sign is not reliable [13]. In most cases, the clinical history and other associated CT findings suggest the correct diagnosis [10,12]. Pulmonary tuberculosis in Turkey is a common condition; histoplasmosis, however, is not common. In 1980, the incidence of tuberculosis in Turkey was 52.2 per 100 000. By 1990, it had dropped to 44.2 per 100 000, and the prevalance was 4.59 per 1000, Nevertheless, more people continue to die from tuberculosis [14]. Calcification within the lymph nodes is the most common cause of a high-attenuation mediastinal mass. Calcified mediastinal or hilar lymph nodes, particularly in endemic areas, and radiologic findings observed in these patients validate the similar healing process. In the reported cases, the CT scan was helpful in the evaluation of the extent and localization of mediastinal masses seen on plain chest radiographs and demonstrated more precisely than standard chest radiographs the extensive calcifications within the masses. Fibrosing mediastinitis or sclerosing mediastimtis represents a late stage of chronic granulomatous infection [3,6,8,9,11]. One of the distinctive characteristics of some cases of fibrosing mediastinitis is its association with a similar fibrotic process elsewhere. The etiologic factors implicated in chronic fibrous mediastinitis are also similar to granulomatous mediastinitis [2,8,91. However, mediastinal fibrosis seen in some cases has been associated with malignant neoplasm, chronic infection, drug ingestion (e.g. methysergide) used for the alleviation of headache or retroperitoneal hematoma, autoimmune disease, and radiotherapy [8-10,15,16]. It may also be idiopathic. It should be considered especially after the elimination of other causes [15,16]. Location of fibromatous masses in fibrosing mediastinitis is the same as that found in granulomatous mediastinitis [8-10]. The radiographic manifestations of fibrosing mediastinitis resemble those of the granulomatous vari-

245

ety [2,8,9,11]. The clinical course of the mediastinal granuloma with fibrosing mediastinitis is usually benign [3,61. One of the most common physical findings is distension of the veins in the neck due to obstruction of the superior vena cava. The syndrome of SVC obstruction may be caused by malignant neoplasm, granulomatous disease, benign mediastinal masses, aneurysm, thrombosis, or trauma [2,3,6,8,13,15-171. However, in a small but significant number of cases the obstruction results from benign conditions [17]. Fibrosing mediastinitis caused by various granulomatous processes is probably the most common cause of the benign syndrome [8,16,17]. Clinically it is difficult to diagnose the benign process of this syndrome. However, some clinical features may allow a precise diagnosis. These patients have a long-term survival compared to that of the malignant causes [3,17]. Conventional superior vena cavography may be helpful in these patients to identify the exact level of venous obstruction before invasive procedures such as mediastinoscopy and thoracotomy [16-18]. Although phlebography reveals the level of obstruction of the superior vena cava, it fails to show the mediastinal masses detected by CT scanning, as was demonstrated in our first patient. CT has been widely used to examine patients with suspected SVC syndrome, because it can demonstrate the cause of the SVC syndrome, the extent of the disease and the site and degree of the venous obstruction, as well as external compression or invasion from mediastinal mass [13,18,19]. In our case 1, the CT scan was also more informative than conventional phiebography. CT scan provides information which is unobtainable with conventional techniques. We do not have MRI facilities to further delineate compression of the major vascular structures or to compare the accuracy of compression demonstrated by CT scans, but some reports support that MRI provides sufficient anatomic information to demonstrate the calcified fibrosing mediastinitis without the need of contrast media. It is insufficient to demonstrate calcifications, but recent reports suggest that the effect of the fibrotic masses on the vascular structures may be clearly demonstrated by this procedure [5,20]. In conclusion, healed granulomatous disease should be considered when large calcified mediastinal masses are readily identified by CT, even though routine radiography does not disclose them. CT is useful in demonstrating the exact location of mediastinal calcified mass lesions and abnormal morphology of the SVC with external compression. Computed tomography is a sensitive technique for demonstrating the presence of a mediastinal abnormality undetectable by conventional techniques. Persistence of calcified lesions during follow-up and the extent of duration of symptoms suggest the non-neoplastic nature of the process. In the case of non-granulomatous fibrosing mediastinitis, the absence of a mass with obliteration of the normal fat

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planes, at the site of obstruction, is usually the clue for diagnosis. However, definitive diagnosis requires histologic examination of the specimens obtained after mediastinoscopic biopsy or thoracotomy. References

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