- Email: [email protected]
Primary mediastinal echinococcosis
CT: THE JOURNAL
PRIMARY
MEDIASTINAL
OF COMPUTED
TOMOGRAPHY
1985;
9:195-197
195
ECHINOCOCCOSIS
RAKESH K. MATHUR, MD, SHYAM SUNDER DODA, MD, TARVINDER BIR SINGH BUXI, MD, AND J. R. TALWAR, MS, FACS,
MAMS
Computed tomography findings with surgical details are presented in a case of hydatid cyst of posterior mediastinum, a rare site of involvementin echinococcosis infestation (1, 2). The computed tomography appearance of posterior mediastinal echinococcosis is quite characteristic and can be readily distinguished from other cystic lesions of the mediastinum. Computed tomography provides additional information regarding the involvement of neighboring structures. In this case, computed tomography detected involvement of the descending aorta. KEY WORDS:
Mediastinum; Cysts; Echinococcis; Computed tomography
CASE REPORT
A 31-year-old man presented for evaluation of complaints of heaviness and pain of the left anterior chest of 8 months duration, accompanied by fever and cough. A clinical diagnosis of left-sided pleural effusion was made. A chest x-ray revealed a large homogenous rounded opacity in the posterior aspect of left lower chest. A few doubtful erosions were seen in the anterior and lateral aspect of lower dorsal vertebrae. A barium swallow test revealed anterior esophageal displacement by an extrapulmonary mass. An ultrasound examination revealed
From the Delhi Scan Research Centre and the Department of Cardiothoracic Surgery, Sir Ganga Ram Hospital, New Delhi, India. Address reprint requests to: Rakesh K. Mathur, MD, Delhi Scan Research Centre, Sir Ganga Ram Hospital, Rajinder Nagar, New Delhi 110 060 India. Received September 1984. 6~ 1985 bq. Elsevier Science Publishing Co., Inc. 52 Vnndrrbilt Ave.. New York. NY 10017 0149-‘J:IO‘X!R5~,F:(.90
a thin-walled, large cystic mass situated posteriorly in the lower thorax. The left dome of diaphragm could not be defined. The abdominal aorta was normal. A computed tomography (CT) scan of the lower chest and upper abdomen revealed a large, well-defined cystic mass in the posterior mediastinum on the left side. It extended inferiorly up to the upper pole of the left kidney. Multiple daughter cysts of varying sizes were seen within this mass as round areas of lower attenuation. The descending thoracic aorta was seen pushed anteriorly, and an aneurysma1 dilatation of its posterolateral wall was seen projecting into the cystic mass [Figures 1 and 2). Some calcified flakes were noticed in the cyst wall and erosion of the bodies of dorsal vertebrae was confirmed (Figure 3). A thoracotomy confirmed the diagnosis of primary hydatid cyst. The extent of the lesion was from the D-7 to L-Z vertebrae. It was 13 cm in diameter and displaced the aorta and esophagus anteriorly. The consistency was cystic, and the aspirate was thin and straw colored. The cyst was opened and hydatid material was found in the form of multiple cysts of varying sizes. Most of these cysts were collapsed and densely packed. The anterior wall of the cyst revealed a 4 x 2.5cm massprojecting into it from the posterolateral wall of the aorta. It was extremely thin walled and nonpulsatile (pseudoaneurysm of aorta). It ruptured when touched. The anterior margins of the dorsal vertebrae were found to be eroded. DISCUSSION
From 15 to 20% of hexacanthene embryos succeed in passing through the pulmonary and hepatic capillary barrier and reaching the systemic circulation (3). Primary mediastinal hydatid is an extremely
196
MATHUR
ET AL.
CT: THE JOURNAL
OF COMPUTED
TOMOGRAPHY
VOL.
9 NO.
1. Enhanced CT scan shows a posterior mediastinal hydatid with multiple daughter cysts.
FIGURE
rare condition,
varying from zero site of occurrence is the posterior mediastinum, with the anterior and middle mediastinum coming next in frequency. Middle mediastinal involvement is very rare. Mediastinal cysts may calcify, as they are not subject to respiration (6, 7). The cysts consist of three layers: a peripheral pericystym, the middle external cuticle layer, and an inner endocyst. The endocyst is responsible for germination of daughter cysts. Posterior mediastinal hydatid cysts are multivesicular--whereas those of the middle mediastinum are univesicular. Generally, the hydatid cyst of the mediastinum is neither clinically nor radiologically distinguishable from other mediastinal tumors. Although eosinoto 6%
with an incidence
(1, 4). The most common
FIGURE 2. Anteriorly pushed descending aorta showing aneurysmal dilatation protruding into the hydatid cyst.
3. A CT scan showing smooth erosion of body of adjacent dorsal vertebra.
FIGURE
philia and results of complement fixation tests and chest x-rays are of diagnostic value, diagnosis is always made at surgery. With the current high-resolution CT scanners, the diagnosis of mediastinal hydatid can be confidently made prior to surgery (4). Computed tomography can be considered diagnostic in that it can actually delineate the exact location of the cyst, its size, and its shape. In addition to its diagnostic value, CT is of immense value to the surgeon in delineating the extent of the cyst, the proximity to other vital vascular structures, and possible bony erosion. The ideal operation for hydatid cyst is the extirpation of the parasite with its pericystic membranes (cystopericytectomy). However, because the cyst usually adheres to important structures, such as nerves and vessels, serious complications may ensue from its dissection (1). Barett (8, 9) aspirated the cyst before removal to avoid rupture, and Ugon (10) removed the entire cyst with aspiration. Other common and uncommon posterior mediastinal masses that have to be differentiated are: neurogenic tumors, neuroenteric cysts, paravertebral masses, esophageal duplication cyst of the foregut, and anterior thoracic meningocele. Usually these abnormalities are diagnosed by routine clinical and radiologic examination and by CT appearance. We believe CT scan to be the procedure of choice in identifying the site and extent of posterior mediastinal hydatid cyst.
JULY
1985
PRIMARY MEDIASTINAI,
Our sincere thanks to Mr. Arya, DR, and Mr. Sharma, SK, for obtaining the scans, and to Mrs. Narang Sushem for typing the manuscript.
REFERENCES 1. Rakower J, Mildwidsky H: Primary cosis. Am J Med 1960;29:73.
mediastinal
echinococ-
2. Lozano RM, Lozano RB, Solsonaf, Martinf: Primary disease of mediastinum. Dis Chest 1969;260:3. 3. Rakower J, Mildwidsky H: Primary cosis. Am J Med 1960;29:73.
mediastinal
hydatid
echinococ-
4. Lozano RM, Lozano RB, Solsonaf, Martinf: Primary disease of mediastinum. Dis Chest 1969;260:3.
hydatid
5. Pandey JN, Guleria JS, Sharma SK: Hydatid disease lung. Indian J Chest Dis Allied Sci 1981;23:208. 6. Lathum WJ: Hydatid disease, 7. Bonakdarpour
part 1.J Fat Radio1 1953;5:65.
A: Am J Roentgen01
8. Barett NR: Removal of simple datid cyst. Lancet 1949;2:234. 9. Bar&t NR, Thomas 1952;40:222.
of the
1967;99:560.
univesicular
D: Pulmonary
hydatid
pulmonary disease.
hy-
Br J Surg
10. Ugon A: La Lebectomia on eltratamiento de las secuelas giete hidatico de pulman. Bol Sol Cirug (Uruguay) 465.
de1
ECHINOCOCCOSIS
197
CONTINUING MEDICAL EDUCATION QUESTIONS Which of the following is the most uncommon tinal cystic mass lesion? a. Neuroenteric cyst. b. Duplication cyst of the foregut. c. Primary mediastinal hydatid cyst. d. Secondary mediastinal hydatid cyst. A confident diagnosis of mediastinal be made by: a. Complement fixation test. b. Chest x-ray, c. Ultrasound. d. Computed tomography. One of the most serious complications hydatid cyst is: a. Rupture of the cyst. b. Involvement of phrenic nerves. c. Involvement of aorta. d. Vertebral erosion.
medias-
hydatid cyst can
of mediastinal
The ideal operation for uncomplicated mediastinal datid is: a. Aspiration of the cyst before removal. b. Aspiration only. c. None of the above.
hy-
PRIMARY
MEDIASTINAL
OF COMPUTED
TOMOGRAPHY
1985;
9:195-197
195
ECHINOCOCCOSIS
RAKESH K. MATHUR, MD, SHYAM SUNDER DODA, MD, TARVINDER BIR SINGH BUXI, MD, AND J. R. TALWAR, MS, FACS,
MAMS
Computed tomography findings with surgical details are presented in a case of hydatid cyst of posterior mediastinum, a rare site of involvementin echinococcosis infestation (1, 2). The computed tomography appearance of posterior mediastinal echinococcosis is quite characteristic and can be readily distinguished from other cystic lesions of the mediastinum. Computed tomography provides additional information regarding the involvement of neighboring structures. In this case, computed tomography detected involvement of the descending aorta. KEY WORDS:
Mediastinum; Cysts; Echinococcis; Computed tomography
CASE REPORT
A 31-year-old man presented for evaluation of complaints of heaviness and pain of the left anterior chest of 8 months duration, accompanied by fever and cough. A clinical diagnosis of left-sided pleural effusion was made. A chest x-ray revealed a large homogenous rounded opacity in the posterior aspect of left lower chest. A few doubtful erosions were seen in the anterior and lateral aspect of lower dorsal vertebrae. A barium swallow test revealed anterior esophageal displacement by an extrapulmonary mass. An ultrasound examination revealed
From the Delhi Scan Research Centre and the Department of Cardiothoracic Surgery, Sir Ganga Ram Hospital, New Delhi, India. Address reprint requests to: Rakesh K. Mathur, MD, Delhi Scan Research Centre, Sir Ganga Ram Hospital, Rajinder Nagar, New Delhi 110 060 India. Received September 1984. 6~ 1985 bq. Elsevier Science Publishing Co., Inc. 52 Vnndrrbilt Ave.. New York. NY 10017 0149-‘J:IO‘X!R5~,F:(.90
a thin-walled, large cystic mass situated posteriorly in the lower thorax. The left dome of diaphragm could not be defined. The abdominal aorta was normal. A computed tomography (CT) scan of the lower chest and upper abdomen revealed a large, well-defined cystic mass in the posterior mediastinum on the left side. It extended inferiorly up to the upper pole of the left kidney. Multiple daughter cysts of varying sizes were seen within this mass as round areas of lower attenuation. The descending thoracic aorta was seen pushed anteriorly, and an aneurysma1 dilatation of its posterolateral wall was seen projecting into the cystic mass [Figures 1 and 2). Some calcified flakes were noticed in the cyst wall and erosion of the bodies of dorsal vertebrae was confirmed (Figure 3). A thoracotomy confirmed the diagnosis of primary hydatid cyst. The extent of the lesion was from the D-7 to L-Z vertebrae. It was 13 cm in diameter and displaced the aorta and esophagus anteriorly. The consistency was cystic, and the aspirate was thin and straw colored. The cyst was opened and hydatid material was found in the form of multiple cysts of varying sizes. Most of these cysts were collapsed and densely packed. The anterior wall of the cyst revealed a 4 x 2.5cm massprojecting into it from the posterolateral wall of the aorta. It was extremely thin walled and nonpulsatile (pseudoaneurysm of aorta). It ruptured when touched. The anterior margins of the dorsal vertebrae were found to be eroded. DISCUSSION
From 15 to 20% of hexacanthene embryos succeed in passing through the pulmonary and hepatic capillary barrier and reaching the systemic circulation (3). Primary mediastinal hydatid is an extremely
196
MATHUR
ET AL.
CT: THE JOURNAL
OF COMPUTED
TOMOGRAPHY
VOL.
9 NO.
1. Enhanced CT scan shows a posterior mediastinal hydatid with multiple daughter cysts.
FIGURE
rare condition,
varying from zero site of occurrence is the posterior mediastinum, with the anterior and middle mediastinum coming next in frequency. Middle mediastinal involvement is very rare. Mediastinal cysts may calcify, as they are not subject to respiration (6, 7). The cysts consist of three layers: a peripheral pericystym, the middle external cuticle layer, and an inner endocyst. The endocyst is responsible for germination of daughter cysts. Posterior mediastinal hydatid cysts are multivesicular--whereas those of the middle mediastinum are univesicular. Generally, the hydatid cyst of the mediastinum is neither clinically nor radiologically distinguishable from other mediastinal tumors. Although eosinoto 6%
with an incidence
(1, 4). The most common
FIGURE 2. Anteriorly pushed descending aorta showing aneurysmal dilatation protruding into the hydatid cyst.
3. A CT scan showing smooth erosion of body of adjacent dorsal vertebra.
FIGURE
philia and results of complement fixation tests and chest x-rays are of diagnostic value, diagnosis is always made at surgery. With the current high-resolution CT scanners, the diagnosis of mediastinal hydatid can be confidently made prior to surgery (4). Computed tomography can be considered diagnostic in that it can actually delineate the exact location of the cyst, its size, and its shape. In addition to its diagnostic value, CT is of immense value to the surgeon in delineating the extent of the cyst, the proximity to other vital vascular structures, and possible bony erosion. The ideal operation for hydatid cyst is the extirpation of the parasite with its pericystic membranes (cystopericytectomy). However, because the cyst usually adheres to important structures, such as nerves and vessels, serious complications may ensue from its dissection (1). Barett (8, 9) aspirated the cyst before removal to avoid rupture, and Ugon (10) removed the entire cyst with aspiration. Other common and uncommon posterior mediastinal masses that have to be differentiated are: neurogenic tumors, neuroenteric cysts, paravertebral masses, esophageal duplication cyst of the foregut, and anterior thoracic meningocele. Usually these abnormalities are diagnosed by routine clinical and radiologic examination and by CT appearance. We believe CT scan to be the procedure of choice in identifying the site and extent of posterior mediastinal hydatid cyst.
JULY
1985
PRIMARY MEDIASTINAI,
Our sincere thanks to Mr. Arya, DR, and Mr. Sharma, SK, for obtaining the scans, and to Mrs. Narang Sushem for typing the manuscript.
REFERENCES 1. Rakower J, Mildwidsky H: Primary cosis. Am J Med 1960;29:73.
mediastinal
echinococ-
2. Lozano RM, Lozano RB, Solsonaf, Martinf: Primary disease of mediastinum. Dis Chest 1969;260:3. 3. Rakower J, Mildwidsky H: Primary cosis. Am J Med 1960;29:73.
mediastinal
hydatid
echinococ-
4. Lozano RM, Lozano RB, Solsonaf, Martinf: Primary disease of mediastinum. Dis Chest 1969;260:3.
hydatid
5. Pandey JN, Guleria JS, Sharma SK: Hydatid disease lung. Indian J Chest Dis Allied Sci 1981;23:208. 6. Lathum WJ: Hydatid disease, 7. Bonakdarpour
part 1.J Fat Radio1 1953;5:65.
A: Am J Roentgen01
8. Barett NR: Removal of simple datid cyst. Lancet 1949;2:234. 9. Bar&t NR, Thomas 1952;40:222.
of the
1967;99:560.
univesicular
D: Pulmonary
hydatid
pulmonary disease.
hy-
Br J Surg
10. Ugon A: La Lebectomia on eltratamiento de las secuelas giete hidatico de pulman. Bol Sol Cirug (Uruguay) 465.
de1
ECHINOCOCCOSIS
197
CONTINUING MEDICAL EDUCATION QUESTIONS Which of the following is the most uncommon tinal cystic mass lesion? a. Neuroenteric cyst. b. Duplication cyst of the foregut. c. Primary mediastinal hydatid cyst. d. Secondary mediastinal hydatid cyst. A confident diagnosis of mediastinal be made by: a. Complement fixation test. b. Chest x-ray, c. Ultrasound. d. Computed tomography. One of the most serious complications hydatid cyst is: a. Rupture of the cyst. b. Involvement of phrenic nerves. c. Involvement of aorta. d. Vertebral erosion.
medias-
hydatid cyst can
of mediastinal
The ideal operation for uncomplicated mediastinal datid is: a. Aspiration of the cyst before removal. b. Aspiration only. c. None of the above.
hy-