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CT in Pulmonary Hydatid Disease
CT in Pulmonary Hydatid Disease* Unusual Appearances Parvaiz A. Koul, MD; Ajaz N. Koul, MD; A. Wahid, MD; and Farhad A. Mir, MD
Objective: To study the CT features of pulmonary hydatid disease. Patients: Thirty-two consecutive patients with surgically proven pulmonary hydatid cysts. Setting: SheriKashmir Institute of Medical Sciences, Srinagar, Kashmir, India, a tertiary-care referral center. Interventions: CT of the chest was obtained in all cases on Somatom DR double rotate CT scanner (Siemens; Erlangen, Germany). Results: Forty cysts of different size and shapes were encountered, 34 of them being ruptured. CT density of the cysts varied from ⴚ 42 to 160 Hounsfield units (HU; median, 15.5 HU). Apart from the classically described features of pulmonary hydatid disease, a crescent-shaped rim of air at the lower end of the cyst (inverse crescent sign) was seen in three cysts, and a bleb of air in the wall of two as-yet unruptured cysts (signet ring sign). Thick wall (>10 mm) was observed in four cysts, and each of them had associated evidence of infection. Conclusions: Inverse crescent sign, signet ring sign, high CT density, and thick wall should be recognized as features of pulmonary hydatid cysts on CT. (CHEST 2000; 118:1645–1647) Key words: CT; cyst; echinococcosis; lung Abbreviation: HU ⫽ Hounsfield unit
disease of the lungs is a common disorder H ydatid in many areas of the world. Conventional radiography is routinely employed for diagnosis of the disease in developing countries. CT has been available only recently in many of such places; as such, the CT findings of hydatid cysts of the lung are only sparsely described,1,2 even though the disease abounds in these areas. The present study addresses the appearances of pulmonary hydatidosis on CT from a developing area where hydatidosis is frequent. The study, to the best of our knowledge, is the first from our part of the globe. Materials and Methods Thirty-two patients with surgically proven hydatid cysts of the lung who presented to the internal medicine department of the SheriKashmir Institute of Medical Sciences, Srinagar, were enrolled for the study. The patients consisted of 13 female patients and 19 male patients, with ages ranging from 11 to 60 years (median, 30 years). The various symptoms experienced by the patients included cough (n ⫽ 16), hemoptysis (n ⫽ 4), fever *From the Departments of Internal Medicine (Drs. P. Koul, A. Koul, and Wahid) and Radiodiagnosis (Dr. Mir), SheriKashmir Institute of Medical Sciences, Srinagar, Kashmir, India. Manuscript received September 14, 1998; revision accepted June 26, 2000. Correspondence to Parvaiz A. Koul, MD, Department of Internal Medicine, SheriKashmir Institute of Medical Sciences, Soura, Post Bag 27, Srinagar 190 011, Kashmir, India; e-mail: [email protected]
(n ⫽ 13), chest pain (n ⫽ 10), and breathlessness, anorexia and weight loss in one patient each. Two patients were asymptomatic. All patients underwent a detailed clinical examination and routine investigations. Eosinophilia of ⬎ 500 ⫻ 109/L was demonstrable in 11 patients, positive Casoni’s test in 13 patients, and IgM antihydatid antibodies in 12 patients. On chest radiography, the hydatid cysts were found to be bilateral in two patients. Special features included meniscus sign (introduction of air between pericyst and endocyst producing a crescent-shaped air shadow toward the top of the cyst)3 in two patients, Cumbo’s sign (air fluid level in the endocyst capped with air between pericyst and endocyst occurring on rupture of the endocyst)3 in one patient, and calcification of the cyst in one patient. All patients were subjected to CT scanning of the lungs with Somatom DR double rotate CT scanner (Siemens; Erlangen, Germany) using 120 mA, 410 kV, 7-s scan time, 512 ⫻ 512 matrix, and 4-mm to 8-mm section thickness. CT scans were analyzed before surgery and reviewed after the diagnosis was secured following surgery. All patients were subjected to surgery, after proper antibiotic therapy for those with suspected infection of the cysts. The cysts were sent for histopathologic examination and the contents for cytologic examination for scolices and hooklets. Gram’s smear and cultures of the cyst fluid were performed routinely.
Results On CT scanning, 40 cysts were localized that were unilateral in 29 patients and bilateral in 3 patients. The cysts were located in right lower lobe (n ⫽ 15), left lower lobe (n ⫽ 12), right middle CHEST / 118 / 6 / DECEMBER, 2000
1645
lobe (n ⫽ 5), left upper lobe (n ⫽ 5), and right upper lobe (n ⫽ 3). The size of the cysts varied from 1.5 to 13 cm (mean ⫾ SD, 5.67 ⫾ 2.80 cm). Various shapes encountered were round (n ⫽ 21), oval (n ⫽ 13), irregular (n ⫽ 3), and pear-shaped, reniform-shaped, and pomegranate-shaped (Fig 1) in one patient each. Thirty-one cysts were uniloculate (Fig 2), whereas internal septae with multiple loculations were seen in one cyst. Thirty-four cysts were ruptured (air having dissected into the cyst causing separation of the membranes), whereas 6 cysts were unruptured. CT density of the cysts ranged from ⫺ 42 to 160 Hounsfield units (HU) [median, 15.5 HU]. The density ranged from 9 to 160.5 HU (median, 35 HU) in ruptured cysts, and from ⫺ 42 to 60 HU (median, 19.75 HU) in unruptured cysts. CT density of the eight infected cysts ranged from 8.5 to 160.5 HU (median, 24 HU). Daughter cysts were demonstrable in four cysts and communication with the bronchus in seven cysts. Five cysts demonstrated a crescent sign, Cumbo’s sign was seen in one cyst, water lily sign (endocyst membrane floating on top of remaining fluid consequent on collapse of endocyst and partial evacuation of fluid)3 in three cysts (Fig 3), and air entrapped in the lower end of the cyst in three cysts in a fashion that was the reverse of the classical crescent sign (Fig 4). Two cysts had a tiny bleb of air dissecting into the wall giving the appearance of a signet ring (Fig 5). Pericystic reaction in the lung tissue was demonstrable in seven patients, with distortion of the lung-cyst interface. Other features included pleural effusion (n ⫽ 4), abscess formation (n ⫽ 3), mediastinal shift (n ⫽ 2), pneumonitis (n ⫽ 2), and atelactasis (n ⫽ 1). The cyst wall was smooth in 31 cysts and irregular in 9 cysts. The wall thickness ranged from ⬍ 1 mm to 20 mm, with four cysts having wall thickness of ⬎ 10 mm (Fig 6), especially in areas abutting the pleura. All
Figure 1. Pomegranate-shaped cyst. 1646
Figure 2. A uniloculate cyst involving almost the whole of the left hemithorax.
four patients with thick walls had evidence of infection clinically as well as on examination of the cyst fluid. CT density of the cyst wall ranged from 15 to 59 HU. Calcification of the cyst wall was found in two cases. Discussion Conventional chest radiography has been the mainstay of the diagnostic armamentarium of patients with hydatid disease of the lungs, often coupled with Casoni’s skin testing and serologic testing for antibodies. However, the two, even in combination, may not yield a definitive diagnosis as a result of many conditions, such as carcinomas, benign tumors, inflammatory masses, metastasis, and solid or fluid-filled cysts mimicking the radiologic features of hydatid cysts of the lung.1,4,5 Not infrequently, serologic and skin testing yields false-positive or false-negative results, adding to the confusion. CT scanning has come to the rescue of the clinician in elucidating the cystic nature of the lung mass and accurate localization for planning of
Figure 3. Membranes floating on the surface of a ruptured cyst, giving the water lily appearance. Clinical Investigations
Figure 4. Inverse crescent sign.
surgical treatment. The present study simply fortifies this view even for developing countries. Two appearances of the hydatid cyst observed in the present study have not been reported earlier. In three of our patients, a crescent-like rim of air was observed at the lower end of the cyst (Fig 4), with an appearance that was morphologically opposite of the classic “crescent” sign. We have termed it the inverse crescent sign, and results from air dissection induced separation of the membranes from the posterior aspect of the cyst without any anterior extension. Perioperative findings of these patients revealed a zone of pericystic fibrosis on the upper end and distortion of the lung cyst interface. Another morphologic appearance that was observed in two patients is a bleb of air dissecting into the wall of the cyst, giving it the shape of a ring; we have termed it the signet ring sign (Fig 5). A similar appearance was also reported by Sakouk et al.1 The sign may be a harbinger of impending cyst rupture. CT densities of the cysts in the present study
Figure 6. Thick-walled cyst situated peripherally.
ranged from ⫺ 40 to 160 HU. Higher attenuation values have been reported earlier, with an unintended aspiration having been performed on one such cyst. A higher attenuation value attracts a differential diagnosis of tumors, infarcts, etc. Higher attenuation values have been reported to result from a fibrosis or infection of the cysts. Such CT findings emphasize the employment of better serologic methods for diagnosing hydatid cysts when the lung mass on CT does not have typical features of a cyst. Wall thickness in the present study was found to range from 0.5 to 20 mm, with a CT density of ⫺ 15 to 59 HU. The wall characteristics of pulmonary hydatid disease have not been reported earlier. The reason for the thickness could be attributed to the infection of the cysts that was observed in all the four cysts with thick wall. No special histologic findings were observed in the hydatid cysts with thick walls. Calcification of the cysts was observed in two cysts on CT as compared to only one case on radiography, emphasizing improved delineation on CT. We conclude that besides the conventional appearances of hydatid cysts of the lung on CT, signet ring sign and inverse crescent sign should be recognized as features of pulmonary hydatidosis. In addition, an increase in the CT density of the lung mass and/or a thick wall should not negate a diagnosis of hydatid disease. References
Figure 5. Membrane separation leading to the signet ring appearance.
1 Sakouk FA, Fahl MH, Rizk GK. Computed tomography of pulmonary hydatid disease. J Comput Assist Tomogr 1986; 10:226 –232 2 Gouliamos AD, Kalovidouris A, Papailiou J, et al. CT appearances of pulmonary hydatid disease. Chest 1991; 100:1578 –1581 3 Schlanger PM, Schlanger H. Hydatid disease and its roentgen picture. AJR Am J Roentgenol 1984; 60:331–347 4 Kegel RFC, Fateni A. ruptured pulmonary hydatid cyst. Radiology 1961; 76:60 – 64 5 Aggarwal S, Kumar A, Mukhopaday S, et al. A new radiological sign of ruptured pulmonary hydatid cyst. Am J Radiol 1989; 152:431– 432 CHEST / 118 / 6 / DECEMBER, 2000
1647
Objective: To study the CT features of pulmonary hydatid disease. Patients: Thirty-two consecutive patients with surgically proven pulmonary hydatid cysts. Setting: SheriKashmir Institute of Medical Sciences, Srinagar, Kashmir, India, a tertiary-care referral center. Interventions: CT of the chest was obtained in all cases on Somatom DR double rotate CT scanner (Siemens; Erlangen, Germany). Results: Forty cysts of different size and shapes were encountered, 34 of them being ruptured. CT density of the cysts varied from ⴚ 42 to 160 Hounsfield units (HU; median, 15.5 HU). Apart from the classically described features of pulmonary hydatid disease, a crescent-shaped rim of air at the lower end of the cyst (inverse crescent sign) was seen in three cysts, and a bleb of air in the wall of two as-yet unruptured cysts (signet ring sign). Thick wall (>10 mm) was observed in four cysts, and each of them had associated evidence of infection. Conclusions: Inverse crescent sign, signet ring sign, high CT density, and thick wall should be recognized as features of pulmonary hydatid cysts on CT. (CHEST 2000; 118:1645–1647) Key words: CT; cyst; echinococcosis; lung Abbreviation: HU ⫽ Hounsfield unit
disease of the lungs is a common disorder H ydatid in many areas of the world. Conventional radiography is routinely employed for diagnosis of the disease in developing countries. CT has been available only recently in many of such places; as such, the CT findings of hydatid cysts of the lung are only sparsely described,1,2 even though the disease abounds in these areas. The present study addresses the appearances of pulmonary hydatidosis on CT from a developing area where hydatidosis is frequent. The study, to the best of our knowledge, is the first from our part of the globe. Materials and Methods Thirty-two patients with surgically proven hydatid cysts of the lung who presented to the internal medicine department of the SheriKashmir Institute of Medical Sciences, Srinagar, were enrolled for the study. The patients consisted of 13 female patients and 19 male patients, with ages ranging from 11 to 60 years (median, 30 years). The various symptoms experienced by the patients included cough (n ⫽ 16), hemoptysis (n ⫽ 4), fever *From the Departments of Internal Medicine (Drs. P. Koul, A. Koul, and Wahid) and Radiodiagnosis (Dr. Mir), SheriKashmir Institute of Medical Sciences, Srinagar, Kashmir, India. Manuscript received September 14, 1998; revision accepted June 26, 2000. Correspondence to Parvaiz A. Koul, MD, Department of Internal Medicine, SheriKashmir Institute of Medical Sciences, Soura, Post Bag 27, Srinagar 190 011, Kashmir, India; e-mail: [email protected]
(n ⫽ 13), chest pain (n ⫽ 10), and breathlessness, anorexia and weight loss in one patient each. Two patients were asymptomatic. All patients underwent a detailed clinical examination and routine investigations. Eosinophilia of ⬎ 500 ⫻ 109/L was demonstrable in 11 patients, positive Casoni’s test in 13 patients, and IgM antihydatid antibodies in 12 patients. On chest radiography, the hydatid cysts were found to be bilateral in two patients. Special features included meniscus sign (introduction of air between pericyst and endocyst producing a crescent-shaped air shadow toward the top of the cyst)3 in two patients, Cumbo’s sign (air fluid level in the endocyst capped with air between pericyst and endocyst occurring on rupture of the endocyst)3 in one patient, and calcification of the cyst in one patient. All patients were subjected to CT scanning of the lungs with Somatom DR double rotate CT scanner (Siemens; Erlangen, Germany) using 120 mA, 410 kV, 7-s scan time, 512 ⫻ 512 matrix, and 4-mm to 8-mm section thickness. CT scans were analyzed before surgery and reviewed after the diagnosis was secured following surgery. All patients were subjected to surgery, after proper antibiotic therapy for those with suspected infection of the cysts. The cysts were sent for histopathologic examination and the contents for cytologic examination for scolices and hooklets. Gram’s smear and cultures of the cyst fluid were performed routinely.
Results On CT scanning, 40 cysts were localized that were unilateral in 29 patients and bilateral in 3 patients. The cysts were located in right lower lobe (n ⫽ 15), left lower lobe (n ⫽ 12), right middle CHEST / 118 / 6 / DECEMBER, 2000
1645
lobe (n ⫽ 5), left upper lobe (n ⫽ 5), and right upper lobe (n ⫽ 3). The size of the cysts varied from 1.5 to 13 cm (mean ⫾ SD, 5.67 ⫾ 2.80 cm). Various shapes encountered were round (n ⫽ 21), oval (n ⫽ 13), irregular (n ⫽ 3), and pear-shaped, reniform-shaped, and pomegranate-shaped (Fig 1) in one patient each. Thirty-one cysts were uniloculate (Fig 2), whereas internal septae with multiple loculations were seen in one cyst. Thirty-four cysts were ruptured (air having dissected into the cyst causing separation of the membranes), whereas 6 cysts were unruptured. CT density of the cysts ranged from ⫺ 42 to 160 Hounsfield units (HU) [median, 15.5 HU]. The density ranged from 9 to 160.5 HU (median, 35 HU) in ruptured cysts, and from ⫺ 42 to 60 HU (median, 19.75 HU) in unruptured cysts. CT density of the eight infected cysts ranged from 8.5 to 160.5 HU (median, 24 HU). Daughter cysts were demonstrable in four cysts and communication with the bronchus in seven cysts. Five cysts demonstrated a crescent sign, Cumbo’s sign was seen in one cyst, water lily sign (endocyst membrane floating on top of remaining fluid consequent on collapse of endocyst and partial evacuation of fluid)3 in three cysts (Fig 3), and air entrapped in the lower end of the cyst in three cysts in a fashion that was the reverse of the classical crescent sign (Fig 4). Two cysts had a tiny bleb of air dissecting into the wall giving the appearance of a signet ring (Fig 5). Pericystic reaction in the lung tissue was demonstrable in seven patients, with distortion of the lung-cyst interface. Other features included pleural effusion (n ⫽ 4), abscess formation (n ⫽ 3), mediastinal shift (n ⫽ 2), pneumonitis (n ⫽ 2), and atelactasis (n ⫽ 1). The cyst wall was smooth in 31 cysts and irregular in 9 cysts. The wall thickness ranged from ⬍ 1 mm to 20 mm, with four cysts having wall thickness of ⬎ 10 mm (Fig 6), especially in areas abutting the pleura. All
Figure 1. Pomegranate-shaped cyst. 1646
Figure 2. A uniloculate cyst involving almost the whole of the left hemithorax.
four patients with thick walls had evidence of infection clinically as well as on examination of the cyst fluid. CT density of the cyst wall ranged from 15 to 59 HU. Calcification of the cyst wall was found in two cases. Discussion Conventional chest radiography has been the mainstay of the diagnostic armamentarium of patients with hydatid disease of the lungs, often coupled with Casoni’s skin testing and serologic testing for antibodies. However, the two, even in combination, may not yield a definitive diagnosis as a result of many conditions, such as carcinomas, benign tumors, inflammatory masses, metastasis, and solid or fluid-filled cysts mimicking the radiologic features of hydatid cysts of the lung.1,4,5 Not infrequently, serologic and skin testing yields false-positive or false-negative results, adding to the confusion. CT scanning has come to the rescue of the clinician in elucidating the cystic nature of the lung mass and accurate localization for planning of
Figure 3. Membranes floating on the surface of a ruptured cyst, giving the water lily appearance. Clinical Investigations
Figure 4. Inverse crescent sign.
surgical treatment. The present study simply fortifies this view even for developing countries. Two appearances of the hydatid cyst observed in the present study have not been reported earlier. In three of our patients, a crescent-like rim of air was observed at the lower end of the cyst (Fig 4), with an appearance that was morphologically opposite of the classic “crescent” sign. We have termed it the inverse crescent sign, and results from air dissection induced separation of the membranes from the posterior aspect of the cyst without any anterior extension. Perioperative findings of these patients revealed a zone of pericystic fibrosis on the upper end and distortion of the lung cyst interface. Another morphologic appearance that was observed in two patients is a bleb of air dissecting into the wall of the cyst, giving it the shape of a ring; we have termed it the signet ring sign (Fig 5). A similar appearance was also reported by Sakouk et al.1 The sign may be a harbinger of impending cyst rupture. CT densities of the cysts in the present study
Figure 6. Thick-walled cyst situated peripherally.
ranged from ⫺ 40 to 160 HU. Higher attenuation values have been reported earlier, with an unintended aspiration having been performed on one such cyst. A higher attenuation value attracts a differential diagnosis of tumors, infarcts, etc. Higher attenuation values have been reported to result from a fibrosis or infection of the cysts. Such CT findings emphasize the employment of better serologic methods for diagnosing hydatid cysts when the lung mass on CT does not have typical features of a cyst. Wall thickness in the present study was found to range from 0.5 to 20 mm, with a CT density of ⫺ 15 to 59 HU. The wall characteristics of pulmonary hydatid disease have not been reported earlier. The reason for the thickness could be attributed to the infection of the cysts that was observed in all the four cysts with thick wall. No special histologic findings were observed in the hydatid cysts with thick walls. Calcification of the cysts was observed in two cysts on CT as compared to only one case on radiography, emphasizing improved delineation on CT. We conclude that besides the conventional appearances of hydatid cysts of the lung on CT, signet ring sign and inverse crescent sign should be recognized as features of pulmonary hydatidosis. In addition, an increase in the CT density of the lung mass and/or a thick wall should not negate a diagnosis of hydatid disease. References
Figure 5. Membrane separation leading to the signet ring appearance.
1 Sakouk FA, Fahl MH, Rizk GK. Computed tomography of pulmonary hydatid disease. J Comput Assist Tomogr 1986; 10:226 –232 2 Gouliamos AD, Kalovidouris A, Papailiou J, et al. CT appearances of pulmonary hydatid disease. Chest 1991; 100:1578 –1581 3 Schlanger PM, Schlanger H. Hydatid disease and its roentgen picture. AJR Am J Roentgenol 1984; 60:331–347 4 Kegel RFC, Fateni A. ruptured pulmonary hydatid cyst. Radiology 1961; 76:60 – 64 5 Aggarwal S, Kumar A, Mukhopaday S, et al. A new radiological sign of ruptured pulmonary hydatid cyst. Am J Radiol 1989; 152:431– 432 CHEST / 118 / 6 / DECEMBER, 2000
1647