Role of Chest CT Scan in Determining Etiology of Primary Spontaneous Pneumothorax

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1 ORIGINAL ARTICLE Role of Chest CT Scan in Determining Etiology of Primary Spontaneous Pneumothorax K.B. Gupta, D.S. Mishra 1, S. Tandon, G. Sindhwani and T. Tanwar Departments of Chest and Tuberculosis and Radiology 1, Pt. B.D. Sharma Post Graduate Institute of Medical Sciences, Rohtak, Haryana, India ABSTRACT Background. Spontaneous pneumothorax occurs subsequent to a disruption in the continuity of visceral pleura and escape of air into pleural space. It is usually difficult, sometimes impossible to detect evidence of pulmonary pathology by clinical or conventional radiographic methods. Computed tomography provides additional informations not obtainable with conventional diagnostic modalities. Methods. To determine the role of CT scan in the aetiological diagnosis and subsequent management of patients with primary spontaneous pneumothorax, a perspective study was undertaken. Results. A total of 40 patients with spontaneous pneumothorax with normal skiagram chest after management of pneumothorax, were included in the study. In 75% of these cases, CT revealed underlying lung pathology as a cause for primary spontaneous pneumothorax. Conclusion. Our study shows that CT scan is a useful imaging modality in determining the aetiology of primary spontaneous pneumothorax. Key words : Primary spontaneous pneumothorax, Computed tomography. [Indian J Chest Dis Allied Sci 2003; 45 : ] INTRODUCTION The term Pneumothorax was coined by Itard 1 in 1803 for presence of air in the pleural cavity. Any pneumothorax occurring spontaneously in the absence of trauma or without demonstrable underlying pathology clinically or radiologically is defined as spontaneous pneumothorax. Spontaneous pneumothorax in apparently healthy subjects with no history of pre-existing lung disease is known as primary spontaneous pneumothorax. Spontaneous pneumothorax has a high risk of recurrence (20-30%) 2. Management of primary spontaneous pneumothorax ranges from simple observation to intercostal drainage 3. However, for definitive treatment of primary spontaneous pneumothorax, an etiological diagnosis is important to plan prevention of recurrence. The present study was carried out to evaluate the role of CT scan thorax in the etiological diagnosis of primary spontaneous pneumothorax. [Received : April 19, 2002, accepted after revision : August 13, 2002] Correspondence and reprints request : Dr K.B. Gupta, 9J/37, Medical Enclave, Pt. B.D. Sharma Post Graduate Institute of Medical Sciences, Rohtak , Haryana, India; Tele. :

2 174 Chest CT Scan in Primary Spontaneous Pneumothorax K.B. Gupta et al MATERIAL AND METHODS A total of 40 patients, all males, aged more than 15 years admitted in the Department of Tuberculosis and Chest Disease, PGIMS, Rohtak with spontaneous pneumothorax were included in the study if the chest skiagram after management of spontaneous pneumothorax showed no obvious parenchymal lung lesions. The study proposal was approved by the Institutional Ethics Committee. Conventional computed tomography was done on SHIMADZU SCT3000TF machine. Scans were obtained using 10 mm collimation at 10 mm interval. Plain and contrast CT were performed by using iodinated contrast media. All the patients were managed either conservatively or by intercostal drainage under water seal. After full expansion of lung, a skiagram chest was done followed by a CT scan thorax after obtaining informed consent. CT scans were evaluated in detail to locate any underlying lung pathology including presence of bullae, blebs, infilterations and cavitations apart from any other findings. RESULTS Majority of patients were young in the age group years (65%). Around 87.5% of patients were either smokers or ex-smokers. Sixty-five percent of patients belonged to a lower socio-economic status. All patients had heights greater than 165 cm and most were in the range of cm (80%). The body mass index (BMI) of most of the patients (65%) was in the range of kg/sq.m indicating malnutrition. Seventy percent of patients were managed conservatively (repeated needle aspiration of air with strict bed rest) and the remaining 30% were managed by intercostal intubation. Fourty percent of patients had developed symptoms of pneumothorax while carrying out daily routine activities, 25% at rest or during sleep, 15% during walking and 20% during strenuous exercise. Pneumothorax was left sided in 22 patients (55%) and right sided in 18 patients (45%). The presenting episode of primary spontaneous pneumothorx was the first one in 87.5% of patients, second in 10% of patients and fourth in 2.5% patients. All patients included in the study had a normal skiagram chest after management of pneumothorax. As shown in the table 1 out of the 40 cases 34 had abnormalities on CT scan suggesting the etiology of pneumothorax. Bullae/blebs were the most common abnormality. In six patients, the CT scan was normal. Thus, the sensitivity of a chest radiography to diagnose primary spontaneous pneumothorax was only 15 percent. Out of 28 cases with bullae/blebs, 20 had bilateral disease, six had ipsilateral and two patients had contralateral disease. Table 1. Findings of CT-scan of the thorax in primary spontaneous pneumothorax Bilateral Ipsilateral Contralateral Bullae and blebs Minimum residual pneumothorax Fibrotic Pneumonitis Cavitary Emphysema Calcified lymph node Pleural thickening Minimal pleural effusion Normal CT 6 - -

3 2003; Vol. 45 The Indian Journal of Chest Diseases & Allied Sciences 175 Figure 3. CT scan of the chest showing bulla on the left side. DISCUSSION Figure 1. Skiagram chest showing pneumothorax on left side. Figure 2. Normal skiagram chest after management of pneumothorax. The present study was undertaken to evaluate the role of computed tomography scan (CT scan) thorax in identifying the underlying etiology of spontaneous pneumothorax in case where skiagram chest was non-contributory. A male predominance ranging from % has been reported by various authors 4. It may be due to larger lungs and commoner smoking habits in males. All the patients in the present study were also males. The finding of younger male preponderance is consistent with other studies in which the proportion of patients in the same age group was found between 70-80% 5. While, no satisfactory explanation has been offered for this, it may be because of greater likelihood of performing strenous activity and mechanical trauma in their active life. In the present study 87.5% of patients were smokers/ex-smokers which is suggestive of an increased risk of development of spontaneous pneumothorax in smokers. This fact has also been reported by Bense 6. This may be because of underlying chronic obstructive pulmonary disease (COPD) in smokers and chronic smoker's cough causing mechanical trauma to the lung. However, none of our patients had COPD.

4 176 Chest CT Scan in Primary Spontaneous Pneumothorax K.B. Gupta et al Most of the patients were tall, with asthenic built with comparatively lower BMI as compared to healthy subjects. The occurrence of spontaneous pneumothorax in tall and thin subjects has also been reported by many workers 7,8. Stature is generally influenced by heredity and there are some reports of familial occurrence of spontaneous pneumothorax 9. Underlying congenital abnormalities causing poor blood supply and aeration have been postulated to explain this association. It may also be due to the relatively poorly perfused apical region in longer lungs, responsible for spontaneous pneumothorax 10. Majority of patients belonged to lower socioeconomic status, were poorly nourished and anaemic. It was observed that many patients (40%) developed pneumothorax while performing daily routine activities and many cases were silent i.e. without remarkable symptoms. One fourth of patients developed pneumothorax during rest or during sleep. Recurrence rate was high (12.5%) among patients of spontaneous pneumothorax. Out of these 80% presented with first recurrence and remaining 20% presented with 3 rd recurrence. Recurrence rate has been reported in past to vary from 20-30% 2. The area of pneumothorax was calculated in all the patients. Seventy percent of patients had an area of pneumothorax greater than 40%, while 15% had an area of pneumothorax less than 15% and rest 15% had an area of pneumothorax between 21-40%. No correlation was evident between the area of pneumothorax and the symptoms of patients. The CT scan demonstrated underlying pathology that could have led to spontaneous pneumothorax in 85% of cases. Therefore, after normal CT scan, only 6 (15%) cases could be labelled as true primary spontaneous pneumothorax. Thus, the sensitivity of skiagram chest to detect underlying cause was very poor (15%). Bullae and blebs were the most common finding (70%) in CT scan and these were bilateral in most (71%) of the cases, ipsilateral in 21% and contralateral in 8% cases approximately. Other lesions found on CT scan were minimum residual pneumothorax (22.5%), fibrotic lesions (10%), pneumonitis (12.5%), emphysema (12.5%), cavitary lesions (7.5%), minimum pleural effusion (7.5%), calcified lesions (5%) and pleural thickening (7.5%). Similar CT findings have also been described by other authors 11. In some studies, blebs and bullae were even more common, occurring in over 90% of patients of primary spontaneous pneumothorax coming for surgery and were frequently multiple and bilateral 12. Blebs occur more frequently at apices as a result of gravity dependent regionl differences in mechanical stress and relative ischaemia at the apices of lungs which makes it more susceptible to infection leading to formation of blebs. Thus, our study reveals that CT scan is useful in determining the underlying aetiology in cases of primary spontaneous pneumothorax. Detection of underlying aetiology of primary spontaneous pneumothorax is important for proper management of the case as the underlying pathology may be treatable (e.g. Bullectomy in cases of bullae). This is important to prevent subsequent recurrence of pneumothorax and hence increased morbidity and mortality. REFERENCES 1. Lippert HL, Lund O, Blevgad S. Independent risk factors for the cumulative recurrence rate after first spontaneous pneumothorax. Eur Respir J 1991; 4 : Kight RW. Pleural Disease. 3 rd edn. Baltimore : Williams & Wilkins; 1995: Kjaergard H. Spontaneous pneumothorax in the apparently healthy. Acta Med Scand 1932; 43 : Scott GC, Berger R, McKean HE. The role of atmospheric pressure variation in the development of spontaneous pneumothoraces. Am Rev Respir Dis 1989; 139 : Myers JA. Simple spontaneous pneumothorax. Dis Chest 1954; 26 : 420.

5 2003; Vol. 45 The Indian Journal of Chest Diseases & Allied Sciences Bense L, Eklund G, Odont D, Wiman LG. Smoking and the increased risk of contracting spontaneous pneumothorax. Chest 187; 92 : Forgacs P. Stature in simple pneumothorax. Guy s Hosp Rep 1969; 118 : Peters RM, Peters BA, Benirschke SK, Friedman PJ. Chest dimensions in young adults with spontaneous pneumothorax. Am J Thor Surg 1978; 25 : Sharpe IK, Ahmad M, Braun W. Familial spontaneous pneumothorax and HLA antigens. Chest 1980; 78 : Kawakami, Irie T, Kamishima K. Stature, lung height and spontaneous pneumothorax. Respiration 1982; 43 : Athavale AU, Singhal PS, Shah AM, et al. Role of HRCT chest in etiology of spontaneous pneumothorax. Lung India 2000; 18 : Killen DA, Gobbel WH. Spontaneous Pneumothorax. Boston : Little Brown and Co.; 1968.