thoracic injury can result in a wide range of clinical manifestations depending on the structures involved like chest wall , diaphragm , mediastinum , trachea , lungs parenchyma etc . the non penetrating trauma to the lungs manifests as contusions , lacerations of pulmonary parenchyma , pneumatocele formation , hematomas , and fractures of trachea and bronchi . while pulmonary contusion is commonly associated with blunt thoracic trauma , appearance of cavitary lesions variably described as traumatic pulmonary pesudocysts , ( tpp ) , traumatic pneumatoceles , traumatic lung cysts are rare , developing in less than 3% of patients with pulmonary parenchymal injuries . a 26 year old unmarried male was referred to us with history of left sided chest pain for two days . he had consulted at local hospital immediately after trauma . a skiagram chest taken there [ figure 1 ] showed non homogenous opacity with central lucency in the region of left hilum . on examination , the patient gave history of trauma - a tractor wheel hitting him on the anterior chest wall , while he was lying down ; following which he developed the pain . there was no history of breathlessness , fever , cough , hemoptysis , cough or expectoration . there was no history suggestive of bronchial asthma or exposure to pets at home or work place . the margins of the lesion were now thinned out and smooth [ figure 2 ] . chest radiograph on day 1 - pa view showing non homogenous opacity with central translucency near left hilum day 3 - chest radiograph pa view showing multiple cavities near left hilum his sputum for afb was negative . other lab investigation revealed haemoglobin 14.4 , leukocyte count 7900 , and differential count of 78 % polymorphs and 19% lymphocytes . his serum was non reactive for hiv antibodies . a ct scan of thorax done on 03 - 09 - 2011 showed a single smooth walled cavity abutting left chest wall with surrounding areas of ground glass haziness , probably suggestive of lung contusion [ figure 3 ] . computed tomogram of chest showing smooth walled cavity in left upper lobe with surrounding ground glass opacity of lung contusion fibre optic bronchoscopy was performed to achieve a microbiological diagnosis and to inspect the trachea - bronchial tree in view of previous reports being inconclusive . bronchoscopy revealed a bleeding spot in left main bronchus , but no active bleeding was seen . bronchial brushings taken from left upper lobe were negative for malignant cells and afb , and the lavage fluid also was sterile . in view of the patient 's history of ancedent recent trauma , negative past and present history for any infectious process , and negative microbiological reports , a diagnosis of post traumatic pulmonary pseudo cyst ( tpp ) was made . serial follow up chest skiagram showed rapid resolution of the cavities [ figure 4 ] without any antibiotics , thus confirming our diagnosis of tpp . among the various names given to the cavitary appearance of pulmonary lacerations , the term traumatic pulmonary pseudo cysts ( tpp ) appears to be the best nomenclature because the wall of these lesions are formed by the inter lobar interstitial connective tissue and shows no epithelial lining or bronchial wall elements . the rarity of the entity can be estimated by the fact that there have been only around 10 large case series with 8 or more patients published since 1967 . tpp following blunt or non penetrating trauma develops through a mechanism that allows transmission of high compressive forces to the lung parenchyma . retraction of normal lung elastic tissue from contusion induced cavities permits the escape of air and fluid into it . laceration of pulmonary parenchyma and appearance of cavity may also occur if there is closure of the glottis at the moment of injury which may prevent fast exit of the air from compressed lung segment . the parenchyma and/or interstitium get lacerated in a bursting manner resulting in a cavity formation . resolution of a pulmonary hematoma or drainage into a bronchus may result in development of tpp at a later stage and it is called secondary tpp . tpp can occur at any age , but they are more often seen in children and young adults , probably because of greater compliance of chest wall which permits a larger transmission of force of impact to the parenchyma . sorsdahl and powell reported that 85% of the patients with tpp were under the age of 30 years with male predominance . impact velocity and degree of chest wall displacement may play an important role in the development of tpp after blunt trauma to the chest . a high velocity impact causes peripheral tpps while a low velocity high displacement impact produces central parenchymal and major bronchial disruption . tpp is a clinical entity that manifests itself with minor clinical and major radiological signs . the usual clinical manifestations include hemoptysis , occurring in about half of the cases , cough , dyspnoea , chest pain , fever and leucocytosis . tpps may appear immediately or within a few hours after injury and their sizes range from 2 to 14 cm in diameter tpp can be differentiated from cavitating hematomas on the basis of radiographic appearance of air within the tpp 's within 48 hours . tpps may be identifiable on chest radiography but ct scans are superior for detecting them . unlike other cystic lesions and cavities , the size , shape , and nature of wall of tpps change relatively quickly . therefore , serial skiagrams of chest , done over several days can help to differentiate pseudo cysts from other lesions . found a greater resolution time in blood filled tpps and those with > 2 cm in size . they may be seen on the site of injury or on the opposite side secondary to countre coup effects . the majority of tpps are found in the lower lobes , the ct appearance of single or multiple thin walled cystic lesions with air space consolidation of the surrounding lung parenchyma in the backdrop of antecedent trauma is diagnostic . differential diagnosis includes ruptured oesophagus , or herniation of viscera , post pneumonia pneumatocele , tuberculosis cavity , cavitating bronchial carcinoma , lung abscess , bronchogenic cysts , and pulmonary sequestration . a history of trauma , rapid sequential changes over days on chest skiagram , and presence of contusion on the base of lesion usually delineates any confusion . if the cavitary lesion does not decrease with time other aetiology must be considered . conservative management is recommended as long as evidence of a decrease in size of the lesion occurs within 6 weeks after trauma in adults and 3 - 4 months in children . the use of antibiotics is controversial and may be used more to provide simple reassurance that the pseudo cyst wo nt get infected . tpp 's can be complicated and may require surgery . they may rupture and cause a secondary pneumothorax that may require tube thoracostomy . the indications for diagnostic and therapeutic bronchoscopy are endobronchial bleeding , thick sputum , large air leak , mediastinal emphysema and lobar collapse . the approach to an infected pseudo cyst is similar to that for a lung abscess . if an infected pseudo cyst is larger than 2 cm , or there are unremitting signs of sepsis after 72 hours of antibiotics , the pseudo cysts may be drained percutaneously . early lobectomy may be considered for complex tpp 's with extensive lung abscess surrounded by necrotic parenchyma , failure of bronchoscopic treatment of massive airway bleeding , infected pseudo cyst more than 6 cm in size , or no response to more conservative treatment . video assisted thoracoscopic surgery ( vats ) may be considered for managing a persistent air leak , hemothorax due to pseudo cyst rupture , failure of lung expansion , progressive enlargement of pseudo cyst and compression of lung parenchyma . late thoracotomy has been reported ( lobectomy , cystotomy , capitonnage ) up to 6 months after trauma because of pneumonic infiltration and persistent cavitary size . our patient presented with few abrasions on anterior chest wall and history of blunt trauma to chest wall of one day duration . there was no previous history of any respiratory illness or unconsciousness during or after trauma . the immediate chest skiagram revealed an area of consolidation with central area of lucency around left hilar region . there was no associated cough , fever , expectoration , hemoptysis or breathlessness which clinically ruled out an infective process . serial skiagrams over next 24 hours showed a rapid development of a cavity which regressed spontaneously and significantly over next 7 days without any antibiotics . ct thorax done was also suggestive of tpp , in view of a cavity adjacent to anterior chest wall with surrounding contusion . exclusion of other infectious diseases like tuberculosis , lung abscess , by absence of relevant clinical history , sputum negativity on zn staining , sterile pyogenic culture , negative mantoux test , negative microbiology of bal , and cytology of bronchial brushing led us to the diagnosis of tpp which was well supported by the available literature . it is generally a self limiting benign condition , diagnosed by excluding other conditions which may present with similar radiological manifestations . a typical history of blunt trauma to chest , rapid radiological changes of the cavity and exclusion of other cavitary pulmonary diseases by adequate laboratory work helps in diagnosing this rare condition . the disease at times might become complicated and becomes life threatening ; hence , should be closely monitored and followed up .
blunt thoracic trauma manifests in various ways , depending on the structures injured and type of injury . commonly manifested as parenchymal contusion , at times , pseudacavitation may also been seen on the chest x ray . 
 they are to be differentiated from other causes of pulmonary cavitations which are often done based on history . 
 the so called pulmonary pseudo cysts usually have a benign course and needs only observation .