Ectopic air: A common finding but when should the radiologist worry? An educational review.

Transcription

1 Ectopic air: A common finding but when should the radiologist worry? An educational review. Poster No.: C-2447 Congress: ECR 2012 Type: Educational Exhibit Authors: T. M. Walshe, C. English, C. Donagh, P. McCarthy; Galway/IE Keywords: Abdomen, Emergency, Lung, Plain radiographic studies, CT, Fluoroscopy, Diagnostic procedure, Ischemia / Infarction, Abscess, Infection DOI: /ecr2012/C-2447 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 34

2 Learning objectives Ectopic air is a common radiological finding, detected on multiple radiological modalities. The presence of ectopic air occurs in both common and rare clinical conditions, it may be idiopathic, is commonly iatrogenic and it may signal a benign incidental finding or a life threatening condition. This exhibit demonstrates the multiple locations in which air is radiologically detected where it should not be, and categorises these scenarios into aetiology and clinical relevance. Background Iatrogenic: Inadvertent injection of air is, at worst life threatening when injected intravenously (air embolus), at best problematic when injected into urinary/biliary tract during contrast studies e.g. nephrostogram, cholangiogram etc. Air bubbles in the contrast may be misinterpreted as filling defects due to calculi etc. Images for this section: Page 2 of 34

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4 Fig. 26: Air bubbles on nephrostogram could be confused with urteric calculi Page 4 of 34

5 Imaging findings OR Procedure details Head & Neck Pneumocephalus: the presence of air within the cranial cavity, air may be within the extradural/ subdural/ subarachnoid/ intraventricular spaces or a combination of the above. Causes of pneumocephalus include:1. Trauma: Air enters the cranial cavity through a traumatic communication with the paranasal sinuses or mastoid air cells. See Fig 1 & 2. Infection : Meningitis/abscess due to gas forming organisms are rare. Air containing cerebral abscesses can develop as a result of sinus infectionwith bony destruction or cerebral abscess formation following trauma. 3. Iatrogenic: Post surgical (Fig. 3). Air within the soft tissue e.g. within the orbit or soft tissues surrounding the skull baseescaped from the mastoid air cells or from the paranasal siuses can alert the radiologist to a fracture. See Figs. 5 and 6. Air in unusual locations within the skull base or facial bones may be normal variants e.g. conchae bullosa - pneumatisation of the nasal turbinates (Fig 7),pneumatisation of the petrous apex (Fig 8). Thorax: Pneumothorax causes include: Trauma Spontaneous (typically tall, thin male patients due to ruptured bullae) Iatrogenic - artificial ventilation, biopsy, surgery, central line insertion Secondary to lung disease (fig. 9 ) e.g. emphysema, cystic fibrosis, bronchopulmonary fistula etc. Secondary to pneumoperitoneum: air passage through a pleuroperitoneal foramen. Pneumomediastinum causes include: Page 5 of 34

6 occurring in association with a pneumothorax perforation of oesophagus, trachea or bronchus peforation of a hollow abdominal viscus with extension of gas through the retroperitoneal space Subcutaneous emphysema - traumatic, iatrogenic etc. (fig 10) Pneumopericardium(distinguished from pneumomediastinum by the superior limitation of air by the anatomic limits of the pericardial reflexion on the proximal great vascular pedicle) causes include: post-surgical, penetrating trauma, infectious endocarditis with gas forming organism etc. (Fig 11). Abdomen Pneumoperitoneum: causes include: 1. Perforation: associated with: - peptic ulcer, - Inflammation e.g. diverticulitis, appendicitis toxic megacolon, necrotising enterocolitis. - infarction - malignant neoplasm - obstruction 2. Traumatic 3. Iatrogenic (may take 3 weeks to reabsorb, faster in obese patients and children. Free air may be seen on CT up to 14 days post surgery) 4. Associated with a pneumothorax/ pneumomediastinum Pneumoretroperitoneum is the presence of gas within the retroperitoneal space. It is always abnormal and has a relatively small differential:- perforated retroperitoneal hollow viscus.e.g. duodenal ulcer- blunt/ penetrating abdominal trauma- endoscopy +/- biopsy (rare)- ERCP especially when a sphincterotomy is performed- ascending / descending colon pathologies e.g. diverticulitis/carcinoma- retroperitoneal surgery e.g. urological / spinal- retroperitoneal abscess Pneumobilia suggests an abnormal communication between the biliary tract and the bowel and causes include- normal variant (patulous/ incompetent sphincter of Oddi), Page 6 of 34

7 iatrogenic (biliary-enteric surgical anastamosis), ascending cholangitis with gas-forming organisms, or a spontaneous biliary enteric fistula such as in gallstone ileus. Gallstone ileus is an uncommon cause of small bowel obstruction, Riglers triad of pneumobilia, bowel mechanical obstruction and ectopic stone is seen. (Fig. 28 ) Pneumatosis portalis(air within the portal vein) is most commonly seen in association with pneumatosis intestinalis due to bowel ischaemia Pneumatosis intestinalis/pneumatosis colirefers to the presence of gas within the bowel wall, causes may be benign or life threatening. Life-threatening causes include: Intestinal ischaemia, Intestinal obstruction (especially strangulation), enteritis, toxic megacolon, trauma. Benign causes include: Idiopathic (pneumatosis cystoides intestinalis), Pulmonary (Asthma, emphysema, CF, positive end expiratory pressure). Intestinal (pyloric stenosis, pseudo- obstruction, scleroderma). Iatrogenic (endoscopy, CT Colonography, post anastomosis), Meds e.g.steroids. Pelvis: Localised/sealed perforation within the pelvis e.g. associated with diverticulitis, appendicitis, sigmoid tumour etc. Perianal/rectal abscess/ fistula Air in the urinary bladder causes include: iatrogenic e.g. post instrumentation, infection by a gas-forming organism or due to a fistula e.g.colovesical Air in the bladder wall (Fig 15)- Emphysematous cystitis (most commonly seen in patients with diabetes mellitus. Musculoskeletal and soft tissues: Air within the soft tissues or skeletal system may be as a result of:- Trauma e.g. penetrating wounds, open fractures, fractures associated with air leak e.g. rib fractures associated with a pneumothorax with resultant subcutaneous emphysema (Fig 16 and 17) -Infections: Osteomyelitis, cellulitis, abscess formation, Fournier gangrene, necrotising fasciitis - Iatrogenic: Post surgical intervention, arthrography, injection sites etc. Page 7 of 34

8 Vacuum effect (fig. 18): A well-known phenomenon, more common in young children whose laxity of joint ligaments allows wide separation of the articular surfaces allowing accumulation of nitrogen gas in the joint space when the joint is placed under strain. Usually a physiological phenomenon but can occur in pathological conditions also e.g. osteoarthritis Spine: Pneumorrhachis refers to a rare phenomenon characterised by the presence of air (either intra or extra dural) within the spinal canal. Patients can be asymptomatic. It can result from a number of causes which include: - Trauma (traumatic pneumorrhachis): can occur in variety of traumatic settings e.g. traumatic pneumothorax, blunt chest trauma, skull fracture, stab wound (Fig 22). - Iatrogenic e.g. epidural anesthesia, myelogram, thoracic/spinal surgery etc. - Non traumatic e.g. spontaneous pneumomediastinum (from bronchial asthma), regional necrotising fasciitis (rare) Vacuum phenomenon within the intervertebral disc space (Fig 20 and 21) Gas formation in intervertebral disc spaces is rare but occurs in degenerative disease, the theory for the appearance of gas in an intervertebral disc lies in the fact that whilst the nucleus pulposus disintegrates the annulus fibrosus remains intact, creating a potential space in the centre of the disc. Under strain this space creates a vacuum in the disc, which, in turn, attracts the gaseous contents dissolved in blood. Images for this section: Page 8 of 34

9 Fig. 1: Fig 1 demonstrates extra-axial air and haemorrhage in this patient who sustained a head injury following a fall from a height Page 9 of 34

10 Fig. 2: Bony window reconstructions of the same examination as Fig. 1 demonstrates haemorrhage within the sphenoid sinus and underlying skull base fracture Page 10 of 34

11 Fig. 3: Small foci of air (white arrows) are visualised within the subdural space in this patient three days post surgical decompression of a subdural haematoma Page 11 of 34

12 Fig. 4: Fig. 4 demonstrates a tension pneumocephalus in a 55 year old patient involved in a road traffic accident. Air within the subdural space causes mass effect on the underlying brain parenchyma, often from a ball valve mechanism causing one way entry of air into the subdural space1.urgent decompression is required Page 12 of 34

13 Fig. 5: Fig. 5 demonstrates air within the soft tissues of the paranasopharyngeal space, due to an undisplaced fracture extending through the right mastoid air cells, air is also Page 13 of 34

14 visualised in the soft tissues lateral and posterior to the left maxillary sinus, due a fracture extending into the left maxillary sinus Fig. 6: This image demonstrates foci of air in the right retro-orbital space, due to a fracture of the right frontal sinus Page 14 of 34

15 Fig. 7: Air in unusual locations within the skull base or facial bones may be normal variants e.g. pneumatisation of the petrous apex (Fig 7). Page 15 of 34

16 Fig. 8: Air in unusual locations within the skull base or facial bones may be normal variants e.g. conchae bullosa - pneumatisation of the nasal turbinates Page 16 of 34

17 Fig. 9: Spontaneous left tension pneumothorax in patient with a background history of Histiocytosis X. Page 17 of 34

18 Fig. 10: Surgical emphysema, pneumomediastinum and small residual pneumothorax, with chest drain in situ Page 18 of 34

19 Fig. 11: Pneumopericardium Page 19 of 34

20 Fig. 12: axial CT images in this patient with a history of complicated Crohn's disease. Air is visualised within an ischioanal abscess. This extends distally along psoas tendon into the anterior thigh. Page 20 of 34

21 Fig. 13: Coronal CT images in the same patient with a history of complicated Crohn's disease, demonstrating air within an ischioanal abscess and extending distally along psoas tendon into the anterior thigh Page 21 of 34

22 Fig. 14: Air within the urinary bladder in this patient with pseudomembranous colitis and a rectovesical fistula Page 22 of 34

23 Fig. 15: Emphysematous cystitis Page 23 of 34

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25 Fig. 16: This cyclist sustained blunt trauma to the neck (impacted on handlebars after collision with car). Plain radiograph demonstrates extensive air within the prevertebral soft tissue. CT confirmed air tracking along soft tissue planes of the neck, extending into the mediastinum. Tracheal rupture was confirmed. Fig. 17: CT in same patient as Fig 17 - This cyclist sustained blunt trauma to the neck (impacted on handlebars after collision with car). Plain radiograph demonstrates extensive air within the prevertebral soft tissue. CT confirmed air tracking along soft tissue planes of the neck, extending into the mediastinum. Tracheal rupture was confirmed. Page 25 of 34

26 Fig. 18: Vacuum effect in the medial joint compartment of the knee Page 26 of 34

27 Fig. 19: subcutaneous emphysema draws attention to an undisplaced rib fracture and underlying pneumothorax in this patient injured during a rugby tackle. Page 27 of 34

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29 Fig. 20: Vacuum phenomenon within the intervertebral disc space Fig. 21: Vacuum phenomenon within the intervertebral disc space(fig Page 29 of 34

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31 Fig. 22: Air in the spinal canal in this patient who sustained a stab wound to the back Fig. 23: intramural air and thickening in terminal ileal crohn's disease Page 31 of 34

32 Fig. 24: Intramural air with air in the portal vein Page 32 of 34

33 Fig. 25: Pneumobila associated with gallstone ileus Page 33 of 34

34 Conclusion Recognition that air is not where it should be on radiographs, computed tomography, magnetic resonance imaging and ultrasonography can be challenging. Determining if this is a benign finding or a critical sign of a life threatening condition that should be rapidly communicated to the referring clinician is important. Personal Information References W.E.Brant, C.A.Helms. Fundamentals of diagnostic radiology. Third Edition Lippincott Williams and Wilkins. Chapman S, Nakielny R. A guide to radiological procedures. 4th Ed. Saunders Zagoria RJ. Genitourinary Radiology - The requisites. 2nd Ed. Mosby Gray's Anatomy, The Anatomical basis of clinical practice. 40th Ed. Page 34 of 34