Acute Epiglottitis Imaging
- Author: Jon E Jaffe, MD; Chief Editor: Eugene C Lin, MD more...
Epiglottitis is a rapidly developing inflammation of the epiglottis and adjacent tissues, usually due to a bacterial infection, that can cause life-threatening airway obstruction. Historically, epiglottitis was a disease of childhood, and the most common pathogen was Haemophilus influenzae type b (Hib). After the introduction of the Hib vaccine in 1985, followed by the recommendation of routine infant vaccination in the United States beginning in 1991, the incidence of epiglottitis dramatically declined in children.[1, 2, 3, 4, 5, 6, 7] Today, there is no predominant pathogen implicated in epiglottitis. Hib epiglottis is still occasionally seen, accounting for 6 out of 19 cases in a series (from 1992 to 2002) by Shah and colleagues. It occurs in vaccinated and nonvaccinated patients, because the vaccine is not 100% effective.[8, 9, 10]
See the images of acute epiglottitis below.
In addition to Hib, bacterial culprits include groups A beta-hemolytic streptococci, particularly Streptococcus pyogenes and S pneumoniae, as well as Staphylococcus aureus. Rare causes include H parainfluenzae, influenza B viruses, herpes simplex virus (HSV), and H influenzae (including type A and type F, as well as nontypeable strains). Infrequently, thermal injury from the consumption of hot liquids, corrosive ingestion, and various lymphoproliferative disorders have been implicated as noninfectious causes of epiglottitis.
Findings on lateral neck radiographs are frequently diagnostic. A single, lateral, upright view of the neck in extension, preferably with a closed mouth, is usually adequate. The radiograph should be obtained with portable equipment in the emergency department (ED), because acute airway obstruction may occur at any time. In severe cases, radiographs should not be acquired until the airway is secured.
An inability to hyperextend the patient's neck because of irritability may interfere with diagnostic accuracy. An image obtained with the patient's mouth open may decrease the probability of seeing true obliteration of the vallecula.
Direct examination of the pharynx or anxiety caused by diagnostic tests may precipitate acute airway obstruction. If crying occurs, rapid inspiration through the swollen epiglottis can cause the airway to close completely. Finally, a suboptimally low kilovolt setting may cause poor depiction of the soft tissues.
The diagnosis can be confirmed by direct nasopharyngolaryngoscopy, which should be performed only when measures to immediately secure the airway are available in the ED or operating room.
Soft-tissue, lateral neck radiography has a sensitivity of 88-100% and a specificity of 87-96% in diagnosing epiglottitis. On plain radiographs, the normal epiglottis is a thin, curved flap of soft-tissue opacity that is separated from the base of the tongue by air in the vallecula. In epiglottitis, the epiglottis appears swollen and enlarged (the thumbprint sign), typically greater than 8 mm in adults.
An enlarged epiglottis may result from various disorders, including irritation from a foreign body or burn, granulomatous disease (eg, sarcoidosis, tuberculosis, Wegener granulomatosis), angioneurotic edema, and tumors, such as epiglottic cysts and neoplasms (eg, lymphomas)
Often, only a pencil-thin airway or no air column is visible in the shadow of the epiglottis. As edema develops, the epiglottis expands, obliterating the vallecula. Loss of the vallecula has been said to be an independently sensitive and specific sign of adult epiglottitis, although further validation is needed.
(See the radiographic images below.)
Thickening of the aryepiglottic folds and thickening of the arytenoids are associated findings in 85% and 70% of cases of epiglottitis, respectively. Aryepiglottic fold thickening greater than 7 mm is a particularly sensitive and specific finding in children and adults.
Prevertebral soft-tissue swelling and hypopharyngeal widening are additional associated findings. In children, ballooning of the hypopharynx, caused by sucking air through an open mouth against an obstruction, is occasionally seen due to laxity of the immature airway. Hypopharyngeal widening and ballooning, however, are nonspecific findings associated with any cause of upper airway obstruction.
The following additional parameters for diagnosing epiglottitis in adults have been proposed:[14, 11]
Epiglottic height-to-width ratio >0.6
Epiglottic to C4 vertebral body width ratio >0.33
Aryepiglottic fold to C3 vertebral body width ratio >0.35
Prevertebral soft-tissue to C4 vertebral body width ratio >0.25
Hypopharyngeal airway to C4 vertebral body width ratio >1.5
The presence of any of these signs should raise the suspicion that epiglottitis is present, although diagnostic accuracy increases when multiple findings exist.
The use of computed tomography (CT) scanning is risky in the diagnosis of epiglottitis, but it may help in the evaluation of complications, such as abscess formation (see the image below), as well as in the exclusion of various conditions, including the presence of a peritonsillar or deep neck space abscess, lingual tonsillitis, or an ingested foreign body. CT scanning should be approached with caution, however, because the supine position increases the risk of acute respiratory distress.
The most common CT scan findings include thickening of the epiglottis, aryepiglottic folds, platysma muscle, and prevertebral fascia; obliteration of the pre-epiglottic fat planes; and reticulation of the subcutaneous fat. Emphysematous epiglottis is further characterized by soft-tissue lucencies representing gas within a swollen epiglottis. The finding of multiloculated fluid-density collections should raise the suspicion that an abscess exists.
Edema and thickening of the supraglottic tissues with obliteration of the surrounding fat planes can also be seen in patients who have received radiation therapy to the neck. In addition, an enlarged epiglottis can result from a variety of inflammatory and infiltrative disorders, as previously discussed.
Magnetic Resonance Imaging
As with CT scanning, magnetic resonance imaging (MRI) is not recommended for initial diagnosis but may be useful for excluding potential mimickers of epiglottitis or for identifying complications. Particular caution should be taken to ensure patient safety, because patients must be supine for a lengthy period of time without direct surveillance.
Few studies have reported MRI findings in acute epiglottitis. T1- and T2-weighted imaging shows thickening of the epiglottis, and there is marked enhancement of the epiglottis and often of the adjacent aryepiglottic folds following gadolinium administration. Areas of nonenhancement may represent necrosis or phlegmon. Cervical lymphadenopathy may also be seen.
Recent wide use of ultrasonography in the ED has led to its use in the diagnosis of acute epiglottitis.[15, 16] Studies thus far have been in adults because they have become the much more common patient. Prospectively, using linear phased array, Ko et al have shown that a measurement of the anterior posterior diameter of the epiglottitis was effective in making the diagnosis.
Faden H. The dramatic change in the epidemiology of pediatric epiglottitis. Pediatr Emerg Care. 2006 Jun. 22(6):443-4. [Medline].
Murrage KJ, Janzen VD, Ruby RR. Epiglottitis: adult and pediatric comparisons. J Otolaryngol. 1988 Jun. 17(4):194-8. [Medline].
Progress toward elimination of Haemophilus influenzae type b invasive disease among infants and children--United States, 1998-2000. MMWR Morb Mortal Wkly Rep. 2002 Mar 22. 51(11):234-7. [Medline]. [Full Text].
Shah RK, Roberson DW, Jones DT. Epiglottitis in the Hemophilus influenzae type B vaccine era: changing trends. Laryngoscope. 2004 Mar. 114(3):557-60. [Medline].
McConnell A, Tan B, Scheifele D, et al. Invasive infections caused by Haemophilus influenzae serotypes in twelve Canadian IMPACT centers, 1996-2001. Pediatr Infect Dis J. 2007 Nov. 26(11):1025-31. [Medline].
Guldfred LA, Lyhne D, Becker BC. Acute epiglottitis: epidemiology, clinical presentation, management and outcome. J Laryngol Otol. 2007 Sep 25. 1-6. [Medline].
Westerhuis B, Bietz MG, Lindemann J. Acute epiglottitis in adults: an under-recognized and life-threatening condition. S D Med. 2013 Aug. 66 (8):309-11, 313. [Medline].
Isakson M, Hugosson S. Acute epiglottitis: epidemiology and Streptococcus pneumoniae serotype distribution in adults. J Laryngol Otol. 2011 Apr. 125 (4):390-3. [Medline].
Shah RK, Stocks C. Epiglottitis in the United States: national trends, variances, prognosis, and management. Laryngoscope. 2010 Jun. 120 (6):1256-62. [Medline].
Rothrock SG, Pignatiello GA, Howard RM. Radiologic diagnosis of epiglottitis: objective criteria for all ages. Ann Emerg Med. 1990 Sep. 19(9):978-82. [Medline].
Schumaker HM, Doris PE, Birnbaum G. Radiographic parameters in adult epiglottitis. Ann Emerg Med. 1984 Aug. 13(8):588-90. [Medline].
Ducic Y, Hébert PC, MacLachlan L, et al. Description and evaluation of the vallecula sign: a new radiologic sign in the diagnosis of adult epiglottitis. Ann Emerg Med. 1997 Jul. 30(1):1-6. [Medline].
Nemzek WR, Katzberg RW, Van Slyke MA, et al. A reappraisal of the radiologic findings of acute inflammation of the epiglottis and supraglottic structures in adults. AJNR Am J Neuroradiol. 1995 Mar. 16(3):495-502. [Medline]. [Full Text].
Ko DR, Chung YE, Park I, Lee HJ, Park JW, You JS. Use of bedside sonography for diagnosing acute epiglottitis in the emergency department: a preliminary study. J Ultrasound Med. 2012 Jan. 31(1):19-22. [Medline].
Hung TY, Li S, Chen PS, Wu LT, Yang YJ, Tseng LM, et al. Bedside ultrasonography as a safe and effective tool to diagnose acute epiglottitis. Am J Emerg Med. 2011 Mar. 29 (3):359.e1-3. [Medline].