Dr Elizabeth Sheffield
Dr David McCreary
Case of the day:
It’s 23:00, when a 3-year old child is brought in by ambulance with a 2-hour history of noisy breathing, fever and cough. On initial assessment she has inspiratory stridor, is miserable and sitting with her head in a sniffing position, without obvious drooling. She’s previously fit and well, and parents tells you that immunisations are up-to-date. You glance at her vitals and note she is febrile at 38.6, heart rate 180, respiratory rate 38 and oxygen saturations 98% room air. You prescribe your tried and tested cocktail of 0.6mg/kg dexamethasone and 5mls of 1:1000 adrenaline neb then stand triumphant at the foot of the bed basking in self-congratulation…unfortunately 15 minutes later the child is not running around the department in the throws of a steroid-induced mania and remains cuddled up to mum/dad displaying much the same picture as before.
What is the highest priority diagnosis?
You can easily take your pick – but this is a toxic child. Sniffing position triggers an exam answer of retropharyngeal abscess – however epiglottitis and inhaled foreign body could certainly give this picture in the right circumstances. Although a bit young for the average bacterial tracheitis it’s definitely within the realm of possibilities.
You decide there is still ambiguity with regards to this patient’s diagnosis, and are looking for a handy way to screen for potential sinister causes that are quick, fast and non-distressing to the child.
So, behold the soft tissue x-rays. This is a historical Part 2 Exam favourite cropping up every few years in some form or another. Just to signpost, for what conditions might soft tissue neck x-rays be used with regards to acute diagnoses in the Emergency Department?
- Retropharyngeal abscess
- Tracheobronchial or oesophageal foreign bodies
- Bacterial tracheitis
- Croup (to screen for alternative causes)
- Neck tumours (although not usually emergent)
So… what makes kids at risk?
- They lack all sense of self-preservation
- They have some difficulty differentiating between “food” and “not food”
- They LOVE to move. They pick-up everything and put in in the nearest orifice, which is (occasionally) their mouths…
- They may be nonverbal, or at the very least unable to adequately communicate to caregivers that they have choked on a [insert nearest small action figure here]
- They’re not just tiny adults: their trachea has a smaller diameter, with immature pliable tracheal rings which make them more prone to hyperflexion/extension and more at risk of airway occlusion from any inflammatory pathology. The epiglottis is large and floppy making direct intubation methods (straight blade) different, and also makes them more likely to choke on their own soft tissue… and their larynx is higher and more anterior (and smaller) so surgical cricothyroidotomy is out til about age 10.
Let’s talk general airway anatomy.
Below is a refresher on anatomy of the head and neck…
And here we have the structures as seen on a normal neck x-ray:
So we’ve got the x-ray, now what?
Let’s discuss some handy tips to approaching that neck soft tissue radiograph:
Some added notes…
- Ensuring that breath has been held in inspiration is key to avoid false positives
- Loss of lordosis or pseudosubluxation indicates the patient is holding their neck in such a way as to avoid collapsibility of their boggy oedematous airways
- Always pay special attention the epiglottis and the pre-epiglottic space (valleculae). The epiglottis should be a thin structure and there should be a nice space just adjacent to it which is the valleculae. Epiglottitis causes those terrifying laryngoscopic images, and this oedematous soft tissue causes a large “thumbprint sign” (a.k.a. boggy oedematous mass) where the epiglottis should be, as well as narrowing of that nice clean valleculae space.
When might we go for soft tissue X-ray of the neck over CT?
Well, unfortunately, it’s that classic medical answer: “it depends”. If the child is drooling and holding themselves in a tripod position, then you aren’t going to want to mess around with a CT – it’s going to be straight to the operating theatre for a gaseous induction with anaesthetics and ENT on stand-by… in the ideal world. With regards to imaging in the more stable patient, my personal experience has been X-ray first, and if there is ambiguity – and the child can tolerate it – then CT is the next line…
Broadly speaking, X-ray has some advantages when:
- you want to minimise ionising radiation
- the patient is too scared to go to the scanner
- any airway apprehension meaning the patient cannot lie flat
- you want a quick test
- you don’t have CT available
Side note: retropharyngeal abscesses – from a systematic review co-authored from our own Ramanan Daniel (Otolaryngology).
- A systemic review (1) comparing X-ray and CT to gold standard of intra-operative pus found high sensitivity and specificity rates in several studies (ranging from 80 to 100% (for all but one study)).
- The exception to the above was a single study performed by (Ravindranath et al 1993 (3)), was very much an outlier, finding a sensitivity and specificity of 0%. A question mark may be able to placed next to their study results however due to small sample size of only 10 patients.
- The authors the systematic review have stated that potentially those finding a higher sensitivity and specificity for X-ray had populations that tended to be severely unwell (however there was not sufficient clinical data in any paper to firmly make this conclusion).
- Essentially, if an effort has been made to obtain as high a quality radiography as possible (with appropriate rotation, neck extension, and respiratory phase) then X-ray in the Emergency Department can prove to be extremely useful in identifying patients requiring theatre for drainage of RPA.
Now, the fun stuff. Let’s look at a few examples:
(Case courtesy of Dr Maxime St-Amant, Radiopaedia.org, rID: 26840)
Can you label the relevant anatomical landmarks on the above image?
This patient has epiglottitis.
NB there is also loss of normal cervical lordosis.
Along with above check the subglottic airway to check for oedema and narrowing of the subglottic space inferiorly.
(Case courtesy of RMH Core Conditions, Radiopaedia.org, rID: 26246)
What pathology do you see on the above radiograph?
This is a subtle retropharyngeal abscess.
Again there is loss of normal cervical lordosis, although C1 and C2 look reasonably normal.
Differential diagnoses: any cause of fluid, so trauma, hereditary angioedema, anaphylaxis or neoplastic disease in that retropharyngeal space.
(Case courtesy of Dr Ian Bickle, Radiopaedia.org, rID: 30018)
What are the main abnormalities are on the above image?
This is a retropharyngeal abscess
(Case courtesy of Assoc Prof Frank Gaillard, Radiopaedia.org, rID: 6258)
What findings are there on the above image?
Distended hypopharynx and subglottic narrowing. There is no swelling of the prevertebral space, the epiglottis is very normal looking and there is a nice and full valeculae.
Differential diagnoses will include viral croup or bacterial tracheitis depending on clinical picture.
(Case courtesy of Dr Michael Sargent, Radiopaedia.org, rID: 6086)
And finally, what do you make of this one?
Another croup X-ray, this time an AP.
Some stenosis is normal, so don’t get caught out when you see it when not clinically indicated, but should not be pronounced.
Also, if you see similar in a slightly older child but with a toxic presentation, don’t forget about that ugly stepsister of the croupy child, bacterial tracheitis.
So – you aced it. But what are we going to know with our new knowledge… are we going to order a soft tissue x-ray on that next child we suspect has croup?
Well, is there a prodrome of coryza, fever and progression to barking cough in a non-toxic child who attended daycare a few days ago? If so, you can likely rest assured with your clinical diagnosis of croup.
If however, you have a toddler who developed a barking cough after playing unsupervised in the garden, maybe with a stick in his hand 2 days ago, no viral illness or clear precipitant, then the lateral soft-tissue is a pretty reasonable go-to as an initial screening test to aid future management… that, and perhaps a baby leash.
- Sometimes you need to have a sneaky plan with radiology and ENT and just wait for the kiddo to have a nap and then do the CT when they are asleep
- Always discuss with ENT early if they can come in and consider performing a naso-endoscopy in the child who you feel may be appropriate (read: not going to obstruct their airway in ED)
- Don’t forget button batteries. Ingestion can present in the vaguest of ways, even just being “off food”. Have a high index of suspicion and have a low threshold to observe or obtain images on the kid who really doesn’t quite fit or seem right.
Some food for thought:
- How might you approach the patient who requires sedation for transport or imaging? What agent would you use and how might you manage this in a resource limited setting (no anaesthetist, no ENT)?
- What would be your approach to the emergent and also crash airway? What options would you consider?
Future scope: USS in the ED?
Limited data on the utility of this… but a developing space. Experiences detailed in a case series in the American Journal of Emergency Medicine (2) suggest that POCUS may aid and expedite medical decision making in the undifferentiated patient. Specifically, the technique (as you would assume) involved identifying a hypoechoic collection or hypoechoic/anechoic collection in the prevertebral space. At this stage, cannot be recommended as an alternative to other modalities of imaging but an interesting area to follow…
Fig 3: A&B hypoechoic collection with irregular borders | Fig 4: A&B circular heterogenous collection with effaced IJ | Right hand image: transducer placement for evaluation of RPA
Senior Registrar, Alfred Health
Dr. Elizabeth Sheffield (BSc (Hons), MA, MA (Hons), MBChB) is a critical care and airway enthusiast from Washington, D.C., working at The Alfred Hospital in Melbourne, Australia. Lover of medical education, SIM, rural medicine and critically ill airway management in the ED, plus exploring the outdoors with her beautiful family and frequently wet dog.