Edited by Teresa Wu, MD
A 20-year-old male presents to your ED complaining of five days of throat pain and tactile fevers. He reports that the pain is worse on the left, and is associated with oropharyngeal swelling and odynophagia.
He denies any other upper respiratory symptoms, but has had multiple sick contacts recently. He is able to tolerate liquids by mouth, but attempting to eat solids causes him significant pain. He has tried some acetaminophen at home with minimal relief and feels like the pain and swelling is getting worse. He denies any headache, posterior neck pain, meningismus, chest pain, back pain, abdominal pain, shortness of breath, foreign body ingestion, or any other associated symptoms.
On review, he has no significant past medical history. Other than over-the-counter medicatios for symptomatic relief, he is not taking anything else. His physical exam reveals a well-appearing, well-hydrated young adult, sitting upright in bed in no acute distress. There is no drooling or stridor noted. His vital signs are within normal limits and he is afebrile. Examination of the posterior oropharynx reveals bilateral erythema with minimal exudate and left-sided peritonsillar swelling. The exam is also notable for mild uvular deviation towards the right. Examination of the neck shows left anterior cervical lymphadenopathy. The rest of his physical examination is within normal limits.
He has all the signs and symptoms suggestive of a peritonsillar abscess (PTA), and you suspect he will need a needle aspiration or incision and drainage of the abscess for definitive management and symptomatic relief. Having performed countless needle aspirations in the past, you know that it is often difficult to provide adequate pain relief and anesthesia prior to the procedure and that there is always the risk of a “dry tap”. Before you commit to putting the patient through a painful and time-consuming procedure, you pause to consider: Is there really an abscess under there or is this just unilateral peritonsillar cellulitis? Should you perform the aspiration attempt now? Or should you bring the patient back to the ED after 48 hours of outpatient antibiotics and reassess for a more obvious PTA then? Should you just have the patient follow-up with ENT or call them down to the ED for a formal consult?
You decide that a bedside ultrasound can help you decide whether or not there is a drainable abscess, and determine how close the abscess is to vital adjacent structures. Prior to the scan, you prep the patient’s oropharynx with topical anesthesia and give him a “lidocaine lollipop” (a 2x2 gauze covered in lidocaine gel, wrapped around the end of a tongue depressor) to press against the affected area. As the patient’s topical anesthetic is kicking in, you prepare your ultrasound probe and machine. You ensure that the intracavitary probe has been properly cleaned and place a protective sheath over a thin layer of gel at the tip of the transducer. You give the transducer to the patient and have him gently insert the probe into his mouth. With gentle pressure, you guide the tip of the transducer towards the area of concern and slowly fan through the cellulitic region.
What do you see on bedside US?
What do you want to do next?
See next page for the case conclusion
Dx: Hypoechoic Mass
As you suspected, the patient has a 1 x 2 cm hypoechoic mass noted on bedside ultrasound. You can visualize the adjacent vessels just posterior/farfield to the abscess on the bedside scan. Using the depth markers on the side of the screen, you can see that the middle of the abscess is approximately 1.5 cm deep to the mucosal surface and should be easily accessible for a needle aspiration or I&D. You map out the adjacent structures and are able to identify the patient’s carotid artery approximately 2.5 cm from the mucosal surface (arrow).
Now that you are sure that the patient has a PTA and you have been able to visualize adjacent structures that you want to avoid, you decide to proceed with a needle aspiration. You obtain a standard 20 gauge spinal needle and remove the plastic guard covering the needle. Using trauma shears, you cut off 2.0 cm of the plastic guard and slip it back over the spinal needle. Having the guard in place will help prevent inadvertent puncture of the carotid artery by limiting the length of needle accessible during the puncture. Under ultrasound guidance, you insert the spinal needle into the center of the PTA and obtain 4 cc of purulent material on aspiration.
The patient feels much better after the successful aspiration, and thanks you for your excellent service. You discharge the patient on antibiotics and pain medications and arrange for 48-hour follow-up with ENT.
How to prevent inadvertent puncture of the carotid artery:
1. Use a standard 20 gauge spinal needle
2. Remove the plastic guard covering the needle.
3. Using trauma shears, cut off 2.0 cm of the plastic guard
4. Slip the modified guard back over the spinal needle.
Continue for Pearls and Pitfalls
Pearls & Pitfalls
1. Use a high-frequency intracavitary transducer to image the peritonsillar area. Be sure to adequately clean the probe and cover the probe with a protective sheath prior to use in a patient’s oral cavity, as this probe is also used for transvaginal exams.
2. When referring to the probe in front of the patient, for obvious reasons, please remember to use the term “intracavitary probe” instead of “transvaginal probe”.
3. Having the patient insert the transducer on their own can help minimize the gag reflex elicited during the procedure. Once the probe has been inserted by the patient, gently guide the face of the transducer until it is resting over the area of interest.
4. Although a peritonsillar aspiration is best performed under direct ultrasound guidance, the space limitations of the oropharynx and associated trismus may make it impossible to have the ultrasound probe and needle inserted at the same time. If it is not possible to perform an ultrasound-guided needle aspiration, use the ultrasound to confirm that a PTA is present, determine if there are multiple pockets present, and estimate the depth of it’s most fluctuant pocket(s).
5. Take advantage of depth markers on the right of the ultrasound image. You can use these marks to estimate the depth of the abscess and the depth of the carotid artery. The depth of the scan (in cm) is indicated by the number on the bottom right of the screen. In general, the large hashmarks are 1 cm apart and the smaller hasmarks are 0.5cm apart. You can use this information to appropriately size your needle guard and guide your needle advancement during the procedure.
6. Always scan around to try to identify adjacent vascular structures. The carotid artery typically lies 2.5 cm deep to the mucosal surface. Once you find a dark, hypoechoic vascular structure, you can use color or spectral Doppler to determine if it is a vein or an artery. Plan your procedure so that you minimize your chances of accidentally puncturing any adjacent vessels.
7. Become familiar with the orientation marker on your intracavitary probe and set up your ultrasound machine so that the indicator marker is on the left side of the image before you begin the procedure. Maintaining the proper orientation will enable you to identify what you are scanning in a quicker and more accurate fashion, and help you complete the procedure in a more timely manner.