Ultrasound Case of the Month
Case # 1: Submitted by Dr. Ravi Sapatwari
This is a 25 year old male who presented to the ED with sore throat, fever, and dysphagia for 5 days. He was recently seen at urgent care, diagnosed with pharyngitis, and given amoxicillin. He had relief of symptoms on "the left side" but had increased pain and swelling of the right throat with persistent dysphagia.
Discussion:
This image was taken with the endocavitary probe directed in the right posterior oropharnx in the transverse plane. A PTA was identified as a well-circumscribed, heterogeneous mass noted in both transverse and sagittal planes, and the depth of the mass was measured. Vascular structures (notably the internal carotid artery) were also identified posterolaterally to the abscess. A 20 gauge 3.5” spinal needle was used with its sheath cut to the appropriate depth to avoid reaching vascular structures. The needle was then visualized entering the mass in real-time and aspirated.
Ultrasound is a useful tool to distinguish between peritonsillar cellulitis and abscess, which can be difficult to distinguish on physical exam alone. This is particularly important as management differs between the two conditions, namely antibiotics versus definite treatment with aspiration or I&D. In a recent study by Constanino et al. of 28 patients with suspected PTA, ultrasound provided increased sensitivity of 100% compared to the physical exam of 64%, as well as a decreased need to consult ENT (7% vs. 50%) (1). Although the sample size of this study was small, other studies appear to confirm an increased sensitivity and specificity of US in the diagnosis of PTA, with the caveat being the skill level of the sonographer (2).
Although aspiration of a PTA can be performed blind, there is risk to this procedure given adjacent structures, particularly the internal carotid artery and jugular vein. These vascular structures can be identified on US, particularly with the use of color doppler, and real-time visualization of the needle can prevent unwanted complications. So the next time you see throat swelling as a chief complaint, be sure to grab an endocavitary probe if available.
Additional Resources:
http://www.ultrasoundpodcast.com/tag/peritonsillar-abscess/
http://sonoguide.com/smparts_ent.html
Case # 2: Submitted by Dr. Dwyer and Liebmann
45 year old ill appearing male with an unclear past medical history who presents with a few days of atraumatic low back pain that radiates down his right leg. Patient also complains of fevers and weight loss. Exam is significant for a thin appearing male. He is febrile with a heart rate of 139. He has lateral low back tenderness, but no midline tenderness. There is no evidence of trauma. His neurological examination is within normal limits.
Discussion:
This patient was diagnosed with an iliopsoas abscess, which was seen on bedside ultrasound. The cat scan showed bilateral psoas abscesses, right side larger than left (12.3cm) with evidence of hematogenous spread to the lungs with pulmonary abscess formation.
This ultrasound was performed with a curvilinear probe in the RUQ and LUQ, as if performing a FAST exam. The marker was pointed to the head of the patient, and obliqued slightly to get between the ribs. In your FAST views it is common to see the iliopsoas muscle posterior-inferior to the kidney on both sides. In this image, we see a large mass, which is heterogenous and represents the abscess also demonstrated on CT.
Normal:
Image 1: Normal RUQ view
Psoas abscesses are associated with high mortality and are often misdiagnosed. Because we see them infrequently, they aren’t always on our differential diagnosis and this results in a delay in identification. Because the musculature is highly vascular, it is predisposed to hematogenous spread as seen in this case.
There is not a significant amount of data available on the identification of psoas abscess with bedside ultrasound, and it can be difficult to differentiate from a hematoma sonographically, however the clinical history should help you differentiate.
Image 2: RUQ US view demonstrating heterogenous mass within the psoas musculature
Faculty Reviewer: Dr. Kristin Dwyer
References:
1: Constantino TG, Satz WA, Dehnkamp W, Goett H. Randomized Trial Comparing Intraoral Ultrasound to Landmark-based Needle Aspiratino in Patients with Suspected Peritonsillar Abscess. Acad Emerg Med. 2012;19(6):626-31.
2: Secko M, Sivitz A. Think ultrasound first for peritonsillar swelling. Am J Emerg Med. 2015;33(4)569-72.