A case of peritonsillar abscess: a diagnostic challenge aided by point-of-care ultrasound
Keywords:
POCUS,
peritonsillar abscess
Article ID: 24-00063
Details
Article ID: 24-00063
A 27-year-old man with no medical history developed a fever and sore throat 5 days before visiting a primary care doctor. He was admitted to our hospital due to worsening symptoms, with a fever of 38.3ºC, redness of the pharynx, left tonsillar hypertrophy, uvular deviation to the right, and left submandibular lymph node enlargement with tenderness. Plain computed tomography (CT) revealed an enlarged left tonsil and lymph node. As it was difficult to differentiate between peritonsillar abscess (PTA) and peritonsillar cellulitis by plain CT, bedside cervical ultrasonography as point-of-care ultrasound (POCUS) was performed. A low echogenic area was observed in the center of the image. The mass with a low signal area on contrast-enhanced CT (CECT) was diagnosed as PTA. The patient was transferred to the otolaryngology department for pus drainage and was discharged 5 days later.
Complications of PTA are rare but potentially fatal, warranting early diagnosis and prompt, appropriate management. CECT is useful for the diagnosis of PTA, but given the risk of complications by contrast agents and radiation, appropriate patient selection is important when performing CECT. POCUS was useful in diagnosing PTA that could not be diagnosed by plain CT.
Peritonsillar abѕceѕs (PTA) is the most common deep neck infection in adolescents1). PTA is a collection of pus between the capsule of the palatine tonsils and the pharyngeal muscle and usually requires drainage by an otolaryngologist2). Complications of PTA occur rarely but are potentially fatal. Infection can spread from the peritonsillar space to other deep neck spaces, adjacent structures, and the bloodstream. Complications include upper airway obstruction, necrotizing fasciitis, mediastinitis, brain abscess, streptococcal toxic shock syndrome, and others3). Early diagnosis and prompt, appropriate management is needed to avoid critical complications. Peritonsillar cellulitis and PTA can present with fever, sore throat, and dysphagia, so differentiating between the two can be difficult. The definitive diagnosis of PTA has traditionally relied on puncture aspiration or incisional drainage of purulent fluid, but due to its invasive nature, there is growing interest in the use of imaging modalities such as computed tomography (CT) and ultrasound (US) for diagnosis4). Today, point-of-care ultrasound (POCUS) is used in a variety of settings5). POCUS is defined as ultrasonography brought to the patient and performed by the provider in real time. POCUS images can be obtained nearly immediately, and the clinician can use real-time dynamic images, allowing findings to be directly correlated with the patient’s presenting signs and symptoms6). We herein report a case of PTA that evaded diagnosis by plain CT but was successfully diagnosed with the help of POCUS .
A 27-year-old man with no medical history developed a fever in the 39°C range and sore throat five days before his admission. Although he visited a primary care doctor and received symptomatic treatment, his symptoms did not improve. Due to worsening symptoms and persistent anorexia, he visited our emergency department and was subsequently admitted to our hospital. On admission, he had a fever of 38.3°C and pharyngeal redness. His condition was characterized by swelling and erythema of the left anterior tonsillar pillar and the soft palate. The left submandibular lymph node was enlarged and tender. Intraoral examination showed swelling and redness of the left soft palate, with deviation to the right (Figure 1). Laboratory data showed elevated C-reactive protein (CRP) and increased white blood cell count with neutrophil predominance. A rapid antigen group A streptococcus test was negative. Plain CT revealed an enlarged left tonsil and lymph node (Figure 2A,B). Differentiation between PTA and peritonsillar cellulitis using plain CT was difficult. We performed transcervical ultrasonography at the bedside using a CX50 Xper (Philips, The Netherlands) with a linear transducer L12-3 (4.4-8.8 MHz). No abnormalities were identified on the right side (Figure 3A). On the left side, a low echogenic area was observed in the center of the ultrasound image (Figure 3B, arrow). When we asked the patient to move his tongue, the high echogenic tissue on the left side moved and was identified as tongue. The low echogenic area adjacent to the tongue was detected as a liquid-filled abscess. Using color doppler, no signal was detected, ruling out blood vessels or blood collection (Figure 3C). The low-signal mass observed on contrast-enhanced CT (CECT) was diagnosed as an abscess after comparison with the plain CT image (Figure 4). He was diagnosed with PTA and started on sulbactam/ampicillin (SBT/ABPC). He was referred to a hospital with an otolaryngology department for pus drainage. He underwent incision and drainage along with antimicrobial therapy using SBT/ABPC. Prevotella melaninogenica was detected in drained pus. He was discharged from the hospital five days after transfer.
Intraoral photograph. Swelling and redness of the left soft palate, with deviation to the right.
Plain computed tomography of the neck
A. Left tonsillar enlargement, with no low-density area (arrow)
B. Left cervical lymph node enlargement (arrow)
Cervical ultrasonography
A. Right side:No findings
B. Left side:Low echoic area was observed in the left tonsil (arrow).
C. Color doppler image of left tonsil. No signal was seen.
Contrast-enhanced computed tomography of the neck. Low density area was diagnosed as peritonsillar abscess (arrow).
To diagnose PTA, clinical impression alone is unreliable7). This case was finally diagnosed with PTA using CECT. Plain CT cannot distinguish peritonsillar cellulitis from PTA, but CECT can be useful in the diagnosis of PTA8). In a meta-analysis from 23 studies involving 1453 patients, Hagelberg et al. reported that CECT had a positive predictive value of 0.83 (95% confidence interval:0.80-0.85) for PTA diagnosis and was useful in differentiating peritonsillar cellulitis from PTA9). However, several disadvantages of CT scanning are known. Ionizing radiation from CT scans is increasingly recognized as a potential carcinogen. Radiation exposure from diagnostic imaging accounts for approximately 50% of a citizen’s lifetime exposure to radiation10). Contrast-induced anaphylaxis occurs in 0.16% of cases, and no predictors of occurrence have been established11). Furthermore, the incidence of acute kidney injury (AKI) due to contrast media is 0-5%, but in patients with comorbidities such as renal impairment, it can be as high as 30%12). Although CECT is useful in diagnosing PTA, it carries a risk of complications;therefore, appropriate considerations are essential when performing CECT.
On the other hand, PTA can be detected by transcervical ultrasound. PTA appears as an echo-free cavity with an irregular border, and peritonsillar cellulitis appears as a homogeneous or striated area with no distinct fluid collection13). Sievert et al. compared the diagnostic performance of cervical ultrasonography in 354 cases of PTA with definitive diagnoses confirmed by puncture or incisional drainage. The sensitivity, specificity, positive predictive value, and negative predictive value after the first ultrasound examination were calculated to be 75.1%, 88.6%, 94.6%, and 57.3%, respectively14).
POCUS has various advantages. POCUS images can be obtained immediately, allowing clinicians to correlate real-time dynamic images with the patient’s presenting signs and symptoms6). POCUS is easily repeatable if a patient’s condition changes and it also facilitates rapid decision-making. The diagnostic accuracy of POCUS for PTA when performed by generalists is estimated to have a sensitivity of 80% and specificity of 81%15). The performance of intraoral US may be hampered by triѕmus, pain, gagging, or lack of cooperation. Submandibular or transcervical US avoids these limitations and is particularly suited for patients who cannot undergo an adequate oropharyngeal examination. Despite these benefits, fewer than 10% of physicians have adopted POCUS in primary care16). Greater familiarity with PTA ultrasound imaging could have allowed referral to an otolaryngologist based on ultrasound finings alone. Clinically, both CECT and ultrasound are used to diagnose PTA17). POCUS enhances imaging and diagnostic accuracy with minimal training. It is predicted that artificial intelligence will be used in the future to assist in POCUS5), but for now, clinicians need to be familiar with cervical ultrasound imaging.
In conclusion, this case demonstrated the utility of POCUS to diagnose PTA that could not be diagnosed by plain CT.
