An Assessment of Peritonsillar Abscess using Single Enhanced Computed Tomography and Treatment

Prashant Sharma^1*, Nufra Senopher Mohamed Sarfraz², Vinod Singhal³

1,2,3. Prime Hospital, Dubai UAE.

*Correspondence to: Prashant Sharma, Prime Hospital, Dubai UAE.

Copyright

© 2025 Prashant Sharma. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: 18 February 2025

Published: 24 February 2025

Introduction

Peritonsillar abscess is a disease in which acute inflammation of the palatine tonsil spreads to the surrounding connective tissue space around the tonsil, forming an abscess. Patients complain of fever, persistent sore throat, and dysphagia. If not diagnosed early or treated appropriately, it can progress to airway obstruction or mediastinitis, so it is a disease that requires attention [1]. The examination findings of peritonsilar abscess mainly include redness and swelling around one side of the tonsil, the uvula is shifted to the opposite side of the abscess, and a foul odor may be emitted from the mouth. Generally, if a peritonsilar abscess is suspected, the suspected area can be aspirated with a needle to confirm the pus and make a diagnosis. Recently, computed tomography (CT) is performed, or ultrasound is used to reduce the damage from radiation exposure, and the presence of a peritonsilar abscess is diagnosed first through imaging, and then the area is aspirated with a needle or incised and drained [2-6]. When diagnosing peritonsillar abscess, cervical CT is generally taken once before using contrast medium, and then taken once more after using contrast medium in the same area (Fig. 1). When comparing the images before and after contrast, a peritonsillar abscess can be diagnosed when rim enhancement is seen in the annular band of the peritonsillar space and central low density is seen inside the post-contrast image (Fig. 1) [7]. Unlike in the past, multichannel CT is recently linked to the picture archiving and communication system (PACS) and can reconstruct images in axial, sagittal, and coronal planes, which is very helpful in interpretation and treatment. Therefore, with the introduction of CT and PACS, pre-contrast images may not be as necessary for diagnosing peritonsillar abscess as in the past, and we aimed to investigate the usefulness of using only post-contrast images in diagnosing and treating peritonsillar abscess.

Fig 1: Computed tomographic findings of peritonsillar abscess. Precontrast axial view (A). Post-contrast axial view (B). Black arrow indicates peritonsillar abscess pocket.

Subjects and Methods

From October to December 2016, 29 patients were hospitalized with suspected peritonsillar abscesses and diagnosed and treated using only post-contrast CT of the neck. We retrospectively compared and analyzed the treatment results, etc. with 36 patients diagnosed and treated using pre- and post-contrast CT of the neck from October to December 2015. This study was conducted after receiving IRB review from our hospital (EMC-2017-11-002). The CT images were interpreted by an otolaryngologist or a radiologist. If a low-attenuation retention was observed inside the peritonsillar space and a ring-shaped enhancement surrounding it was prominently observed, a radiological judgment of peritonsillar abscess was made. Incision and drainage were performed to confirm the abscess, and the final diagnosis of peritonsillar abscess was made. When a homogeneous soft tissue opacity swelling around the tonsils was observed on CT but no clear abscess was observed, it was diagnosed as peritonsillar abscess based on imaging. In addition, when the abscess was not prominent on CT or the opacity was difficult to determine due to dental prosthesis, it was diagnosed as peritonsillar abscess only when pus was confirmed during incision and drainage, and when pus was not confirmed during incision and drainage, it was diagnosed as peritonsillar abscess. The cases where the abscess site identified on CT was incised and drained and the pus was confirmed visually were compared, and the treatment results such as the period of hospitalization and post-treatment complications were analyzed retrospectively. After incision and drainage, a drainage tube was inserted, and the drainage tube was a silicone tube coated with a radioactive marker cut and inserted into the abscess site. If the swelling around the tonsils improved and pus did not seep out through the drainage tube, it was removed the next day. When an abscess was identified on CT but the abscess was not confirmed visually during incision and drainage, the incision site was opened for 1 to 2 days and the drainage of pus was continuously observed. All patients hospitalized with peritonsillar abscess received intramuscular injection of dexamethasone 5 mg (Huons, Seongnam, Korea) on the first day, and intravenous injection of broad-spectrum antibiotic Augmentin 3.6 g (Ilsung, Seoul, Korea) three times a day. When the bacterial isolation results were obtained during hospitalization, the antibiotic was changed according to the antibiotic sensitivity. In cases of adverse reactions to Augmentin, empirically, ceftriaxone 2 g (Boryung, Seoul, Korea) was administered once a day and Flagyl 1.5 g (Albogen Korea, Seoul, Korea) was administered three times a day as a combined therapy.

Evaluation of peritonsillar abscess using CT

Two otolaryngology residents (2 years of experience and 3 years of experience) were asked to evaluate the presence or absence of abscesses by randomly mixing 60 images of neck CT of 35 patients confirmed with peritonsillar abscess and 25 neck CTs of patients with tonsillitis or peritonsillar cellulitis without abscess. For the 2-year-experienced trainees, both pre- and post-contrast CT images were used, while for the 3-year-experienced trainees, only the post-contrast CT images were used to determine the presence or absence of peritonsillar abscess. The sensitivity and specificity of the two evaluators were calculated, and the agreement of the judgments was calculated.

Statistical Analysis

SPSS 18.0 (SPSS Inc., Chicago, IL, USA) was used for statistical analysis. When comparing peritonsillar abscesses treated using pre- and post-contrast images and post-contrast images, the chi-square, Fisher’s exact test, and t-test were used to compare the two groups. In the experiment of interpreting the images of peritonsillar abscesses, the agreement between the two groups was compared using the kappa value. A p value of 0.05 or less was considered significant. Go to : Goto

Results

Thirty-six patients treated using both pre- and post-contrast images were 23 male and 13 female, respectively. The average age was 29 years. Of the 36 patients, 32 (88.9%) were able to drain the abscess clearly (Table 1). The average treatment period was 5.9 days, and there were no complications. Twenty-nine patients treated using post-contrast images were 16 male and 13 female, respectively. The average age was 34 years. Of the 29 patients, 26 (89.7%) were able to drain the abscess clearly (Table 1). The average treatment period was 6 days, and there were no complications. There was no significant difference in age, sex, length of hospitalization, or success in draining the abscess between the group that used both pre- and post-contrast images and the group that treated using only post-contrast images.

When two residents diagnosed peritonsillar abscesses, one using pre- and post-contrast images and the other using only post-contrast images, the two residents had a high level of agreement (kappa value of 0.825) (p<0.01). Of the 35 peritonsillar abscesses, the resident using pre- and post-contrast images judged 33 to have abscesses, while the resident using only post-contrast images judged 34 to have abscesses (Table 2). Of the 25 tonsillitis or peritonsillar abscess images, the resident using pre- and post-contrast images judged 21 to have no abscesses, while the resident using only post-contrast images judged 23 to have no abscesses (Table 2). The sensitivity and specificity of the trainees using pre- and post-contrast images were 94.3% and 84.0%, respectively, and those using only post-contrast images were 97.1% and 92.0%, respectively.

Fig 2

Notes:

• *Chi-square test
• † t-test
• ‡ Fisher’s exact test

Discussion and Conclusion

Recently, the usefulness of CT in the field of medical diagnosis has gradually increased, and the scope of cases included as essential for diagnosis has gradually expanded. According to the data of the Health Insurance Review and Assessment Service, the number of CT scans has increased sharply every year from 2,411,327 in 2006 to 9,841,215 in 2014. In addition to CT, the use of radiation in the field of medical diagnosis and treatment has expanded even further, with devices such as positron emission computed tomography, gamma cameras, angiography, mammography, and radiotherapy equipment. The unit representing radiation exposure is millisievert (mSv), and it is known that the radiation dose that Koreans are exposed to in their daily lives over the course of a year is 3.6 mSv [8]. While a general chest X-ray exposes about 0.01 to 0.1 mSv, a head and neck CT exposes about 2 mSv, and a chest or abdominal CT exposes about 8 to 10 mSv [9]. Efforts to reduce the increasing radiation usage are being attempted in various fields. A system has been implemented to mandatory record and manage the radiation dose of patients undergoing CT examinations, and duplicate CT scans performed on the same area at other hospitals are being avoided. In addition, many protocols have been developed and studied to reduce the radiation dose while obtaining appropriate resolution using low-dose CT [10-12]. In the field of otolaryngology, temporal bone CT or paranasal sinus CT are mainly used to analyze bone structures, so images are obtained with only one radiation exposure without using contrast agents. However, since neck CT using contrast agents evaluates the difference in the degree of contrast by comparing images before and after contrast, pre-contrast CT images are usually performed together, resulting in twice the radiation exposure compared to pre-contrast CT. Comparison before and after contrast is essential for the differentiation of neoplastic diseases. However, unlike neoplastic diseases, pre-contrast images may be less useful for infectious tonsillar diseases such as peritonsillar abscesses. In addition, when a simple peritonsillar abscess is suspected, it is important to confirm the pus by aspirating the suspected area around the tonsil with a needle rather than performing a CT right away based on the patient's medical history and a thorough physical examination. If the pus cannot be confirmed even after multiple needle aspirations, if the patient's cooperation is difficult, or if the physical examination is difficult due to severe trismus, performing a CT or ultrasound using contrast medium in situations where the peritonsillar abscess is suspected to have spread to the adjacent deep cervical space based on the physical examination can also reduce unnecessary radiation exposure or examination. This study showed that there is no difference in the diagnosis or treatment of peritonsillar abscess even in the absence of pre-contrast images. In this study, the CT diagnosis was performed by otolaryngology residents with 2-3 years of experience. Even for non-specialist residents, the sensitivity for diagnosing peritonsillar abscess was over 94%, and the specificity was also relatively high at over 84%. Peritonsillar abscess is not rare and can be encountered frequently, and it is a disease that can be diagnosed relatively easily by otolaryngology trainees due to its characteristic CT imaging findings. However, even localized low-attenuation areas inside the tonsils tend to be diagnosed as peritonsillar abscesses, so although the sensitivity was high, the specificity tended to be lower than the sensitivity. In the case of otolaryngologists, since the sensitivity and specificity of CT diagnosis are almost 100%, they were not included in this study. Despite the high diagnostic rate of CT, many studies have been reported on diagnosing peritonsillar abscesses using ultrasound to reduce the damage of radiation exposure [2-6]. In Korea, Kim et al. [2] reported a sensitivity of 91.7% and a specificity of 100% using intraoral ultrasound and color Doppler. In a study that diagnosed peritonsillar abscesses using transcervical ultrasound instead of oral cavity, the sensitivity was 94.7% and the specificity was 83.3% in diagnosing peritonsillar abscesses in 44 cases, which was almost similar to the results of the oral cavity [3]. A study comparing the accuracy of CT and ultrasound in diagnosing peritonsillar abscesses reported that CT had a sensitivity of 100% and a specificity of 75%, while transoral ultrasound had a sensitivity of 89% and a specificity of 100%, indicating that CT was slightly more sensitive than ultrasound, but transoral ultrasound also showed considerable utility [13]. Although not included in this study, our own results showed that in laryngeal inflammatory diseases such as laryngeal abscess and posterior pharyngeal abscess, the diagnostic effect of post-contrast CT images alone was not significantly different from that of two CT images before and after contrast. Recently, CT and PACS systems have been linked, so that CT images can be reconstructed in coronal and sagittal planes in addition to axial images on a computer monitor, allowing three-dimensional identification of the desired area, which is very helpful for incision and drainage. In addition, even for post-contrast CT images, if the contrast is adjusted in PACS, the contrast effect can be eliminated and bone shadows can be highlighted, so that an effect almost similar to that of a pre-contrast image can be obtained.

Through this study, it was shown that post-contrast CT alone is no different from conventional CT in the diagnosis and treatment of peritonsillar abscesses, and this can reduce radiation exposure by half.

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