From January 2020 to December 2022, 76 children with parapharyngeal or retropharyngeal cellulitis or abscess in neck CT were initially enrolled in this study. After excluding cases of trauma, cervical structural anomalies, and clear confounding factors, 56 cases were included in this study. This study was approved by the Ethics Committee, and informed consent was waived. The inclusion evaluation team consisted of radiologists, otolaryngologists, and cardiologists.

This study retrospectively analyzed the medical records of enrolled children. We collected demographic data, including gender and age, and clinical data, including the final diagnosis, fever duration before and after admission, accompanying symptoms, head and neck examination results, treatment methods, and outcomes. White Blood Cell Count (WBC), C-Reactive Protein (CRP), absolute neutrophil count, absolute monocyte count, hemoglobin level, platelet count, Erythrocyte Sedimentation Rate (ESR), pre-calcitonin, Lactate Dehydrogenase (LDH), Aspartic Acid Transaminase (AST), and Alanine Transaminase (ALT) levels, and other data were collected. The location (parapharyngeal or retropharyngeal space) and type (cellulitis or abscess) of deep neck inflammation were determined based on enhanced neck CT. The basis for determining cellulitis or abscess came from Kyungmin Roh et al.22: Cellulitis was defined as the presence of unreinforced low-density lesions in the parapharyngeal or retropharyngeal space, while abscess was defined as the presence of low-density lesions with completely enhanced edges (Fig. 1).

Figure 1.

Enhanced neck computed tomography. (A) Retropharyngeal and right parapharyngeal cellulitis (arrowheads). (B) Right parapharyngeal cellulitis (arrowheads). (C) Retropharyngeal abscess with rim enhancement (arrowheads). (D) Left parapharyngeal abscess with rim enhancement (arrowheads).

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This study analyzed the cases of KD mimicking deep neck abscess in children who underwent incision and drainage surgery. We collected the basic information, disease course, treatment process, and prognosis of the patients to analyze the timing and effectiveness of surgery in KD mimicking deep neck abscesses.

The collected children were divided into DNIs and KD groups based on the final diagnosis before being discharged. Demographic, clinical, and laboratory data were compared between the two groups. Categorical and continuous variables were compared using Fisher’s exact and Independent sample t-tests, respectively. The SPSS version 22.0 (IBM Corp., USA) was used for statistical analyses, and statistical significance was defined as p<0.05.

We initially collected 76 children with cervical CT findings in favor of cellulitis and/or abscess in the parapharyngeal or retropharyngeal space. Two cases with incomplete data and all cases with clear confounding factors, including 5 children with immunosuppression due to hematologic diseases and cancer, 3 cases with neck trauma, 3 cases with pyriform sinus fistula, 2 cases with immunodeficiency, 2 cases with Kikuchi disease (pathologically confirmed), 1 case with connective tissue disease, 1 case with type I diabetes, and 1 case with spinal muscular atrophy, were excluded, and 56 cases remained.

The median age of the collected children was 5-years and 6-months (range 9-months to 10-years), and 30 (53.6%) children had male gender. The most common clinical symptoms were fever 55 (98.21%), neck pain 45 (80.4%), and limited neck motion 36 (64.3%). Other symptoms, such as sore throat 16 (28.6%) or cough 10 (17.9%) occurred occasionally. Trismus 7 (12.5%), anhelation or snore 7 (12.5%), dysphagia 6 (10.7%), headache 6 (10.7%), sputum discharge 6 (10.7%), and rhinorrhea 3 (5.4%) were less. All patients had cervical lymphadenopathy 56 (100%); the vast majority of patients had Pharyngeal congestion 51 (91.1%); and nearly half of the physical examinations showed asymmetrical protrusions and pharyngeal tonsil deviation 26 (46.4%) (Table 1).

Deep neck abscess and cellulitis were identified in neck CT of 31 (55.4%) and 26 (46.4%) children, respectively. One child (1.9%) had both deep neck abscess and cellulitis. Eight (25.8%) of the 31 children with deep neck abscesses had concurrent parapharyngeal and retropharyngeal abscesses. Seven (26.9%) of the 26 children with deep neck cellulitis had concurrent parapharyngeal cellulitis and retropharyngeal cellulitis. Deep neck abscess was defined as parapharyngeal abscesses in 26 (83.9%) cases and retropharyngeal abscesses in 13 (41.9%) cases. There were 18 (69.2%) cases of parapharyngeal cellulitis and 15 (57.7%) cases of retropharyngeal cellulitis among deep neck cellulitis (Table 2).

Among 56 collected children, the final diagnosis was KD in 22 cases (39.3%) and DNIs in 34 cases (60.7%). Twenty-two children with KD and initial symptoms of deep neck infection were diagnosed after observing characteristic clinical manifestations in the later stages. Among them, 19 cases had 2 or 3 clinical features of KD, which appeared within a median of 6-days after fever (range 4–15). However, three patients did not show characteristic clinical manifestations of KD, and physicians diagnosed KD based on the duration of fever and coronary artery abnormalities on echocardiography. The median duration of fever on admission for children diagnosed with KD was 5-days (range 2–13 days), and the median duration of fever after their admission was 4-days (range 1–11 days).

There was no significant difference in gender and age between the DNIs and KD groups. There was a significant difference in the highest body temperature between the two groups (p=0.007), and the KD group had a higher body temperature. Regarding the clinical symptoms, dysphagia is rare in KD group (p=0.041) compared to DNIs group.

Laboratory results upon admission revealed significant elevations in WBC, CRP, and absolute neutrophil count in both groups, with no significant distinction between them (p>0.05). Furthermore, ESR levels were significantly elevated in both groups, with a notably higher level in the KD group when compared to the DNIs group (p=0.030). The KD group exhibited higher levels of AST (p=0.040) and ALT (p=0.027) compared to the DNIs group. In addition, the KD group displayed a higher incidence of deep cervical cellulitis (p=0.005) on neck CT scans, whereas deep neck abscesses were more common in the DNIs group (p=0.002), with parapharyngeal abscesses being the most frequently observed (p=0.004) (Table 3).

Among the 34 cases of DNIs, 29 cases (85.3%) were cured after antibiotic therapy, of which 19 cases (55.9%) were treated with a combination of the two drugs. The median duration of fever after treatment was 2.5 days (range 0–14 days).

In the DNIs group, 5 patients (14.7%) underwent surgical intervention. Four patients underwent oropharyngeal incision and drainage, and one patient had a deep abscess and underwent ultrasound-guided drainage. The 5 children who underwent surgical treatment were all diagnosed with large abscess, manifesting with respiratory obstruction and snoring. Therefore, incision and drainage were considered to protect respiratory and airway.

Twenty-two children finally diagnosed as KD were treated with intravenous immunoglobulin (IVIG, 2g/kg) and aspirin (80mg/kg). The median duration of fever after treatment was 3-days (range 1–8 days). Among them, there were 5 patients whose body temperature did not improve within 3 days after treatment. Among them, two patients improved on the 4th day, and one patient improved on the 5th day but experienced Kawasaki shock syndrome and liver injury. One patient improved on the 7th day and was defined as unresponsive Kawasaki. One patient improved on the 8th day and was defined as unresponsive Kawasaki, experiencing knee arthritis in the later stage. Children with KD who have a high body temperature for more than 3 days after using IVIG and aspirin have a relatively poor prognosis. In addition, 12 (54.5%) children in the KD group received a combination of two antibiotics, and ten cases (45.5%) received one antibiotic for suspected deep neck infections before being diagnosed with KD. However, there was no significant improvement in clinical symptoms, such as fever, after antibiotic use.

Two children (9.1%) in the KD group underwent oropharyngeal incision and drainage surgery due to respiratory obstruction and snoring. One of the cases was a 10-month-old boy admitted to the hospital for 13 days due to high fever (up to 40°C), left neck pain, and upper respiratory obstruction. Early use of antibiotics did not resolve the fever. On the 15th day of fever, KD was diagnosed by echocardiography. His body temperature improved 4 days after receiving IVIG and aspirin, but the abscess still did not shrink. After one week of close observation, CT still showed a large abscess in the neck, and snoring was still severe. After incision and drainage, breathing became smooth. However, there was no bacterial growth in the drainage culture (Fig. 2 A–C).

Figure 2.

Case 1: a patient with KD and deep neck abscess who underwent incision and drainage surgery. (A, B, and C) Enhanced neck computed tomography showing a neck abscess.

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Another case was a 4-year-old (50-months old) female without comorbidities admitted to the hospital for 5-days due to fever (39.5–40°C), right neck pain, upper respiratory obstruction, and snoring. On the 10th day of fever, echocardiography showed dilation of the left main coronary artery, confirming KD. IVIG and aspirin were immediately given. On the same day, an neck CT showed a parapharyngeal abscess. Due to the significant compression of the pediatric airway by the abscess, the patient was transferred to the Otolaryngology Department for surgery (Fig. 3 A–C). Her fever subsided 24h after IVIG infusion (37.6°C), and the upper respiratory tract obstruction was alleviated. Otolaryngologists and anesthesiologists were not sure if the surgery was necessary. Due to the possibility of upper airway obstruction and abscess rupture, surgery was performed on the 13th day of fever (36h after initiating treatment with IVIG and aspirin). Surprisingly, during the surgery, it was found that the right pharyngeal wall and tonsil were significantly smaller than before using IVIG. The abscess (approximately 1cm deep) was discharged through oral incision and drainage. However, only 1mL of viscous bloody fluid was discharged (Fig. 3 D–F), resulting in significant intraoperative bleeding (approximately 7mL). We expanded the incision by approximately 1.0cm. No bacterial growth was found in the pus culture. Postoperative upper respiratory tract obstruction was alleviated. Due to parapharyngeal surgery, the patient received a liquid diet through a nasogastric tube for 3 days.

Figure 3.

Case 2: a patient with KD and deep neck abscess who underwent incision and drainage. (A, B, and C) Enhanced neck computed tomography showing a neck abscess. (D) Right parapharyngeal and retropharyngeal eminence (arrowhead). (E) After incision and drainage (arrowhead). (F) One milliliter of serous fluid was drained without bacterial growth in cultures.

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