Laboratory Studies
See the list below:
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Complete blood count
The mean white blood cell (WBC) count in one study was 17,000, with a range of 3100-45,900.
WBC counts in 18% of the patients were less than 8000; thus, a normal WBC count does not rule out the diagnosis of retropharyngeal abscess.
In a study in Germany, the mean WBC (±standard deviation was 14,700 [±10,500]), with a range from 200-114,000.
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Blood cultures are indicated before administration of intravenous antibiotics, but culture results may be negative in as many as 82% of retropharyngeal abscess cases.
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A culture of pus, aspirated at the time of surgical drainage of the retropharyngeal abscess, can grow one or more organisms 91% of the time.
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C-reactive protein
In one study of adults and children with deep cervical space infections, patients with C-reactive protein level greater than 100 had longer hospital stays.
In a German study, mean (±standard deviation) C-reactive protein level was 15.7 (±12.9), with a range from 0.0-74.
A study in Taiwan reveals that deep neck infection patients with C-reactive protein values greater than 100 tend to develop complications and have prolonged hospitalizations. [50]
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Erythrocyte sedimentation rate [5]
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COVID-19 testing - In adult or pediatric patients who present with a sore throat [6]
Imaging Studies
See the list below:
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Lateral neck radiography
Widening of the retropharyngeal soft tissues was observed in 88% of patients with retropharyngeal abscess in a series that defined soft tissue swelling as more than 7 mm at C2 and more than 14 mm at C6. There is some variability in the literature as to what dimensions define retropharyngeal widening on soft tissue lateral neck radiographs. Some authors define retropharyngeal soft tissue swelling as more than 7 mm at C2 and more than 14 mm at C6 in children and more than 22 mm at C6 in adults. Others define retropharyngeal widening as greater than 5-7 mm at C2 and more than 14mm at C6 in children and greater than 20 mm at C6 in adults. Thus, lateral neck radiographs may be considerably less sensitive for detecting retropharyngeal abscess than the above-mentioned study indicates. [1, 4, 5, 6, 7, 51, 52, 53, 54]
Klein found the prevertebral space to widen in children if it measures more than 7 mm at C2 or greater than 14 mm at C6. [51]
Generally, the anteroposterior diameter of the prevertebral soft tissue space in children should not exceed half that of the contiguous vertebral bodies from C1-4 or the full thickness of contiguous vertebral bodies from C5-7. [6]
In addition to showing widening of the prevertebral space, the lateral neck radiograph rarely may show a gas-fluid level, gas in the tissues, or a foreign body.
A hospital in Ireland reports a case series of 3 children with RPA who had negative lateral soft tissue neck x-ray films. Diagnosis was made using CT scan in all 3 cases. [55]
A 5-year-old boy presented to the ED with 2 days of neck pain and fever but with no sore throat. The child had vomited once, and the mother reported that he was irritable. The child's temperature was 101.7° F, pulse was 118 beats per minute, respirations were 24 per minute, and blood pressure was 122/65 mm Hg. A decreased range of motion of the neck and a right anterior cervical node were observed; the child refused to swallow. Lateral neck radiographic findings show increased retropharyngeal space (white arrow). The CT scan did not demonstrate an abscess. The child was seen by an ear, nose, and throat specialist; he was admitted and started on intravenous clindamycin. He improved for 2-3 days and then worsened. Repeat neck CT scan findings demonstrated a retropharyngeal abscess. Incision and drainage was performed in the operating room. Cultures of the pus grew group A beta-hemolytic streptococci and alpha-streptococci, both sensitive to clindamycin. He improved and was discharged on the tenth hospital day on oral clindamycin.
An 8-month-old infant boy presented with fever and a stiff neck. According to the mother, the baby was not moving his neck as much as usual. The mother also reported decreased oral intake. His temperature was 100° F, pulse was 104 beats per minute, respirations were 48 per minute, oxygen saturation was 98% (room air [RA]). The left tympanic membrane (TM) was inflamed and nonmobile. Left submandibular and left postauricular nodes were noted. The lateral neck radiograph shows increased retropharyngeal space. The CT scan demonstrated a small retropharyngeal abscess. The WBC count was 26,000 (24 polymorphonuclear leukocytes [P], 5 bands [B], 63 lymphocytes [L], 8 monocytes [M]). The baby was examined by an ear, nose, and throat specialist; he was admitted and started on intravenous clindamycin. He improved over the next few days and was discharged on the fifth hospital day on oral clindamycin with a plan for repeat CT scans of the neck on an outpatient basis.
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CT scan of the neck
A CT scan of the neck with intravenous contrast is very useful in the diagnosis and management of retropharyngeal abscess. Retropharyngeal abscess appears as a hypodense lesion in the retropharyngeal space with peripheral ring enhancement. Other findings on CT scan include soft-tissue swelling, obliterated fat planes, and mass effect.
Obtain a CT scan of the neck with intravenous contrast when the findings on the lateral neck radiograph are equivocal or if the clinical suspicion for retropharyngeal abscess is high in patients with negative findings on lateral neck radiograph. Lateral neck radiographic findings may be misleading, especially in young children.
A CT scan of the neck with intravenous contrast also may be useful if the radiographic findings are positive because the CT scan can differentiate between retropharyngeal abscess and cellulitis. The CT scan also shows the extent of the retropharyngeal abscess and its relation to the great vessels, which is very helpful to the surgeon.
CT scan of the neck can also differentiate between retropharyngeal abscess and retropharyngeal lymphadenopathy in children, which may help the ear, nose, and throat (ENT) surgeon decide whether to treat with intravenous antibiotics alone or intravenous antibiotics plus surgical drainage.
Li and Kiemeney reported that the size of the abscess can be determined through CT scanning of neck; surgical intervention is generally required when abscesses exceed 2.2 cm in size. [12]
Wilkie et al reported that abscess size greater than 2.5 cm significantly predicts whether surgical intervention is required. [56]
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A chest radiograph is indicated to look for aspiration pneumonia and mediastinitis.
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An MRI with gadolinium enhancement can demonstrate the presence and size of a retropharyngeal abscess, but this modality takes longer to obtain than does CT scanning. [7]
Procedures
See the list below:
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Nasopharyngolaryngoscopy
A review of the literature did not reveal a role for nasopharyngolaryngoscopy use in the diagnosis of retropharyngeal abscess.
Safety of this procedure in the setting of retropharyngeal abscess is unclear.
Nasopharyngolaryngoscopy has been performed preoperatively in two adults, but no reports of its use in children have been found.
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Endotracheal intubation
Securing the airway may be required if the patient with retropharyngeal abscess is exhibiting signs of impending upper airway obstruction. Endotracheal intubation may be attempted, but it may be difficult because of distortion of the upper airway. [8]
Prophylactic intubation for a patient with retropharyngeal abscess but without respiratory distress generally is not indicated unless an interhospital transfer is planned.
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A literature review did not reveal the role of surgical or needle cricothyrotomy in RPA, but If a patient with signs of upper airway obstruction cannot be intubated, a surgical or needle cricothyrotomy may be required; the procedure may be difficult to perform, however, due to tissue edema and distortion.
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A tracheostomy may be required as definitive airway management in patients with retropharyngeal abscess and respiratory distress, but the procedure may be difficult to perform due to tissue edema and distortion. [9]
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Airway management in the operating room is preferred, with surgeon and anesthesiologist present, if clinical condition and time allow it. [8]
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A 5-year-old boy presented to the ED with 2 days of neck pain and fever but with no sore throat. The child had vomited once, and the mother reported that he was irritable. The child's temperature was 101.7° F, pulse was 118 beats per minute, respirations were 24 per minute, and blood pressure was 122/65 mm Hg. A decreased range of motion of the neck and a right anterior cervical node were observed; the child refused to swallow. Lateral neck radiographic findings show increased retropharyngeal space (white arrow). The CT scan did not demonstrate an abscess. The child was seen by an ear, nose, and throat specialist; he was admitted and started on intravenous clindamycin. He improved for 2-3 days and then worsened. Repeat neck CT scan findings demonstrated a retropharyngeal abscess. Incision and drainage was performed in the operating room. Cultures of the pus grew group A beta-hemolytic streptococci and alpha-streptococci, both sensitive to clindamycin. He improved and was discharged on the tenth hospital day on oral clindamycin.
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An 8-month-old infant boy presented with fever and a stiff neck. According to the mother, the baby was not moving his neck as much as usual. The mother also reported decreased oral intake. His temperature was 100° F, pulse was 104 beats per minute, respirations were 48 per minute, oxygen saturation was 98% (room air [RA]). The left tympanic membrane (TM) was inflamed and nonmobile. Left submandibular and left postauricular nodes were noted. The lateral neck radiograph shows increased retropharyngeal space. The CT scan demonstrated a small retropharyngeal abscess. The WBC count was 26,000 (24 polymorphonuclear leukocytes [P], 5 bands [B], 63 lymphocytes [L], 8 monocytes [M]). The baby was examined by an ear, nose, and throat specialist; he was admitted and started on intravenous clindamycin. He improved over the next few days and was discharged on the fifth hospital day on oral clindamycin with a plan for repeat CT scans of the neck on an outpatient basis.
