What is the role of imaging studies in the workup of retropharyngeal abscess (RPA)?

Updated: Jan 08, 2021
  • Author: Joseph H Kahn, MD; Chief Editor: Gil Z Shlamovitz, MD, FACEP  more...
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Answer

See the list below:

  • 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.
      A 5-year-old boy presented to the ED with 2 days o 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.
      An 8-month-old infant boy presented with fever and 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.
  • 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]

  • A chest radiograph is indicated to look for aspiration pneumonia and mediastinitis.

  • 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]

  • Ultrasonography may demonstrate the presence of a retropharyngeal abscess, but its use has not yet been clarified. [12, 57]


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