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Distinguishing Peritonsillar Abscess from Cellulitis

Roberts, James R. MD

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doi: 10.1097/01.EEM.0000547695.59089.5d
    peritonsillar abscess, cellulitis
    peritonsillar abscess, cellulitis:
    Patients with peritonsillar abscess are usually more symptomatic than those with a simple strep throat. Drooling can occur, and this patient had so much trouble swallowing his saliva that he used suction to remove it.

    An infection or collection of pus in the peritonsillar area is a rather common ED presentation. The process can be cellulitis or a distinct peritonsillar abscess (PTA), also called a quinsy. The infection is characterized by severe sore throat, painful swallowing, fever, drooling, tender adenopathy, muffled voice, and sometimes trismus.

    It may be clinically difficult to differentiate between cellulitis and abscess initially. Treatment consists of draining the pus if an abscess is present, and this can be done by needle aspiration or incision and drainage. Both interventions can be performed in the ED, but most emergency clinicians prefer needle aspiration. A formal I&D is eschewed because it is a somewhat complex and seemingly more difficult intervention. Cellulitis is treated with antibiotics, but may progress to an abscess.

    This column will discuss the presentation and diagnosis of PTA, and next month I will focus on the specifics of needle aspiration.

    Peritonsillar Abscess

    Galioto NJ

    Am Fam Physician


    This review for general practitioners noted that the highest incidence of PTA is in adults 20-40 years old, but it also occurs in children. PTA is the most common deep infection of the head and neck. Abscess formation is the most common complication of streptococcal tonsillitis, but some cases first present with an abscess that formed rapidly. The tonsils are surrounded by a capsule between it and the adjacent muscles, and abscess formation occurs in this space. The tonsil itself does not contain the abscess.

    The exact relationship between tonsillitis and abscess is unclear, and an abscess may form without preexisting tonsillitis. Patients with PTA appear ill, and they have pain and difficulty swallowing. Common symptoms and physical finding are noted in the table.

    The diagnosis is usually made by physical examination alone, but one must also consider retropharyn-geal abscess, mononucleosis, and epiglottitis. Up to six percent of cases are associated with mononucleosis, making this an alternative diagnosis or comorbidity especially in adolescents and young adults. Stridor and shortness of breath should prompt the clinician to consider epiglottitis.

    It may be difficult to differentiate peritonsillar cellulitis from true abscess by physical examination alone. It may require attempts at needle aspiration searching for pus to differentiate cellulitis (no pus) from abscess. A CT scan with contrast or intraoral ultrasound may be used to confirm the diagnosis. Most patients are too ill to remain supine for the time it takes for an MRI.

    Drainage, antibiotics, hydration, and pain control are required to treat an abscess adequately. The penicillin resistance rate is about 50 percent for pathogens other than streptococcus, so penicillin alone is probably not adequate.

    Comment: Consider a few caveats when approaching the diagnosis and treatment of peritonsillar abscess in the ED. It is generally accepted that ED treatment, drainage, and outpatient follow-up is safe and effective in the vast majority of patients. Some physicians may be reluctant to stick a needle into the pharynx to aspirate pus, but few complications have been reported from this procedure, and it seems like fair game for the emergency physician.

    It is important to try to identify if a peritonsillar abscess is actually present before attempting any invasive procedure. That is not always easy, and diagnosis can rest with the results of needle aspiration, though attempts at needle aspiration may fail even if an abscess is present. Pus can be loculated and difficult to extract.

    Common Signs/Symptoms of a Peritonsillar Abscess

    Symptoms are usually rather severe and sometimes patients have enough trismus that adequate visualization of the area is difficult. The abscess is medial and slightly superior to the tonsil in the peritonsillar space. With a true abscess, there is obvious swelling in the soft palate near the tonsil as well as deviation of the uvula away from the abscess. Abscesses are usually one side only. Intraoral ultrasound can rapidly and accurately identify a peritonsillar abscess, but it is generally underused, and most emergency physicians have no extensive experience with this. I find that using my index finger to examine the posterior pharynx around the tonsil is a good way to feel the distinct abscess, usually confirming that pus is likely present. Abscess formation is actually part of the spectrum of disease, from tonsillitis to peritonsillar cellulitis, culminating in a distinct abscess.

    Most abscesses resolve with ED management, but inadequately treated peritonsillar abscess carries some risks and complications, such as airway obstruction, abscess rupture, septic necrosis of the carotid sheath, and extension into the deep tissue of the neck or posterior mediastinum. I have never seen any of these complications.

    The clinician may sometimes be led astray by infective mononucleosis, an alternative diagnosis, or even a comorbidity of peritonsillar abscess. Epstein-Barr virus IGM antibody testing is the preferred method to confirm mononucleosis, but the monospot test is usually available in the ED. Mono is usually a disease of teenagers and young adults. It is not standard of care, however, to perform a mono test on all patients with signs and symptoms of peritonsillar abscess. I see no particular reason to do any routine blood tests on most of these patients.

    PTA can be diagnosed by CT or MRI, but these studies are not generally indicated. They may be considered if the patient has disproportionately severe symptoms with minimal findings (also consider epiglottitis). Intraoral ultrasound is probably the easiest way to differentiate between PTA and cellulitis. But emergency physicians are not routinely using intraoral ultrasound when evaluating a possible peritonsillar abscess because most clinicians are not skilled at this procedure. (See a review of ultrasound-guided peritonsillar abscess evaluation by emergency clinicians: Am J Emerg Med 2003;21[2]155;

    A peritonsillar abscess can usually be considered from physical examination of the posterior pharynx. There is soft tissue swelling medial to the tonsil, often with deviation of the uvula to the other side. One can use a gloved index finger to palpate the area, looking for the feel of pus accumulation. If still uncertain, consider a CT with contrast or intraoral ultrasound. A trial of aspiration is also a method to confirm an abscess.

    Antibiotics are routine post-aspiration. Recommendations for oral antibiotics vary and include penicillin plus metronidazole, clindamycin (my first choice), or amoxicillin clavulanate. It's common but of no distinctly proven benefit to give the first dose of antibiotics IV in the ED. IV choices include clindamycin, ampicillin/sulbactam, ceftriaxone, and piperacillin/tazobactam. One 10 mg dose of IV dexamethasone is recommended by many clinicians. The evidence is not outstanding, but routine steroids appear to offer some benefit to reduce symptoms and hasten recovery. Importantly, an abscess should be markedly improved in 24-36 hours when the first follow-up is scheduled. If not, consider another aspiration, CT scan, or a possible MRSA infection (and add vancomycin and admit).

    Most patients with PTA are dehydrated, and it seems reasonable to start IV fluids in all who have significant symptoms. One to two liters in the ED over a four-hour period should suffice with most patients, but dehydration is a common indication for admission in children.

    The majority of patients can be treated as outpatients, but it is best to observe aspirated patients in the ED for three or four hours. Some relief can be rather rapid following the removal of pus. The hospital admission rate is about 10 percent, usually based on clinician judgment and severity of illness.

    A large peritonsillar abscess. Note the soft tissue swelling (arrow) on the left soft palate and marked deviation of the uvula.

    The microbiology of PTA is rather complex and includes anaerobic or aerobic organisms. (J Oral Maxillofac Surg 2004 62[12]:1545.) Infections are polymicrobial with the predominant species being streptococcal pyogenes, other streptococcal species, Staphylococcal aureus, a variety of respiratory anaerobes, and Haemophilus species. MRSA can also be cultured, but coverage is not usually included in the initial antibiotic choices. One may consider culturing pus from an abscess, but studies have indicated that the results of cultures obtained from PTA do not alter management so are not routine. A gram stain of the pus is of no benefit.

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