Definition and Pathophysiology
A quinsy — formally known as a peritonsillar abscess (PTA) — is a collection of pus that has accumulated in the peritonsillar space: the potential space between the tonsillar capsule and the superior constrictor muscle of the pharynx. It develops as a complication of acute tonsillitis, when infection spreads beyond the tonsillar capsule. Most quinsies are polymicrobial, with Group A Streptococcus being the most common aerobic pathogen and anaerobes (particularly Fusobacterium, Prevotella, and Veillonella species) being the most important co-pathogens — explaining why metronidazole is added to penicillin in treatment.
Clinical Features
The cardinal feature of a quinsy is trismus — difficulty or inability to open the mouth fully, caused by spasm of the medial pterygoid muscle adjacent to the peritonsillar space. A patient with a sore throat who cannot open their mouth has a quinsy until proven otherwise. Other features:
- Trismus: Typically progressive. The patient will often be unable to open their mouth more than a finger-width or two.
- Muffled "hot potato" voice: A characteristic altered voice quality caused by oedema of the soft palate and pharynx.
- Drooling: The patient cannot swallow their own saliva and will be seen constantly spitting.
- Severe unilateral throat pain: Often radiating to the ipsilateral ear (referred otalgia via the glossopharyngeal nerve).
- High fever and systemic illness.
- Dysphagia: Pain and swelling prevent swallowing — patients are at risk of dehydration.
- Uvular deviation: On examination (when the mouth can be opened sufficiently), the uvula is deviated away from the affected side by the pressure of the peritonsillar mass. The superior pole of the tonsil will appear pushed medially and inferiorly, while the peritonsillar space is bulging and erythematous.
Normal Oropharynx for Comparison
The image below shows a normal oropharynx — note the symmetrical uvula, bilateral tonsils, and visible soft palate. This is what normal looks like before studying the pathological examples below.
Quinsy: Clinical Photographs
The image below shows a left-sided quinsy. The uvula and tonsil have been pushed to the right by the peritonsillar abscess on the left side.
Here is another example of a quinsy, this time on the right side:
Management
Immediate management on presentation:
- Insert IV cannula and take bloods: FBC, U&Es, LFTs, CRP, glandular fever screen
- Benzylpenicillin 1.2 g IV QDS (covers Streptococcus)
- Metronidazole 500 mg IV TDS (covers anaerobes — essential in peritonsillar abscess)
- Diclofenac 50 mg orally TDS (NSAIDs are highly effective for oropharyngeal pain)
- Codeine phosphate 60 mg orally QDS
- Paracetamol 1 g orally or IV QDS
- Difflam (benzydamine) spray — two sprays every 4 hours
- IV fluid replacement with normal saline if the patient is clinically dehydrated (usually 1 litre or more)
The abscess must be drained. Depending on the time of admission and your hospital's protocol, this is performed by the ENT SHO on call or the patient is admitted to the ward for drainage in the morning. Patients admitted overnight should be kept nil by mouth (NBM) in case drainage is required under general anaesthesia.
Aspiration Technique
Aspiration of a quinsy is the preferred first-line drainage procedure. Technique:
- Spray local anaesthetic: Apply Xylocaine (lidocaine 10%) spray to the peritonsillar mucosa and allow the patient to spit it out. It tastes unpleasant. Wait 2 minutes.
- Inject local anaesthetic: Using the smallest available needle (orange [25 G] or a dental needle), inject 1 to 2 ml of 1% lidocaine with adrenaline into the mucosa overlying the bulging area. This is significantly more effective than spray alone and reduces pain markedly, though it takes approximately 3 minutes to work fully.
- Prepare the aspiration needle: Take the largest available IV cannula (brown, 14 G). Remove the plastic cannula from the needle assembly, leaving only the needle, and attach it to a 20 ml syringe. Alternatively, cut the cannula protector at the appropriate level and leave it as a depth stop. Wrap sticky tape around the base of the needle so that only 1.5 to 2 cm of the needle tip is exposed — this is your safety guard to prevent going too deep and hitting the carotid artery.
- Identify the aspiration point: The classic aspiration point is where a vertical line drawn superiorly from the last upper molar tooth intersects with a horizontal line drawn parallel to the base of the uvula — at approximately the superior pole of the tonsil and the junction of the anterior tonsillar pillar and the soft palate.
- Insert the needle: Using a headlight and tongue depressor, steadily insert the needle into the most prominent point of the swelling, staying as horizontal as possible and aiming medially. Aspirate as you advance.
- Aspirate pus: Typically 5 to 10 ml of green or yellow-brown pus is aspirated. This provides near-immediate relief — the trismus often begins to resolve within minutes and the voice normalises rapidly.
- If no pus is aspirated, try a maximum of three separate aspiration sites before moving to incision and drainage. Loculation (pus divided into multiple compartments) is the most common reason for failed aspiration.
Incision and Drainage
Incision and drainage (I&D) is used if aspiration fails (no pus obtained after three attempts), if the abscess is clearly loculated, or as the first-line procedure in some centres. It is more painful than aspiration and requires more experience.
With the local anaesthetic still working, using a scalpel with a No. 11 or No. 15 blade, make a small curved incision (approximately 1 cm) at the same location used for aspiration — the superior pole of the peritonsillar space. Then use a small closed pair of sinus forceps (such as Tilley's forceps or a similar instrument) to gently open the cavity and break down any loculations, allowing the pus to drain freely. Apply gentle pressure with gauze to encourage drainage. The patient should lean forward to allow pus and blood to drain from the mouth — give them a bowl.
Post-Procedure Management and Admission
Patients are admitted for at least 24 hours after drainage for the following reasons:
- Risk of laryngospasm in the immediate post-procedure period
- Risk of abscess re-accumulation within the next 12 hours
- Ongoing IV antibiotic therapy and IV fluid replacement
- Monitoring of airway and ability to tolerate oral fluids before discharge
Continue the antibiotic regimen (benzylpenicillin and metronidazole IV), analgesia, and IV fluids. When the patient is tolerating oral fluids, switch to oral amoxicillin-clavulanate (co-amoxiclav) 625 mg TDS for 7 days, or phenoxymethylpenicillin 500 mg QDS with metronidazole 400 mg TDS.
Tonsillectomy after Quinsy
There are two timing strategies for tonsillectomy after quinsy:
- Interval (hot) tonsillectomy: Tonsillectomy performed 4 to 6 weeks after the acute episode, once infection has fully resolved. This is the most common approach in the UK. Indications: recurrent quinsy, or recurrent tonsillitis meeting Paradise criteria. Approximately 10 to 15% of patients will have a second quinsy without tonsillectomy.
- "Quinsy tonsillectomy" (immediate or abscess tonsillectomy): Tonsillectomy performed at the time of drainage, under the same general anaesthetic. This is technically more difficult due to oedema and altered anatomy, with a slightly higher risk of bleeding and airway complications. It is usually reserved for patients with recurrent quinsy, failed aspiration/I&D, or those who refuse follow-up. Some ENT surgeons advocate it as a definitive one-stage treatment.
Frequently Asked Questions
What is the most important clinical sign of a quinsy?
Trismus — difficulty or complete inability to open the mouth — is the most important and reliable clinical sign of a quinsy. It is caused by reactive spasm of the medial pterygoid muscle, which lies immediately adjacent to the peritonsillar space. A patient with a sore throat and trismus has a quinsy until proven otherwise. Absence of trismus makes quinsy significantly less likely, though early or small abscesses may occasionally not yet produce trismus.
Why is metronidazole added to penicillin for quinsy?
Peritonsillar abscesses are polymicrobial infections. Although Group A Streptococcus is the most common aerobic pathogen, anaerobic bacteria — particularly Fusobacterium necrophorum, Prevotella, and Veillonella species — are consistently isolated from quinsy aspirates. Penicillin is effective against Streptococcus but has variable activity against many anaerobes. Metronidazole specifically targets anaerobic bacteria by disrupting their DNA. The combination of benzylpenicillin (or amoxicillin) plus metronidazole therefore provides broader antimicrobial coverage appropriate for this polymicrobial infection.
Where exactly should I aspirate a quinsy?
The classic landmark for quinsy aspiration is the intersection of: (1) a vertical line drawn superiorly from the posterior edge of the last upper molar tooth, and (2) a horizontal line drawn parallel to the base of the uvula. This corresponds to the superior pole of the peritonsillar space, at the junction of the anterior tonsillar pillar and soft palate. In practice, aim for the most prominent or fluctuant point of the swelling. Never insert the needle more than 1.5 to 2 cm — use a depth guard. Every quinsy is slightly different, and anatomical landmarks may be distorted by swelling; experience significantly improves aspiration success.
Aspiration produced no pus — what should I do?
If the first aspiration is dry, consider: repositioning the needle slightly — try a maximum of three separate points around the suspected abscess before abandoning the technique. If three attempts produce no pus, the diagnosis may be peritonsillar cellulitis (no abscess yet formed) rather than a frank quinsy, or the abscess may be deeply loculated or in an atypical position. Options: (1) proceed to incision and drainage, which allows better access and breakdown of loculations; (2) arrange an urgent ultrasound (intraoral or cervical) to confirm the presence and location of pus; (3) re-examine in 12 to 24 hours after IV antibiotics — a cellulitis may resolve or a true abscess may become more apparent.
What is the risk of missing the carotid artery during quinsy aspiration?
The internal carotid artery passes approximately 2 to 2.5 cm posterior and lateral to the peritonsillar space. The risk of carotid artery injury is real if the needle is advanced too deeply or angled posterolaterally. This is why a needle depth guard (tape or a cut cannula protector) that exposes only 1.5 to 2 cm of the needle is essential. Keep the needle orientated medially and horizontally. Never angle it posteriorly toward the carotid. Carotid injury during quinsy aspiration, while rare, is a catastrophic complication that has been reported in the literature — technique matters enormously.
How would you decide between aspiration and incision and drainage?
Aspiration is the preferred first-line approach in most centres because it is less painful, equally effective (success rates of 85 to 95% for frank abscesses), and avoids the need for a formal incision under local anaesthesia. It is also appropriate for first-time procedures by less experienced operators under supervision. Incision and drainage is preferred when: aspiration has failed (three dry attempts); the abscess appears to be multiloculated on imaging; it is a recurrent quinsy (likely scarred and loculated); or the operator is experienced and comfortable with the technique. Both approaches have equivalent cure rates when performed correctly.
How would you counsel a patient about tonsillectomy after a first quinsy?
After a single quinsy, the risk of recurrence is approximately 10 to 15% over the following years. Tonsillectomy is not routinely indicated after a single quinsy in isolation — it is indicated if the patient also has a history of recurrent tonsillitis meeting Paradise criteria, or if the patient experiences a second quinsy. The patient should be counselled: (1) the risk of another quinsy is real but not certain; (2) tonsillectomy would prevent both further quinsies and recurrent tonsillitis; (3) tonsillectomy carries its own risks, including a small but serious risk of post-operative haemorrhage (approximately 2 to 5%); (4) the decision should be made jointly with the patient in outpatient follow-up.
What are the complications of an untreated or inadequately treated quinsy?
Untreated or inadequately managed quinsy can lead to: (1) parapharyngeal abscess — spread of infection into the adjacent deep neck space, which can extend into the retropharyngeal space or mediastinum (descending necrotising mediastinitis — a life-threatening emergency); (2) Lemierre's syndrome — thrombophlebitis of the internal jugular vein caused by Fusobacterium necrophorum, with risk of septic emboli to the lungs, liver, and joints; (3) airway compromise from progressive oedema and medial displacement of the lateral pharyngeal wall; (4) aspiration of abscess contents; (5) septicaemia. Early diagnosis and drainage are therefore essential.
References
- Klug TE, Rusan M, Fuursted K, Ovesen T. Peritonsillar abscess: complication of acute tonsillitis or Weber's glands infection? Otolaryngol Head Neck Surg. 2016;155(2):199–207.
- Scott-Brown WG, Gleeson MJ, Clarke R, eds. Scott-Brown's Otorhinolaryngology, Head and Neck Surgery. 8th ed. London: CRC Press; 2018.
- ENT UK. Tonsillitis and Quinsy: Clinical Guidelines. ENT UK; 2019.
- Mehanna HM, Al-Bahnasawi L, White A. National audit of the management of peritonsillar abscess. Postgrad Med J. 2002;78(923):545–548.
- Herzon FS. Peritonsillar abscess: incidence, current management practices, and a proposal for treatment guidelines. Laryngoscope. 1995;105(8 Pt 3 Suppl 74):1–17.
- Passy V. Pathogenesis of peritonsillar abscess. Laryngoscope. 1994;104(2):185–190.