INTRODUCTION

The incidence of retropharyngeal ab­scess (RPA) is rare with the advent and wide usage of potent antibiotics. On the other hand, the diagnosis could be diffi­cult due to its masked clinical symptoms (Ameh 1999, Philpott et al. 2004). Retro­pharyn­geal abscess is common in chil­dren, with peak incidence at the age of three to five years old (Philpott et al. 2004, Kamath et al.2007). Suppuration of retropharyngeal lymph nodes secondary to upper respi­ratory infection is the main cause in pae­diatric population (Kamath et al. 2007). In adults, it usually follows for­eign body in­gestion, trauma and in a rare occasion due to tuberculous infection of the cervi­cal spine (Kamath et al. 2007, Goldenberg et al. 1997). Pak et al. (1999) have reported retropharyngeal abscess as a rare presentation in two patients with nasopharyngeal carcinoma.

Retropharyngeal abscess is a poten­tially serious infection due to its compli­cations which involves upper airway ob­struction, internal jugular vein thrombo­sis, mediastinitis, pericarditis, empyema, and carotid blow out (Pak et al. 1999, Craig & Schunk 2003, Chao et al. 1999, Siou & Yates 2000). Current mortality rate due to these complications accounts to 25% (Furst et al. 2000).

Patients with retropharyngeal abscess commonly present with neck pain, sore throat, fever, neck mass, respiratory dis­tress or stridor and limitation of neck movement (Craig & Schunk 2003). Physical examination may reveal bulging of the pharyngeal wall, pooling of saliva, swollen, and inflammed mucosa (Goldenberg et al. 1997).

Lateral neck radiograph may show loss of lordosis of the cervical spine, widening of the prevertebral soft tissue, and pres­ence of air or foreign body in the soft tis­sue (Goldenberg et al. 1997, Craig & Schunk 2003, Boucher et al. 1999). Computer­ized Tomography (CT) scan is the pre­ferred imaging technique since it helps in identifying the extent of the le­sion and its relation to the important structures in the neck. It is useful in dif­ferentiating be­tween cellulitis and ab­scess(Boucher et al. 1999).

Treatment of retropharyngeal abscess consists of securing the airway, intrave­nous antibiotics and intra oral incision and drainage (Goldenberg et al. 1997, Craig & Schunk 2003).

The aim of this study was to review demographic patterns, clinical presenta­tions and management of RPA.

MATERIALS AND METHODS

Operative records from 2000 to 2007 were retrospectively reviewed from two ENT referral centers in Malaysia. All cases of RPA were included. Eight pa­tients were identified. Patients’ demo­graphic information, presenting signs and symptoms were reviewed. Other findings which were reviewed are full blood count results especially the total white cell count, the culture and sensitivity results which were obtained intra-operatively, the imaging findings which includes lat­eral neck x-ray and CT scan as well as the record of treatments which comprised of operative procedures and antibiotics.

RESULTS

In our series, the patients were predomi­nantly female. There were five females and three males. The median age was 47 years old. The age group and sex distri­bution is illustrated in Table 1.

The presenting symptoms were varied and are summarized in Table 2. Most of the patients presented with dysphagia and or odynophagia, followed by short­ness of breath with or without stridor, neck pain or swelling, restricted neck movement and hoarseness. Surprisingly, none of the patients had fever at the time of presentation.       

Precipitating or predisposing factors are listed in Table 3. Four patients were di­abetics. Being diabetics, these patients are prone to infection. Three patients had a history of fish bone inges­tion. Among them was a 10 year old girl who was the youngest in the series.

Total white cell count was raised in all patients with predominantly neutrophilia. All patients underwent imaging studies. One patient underwent more than one im­aging modalities i.e lateral neck radio­graph and cervical contrast-enhanced computed to­mography (CECT) scan which was sug­gestive for retropharyngeal ab­scess. Lat­eral neck radiograph mostly showed wi­dening of prevertebral soft tissue, air in the soft tissue, foreign body and loss of cer­vical lordosis (Figure 1). CECT of neck confirmed the diagnosis and demonstrated ring enhancement and the extent of the abscess and its relation to important struc­tures in the neck (Figure 2).

The patients were treated hydrated and medication was given to relief pain. Broad spectrum IV antibiotics were commenced based on most likely pathogens and surgeons preference. A combination of IV Rocephine and flagyl was used in one pa­tient while IV cefuroxime and flagyl was administered to another pa­tient. Other pa­tients were treated with IV ampicillin and cavulanate. All patients underwent inci­sion and drainage under general anes­thesia.

Only two organisms were isolated from two patients in our study, i.e Klebsiella and Psuedomonas species, respectively. There were no growths in the rest of the patients. A Ziehl-Neelsen stain was per­formed in all patients, for which none tested positive.

Two approaches were performed i.e transoral approach and cervical approach were treated with cervical drainage in view of the extension of the abscess lat­erally to the parapharyngeal space. One pa­tient had spontaneous rupture of the ab­scess into the oral cavity while waiting for the operation.

Two patients who presented with air­way obstruction underwent tracheostomy under local anesthesia. Tracheostomy tube were decanulated two days post-operatively. One patient underwent elec­tive tracheostomy under general anes­thesia for prolonged intubation secondary to septicaemia. Nasogastric tube was inserted in four patients who underwent intraoral drainage of abscess. The tube was kept for two days on average, post operatively.

All patients recovered well. Only one patient had septicaemia secondary to RPA and passed away on the thirteenth day of admission despite vigorous treat­ment.

DISCUSSION

RPA is common in children (Goldenberg et al. 1997).  This is due to the fact that retropharyngeal nodes disappear by the age of five years. Most infections begin in the nose or nasopharynx, adenoids, and paranasal sinuses which drain to these nodes which later suppurate. There is a frequent history of an upper respiratory tract infection in children. In adults, retro­pharyngeal abscess are caused by in­strumentation, foreign body and trauma, and interestingly it is also a manifestation of tuberculosis of cervical spine (Kamath et al. 2007).

In our series, seven out of eight pa­tients were adults and the only child was aged 10 years. RPA in this child was secondary to fish bone ingestion. Perfo­ration of the posterior pharyngeal wall by the fish bone would have caused RPA in this patient. Four of them had diabetes and they were generally prone to infec­tion.

Acute RPA is characterized by fever, dysphagia, difficulty in breathing, stridor and torticollis in which the neck becomes stiff and the head is kept extended. Pa­tients with chronic RPA also complain of dysphagia and discomfort in the throat. How­ever, these symptoms are less marked. In our series, most of the pa­tients presented with ody­nophagia and or dysphagia (75%), neck pain (37.5%) and difficulty in breathing or stridor (37.5%) as the abscess caused an obstruction to the airway and food pas­sage. Examina­tion commonly revealed bulging of post­erior pharyngeal wall (Figure 3).

Sometimes, it is difficult to differentiate simple pharyngitis and RPA especially in the early stages of the disease whereby the signs and symptoms are not very prominent. We had one patient who was initially treated for pharyngitis. The pre­senting complaints were mild odynopha­gia and sore throat without fever. She was treated with oral antibiotics for a few days by her panel doctor.

Despite the administration of antibiotics, the symptoms persisted. She presented again with history of worsening sore throat and stridor without fever. She was intubated and blood investigation showed increased in total white cell count. CECT of neck was suggestive of RPA. The ab­scess was drained via cer­vical approach and Klebsiella species was isolated from the abscess. Unfortu­nately, she devel­oped septicaemia. A tracheostomy was performed due to prolonged intubation. However, despite the vigorous treatment, the patient passed away. These masked symptoms in RPA could be attributed to partially treated RPA, improper antibiotics and inade­quate duration of treatment.

The use of antibiotics has modified the presentation of deep neck space infec­tions. Most of the patients who presented with deep neck space abscesses had already received some form of antibiotic therapy as an outpatient. Signs and symptoms of infection could be masked.

This could result in missed or delayed diagnosis with development of complica­tions.

Organisms which responsible in para­pharyngeal abscess could be mixed aerobic and anaerobic. Among the aero­bic organisms include streptococci, pre­dominantly Streptococcus viridans and Beta-hemolytic streptococci (Page et al. 2008). Anaerobes are difficult to isolate and often are overlooked. Their exact role is difficult to ascertain from the medi­cal literature because of the inconsistent methodologies used for their isolation and identification in many studies. Their isolation and identification requires ap­propriate methods of collection, trans­portation, and cultivation of specimens (Brook 2008). In our series, only two or­ganisms were isolated from two patients, they were Klebsiella species and Pseu­domonas species respectively. There was no growth in the rest of the patients. Anaerobe organisms could possibly be involved and as mentioned, it is difficult to detect such by culture and sensitivity study.

Soft tissue radiograph i.e. lateral neck radiograph in RPA is often diagnostic. It helps to localise the abscess in the neck and retropharynx (Flaup-Precaurariu et al. 2009). All radiographs must be in the true lateral position so that the preverte­bral soft tissue could be measured cor­rectly and must be obtained in maximum extension and in the inspiratory phase of respiration to prevent a false positive re­sult. False positive radiographs com­monly occur when an oblique view is obtained as well as during flexion of the neck in which the soft tissues bow into the airways. The lateral neck radiograph will demonstrate widening of preverte­bral soft tissue, air in the soft tissue, for­eign body and loss of cervical lordosis due to muscle spasm (Ameh 1999, Goldenberg et al. 1997). At the second cervical verte­bral body level, soft tissue in excess of 7 mm in thickness is considered abnormal. At the sixth cer­vical vertebra, tissue thicker than 22 mm in adults or 14 mm in children is also considered to be abnor­mal. Sometimes, the widening of the pre­vertebral soft tissue may also be due to retropharyngeal cel­lulitis. Further evalua­tions with CECT scan are useful in diffe­rentiating an abscess from cellulitis (Goldenberg et al. 1997). It will show the extent of the abscess and its relation to important structures in the neck. Another non-invasive, inexpensive and reliable method is ultrasonography. It is capable in differentiating cellulitis from an ab­scess (Chao et al. 1999).  All of our pa­tients underwent imaging studies. Sim­ple lateral neck radiograph and CECT neck were found to be useful investiga­tive tools in the diagnosis of RPA in our pa­tients. If CT suggests presence of frank pus, we proceeded for surgical incision and drainage (I&D) and if CT suggested a cellulitis we administered intravenous antibiotics therapy.

Most of the time, intubation is possible in patients with RPA. Intubation must be performed with great care to prevent rupture of the abscess and it is essential to have the head in a dependent position to prevent aspiration. However, in cases of difficult intubation due to the large swel­ling of the posterior pharyngeal wall which obstructs the view of the laryngeal inlet, tra­cheostomy is indicated. In our series, two patients underwent emer­gency tra­cheostomy under local anes­thesia due to upper airway obstruction at the time of presentation. A tracheostomy was per­formed to secure the airway in patients with large abscess.  

Transoral incision and drainage to­gether with intravenous antibiotics are the preferred treatments for retropharyn­geal abscess (Ameh 1999, Craig & Schunk. 2003).  It is performed under general anaesthesia since aspiration un­der local anaesthesia will worsen respi­ratory obstruction (Ameh 1999). We used two criteria proposed by Kirse & Roberson (2001) for safe transoral drainage. First, the abscess should be medial to the great vessels. Second, the abscess should be confined: there should not be free pus in the fascial spaces of the neck. If the lateral space is involved, cervical approach is required. For transoral drai­nage, the patient is po­sitioned as for adenoidectomy. In our se­ries, three of the patients underwent cervical incision due to the large RPA which ex­tended to the parapharyngeal space. All of our pa­tients underwent adequate inci­sion and drainage with IV anti­biotics coverage. Except one mortality, all of them fully re­covered.

In conclusion, retropharyngeal abscess is a serious deep neck space infection with lethal complications. The diagnosis needs to be excluded in patients pre­senting with vague symptoms of sore throat and odynophagia without fever. Partially treated retropha­ryngeal abscess will mask the symptoms. Thus, thorough assessment of the patient is mandatory. A correct diagnosis should be achieved so that adequate treatment can be given to prevent mortality.