What is it?

A pharyngeal pouch (also known as a Zenker's diverticulum) is an out pouching of the pharyngeal mucosa through the muscle wall of the organ. This can be congenital or - more commonly - acquired. Of the acquired pouches a pulsion diverticulum (or Zenker's diverticulum) is by far the predominant type.

How does it develop?

Swallowing is a complex mechanism consisting of a series of carefully choreographed steps both conscious and unconscious. Part of this process involves food passing from the pharynx into the upper oesophagus. In order for the food to pass freely the upper oesophageal sphincter (consisting of the cricopharyngeus muscle) needs to relax as the food bolus approaches.
An anatomical weakness exists between the transverse (cricopharyngeus) and oblique fibres (thyropharyngeus) of the lower pharyngeal muscles- sometimes called Killian's dehiscence. It is thought that the lower, transverse fibres (cricopharyngeus) of the pharyngeal muscles do not relax adequately during swallowing causing increased pressure above cricopharyngeus. This pressure forces the mucosa of the pharynx through and this pressure causes the out pouching of the mucosa through Killian's dehiscence resulting in a pouch.

How does it present?

The most common symptom is difficulty in swallowing food/solids with a feeling of a lump in the throat. This dysphagia can lead to weight loss and malnutrition. This can be accompanied by regurgitation on undigested food several minutes to hours after eating. Regurgitation of food can lead to pulmonary aspiration, especially at night when the patient is recumbent, and resultant pneumonia. Patients may also report gurgling noises in the throat. Although the pouch may present with a palpable lump in the neck, this is very rare. Pouches are typically painless and pain may signify ulceration of the mucosa or carcinoma within the pouch.
As the pouch is an acquired condition it is more common with age. It is unusual to find a pouch in patients under the age of fifty, although it does occur. The patient usually has a long history of symptoms prior to diagnosis due to the insidious nature of the condition and may be misdiagnosed as globus pharyngeus. Pouches are more common in men (M:F = 2:1) and rare in the Black population.
The severity of symptoms does not always correlate to the size of the pouch.

Making the Diagnosis

Although the history and examination may be suggestive of a pouch the most reliable and common method of diagnosis is Barium swallow or videofluoroscopy demonstrating the pouch. The pouch may be made to fill with a Valsalva manoeuvre at the time of investigation causing contrast to track into the pouch.
A soft tissue x-ray of the neck may show a soft tissue swelling between the vertebral column and the oesophagus and may have a air/fluid level if partially filled at the time.
A plain chest x-ray may demonstrate changes of aspiration pneumonia.

How is it treated?

A pharyngeal pouch only needs to be treated if the patient has significant symptoms or if it has complications such as aspiration, ulceration or carcinoma. Leaving the pouch alone is a reasonable management option especially if the patient is not medically fit for surgery.

Surgical intervention consists of two parts. The first is to treat the cause of the pouch i.e. reducing the resistance of the cricopharyngeus and secondly to treat the pouch itself. This can be achieved either by an open procedure or by an endoscopic approach.

The simplest procedure is dilatation of the cricopharyngeus. This relieves the symptoms temporarily and carries the risk of perforation although this is rare. If uncomplicated the patient recovers quickly and can commence sterile water the following day.

The endoscopic approach is the preferred method of many surgeons currently. A specialised oesophagoscope is used which has two blades distally. One blade passes down the oesophagus whilst the other passed into the pouch. This allows the wall/bar separating the pouch and oesophagus to be identified. Contained within the wall of this bar of tissue is the cricopharyngeus muscle. This wall can then be divided by various means such diathermy (Dohlman), laser or by a stapling device. This procedure does not get rid of the pouch but opens up the neck of the pouch so that any food that enters the pouch can drain freely into the oesophagus. At the same time the cricopharyngeus muscle is divided reducing the risk of recurrence.

Although most surgeons prefer the endoscopic approach some still prefer the open approach. It is a useful technique for particularly large pouches or for failure of the endoscopic method. In the open approach the pouch is dealt with through a neck incision. The pouch is first inspected endoscopically and concomitant pathology excluded. The pouch is then packed with antiseptic gauze to help identify it intraoperatively. At operation the pouch is identified and dissected free from the surrounding structures. The pouch is then either excised and removed or inverted into the oesophagus. The cricopharyngeus muscle (cricopharyngeal myotomy) is then divided.

Post-operative Care

All post-operative patients need careful monitoring especially with regard to temperature, pulse, blood pressure and chest pain. The most important complication after treatment of a pharyngeal pouch is a leak of contents into the surrounding tissues leading to a mediastinitis. This manifests itself as pyrexia, tachycardia and chest pain. Any of these signs or symptoms should be noted and the appropriate people informed immediately as this is a potentially fatal condition.

For endoscopic procedures most patients can commence sterile water the following morning post-operatively. The patient then progresses to free fluid, soft diet and normal diet over the next 1-2 days.

For open procedures (or if the surgeon thinks there is any possibility that the endoscopic procedure is at all compromised) the post-operative recovery and monitoring continues for longer. A suction drain is normally in situ post-operatively and should be removed once drainage is minimal - usually 2-3 days. The patient usually has a feeding tube in place, having been passed in theatre. The patient will be nil by mouth and fed through the N.G. tube for 5-7 days. The N.G. tube will be initially on free drainage and then sterile water is commenced. A referral to the dietician should be made for a feeding regime. The surgeon will decide the appropriate time (about 5-7 days post-op.) to spigot the N.G. tube and start the patient drinking small amounts of sterile water. If this is tolerated the tube is removed and free fluids building up to solids are introduced. The oral intake continues providing the patient is asymptomatic and the observations are stable.

If the pouch has been inverted the patient commenced fluid the following morning and discharged home 2-3 days post-operatively.

Complications

Complications include: bleeding (primary and secondary), mediastinitis, surgical emphysema, fistulae, oesophageal stenosis and recurrence.

Follow-up

Both endoscopic and open procedures are followed up four to six weeks in Outpatients. If the patients are well and asymptomatic then they are discharged. There is no need for follow-up barium swallow unless symptoms persist. In large pouches treated endoscopically a second (or more) procedure may be required.

Kevin Webb