Zenker's diverticulum (pharyngeal pouch)

1. Anatomy and site

• It arises through Killian's dehiscence (Killian triangle), a weak posterior area between:
  • Oblique fibers of the inferior pharyngeal constrictor superiorly
  • Transverse fibers of the cricopharyngeus inferiorly
• The sac projects posteriorly, often toward the left, from the hypopharynx.
• It is a pharyngoesophageal diverticulum.
• Differentiate it from a Killian-Jamieson diverticulum, which arises below the cricopharyngeus and is anterolateral.

2. Etiology and pathogenesis

Etiology

1. Age-related reduction in cricopharyngeal compliance
2. Cricopharyngeal fibrosis or inflammation
3. Failure of relaxation of the upper esophageal sphincter (UES)
4. Impaired laryngeal elevation and impaired opening of the UES during swallowing
5. Incoordination between pharyngeal contraction and cricopharyngeal relaxation
6. Possible association with gastroesophageal reflux, though this does not by itself establish causation

Pathogenesis

1. During swallowing, the pharyngeal constrictors contract.
2. The cricopharyngeus fails to relax or open adequately.
3. Intraluminal hypopharyngeal pressure rises.
4. Mucosa and submucosa are forced posteriorly through Killian's dehiscence.
5. Repeated pulsion produces an enlarging pouch.
6. The pouch retains food and secretions, causing regurgitation, halitosis, and aspiration.

Zenker's diverticulum is an acquired pulsion pseudodiverticulum caused by impaired cricopharyngeal relaxation, producing high hypopharyngeal pressure and posterior mucosal herniation through Killian's dehiscence.

3. Clinical features

Typical symptoms

Clinical signs

• Thin or malnourished older patient
• Occasionally a soft compressible left anterior neck swelling
• Palpation may produce gurgling, termed Boyce sign
• Pooling of saliva in the hypopharynx may be seen on endoscopic examination
• A "rising tide" phenomenon can be seen during swallow assessment: retained fluid returns upward from the postcricoid region after swallowing.

4. Diagnosis

Investigation of choice: barium swallow with videofluoroscopy

• Posterior contrast-filled pouch at the pharyngoesophageal junction
• Best seen in the lateral projection
• Demonstrates sac size, neck, retention, emptying, aspiration, and the functional swallowing abnormality
• Large pouches may compress and displace the cervical esophagus.

Other investigations

• Flexible endoscopy or upper GI endoscopy: evaluates mucosa, clears retained food, excludes tumor or other esophageal pathology. It must be performed carefully because the scope may enter the pouch and cause perforation.
• FEES or modified barium swallow: useful where aspiration and pharyngeal dysphagia need functional assessment.
• Manometry: not routinely required. It can be difficult to perform and may not alter management.
• CT neck/chest: reserved for diagnostic uncertainty, complications, or concern for malignancy.

5. Treatment

Indications for intervention

• Significant dysphagia
• Regurgitation
• Weight loss or malnutrition
• Aspiration, recurrent chest infections, or aspiration pneumonia
• Large or progressively enlarging sac
• Impaired quality of life

Principle of definitive treatment

The essential treatment is division of the cricopharyngeal muscle.

Treatment options

6. Open transcervical surgery: operative steps

A. Preparation

1. Confirm anatomy and pouch size on contrast swallow.
2. Correct dehydration, malnutrition, and pulmonary infection if present.
3. General anesthesia with careful airway planning because the pouch may contain retained material and aspiration is a risk.
4. Position supine with shoulder roll and neck extension.
5. Consider endoscopic evacuation of retained debris before dissection.

B. Exposure

1. Make a left-sided transverse cervical incision, generally along a skin crease at the level of the cricoid.
2. Divide platysma and enter the plane anterior to the sternocleidomastoid muscle.
3. Retract carotid sheath laterally and thyroid/trachea medially as needed.
4. Expose the cervical esophagus and identify the diverticular sac.
5. Mobilize the sac gently, preserving the recurrent laryngeal nerve and surrounding vascular structures.
6. Identify the neck of the pouch and the cricopharyngeus. A bougie may be passed in the esophagus to define the lumen and facilitate safe resection.

C. Cricopharyngeal myotomy

1. Perform a longitudinal myotomy through the cricopharyngeus.
2. Extend the division adequately across the dysfunctional cricopharyngeal segment and onto the proximal esophageal muscle as required.
3. Confirm that the restrictive muscle has been fully divided.

D. Management of the sac

Option 1: Diverticulectomy

1. Apply a linear stapler or carefully close the pouch neck after placing a bougie within the esophageal lumen.
2. Excise the diverticulum.
3. Inspect the staple or suture line for integrity.
4. Perform a leak test where appropriate.

Option 2: Diverticulopexy

1. Mobilize the pouch.
2. Suspend the sac superiorly by suturing its apex to prevertebral fascia or nearby cervical musculature.
3. This keeps the pouch above the food stream, reducing filling.
4. Complete the cricopharyngeal myotomy.

Option 3: Myotomy alone

• Consider for a very small pouch, where correction of the outflow obstruction may relieve symptoms and prevent progression.

E. Closure and postoperative care

1. Secure hemostasis and place a drain selectively.
2. Close the wound in layers.
3. Keep the patient nil by mouth initially.
4. Perform a contrast swallow according to local protocol before oral intake, particularly after diverticulectomy.
5. Start liquids if there is no leak, then advance to a soft diet.
6. Monitor for aspiration, neck swelling, fever, dysphonia, leak, and mediastinitis.

7. Rigid endoscopic stapled diverticulotomy: key steps

1. General anesthesia and supine positioning with neck extension.
2. Insert a rigid diverticuloscope to expose the common septum between the esophageal lumen and diverticulum.
3. One blade of the endoscopic stapler enters the esophagus and the other enters the pouch.
4. Fire the stapler across the septum.
5. This divides the septum and simultaneously creates:
   • A common channel between pouch and esophagus
   • A cricopharyngeal myotomy
   • A stapled sealed edge
6. Inspect for adequate division, hemostasis, and mucosal integrity.
7. Contrast swallow and diet advancement follow institutional practice.

8. Flexible endoscopic septotomy / Z-POEM: essential concept

Flexible endoscopic septotomy

• The septum between the pouch and esophagus is divided with an endoscopic knife.
• Division includes the cricopharyngeal muscle.
• The aim is to form a common cavity so retained food drains into the esophagus.

Z-POEM

1. Inject submucosa proximal to the septum.
2. Make a mucosal entry and create a submucosal tunnel on both sides of the septum.
3. Expose the cricopharyngeal muscle.
4. Divide the muscle completely along the septum.
5. Achieve hemostasis.
6. Close the mucosal entry with endoscopic clips or suturing.

9. Complications of treatment

• Cervical esophageal or pharyngeal leak
• Pharyngocutaneous fistula
• Mediastinitis
• Retropharyngeal or parapharyngeal abscess
• Recurrent laryngeal nerve injury and vocal cord paralysis
• Bleeding
• Perforation
• Subcutaneous emphysema
• Aspiration
• Persistent dysphagia or recurrence from incomplete myotomy
• Residual large pouch after endoscopic treatment

Short exam answer

Zenker's diverticulum is an acquired false pulsion diverticulum through Killian's dehiscence, above the cricopharyngeus. Cricopharyngeal dysfunction causes raised hypopharyngeal pressure, resulting in posterior herniation of mucosa and submucosa. It presents in elderly patients with progressive dysphagia, regurgitation of undigested food, halitosis, cough, aspiration, weight loss, and cervical borborygmi. Barium swallow with lateral videofluoroscopy confirms the diagnosis. Symptomatic disease is treated by cricopharyngeal myotomy with diverticulectomy, diverticulopexy, or endoscopic stapled/laser/flexible endoscopic septotomy.