Trilobed Zenker’s diverticulum: A case report and proposed pathogenesis
Objectives/Hypothesis: To report the first described case of a trilobed Zenker’s Diverticulum (pharyngeal pouch) and review the current theories advocated on the pathogenesis of Zenker’s diverticulum.
Study Design: A case report with review of the literature.
Methods: A review of the case notes of a patient presenting with a trilobed Zenker’s diverticulum and a literature search to identify, review and report similar cases.
Results: No previous report of a trilobed Zenker’s diverticulum exists in the literature but seven cases of bilobed pouches are reported. Although it is agreed the diverticulum forms at Killian’s dehiscence, there is no universally accepted theory on the mechanism of Zenker’s diverticulum formation. We propose a theory for the formation of trilobed and bilobed Zenker’s diverticulum.
Conclusion: Bilobed and trilobed Zenker’s diverticulum are rare but can be treated in a similar manner as the commoner unilobed diverticulae.
Keywords: Pharynx, Zenker’s Diverticulum, Pathogenesis.
Pharyngeal pouches occur with an incidence of only 2 per 100,000 people per year1 Bilobed pouches are a rarity with just seven cases described in the literature to date.2-7 Contrast imaging swallows diagnosed all reported cases. We report the first recorded case of a trilobed pharyngeal pouch. We describe the unique findings on barium swallow, the surgical treatment offered and a six months follow-up to satisfactory patient discharge. A proposed theory for the mechanism of formation of bilobed and trilobed pouches is proposed.
A 73-year-old man presented to the Orl-HNS clinic with a 6-month history of increasing dysphagia predominantly for solid foods. He also complained of post-prandial regurgitation one to two hours following intake. He denied pharyngeal borgorygmi but did have a constant globus sensation. He had moderately severe Chronic Obstructive Pulmonary Disease (COPD) although this was adequately controlled with medication. At the time of presentation he had no documented evidence of repeated lower respiratory chest infections. Clinical examination of the head and neck was unremarkable.
A barium swallow reported the presence of a trifid pharyngeal pouch. The antero-posterior film demonstrated the trilobed pouch that was not demonstrated on the lateral view. (Figure 1). Rigid endoscopic assessment prior to surgical treatment revealed a pharyngeal pouch with a single neck and a trilobed fundus. (Figure 2). Using a distending diverticuloscope and an Endo GIA-30 stapling gun (Ethicon, Cincinnati, USA) an endoscopic stapling and division of the cricopharangeal bar was performed. No attempt was made to divide the septae within the pouch. (Figure 3). Normal diet was established on the day following surgery and the patient was discharged home at 36 hours. At six months follow up he remains symptom free.
Since the first description of Zenker’s diverticulum (Pharyngeal pouch) in 1769 by Ludlow8 only 7 cases of bilobed pharyngeal pouches have been reported. The first report of a bilobed pouch was in 1945 when Harrington2 described what he called a double diverticula. There followed in 1948 two further cases where the fundus was described as bilobed3. Another case in 1954 described a pouch with a single neck and a bilobed fundus4. Stafford and Frootko5 reported a case with two distinct pouches and necks that was treated conservatively. Meehan and Henein6 found a pouch with two necks leading to a double pouch with a dividing midline septum. This case was treated using an external approach with excision of the pouch and cross stapling of the herniated neck of the pouch. More recently Izzat and Dezso7 described a bilobed pouch treated successfully with endoscopic stapling.
The use of endoscopic stapling for symptomatic pouches has become popular during the late 1990’s due to its ability in alleviating symptoms with minimal morbidity. This procedure permits early discharge from hospital, usually the following day, and the surgical procedure can be repeated should the symptoms persist or subsequently return.9
The theories of pharyngeal pouch formation were reviewed with the knowledge of the existence of bilobed and trilobed pouches. Despite much research and investigation the cause of pharyngeal pouch formation remains unresolved. It is agreed that abnormal pharyngeal muscle function results in herniation of mucosa through the potential weak muscle crossing, called Killian’s dehiscence. Van Overbeek10 has defined this area as being “between the propulsive oblique fibres of the inferior constrictor muscle and the horizontal fibres of the cricopharyngeus muscle, with its sphincter function at the oesophageal inlet, there is a triangular area with only scanty muscle fibres”. This proposal was originally made by Zenker and von Ziemssen in 1878 11 when they suggested that high hypopharyngeal pressures was the probable cause of pharyngeal pouch herniation at a zone of weakness. The exact mechanism of pouch formation centres on altered pharyngeal muscle pressures and the area of weakness, but as yet there is no universally agreed or accepted theory. Cook et al.12 carried out simultaneous manometry and videoradiography study on 14 patients who had pouches and 9 controls. They reported that the primary abnormality was incomplete opening of the upper oesophageal sphincter (UOS), perhaps a form of achalasia, which they thought was probably caused by muscle degeneration and resulted in fibro-adipose replacement of the UOS 13. They proposed that the UOS dysfunction caused a marked increase in hypopharyngeal intra-bolus pressure and hence the outcome of pharyngeal mucosal herniation leading to pouch formation. This proposed theory for pouch development has been supported by other workers14,15. Another study on 10 patients who had a pharyngeal pouch 16, combined manometry and fluoroscopy and concluded that cricopharyngeal dysfunction caused increased intrabolus pressure and thereby resulted in a pulsion diverticulum. However, other groups who have performed manometry have been unable to show similar abnormalities in the UOS segment.17,18,19. An alternative argument8 is that the manometric changes may be due to the presence of the pouch itself rather than being the cause of its formation. It is also possible that a structural change in the UOS muscle13,14 could be as a result of the pouch and not the cause of its development19. Furthermore, many patients symptoms resolve after simple diverticulectomy without myotomy which should not be the case if the primary disorder were due to morphological changes in the UOS 10. It may also be possible that individual variations in the size of the area around Killian’s dehiscence predispose to pouch formation in certain individuals: people with longer necks and larger laryngeal skeletons (males). In support of this evidence, it is noted that Zenker’s diverticulum is common in USA, Canada and Australia but rare in Japan and Indonesia. 10
One possible mechanism for the finding of a bilobed and/or trilobed pharyngeal pouches is that a muscular raphe (which is present and extends from the cricopharyngeus superiorly across the area of Killian’s dehiscence to the posterior midline portion of the thyropharyngeus10) may persist and the herniating mucosa, instead of breaking the raphe, spreads around it causing septation of the pouch. If the raphe is particularly robust it may result in a doublenecked pouch 5,6. Alternatively the necks might merge and the raphe may persist – resulting in a pouch with a bilobed or trilobed septae and a single neck. This theory is supported by an anatomical study of the muscles of the hypopharyngeal area in cadavers20. Despite classical textbook descriptions, in reality, several different fibre arrangements are found in the gap between the cricopharyngeus muscle and the thyropharangeus muscle2.
Surgical management remains the optimal treatment for Zenker’s diverticulum. There are essentially two surgical options: either an external approach or an endoscopic approach. The open approach, with either pouch inversion or diverticulotomy, can be associated with significant morbidity. The major complications include pharyngocutaneous fistula, recurrent laryngeal nerve palsy, mediastinitis and death. A recent non-randomised retrospective study compared the open approach to microendoscopic myotomy. With an open approach in 66 patients, complications included a 10.6% fistulas rate, a 4.5% incidence of recurrent nerve palsy and one death from mediastinitis. Only 2 from a total of 31 in the microendoscopic and CO2 laser myotomy group had complications. The average length of hospitalisation was 11.4 days for open procedures and 8 days for the endoscopic group2l. Other series have reinforced the fact that endoscopic approaches minimise post-operative morbidity10. Since it was first described in 1993 22, endoscopic stapling has become established as preferable to standard Dohlman’s methods because of the lower morbidity associated with the procedure9,23,24,25. It is possible to commence feeding and discharge the patient on the first post-operative day. The low complication rate and possibility of early discharge has been confirmed by many studies.9,23,24,25 and it is now the technique of choice in our unit for elderly patients with pharyngeal pouches. Where the pouch has more than one lobe, the staple gun divides the cricopharyngeal bar but the presence of a persistent raphe between the lobes does not seem to restrict postoperative function. The evidence from this case would seem to imply that multiple staple divisions (one in each lobe) is not required in the treatment of these rare cases.
The finding of a bilobed/trilobed Zenker’s diverticulum or pharyngeal pouch is extremely rare. Similar diagnostic investigation, endoscopic assessment and surgical treatment should be offered, as would a patient who presents with the more common unilobed pouch. With the current limited evidence available, a successful relief of symptoms should be anticipated in all patients treated by a single endoscopic stapling diverticulotomy technique.
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COLM FAHY, A.SIMON CARNEY AND PATRICK J. BRADLEY
Queen’s Medical Centre, Nottingham
Colm Fahy, FRSCI (Otol), A. Simon Carnet, FRCS (ORL-HNS), FRACS
Patrick J Bradley, FRCS
Department of Otolaryngology and Head and Neck Surgery Queen’s Medical Centre, Nottingham, NG7 2UH
Address for Correspondence: Dr A Simon Carney FRCS, FRACS
Senior Lecturer in ENT
Flinder Medical Centre, Bedford Park, SA 5022
Telephone: (08) 8204-5511
Fax: (08) 8374-0832
Address for Correspondence:
Dr A.Simon Carney FRCS, FRACS. Senior Lecturer in ENT,
Flinders Medical Centre, Bedford Park,
Telephone: (08) 8204-5511 Fax: (08) 8374-0832
Copyright Australian Society of Otolaryngology Head & Neck Surgery Ltd. Apr 2002
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