Zenker’s Diverticulum: Can Protocolised Measurements with Barium SWALLOW Predict Severity and Treatment Outcomes? The “Zen-Rad” Study

Zenker’s diverticulum (ZD) is the most common diverticulum of the upper gastrointestinal tract and is a treatable cause of dysphagia [1, 2]. Over the last two decades, the treatment paradigm for ZD has shifted away from surgical stapling towards less invasive endoscopic means [3]. With its favourable efficacy and safety profile [4], flexible endoscopic septal division (FESD) has established itself as the primary therapeutic modality for both treatment naïve and recurrent ZD [3, 5].

Currently, barium swallow remains the mainstay imaging modality for patients with suspected ZD. Multi-frame fluoroscopic imaging is typically performed with at least lateral and anteroposterior projections of the hypopharynx and cervical oesophagus, although oblique views may also be helpful to adequately image the cricopharyngeus muscle (CP). In addition to the initial diagnosis, this technique differentiates ZD seen on the posterior wall, with the neck of the diverticulum seen above the level of the cricopharyngeus muscle, from the less common, smaller and less symptomatic Killian-Jamieson diverticulum that arises from the lateral wall below the level of the CP. Following on from the diagnosis, the typical radiological barium swallow assessment of ZD usually involves anatomical and functional elements with the lateral projection being most useful. The anatomical assessment traditionally consists of an estimate of pouch size and neck width. Functional assessment includes Queryevaluating for pooling of contrast, regurgitation and aspiration, with exploration of the effects of the diverticulum on the adjacent oesophagus which may contribute to symptomatic dysphagia [6]. Specific assessment and measurement of the cricopharyngeus muscle that is central to FESD is less commonly undertaken.

Despite its role in the diagnosis and functional assessment of ZD, there is no accepted protocol for the standardised reporting of ZD dimensions based on barium swallow. This is relevant as certain dimensions correlate with treatment outcomes. The study by Costamagna et al. found “ZD size” to be an independent factor associated with FESD treatment failure [7]. It was assumed that the ZD size represented the width of the pouch, although the precise plane of measurement was not defined. There is, therefore, a need to establish a protocol to standardise the nomenclature of ZD dimensions, both for radiological and endoscopic usage, and to facilitate such measurements. Accordingly, this study aimed to develop a protocol for the fluoroscopic measurement of ZD dimensions, assess for interobserver reliability and to correlate these measurements with pre-treatment symptoms and post-treatment outcomes.

Barium swallow is the primary radiological investigation for dysphagia [2]. The technique is dependent upon practitioner experience and local protocols, with variation in terms of radiographic projections and fluoroscopic capture rates. In order to standardise the assessment and reporting of ZD dimensions on barium fluoroscopy, we have developed a novel and purpose-specific protocol for quantifying ZD morphometrics. In this prospective single-centre study, we show that, by using this protocol, ZD measurements can be reproducible amongst GI radiologists, as evidenced by inter-rater reliability analyses (ICCs). Importantly, we demonstrate that specific dimensions correlated with symptom severity, procedure time and the outcome of durable therapeutic success. These results provide validity evidence in support of our ZD measurement protocol.

Although endoscopy is often first line in the evaluation of dysphagia, the hypopharynx represents a potential blind spot which may lead to a false negative diagnoses of ZD. It is also recognised that ZD can hinder endoscopic intubation of the oesophagus. Thus, there is a role for fluoroscopic assessment in patients with intubation failure [12], or in patients with oropharyngeal dysphagia for which a high index of suspicion for structural abnormality remains despite normal endoscopy. This may be particularly helpful in patients with regurgitation-predominant symptoms, as our analyses demonstrate a positive correlation between pouch dimensions and the regurgitation subset of the DRC symptom severity scale. Although designed to assess patients with endoscopically confirmed ZD for pre-FESD workup, our Barium protocol could also be adopted for use in the evaluation of oropharyngeal dysphagia.

In our experience, the anteroposterior and lateral views of the pharynx and upper oesophagus were most helpful for determining ZD morphometrics. An image acquisition rate of 3 or 4 frames per second (dependent on equipment manufacturer) was felt to be a pragmatic balance between minimising radiation exposure to as low as reasonably achievable (ALARA) and providing adequate temporal resolution for functional assessment to evaluate for pooling of contrast, regurgitation and aspiration, and mass effect on the adjacent oesophagus. Routine oblique views and spot radiographs of the ZD were not felt to be as useful with problematic quantification of the ZD measurements and inherently lacked real-time functional information, although some radiologists prefer oblique views as the ZD projects posterolaterally (and usually to the left). The externally referred images had a variety of pulse rates and frame rates, some being spot films, with inherent limitations of non-standardised image acquisition. The local operators comprised radiographers, radiology registrars an consultants and we presume a similar spread for external sites. Clearly given the radiation exposure we did not repeat examinations if the measurements could be derived from the referral source. We hope discussion of these factors will lead to an awareness of measurements used in ZD, particularly for patients who may be considered for FESD. Whilst we did use a ball-bearing for calibration, this was sometimes found to be cumbersome and could obscure assessment of the underlying anatomy, requiring repositioning during the examination. The utility of using a ball-bearing over calibrating from the ever-present posterior height of the C4 vertebral body was not separately investigated; however, given the inherently dynamic nature of ZD filling and opacification, theoretical discrepancies between the two methods were felt to be small and unlikely to have a significant impact on the ultimate procedural outcome. For these reasons, we suggest an alternative method for extrapolating ZD dimensions by using 14 mm as the height of the C4 vertebral body [9].

Correlations between ZD dimensions can provide insights on its pathophysiology. There was significant inter-correlation between the pouch height, width, depth and the CP length, but not CP thickness. Male patients were associated with significantly larger pouch height, depth and width, which complements the observation that ZD, is nearly twice as common in men [13]. The observation that patients with recurrent ZD had larger dimensions may be due to selection bias. It is possible that, in patients who have failed previous therapy, clinicians may have a higher threshold to refer for further endoscopic therapy.

Several limitations should be discussed. First, our study size was small (N = 67) which did not permit multivariable analyses of therapeutic efficacy. For the evaluation of reliability, only the first 10 cases were reviewed by two GI radiologists (blinded to the results) due to resource constraints, which may have influenced the precision of reliability estimates. Some cases were performed externally, which may affect the accuracy and consistency of ZD measurements. The success rate of 64.2% is lower than other series, and may be due to several factors. Our study outcome of therapeutic success was based on a stringent definition of durable remission at 6 months after index FESD. It should be noted that the definition of procedural success within the literature is heterogeneous. Some defined success as symptomatic improvement after three episodes of FESD, improvement of symptoms, or after 3 months of follow-up. Procedures were mainly performed in elderly patients (mean age of 74) with co-morbidity (43.4% had ASA grades of III or IV), of which a significant proportion (44.8%) of patients were patients with recurrent ZD who had previously failed endoscopic stapling. These factors may affect the generalisability of our data towards other patient populations. Finally, patients post-FESD may have a degree of bridging fibrosis, i.e. scarring, which may result in dysphagic symptoms but may not necessary have recurrent ZD. Due to the tertiary nature of referrals from throughout the UK, it was not feasible to repeat barium fluoroscopy in all patients post FESD. This may have been useful to confirm recurrence and to study pairwise comparisons of pre- and post-FESD dimensions. Indeed, there is little evidence that assessment of residual pouch size post-procedure predicts a successful outcome or future symptomatic recurrence [14, 15].

In summary, a measurement protocol for the assessment of ZD on barium radiology has been developed. These measurements are reproducible and correlate with symptom severity, procedure time and post-FESD outcomes, and may inform FESD planning and patient counselling of post-FESD outcomes. Further studies are required to inform whether volumetric analyses can be used in conjunction with Barium dimensions to benefit patient selection, procedural selection (e.g. FESD vs. submucosal tunnelling techniques) and ultimately, on patient outcomes. Further studies are required to inform whether volumetric analyses can be used in conjunction with Barium dimensions to benefit patient selection, procedural selection (e.g. FESD vs. submucosal tunnelling techniques) and ultimately, on patient outcomes.