The sheath of Waldeyer is not a specific anatomical trait of the ureterovesical junction

Summary

The function of the ureterovesical junction depends upon a peculiar structure, the adventitial fibromuscular sheath of Waldeyer, which coats the distal end of the ureter. The origin of the smooth muscle of Waldeyer's sheath (WS) is disputed. Evidence points more likely to an ureteral one. In this regard we hypothesized the WS is not specific to the distal ureter but is rather a common trait. We therefore aimed at exploring whether or not the proximal ureter is provided with a similar adventitial fibromuscular coat. We performed an immunohistochemical study on human samples of proximal ureter resulted after nephrectomies in ten patients. We applied myoid immunohistochemical markers: α-smooth muscle actin (α-SMA), desmin, and heavy chain of smooth muscle myosin (SMM) which labeled additional adventitial smooth muscle bundles, a discontinuous inner circular one applied on the muscular coat, and outer longitudinal cords specifically located on one side of the ureter, as is the case for WS. Moreover, the lamina propria myoid deep layer showed isolated smooth muscle fibers and spindle-shaped stromal cells with telocyte morphology. Our results support the idea that WS may not be a specific structure of the distal ureter, instead being just a common anatomical characteristic of the ureter.

Résumé

La fonction de la jonction urétéro-vésicale dépend d’une structure particulière : la gaine fibro-musculaire adventitielle de Waldeyer, qui recouvre l’extrémité distale de l’uretère. L’origine du muscle lisse de la gaine de Waldeyer (WS) est contestée. Elle semble plus susceptible d’être d’origine urétérale. À cet égard, nous avons émis l’hypothèse que la WS n’est pas spécifique à l’uretère distal mais qu’il en est plutôt une caractéristique commune. Nous avons donc cherché à explorer si l’uretère proximal est muni d’une couche fibro-musculaire adventitielle similaire. Nous avons réalisé une étude immunohistochimique sur des échantillons humains d’urètre proximal résultant de néphrectomies chez dix patients. Nous avons recherché par immunohistochimie des marqueurs myoïdes : l’α-SMA, la desmine et la chaîne lourde de la myosine du muscle lisse (SMM) qui marquait d’autres faisceaux musculaires lisses adventitiels, un anneau circulaire interne discontinu appliqué sur la gaine musculaire et des faisceaux longitudinaux externes situés spécifiquement sur un côté de l’uretère, comme c’est le cas pour la WS. De plus, la couche myoïde profonde de lamina propria comportait des fibres musculaires lisses isolées et des cellules stromales fusiformes présentant la morphologie des télocytes. Nos résultats confortent l’idée que la WS peut ne pas être une structure spécifique à l’uretère distal mais qu’il s’agit simplement d’une caractéristique anatomique commune à la totalité de l’uretère.

Introduction

Waldeyer (1892, as quoted in [1]), introduced the term “Ureterscheide” to identify the fibromuscular sheath coating the distal end of the ureter (the juxtavesical ureter). This structure was previously reported by Krause (1876, quoted in [2], [3]) as an extension of the bladder musculature around the distal part of ureter.

It is considered that the Waldeyer's sheath (WS) is the adventitia or outer fibrous coating of the distal 1-3 cm of the ureter, which is reinforced by longitudinal muscle bundles specifically located on one side of the ureter [1], [4]. Elsewhere, the WS is presented as “an external layer of longitudinal smooth muscle”, which “surrounds the ureter” [5]. The WS is also described as a non-striated “collar” [6], which leads to the perception of a circular muscle component. Such a fibromuscular sheath cannot be truly individualized over the transparietal segment of the ureter [7].

There are disputes on the ureteral, or bladder origin of the adventitial muscle layer of the WS. We therefore aimed at evaluating the muscular coats of the proximal end of the ureter, to check whether or not they include such an "Ureterscheide". This was also suggested by our dissection studies in which the proximal ureter was seemingly provided with a muscularized adventitia, as was the distal ureter (Fig. 1).