Small Animal Department, Faculty of Veterinary Medicine, University of Leipzig, Leipzig, Germany.
Department of Computer Science, Technische Universität Bergakademie Freiberg, Freiberg, Germany.
PLoS One. 2021 Sep 7;16(9):e0257020. doi: 10.1371/journal.pone.0257020. eCollection 2021.
This study aimed to investigate and compare the anatomical features of the nasolacrimal drainage system (NDS) in three brachycephalic dog breeds with those of normocephalic dogs, taking into account how the NDS was related to the malformed brachycephalic head.
Fifty-one brachycephalic dogs were examined, comprising 23 Pugs, 18 French Bulldogs, and 10 English Bulldogs. Six normocephalic dogs of different breeds served as a comparison.
Computed tomographic dacryocystography was performed. Parameters such as length, angulation, and gradient were determined. Crossing of the nasolacrimal duct (NLD) beneath the maxillary canine root, as well as the incidence of an accessory opening, were also analyzed.
In all three brachycephalic breeds, the NDS was grossly malformed. We regard this as a further consequence of exaggerated breeding for a short head conformation. While the length of the NLD was substantially reduced by 41 to 57 percent in brachycephalic dogs, their lacrimal canaliculi were two to three times as long as those of normocephalic dogs. Varying parts of the nasolacrimal drainage system followed an inverse direction in short-headed dogs, giving the entire nasolacrimal apparatus an anomalous U- or V-shaped appearance. The NLD exhibited a three to five times steeper alignment in brachycephalic dogs than in normocephalic ones. Obviously, this strong slope did not cause clinical symptoms only because there was an aberrant outflow pathway. The brachycephalic dogs consistently exhibited an accessory opening, through which most of fluid escaped into the posterior nasal cavity instead of through the common route into the nasal vestibule via the nasolacrimal ostia.
本研究旨在探讨和比较三种短头颅犬种与正常头颅犬种的鼻泪管系统（NDS）解剖特征，同时考虑 NDS 与畸形短头颅之间的关系。
检查了 51 只短头颅犬，包括 23 只哈巴狗、18 只法国斗牛犬和 10 只英国斗牛犬。6 只不同品种的正常头颅犬作为对照。
进行了计算机断层泪囊造影术。确定了长度、角度和梯度等参数。还分析了鼻泪管（NLD）在犬齿根下交叉以及副开口的发生率。
在所有三种短头颅品种中，NDS 均严重畸形。我们认为这是为了夸张短头颅形态而进行过度繁殖的又一后果。虽然 NLD 的长度在短头颅犬中减少了 41%至 57%，但其泪小管的长度是正常头颅犬的两到三倍。短头颅犬的部分鼻泪管系统呈反向方向，使整个鼻泪管装置呈现异常的 U 形或 V 形。NLD 在短头颅犬中的倾斜度是正常头颅犬的三到五倍。显然，这种强烈的坡度仅因为存在异常的流出途径，所以没有引起临床症状。短头颅犬始终表现出一个副开口，大部分液体通过该开口进入后鼻腔，而不是通过鼻泪管口通过正常途径进入鼻前庭。
