This study aimed to investigate the course of the nasolacrimal drainage system in three different brachycephalic dog breeds in comparison to normocephalic dogs and to draw conclusions on potentially adverse consequences for the drainage function. A computed tomographic-dacryocystography (CT-DCG) was performed in 51 brachycephalic dogs, consisting of 23 Pugs, 18 French and 10 English bulldogs. Six normocephalic dogs of different breeds and body size served as a comparison. Two- and three dimensional images were obtained and evaluated. Several parameters (length, angulation, gradient) were used to describe the nasolacrimal drainage system and to quantify distinctions between different breeds. Furthermore several additional characteristics were analysed, including the relative position of lacrimal foramen and nasolacrimal ostium, crossing of the nasolacrimal duct below the root of the upper canine tooth, the patency of the lacrimal drainage system and the presence of an accessory opening. While the length of the nasolacrimal duct is substantially reduced in brachycephalic dogs, their lacrimal canaliculi have much larger dimensions than those of normocephalic dogs. Additionally varying parts of the nasolacrimal drainage system follow an inverse direction in short-headed dogs, giving the entire nasolacrimal apparatus a characteristic U- or V-shaped appearance. The nasolacrimal duct exhibits a much steeper alignment in brachycephalic dogs compared to normocephalic ones. This strong slope however does not interfere with drainage function because of a consistently present accessory opening, being the main or only outflow pathway in all brachycephalic dogs and hence facilitating proper tear drainage regardless of the steepness.

This study aimed to investigate the course of the nasolacrimal drainage system in three different brachycephalic dog breeds in comparison to normocephalic dogs and to draw conclusions on potentially adverse consequences for the drainage function. A computed tomographic-dacryocystography (CT-DCG) was performed in 51 brachycephalic dogs, consisting of 23 Pugs, 18 French and 10 English bulldogs. Six normocephalic dogs of different breeds and body size served as a comparison. Two- and three dimensional images were obtained and evaluated. Several parameters (length, angulation, gradient) were used to describe the nasolacrimal drainage system and to quantify distinctions between different breeds. Furthermore several additional characteristics were analysed, including the relative position of lacrimal foramen and nasolacrimal ostium, crossing of the nasolacrimal duct below the root of the upper canine tooth, the patency of the lacrimal drainage system and the presence of an accessory opening. While the length of the nasolacrimal duct is substantially reduced in brachycephalic dogs, their lacrimal canaliculi have much larger dimensions than those of normocephalic dogs. Additionally varying parts of the nasolacrimal drainage system follow an inverse direction in short-headed dogs, giving the entire nasolacrimal apparatus a characteristic U- or V-shaped appearance. The nasolacrimal duct exhibits a much steeper alignment in brachycephalic dogs compared to normocephalic ones. This strong slope however does not interfere with drainage function because of a consistently present accessory opening, being the main or only outflow pathway in all brachycephalic dogs and hence facilitating proper tear drainage regardless of the steepness.