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Diagnostic imaging features of normal anal sacs in dogs and cats

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ABSTRACT

This study was conducted to provide normal reference features for canine and feline anal sacs using ultrasound, low-field magnetic resonance imaging (MRI) and radiograph contrast as diagnostic imaging tools. A total of ten clinically normal beagle dogs and eight clinically normally cats were included. General radiography with contrast, ultrasonography and low-field MRI scans were performed. The visualization of anal sacs, which are located at distinct sites in dogs and cats, is possible with a contrast study on radiography. Most surfaces of the anal sacs tissue, occasionally appearing as a hyperechoic thin line, were surrounded by the hypoechoic external sphincter muscle on ultrasonography. The normal anal sac contents of dogs and cats had variable echogenicity. Signals of anal sac contents on low-field MRI varied in cats and dogs, and contrast medium using T1-weighted images enhanced the anal sac walls more obviously than that on ultrasonography. In conclusion, this study provides the normal features of anal sacs from dogs and cats on diagnostic imaging. Further studies including anal sac evaluation are expected to investigate disease conditions.

No MeSH data available.


Diagram of a dorsal section of the anal sac of a dog. (A) Anal sac cavity. (B) Anal sac duct opening. (C) Apocrine glands. (D) External sphincter muscle. (E) Internal sphincter muscle. (F) Fat of rectoischial fossa. (G) Anal canal. (H) Levator ani muscle. (I) Longitudinal muscle layer of rectum [15].
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Figure 1: Diagram of a dorsal section of the anal sac of a dog. (A) Anal sac cavity. (B) Anal sac duct opening. (C) Apocrine glands. (D) External sphincter muscle. (E) Internal sphincter muscle. (F) Fat of rectoischial fossa. (G) Anal canal. (H) Levator ani muscle. (I) Longitudinal muscle layer of rectum [15].

Mentions: Most carnivores have a pair of anal sacs, also referred to as paranal sinuses (sinus paranalis) [116]. The anal sacs are located between the internal and external anal sphincter muscles and each sac opens to the lateral margin of the anus through a single duct [110]. The anal sacs and ducts are lined by stratified squamous epithelium and surrounded by fibrous connective tissue in which sebaceous and apocrine glands are embedded (Fig. 1) [11015]. In dogs, the apocrine glands are concentrated in the fundus, and the sebaceous glands are lined by the ductal area of the anal sac [17]. In cats, both glands exist in the anal sac wall [10]. The anal sacs normally contain secretions [6]. The contents of normal canine and feline anal sacs vary highly in gross appearance. The consistency also varies from watery to creamy to thick or pasty and to the presence or absence of solid material [914].


Diagnostic imaging features of normal anal sacs in dogs and cats
Diagram of a dorsal section of the anal sac of a dog. (A) Anal sac cavity. (B) Anal sac duct opening. (C) Apocrine glands. (D) External sphincter muscle. (E) Internal sphincter muscle. (F) Fat of rectoischial fossa. (G) Anal canal. (H) Levator ani muscle. (I) Longitudinal muscle layer of rectum [15].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037300&req=5

Figure 1: Diagram of a dorsal section of the anal sac of a dog. (A) Anal sac cavity. (B) Anal sac duct opening. (C) Apocrine glands. (D) External sphincter muscle. (E) Internal sphincter muscle. (F) Fat of rectoischial fossa. (G) Anal canal. (H) Levator ani muscle. (I) Longitudinal muscle layer of rectum [15].
Mentions: Most carnivores have a pair of anal sacs, also referred to as paranal sinuses (sinus paranalis) [116]. The anal sacs are located between the internal and external anal sphincter muscles and each sac opens to the lateral margin of the anus through a single duct [110]. The anal sacs and ducts are lined by stratified squamous epithelium and surrounded by fibrous connective tissue in which sebaceous and apocrine glands are embedded (Fig. 1) [11015]. In dogs, the apocrine glands are concentrated in the fundus, and the sebaceous glands are lined by the ductal area of the anal sac [17]. In cats, both glands exist in the anal sac wall [10]. The anal sacs normally contain secretions [6]. The contents of normal canine and feline anal sacs vary highly in gross appearance. The consistency also varies from watery to creamy to thick or pasty and to the presence or absence of solid material [914].

View Article: PubMed Central - PubMed

ABSTRACT

This study was conducted to provide normal reference features for canine and feline anal sacs using ultrasound, low-field magnetic resonance imaging (MRI) and radiograph contrast as diagnostic imaging tools. A total of ten clinically normal beagle dogs and eight clinically normally cats were included. General radiography with contrast, ultrasonography and low-field MRI scans were performed. The visualization of anal sacs, which are located at distinct sites in dogs and cats, is possible with a contrast study on radiography. Most surfaces of the anal sacs tissue, occasionally appearing as a hyperechoic thin line, were surrounded by the hypoechoic external sphincter muscle on ultrasonography. The normal anal sac contents of dogs and cats had variable echogenicity. Signals of anal sac contents on low-field MRI varied in cats and dogs, and contrast medium using T1-weighted images enhanced the anal sac walls more obviously than that on ultrasonography. In conclusion, this study provides the normal features of anal sacs from dogs and cats on diagnostic imaging. Further studies including anal sac evaluation are expected to investigate disease conditions.

No MeSH data available.