Ultrasonographic, endoscopic and histological appearance of the caecum in clinically healthy cats

Abstract

Objectives The aim of the study was to describe the ultrasonographic and endoscopic appearance and characteristics of the caecum in asymptomatic cats, and to correlate these findings with histology. Methods Ex vivo ultrasonographic and histologic evaluations of a fresh caecum were initially performed. Then, 20 asymptomatic cats, privately owned or originating from a reproductive colony, were recruited. All cats had an ultrasonographic examination of the ileocaecocolic junction, where the thickness of the caecal wall, ileocolic lymph nodes and the echogenicity of the local fat were assessed. They all underwent a colonoscopy with a macroscopic assessment of the mucosa and biopsies for histology. Results An ultrasonographic hypoechoic nodular inner layer, which corresponded to the coalescence of multiple lymphoid follicles originating from the submucosa and protruding in the mucosa on histology, was visible in all parts of the caecum. The combined mucosa and submucosa was measured ultrasonographically and defined as the follicular layer. Although all cats were asymptomatic, 3/19 cats showed mild caecal inflammation on histology. The most discriminatory ultrasonographic parameter in assessing this subclinical inflammation was the thickness of the follicular layer at the entrance of the caecum, with a cut-off value of 2.0 mm. All cats (20/20) showed some degree of macroscopic 'dimpling' of the caecal mucosa on endoscopy. Conclusions and relevance Lymphoid follicles in the caecal mucosa and submucosa constitute a unique follicular layer on ultrasound. In asymptomatic cats, a subtle, non-clinically relevant inflammation may exist and this is correlated with an increased thickness of the follicular layer on ultrasound. On endoscopy, a 'dimpled aspect' to the caecal mucosa is a normal finding in the asymptomatic cat.

Ultrasonographic, endoscopic and histological appearances of the caecum in cats presenting with chronic clinical signs of caecocolic disease

“…The following parameters were recorded: the full thickness of the ileal, colonic and caecal walls on longitudinal planes of the wall in the near field; the appearance of wall layering; the thickness of the follicular layer in the proximal and distal caecum (combination of the mucosal and submucosal layers, with the proximal part being the closest to the colon and the distal part closest to the cul-de-sac) ( Figure 1); the content (gas, solid, liquid) of the caecum and the colon; the thickness, number, shape, echogenicity and homogeneity of the ileocolic LNs; the presence of peritoneal effusion; and the echogenicity of the mesenteric surrounding fat. 11 The last was qualified as follows, according to a grading scheme defined by the authors and used in a previous publication: grade 0 = normoechoic fat compared with adjacent mesenteric fat and well-defined contours of the LNs; grade 1 = hyper echoic fat and well-defined contours of the LNs; and grade 2 = hype rechoic fat and blurred contours of the LNs. 11 Normal ileal and colonic upper limit wall thicknesses used were 3.2 mm and 2.5 mm, respectively.…”

“…11 This dimpled aspect could be of variable intensity, usually mild to moderate in healthy cats, although a severe dimpled aspect could occasionally be found. 11 The aim of this study was to determine and describe the association between the ultrasonographic changes, the macroscopic appearance during colonoscopy, and the histological findings in cats presented with clinical signs suggestive of caecocolic disease.…”

“…10 The association of the ultrasonographic, endoscopic and histological appearances of the caecum in healthy cats was reported in 2015 by the present authors. 11 Ultrasonographically, a caecal follicular layer was described as a combination of mucosal and submucosal layers, considered as a unique ultrasonographic layer because of the lymphoid follicles overlapping them both. 11 An ult ra sonogra phic cut-off value for this follicular layer in cats without clinical signs ascribable to ICC pathology has been established to differentiate non-invasively cats with and without mild histological inflammation.…”

“…11 Ultrasonographically, a caecal follicular layer was described as a combination of mucosal and submucosal layers, considered as a unique ultrasonographic layer because of the lymphoid follicles overlapping them both. 11 An ult ra sonogra phic cut-off value for this follicular layer in cats without clinical signs ascribable to ICC pathology has been established to differentiate non-invasively cats with and without mild histological inflammation. 11 On endoscopy, the normal caecal mucosa showed a 'dimpled aspect' in all cats due to the presence of small surface depressions.…”

“…11 An ult ra sonogra phic cut-off value for this follicular layer in cats without clinical signs ascribable to ICC pathology has been established to differentiate non-invasively cats with and without mild histological inflammation. 11 On endoscopy, the normal caecal mucosa showed a 'dimpled aspect' in all cats due to the presence of small surface depressions. 11 This dimpled aspect could be of variable intensity, usually mild to moderate in healthy cats, although a severe dimpled aspect could occasionally be found.…”