High-frequency ultrasound of Peyer's patches in the small intestine of young cats.

OBJECTIVES: A previously unreported, asymmetrically positioned hypoechoic extra layer (APHEL) in the submucosa of the feline distal jejunum and ileum has been recognised using high-frequency ultrasound. The objectives of this study were to characterise the APHEL histologically, and to describe the prevalence and ultrasonographic features of the APHEL in a population of clinically healthy young cats. METHODS: In an anatomical study, two cats were autopsied and histopathology of the small intestine was performed. An APHEL was detected with ultrasound in the distal jejunum and ileum ante-mortem in the first cat and post mortem in the second cat. Samples for histopathology were obtained from these areas. In the second, prospective part of the study, to document the presence or absence of an APHEL, high-frequency (18 MHz) ultrasound was performed of the intestinal tract in 20 other cats. These cats were client-owned cats aged 6-18 months presented for neutering. The cats were included in the study based on a normal clinical examination, lack of previous or concurrent signs of disease, and having no abnormalities detected at abdominal ultrasound. RESULTS: Histopathology from the distal jejunum and ileum in the two cats in the anatomical part of the study showed that the APHEL represented asymmetrically positioned normal lymphatic tissue (Peyer's patches) in the lamina propria and submucosa. In the second part of the study, an APHEL was identified in the submucosa of the distal part of the jejunum and ileum in all 20 cats. Additionally, a similar layer could also be seen further proximally in the jejunum in 10 (50%) of the cats. The thickness of the APHEL was 1.0 mm in both jejunum and ileum. CONCLUSIONS AND RELEVANCE: Presumed normal lymphatic tissue in the small intestinal submucosa can be seen with high-frequency ultrasound and is a common finding in young cats.