SAEVA Proceedings 2015 | Page 24

South African Equine Veterinary Association Congress 2015  Protea Hotel  Stellenbosch The stomach is seen on the left hand side, ventral to the lung and dorsal to the costochondral junction, at the level of the shoulder. It is normal for the stomach to extend over 3 intercostal spaces in horses (usually from ICS 9-11) and it has a characteristic smooth, curvilinear echo adjacent to the spleen and splenic vein, with colon ventrally. The thickness of the stomach wall can vary from 4mm up to 7.5mm in adult horses; reduced wall thickness has been reported when the stomach is distended and also post feeding. The wall thickness may be greatest post gastroscopy as the stomach contracts and deflates. Motility is not evident. Fluid distension of the stomach (reflux) will give a horizontal fluid/gas line. The appearance of the stomach can change following gastroscopy and air-insufflation, and therefore possibly also following nasogastric intubation. An undulating stomach wall is a common finding post gastroscopy, with more distinct gastric wall folding (of the mucosa and submucosa) sometimes seen, most distinctly 2-4 hours post gastroscopy. Rugal folds may also be seen in horses undergoing food restriction. Ultrasonography of the stomach is useful to identify dilatation, impaction and neoplasia. Identification of the stomach extending over more than 3 intercostal spaces suggests gastric distension, either due to gastric impaction or reflux. The enlarged stomach may also be imaged adjacent to the left lateral wall as the spleen is pushed caudally and ventrally. Gastric neoplasia is most commonly imaged as a mural mass, rather than seen gastroscopically. There may be increased peritoneal fluid and involvement of the adjacent organs, particularly the spleen. Ponies differ in that the stomach can be imaged over a greater number of intercostal spaces than in horses (average 5 intercostal spaces, sometimes up to 8). Small intestine Small intestine can be imaged transabdominally and transrectally. Normal small intestinal wall thickness is less than 4 mm, with a diameter of less than 5 cm and 6-15 contractions per minute. Normal wall thickness does vary between studies according to the probe used and the stage of contraction/distension at which measurements are taken. The contents may be fluid (hypoechoic), ingesta (hyperechoic, heterogenous) or gas (hyperechoic with gas shadowing). The duodenum can be seen reliably on the right hand side of the abdomen, in intercostal spaces (ICS) 16-17 ventral to the caudal pole of the right kidney, and medial to the liver in ICS 14-16. The duodenum is commonly seen to fill with ingesta and then collapse. The jejunum varies in location; whilst some studies suggest that jejunum is not consistently found, reasonably reliable locations include the left inguinal region, deep to the spleen in ICS 1216 in the gastrosplenic region and dorsal to the left colon in the left ventral caudal region. Small intestine is seen in the cranioventral abdomen in only 10% of normal horses. Fasting increases the likelihood of finding small intestine in the cranioventral abdomen (due to emptying of the colon and caecum). The normal small intestine has 5 layers visible on ultrasound, however these are not always easily identified in the normal horse during transabdominal ultrasound, due to the poor resolution from lower frequency probes. The 5 layers are serosa (hyperechoic), muscularis (hypoechoic), submucosa (hyperechoic), mucosa (hypoechoic) and the mucosal/ingesta interface (hyperechoic). The ileum has a 7 layer appearance due to the additional muscular layer and can be imaged transrectally, medial to the caecum. The small intestine should be assessed in terms of location, wall thickness, diameter, motility and contents. Disease processes that can be identified ultrasonographically include simple and strangulating obstructions, infiltrative/inflammatory bowel disease, intraluminal masses and enteritis. Ultrasonography is more sensitive than rectal palpation for detection of distended small intestine, particularly in the early stages of a proximal obstruction. Distended loops will fall to the 24