Horses admitted to University of California’s Veterinary Medical Teaching Hospital for signs of colic, diarrhea, weight loss, reduced appetite, lethargy, fever or hematuria were examined with transabdominal ultrasound. A retrospective study evaluated the presence of intestinal wall thickening and its effect on clinical features and outcome [Biscoe, E.W.; Whitcomb, M.B.; Vaughan, B.; Dechant, J.E.; Magdesian, K.G. Clinical features and outcome in horses with severe large intestinal thickening diagnosed with transabdominal ultrasonography: 25 cases (2003-2010). JAVMA July 1 2018, vol. 253 no. 1, pp. 108 – 116].
Inclusion in the study was based on severe diffuse or regional intestinal wall thickening—9 to 46.6 mm. Twenty-five horses met the criteria.
In 80% of the cases, the thickening was visualized in the ventral intestinal portions. While lesions were present more often in the right abdomen than the left, lesions did occur in both sides. Therefore the authors recommend a thorough and complete exam of the entire abdomen.
Of the 22 cases available for follow-up, 11 (50%) survived and resolved their clinical signs. One horse survived but continued to experience intermittent colic. Ten (45%) of the horses died or were euthanized; of these, three had neoplasia and three had colitis.
According to the authors, “Severity of thickening and number of zones affected were not significantly different between survivors and non-survivors.”
Normal horses tend to have intestinal wall thickness of 1.8–4.2 mm. Large intestinal wall thickening of >9 mm is associated with a variety of pathologic conditions.
Fifty-two percent of the horses (13/25) were referred due to colic pain. Previously, it has been reported that acute colic in horses with intestinal wall thickness >9 mm should undergo surgical intervention due to the likelihood of colon torsion. However, this study indicated that this could be a false positive reason for surgery due to the possibility of the presence of a number of non-surgical reasons for large intestinal wall thickening. In fact, only one of the 25 horses in the study required surgery for colon torsion. Four mares were referred to the hospital with suspect colon torsion, but they responded well to medical management without surgical intervention.
Corroboration of clinical signs and diagnostic imaging of transabdominal wall thickness help practitioners identify any of a number of intestinal abnormalities that might not need surgical intervention.