IN-DEPTH: COLIC


cipiens) appears thickened and edematous and may be separated from the incarcerated bowel (intussus- ceptum) by a small layer of fluid.8 Although colitis is rarely a cause of acute colic without other sugges- tive signs, the ability of ultrasound to visualize fluid intestinal contents and measure colonic wall thick- ness can aid in the diagnostic and prognostic evalu- ation of these patients.


4. Evaluation of the Stomach


The stomach is not palpable on per rectum exami- nation. An assessment of the size, position, and fluid content of the stomach may be helpful in mak- ing management decisions about when to manually evacuate the stomach in cases of small intestine obstruction. In addition, gastric impaction can be sonographically diagnosed by detecting a markedly enlarged stomach, which may encompass 5 or more intercostal spaces on the left and may even be visible in the right abdomen.8 Although rarely a cause of acute colic, gastric masses can also be sonographi- cally visualized if the mass is located along the greater curvature of the stomach, which lies along the left body wall, or if the stomach is filled with fluid contents to transmit the sound waves.


5. Evaluation of the Small Intestine


Disorders of the small intestine causing acute colic include simple luminal obstruction, which may be functional or physical, and strangulating lesions. The small intestine is not palpable in the normal horse; the discovery of distended or thickened small intestinal loops on rectal palpation is abnormal.1,3,4 Percutaneous ultrasound of the normal equine ab- domen may reveal several loops of small intestine, especially if the horse has been held off of feed15,16 or has been administered an-2 agonist sedative.9,16,17 However, the presence of multiple loops of distended submotile or amotile small intestine on sonographic evaluation is abnormal. This finding is most com- monly seen in the inguinal regions of the ventral abdomen but may be seen in various other locations. Motility assessment can be sonographically evalu- ated, as described by several authors,17,18 but in the acute colic, so many factors can potentially influence motility that the clinical utility of this information is in question. The appearance of the small intestine can offer valuable information about the nature and chronic- ity of small intestinal disease. In addition, sono- graphic assessment may be more sensitive than palpation per rectum at detecting abnormal small intestine, especially early in the course of the dis- ease.19 Distal obstructions may fail to produce na- sogastric reflux or palpable loops of small intestine until ample time has elapsed to build fluid that fills the intestine in an orad direction. It has been suggested that small intestinal wall thickness measurements may be a poor predictor of the etiology of small intestinal pathology because of the small area measured and the difficulty in accu-


rate measurement of a curved line,19 but the pres- ence of edema in the wall of dilated small intestine in a horse with acute abdominal pain is suggestive of inflammation or vascular compromise in the visual- ized loops. Distended fluid-filled loops seen in con- junction with thickened amotile small intestine is consistent with a focal strangulation. Diffusely fluid distended small intestine, which appears as multiple circular loops stacked in multiple areas of the abdomen, may be seen with small intestinal mesenteric volvulus, global ileus, or proximal duo- denitis/enteritis. Grossly thickened small intesti- nal wall seen focally may suggest the cause of an obstruction, as in the case of an intramural tumor or intramural abscess. Sonographic visualization of abnormal small in- testinal loops can also reflect the duration of an obstruction. Sedimented feedstuff in intestinal loops indicates complete stasis or obstruction of the loops for a period of time sufficient to allow settling of particulate matter out of suspension. The loca- tion of distended small intestinal loops can be sug- gestive of the etiology of the disorder. Several authors19,20 have noted that epiploic foramen en- trapment is associated with finding distended small intestinal loops in the right abdomen and, particu- larly, in the dorsal right abdomen. Rarely, dis- tended, atonic, and/or edematous loops of small intestine are identified in the nephrosplenic and gastrosplenic spaces. Although the presence of small intestine in these spaces is generally consid- ered a normal finding, the small intestine can be- come incarcerated in these ligaments and thus abnormal bowel in these locations should alert the practitioner to the possibility of entrapment.19,21 Small intestinal intussusception is rare in adult


horses, but has been reported in horses from 6 months to 3 years of age. The most common site for small intestinal intussusception is the ileum, but jejunojejunal intussusception has also been de- scribed.14 These lesions may be palpated per rectum, depending on their location in the abdomen. Sono- graphically, they have the same general appearance as intussusception of the large bowel.8,19


6. Evaluation of the Peritoneal Space


Palpation per rectum of the caudal abdomen yields information about the caudal peritoneal and retro- peritoneal spaces. Pneumoperitoneum secondary to bowel rupture can be palpated as a dorsal empti- ness in the abdomen, with the rectum snug against the examiner’s arm.4 Sometimes, emphysema of the serosal surfaces can be detected as crepitus and free ingesta within the abdomen gives the peritoneal surfaces a gritty texture.3 Pneumoperitoneum is readily detected sonographically, and with leakage or rupture of the gastrointestinal tract, increased peritoneal fluid containing free gas echoes and par- ticulate matter is ventrally visualized. Increased peritoneal fluid is very readily identi-


fied sonographically and the fluid can be character- AAEP PROCEEDINGS  Vol. 60  2014 207


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