North American Veterinary Licensing Examination (NAVLE) Practice Test

A digital exam of the rectum is the most appropriate diagnostic test for meconium impaction in a newborn foal. This procedure involves the veterinarian inserting a gloved finger into the rectum to feel for any impacted meconium, which can cause colic and distress in the foal. Meconium impaction is a common condition in foals, and a rectal examination allows for immediate assessment of fecal consistency and obstruction.

Ultrasound of the umbilicus or urachus, while useful in evaluating abnormalities in the umbilical region, does not provide information about the condition of the intestines or the presence of meconium impaction. Similarly, cystocentesis is a technique used to obtain a urine sample, which is unrelated to diagnosing gastrointestinal issues in the foal. Endoscopy of the gastric mucosa could assist in identifying gastric conditions but would not address potential blockages in the rectum or colon that are indicative of meconium impaction.