Postoperative Colic After Small Intestinal Resection in a Horse
A 9-year-old Thoroughbred gelding underwent 60 cm of distal jejunal resection and end-to-end anastomosis for a strangulating lipoma 36 hours ago. He is now showing mild colic signs, heart rate 60/min, and reduced manure output. Reflux via nasogastric tube is 4 L and serosanguineous. Abdominal ultrasound shows a dilated small intestine with reduced motility and a small amount of peritoneal fluid. Bloodwork shows PCV 48%, lactate 2.8 mmol/L, and total protein 5.8 g/dL. The horse is receiving IV fluids, NSAIDs, and antimicrobials.
1. What are the leading differentials for post-operative colic in this horse, and how do you prioritize them?
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Differentials: (1) Postoperative ileus - most common after small intestinal surgery; supported by reduced motility, mild reflux, and gradual onset. (2) Anastomotic leakage/peritonitis - suggested by serosanguineous reflux, rising lactate, and peritoneal fluid; this is the most life-threatening and must be excluded early. (3) Adynamic/obstructive ileus from inflammation or adhesions - early adhesions are less likely at 36 h but possible. (4) Incisional or anastomotic edema/obstruction. Prioritize excluding leakage (peritoneal fluid analysis, serial lactate, ultrasound for free fluid/fluid character) because delay is fatal, while managing ileus supportively in parallel.
2. How do you use peritoneal fluid analysis and serial lactate to distinguish ileus from leakage?
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Peritoneal fluid: in uncomplicated ileus, fluid is typically a modified transudate with low nucleated cell count and no intracellular bacteria. In leakage/peritonitis, expect a degenerate neutrophilic exudate, intracellular bacteria, and fluid glucose lower than blood with lactate higher than blood. Serial lactate: a rising lactate despite fluids suggests ongoing ischemia/sepsis (leak), whereas a stable or falling lactate with improving reflux supports ileus. Ultrasound showing increased free fluid or a focal wall defect raises concern. If suspicion of leak is high, exploratory celiotomy is warranted rather than continued observation; a single normal tap does not exclude a sealed leak.
3. Outline the medical management of postoperative ileus and the criteria for reoperation.
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Medical management: aggressive IV balanced crystalloids to maintain perfusion and correct electrolyte deficits (especially potassium, calcium, magnesium); nasogastric decompression at intervals; prokinetics (e.g., lidocaine CRI, erythromycin or metoclopramide with caution) as appropriate; analgesia (NSAIDs, +/- opioids) to reduce sympathetic inhibition; hand-walking and enteral stimulation (small frequent feedings once reflux resolves); monitor PCV/TP, lactate, and reflux volume. Reoperation criteria: worsening pain despite analgesia, increasing reflux, rising lactate, deteriorating peritoneal fluid (exudate, bacteria, low glucose), ultrasound evidence of leak or obstruction, or lack of improvement over 12-24 h. Reoperate promptly when these are met; delay worsens prognosis.