Colic

Colic is the most common equine emergency and a leading cause of death in horses. It is a clinical sign (abdominal pain), not a diagnosis.

Classification by pathophysiology:

• Obstructive (non-strangulating): Simple impaction, enterolith, fecalith, ileal hypertrophy — lumen blocked but blood supply intact
• Obstructive (strangulating): Volvulus, torsion, incarceration — lumen blocked AND blood supply compromised → rapid ischemia, necrosis, shock
• Vascular: Mesenteric thromboembolism (Strongylus vulgaris), non-strangulating infarction
• Inflammatory: Proximal enteritis, colitis, peritonitis
• Non-GI / non-abdominal: Rhabdomyolysis (tying-up), pleuropneumonia, urolithiasis, uterine torsion

Clinical signs: Pawing, flank-watching, rolling, kicking at belly, lying down/getting up repeatedly, anorexia, decreased manure, sweating, tachycardia, tachypnea.

Heart rate: The single most reliable predictor of surgical need.

• HR < 40 → usually medical
• HR 40–60 → intermediate; monitor closely
• HR > 60 → strongly suggests surgical lesion

Mucous membranes: Pink = good; injected = early; toxic (injected + line) = ischemia; pale/cyanotic = shock

Capillary refill time: Prolonged (> 2 sec) = dehydration/hypovolemia

Intestinal borborygmi: Absent or hypermotile depending on lesion

Rectal exam: Assess gastric distension, small intestinal distension (> 4 cm = abnormal), cecal/ventral colon position, masses, sand impaction

Nasogastric intubation: Critical! Check for gastric reflux. > 2–4 liters of reflux = obstruction proximal to duodenum (surgical or enteritis)

Abdominal ultrasound: Assess small intestinal diameter, motility, presence of peritoneal fluid

Large colon volvulus:

• Most common strangulating lesion in adults
• Severe pain, distended colon on rectal, HR > 80, toxic membranes
• Surgery: Exploratory celiotomy, de-rotate, assess viability; resection if necrotic

Left dorsal displacement (nephrosplenic entrapment):

• Colon drapes over nephrosplenic ligament
• May try rolling under anesthesia or phenylephrine + exercise; surgery if fails

Right dorsal displacement:

• Colon shifts cranially to right side; surgical

Simple impaction (pelvic flexure, cecum):

• Medical: IV fluids, laxatives (mineral oil, dioctyl sodium succinate), analgesia, walking

Proximal enteritis (anterior duodenitis-jejunitis):

• Massive gastric reflux (> 4L); medical; keep NG tube in place; IV fluids, anti-inflammatories
• Differentiate from small intestinal strangulating obstruction (surgical)

Laboratory: ↑ PCV/dehydration, ↑ lactate (> 4–6 mmol/L = poor prognosis/surgical), ↑ creatinine (prerenal), leukopenia (endotoxemia), metabolic acidosis