⚡ Colic is Always a Possible Emergency

Any horse showing signs of abdominal pain should be assessed immediately. Colic signs range from mild (repeated lying down, reduced appetite) to severe (violent rolling, profuse sweating). The most important first step is determining whether medical or surgical management is appropriate. Early veterinary assessment and referral to a surgical center — before cardiovascular deterioration — offers the best prognosis. Never administer NSAIDs (bute, Banamine) without veterinary guidance if surgery is a possibility — it can mask worsening signs.

Overview

The large colon (ascending colon) is the most mobile and widest-diameter segment of the equine GI tract — and therefore the most prone to abnormal positioning. Left dorsal displacement (LDD), also called nephrosplenic entrapment, occurs when the large colon passes between the spleen and left kidney, becoming trapped in the nephrosplenic space. Right dorsal displacement (RDD) occurs when the cecum tips and the large colon slides up the right side of the abdomen. Both displacements cause partial obstruction of the large colon lumen with gas and fluid accumulation. A large colon volvulus (rotation of the mesocolon) is far more serious — a 180-360° rotation causes complete obstruction, rapid ischemic necrosis, and shock. Volvulus requires emergency surgery and carries a 25-60% survival rate depending on severity. Impending Cecal and Large Colon Impaction is a separate non-displacement form addressed as a differential.

Common Clinical Signs

Mild to moderate abdominal pain (colic) — pawing, flank-watching, lip-curling Repeated lying down or curling up Rolling or attempts to roll Reduced or absent fecal output Reduced gut sounds (particularly in left upper abdomen in LDD) Tachycardia (often 50-80+ bpm — correlates with pain) Abdominal distension (moderate in LDD/RDD, severe in volvulus) Mucous membranes: normal (early) → dry/tacky (dehydration) Reduced appetite Profuse sweating in severe cases

Diagnostic Approach

Diagnostic Test Expected Findings in Large Colon Displacement
Abdominocentesis (Peritoneal Fluid Analysis) Normal to mildly increased protein in LDD/RDD (transudate). Markedly elevated protein and elevated WBC — peritoneal fluid is pink/turbid/ hemorrhagic if colon is compromised or rupturing. Elevated lactate in peritoneal fluid >2 mmol/L is a negative prognostic sign.
Abdominal Ultrasound (Left & Right Flank) LDD: Large colon gas-filled, positioned between spleen and left kidney, loss of normal splenic-capsular space. RDD: Large colon displaced to right side, dorsal to cecum. Volvulus: Loss of normal large colon architecture, free abdominal fluid, edematous bowel wall. Most useful non-invasive diagnostic tool.
Abdominal Radiographs Useful in small horses and foals. In adult horses, large colon gas distension may be visible. Not routinely diagnostic for displacement — ultrasound is preferred.
Nasogastric Intubation Reflux of gastric contents (>2 liters) suggests gastric outflow or small intestinal obstruction — concerning for small intestinal strangulation (not large colon displacement). Small-volume or no reflux in large colon displacement.
Rectal Examination LDD: Left kidney palpable, colon displaced laterally and ventrally away from kidney, taut band at nephrosplenic ligament. RDD: Large colon palpable on right dorsal abdomen. Volvulus: Distended, gas-filled colon, often in dorsal abdomen with taut mesocolon.
CBC / Serum Chemistry May show hemoconcentration (increased PCV from dehydration) in advanced cases. Electrolyte abnormalities (hypochloremia, hypokalemia) if prolonged vomiting or reflux. Elevated lactate if tissue ischemia present — lactate >5 mmol/L at admission is a negative prognostic indicator.

Differential Diagnoses

  • Large colon impaction (pelvic flexure) — Most common non-displacement large colon cause. Pain is usually mild to moderate. Ultrasound shows dry, impacted colon content. Usually resolves with medical management (fluids, analgesics, motility drugs). Rectal: hard, dry mass in pelvic flexure region.
  • Small intestinal strangulation — Epiploic foramen entrapment, pedunculated lipoma, volvulus. Large-volume gastric reflux (>2 liters), severe pain. Ultrasound: distended, fluid-filled small intestine. Requires emergency surgery.
  • Sand impaction — Chronic, subacute presentation. Pain is mild to moderate. Abdominal radiographs show sand in ventral colon. History of grazing on sandy soil or being fed on sand.
  • Enteritis / Ileus — Diffuse small and large intestinal inflammation. Often associated with fever, diarrhea. Ultrasound: fluid-distended small intestine, normal large colon. Responds to medical management.
  • Gastric ulcer syndrome (EGUS) — Mild colic signs, often post-prandial. Weight loss and poor appetite. Gastroscopy confirms. No abdominal distension.
  • Cecal impaction or typhlitis — Pain is usually moderate. Right flank pain and distension. Ultrasound: distended cecum with impacted content. May progress to cecal rupture if untreated.

Treatment & Prognosis

LDD (nephrosplenic entrapment): Can sometimes be resolved medically using IV phenylephrine (alpha-agonist vasoconstrictor) + controlled hand-walking exercise in early, mild cases — the colon may disengage from the nephrosplenic space. Success rates are variable. Most cases require surgical correction via flank or midline celiotomy. LDD surgery carries a good prognosis (~80-90% short-term survival). RDD requires surgical repositioning. Large colon volvulus requires immediate emergency surgery — the bowel is often non-viable by the time the abdomen is opened. Survival rates drop significantly if resection is needed (25-50%). Post-op complications include ileus, colic recurrence, and septic peritonitis.