How do I assess severity of colic in a horse and determine when surgical referral is indicated?

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The most reliable indicators for surgical referral are moderate-to-severe abdominal pain, recurrence of pain after appropriate analgesia, and absence of intestinal borborygmi. These three findings remain the most accurate predictors of surgical necessity despite advances in laboratory diagnostics and imaging.2 Cardiovascular parameters are the cornerstone of severity assessment. Heart rate, mucous membrane color, and capillary refill time are significantly different in critical cases compared to medically managed cases, and these differences are detectable on the initial examination.3 Reduced gut sounds are present in 75.8% of large colon impaction cases, and critical cases show significantly more pronounced reductions — particularly in the upper left and upper right quadrants — compared to medical cases.3 Approximately 20% of colic cases overall are critical, defined as requiring referral medical or surgical treatment, euthanasia, or death.8 Peritoneal lactate is a stronger predictor of lesion type and survival than blood lactate. Mean peritoneal lactate in strangulating lesions is 7.33 mmol/L versus 3.06 mmol/L in non-strangulating cases. Mean blood lactate in strangulating lesions is 5.11 mmol/L versus 3.54 mmol/L in non-strangulating cases. For survivors, mean peritoneal lactate is 2.42 mmol/L versus 7.13 mmol/L in non-survivors; mean blood lactate is 3.43 mmol/L in survivors versus 4.84 mmol/L in non-survivors. Neither blood nor peritoneal lactate reliably predicts whether a case will require surgical versus medical management (therapeutic referral).4 Abdominal ultrasonography adds diagnostic specificity beyond physical examination. The Fast Localized Abdominal Sonography of Horses (FLASH) protocol is performed routinely in field and clinical settings, typically takes less than 15 minutes, and identifies major pathologies warranting surgical intervention.7 Large intestinal wall thickness ≥ 9 mm on transabdominal ultrasound is an indicator for colon torsion in h