Serum and peritoneal fluid phosphate concentrations as predictors of major intestinal injury associated with equine colic

Abstract

Summary To determine the reliability with which inorganic phosphorus (phosphate) concentrations can be used to predict major intestinal injury associated with equine colic, phosphate concentrations were measured in serum, peritoneal fluid, or both from 9 clinically normal adult horses (group A), 37 horses successfully managed medically for signs of abdominal pain (group B), 26 horses with signs of abdominal pain and undergoing exploratory laparotomy without intestinal resection (group C), and 26 horses undergoing intestinal resection or euthanasia for extensive intestinal lesions (group D). Peritoneal fluid phosphate concentration was significantly greater in horses in group D (mean, 4.58 ± 0.34 mg/dl) than in horses in group A (mean, 2.78 ± 0.21 mg/dl), group B (mean, 2.92 ± 0.27 mg/dl), and group C (mean, 2.98 ± 0.28 mg/dl; P ≤ 0.01). Serum phosphate concentration was significantly greater in horses in group D (mean, 3.87 ± 0.30 mg/dl) than in horses in group A (mean, 2.73 ± 0.22 mg/dl), group B (mean, 2.80 ± 0.21 mg/dl), and group C (mean, 2.78 ± 0.22 mg/dl; P ≤ 0.05). There was significant (P ≤ 0.001) correlation between serum and peritoneal fluid phosphate concentrations within each group and when pairs from all groups were pooled. When peritoneal fluid phosphate concentrations exceeded 3.6 mg/dl, intestinal lesions requiring resection or euthanasia were predicted with sensitivity of 77% and specificity of 76%. When serum phosphate concentrations exceeded 3.3 mg/dl, such lesions were predicted with sensitivity of 60% and specificity of 73%. These findings demonstrated that determination of peritoneal fluid phosphate concentration is of diagnostic value in adult horses requiring intestinal resection. Determination of serum phosphate concentration may be of value when peritoneal fluid is not obtainable.