| Stage | 1 | 2A | 2B | 3A | 3B |
| Description | Suspected | Mild | Moderate | Severe | Severe |
| Systemic signs | Temperature instability, apnea, bradycardia | Similar to stage 1 | Mild acidosis, trombocytopenia | Respiratory and metabolic acidosis, need for mechanical ventilation, hypotension, oliguria, disseminated intravascular coagulopathy | Further deterioration and shock |
| Intestinal signs | Increased gastric residuals, mild abdominal distention, occult blood in the stool | Marked abdominal distension ± tenderness, absent bowel sounds, grossly bloody stools | Abdominal wall edema and tenderness ± palpable mass | Worsening wall edema with erythema and induration | Evidence of perforation |
| Radiographic signs | Normal or mild ileus | Ileus, dilated bowel loops, focal pneumatosis | Extensive pneumatosis, early ascites ± portal venous gas | Prominent ascites, fixed bowel loop, no free air | pneumoperitoneum |