Two grades of clinical severity are described.
Grade 1: 2 or more of the following:
(1) pneumatosis intestinalis
(2) (abdominal distension) OR (abdominal radiograph showing gaseous distension or frothy bowel lumen)
(3) blood in the stool
(4) lethargy, hypotension and/or apnea (clinical deterioration)
Grade 2: Grade 1 plus one or more of the following:
(1) abdominal tenderness or rigidity
(2) tissue (mucosa) in the stool (sloughing)
(3) peripheral white blood cell count <= 6,000 per µL
(4) thrombocytopenia (platelet count <= 100,000 per µL)
(5) abnormal bleeding after trauma OR spontaneous bleeding
(6) gas in portal vein on abdominal X-ray
(7) free air in abdomen
