Necrotizing enterocolitis Intraperitoneal blood (trauma, ruptured ectopic pregnancy, aneurysm) Electrolyte abnormalities Hypokalemia Hypercalcemia Irritable Bowel Syndrome Poisoning/medications (e.g., anticholinergic, opiate, loperamide, botulism) Trauma Shock Severe pain secondary to Biliary colic Renal colic Malabsorption Congenital causes Bacterial overgrowth Parasites Formula enteropathy Lactose intolerance Celiac disease Obstipation Functional Hirschsprung disease Hypothyroidism Free peritoneal air Intestinal perforation Pneumomediastinum Extraluminal fluid Hypoproteinemia Malnutrition Nephrotic syndrome Renal failure