Short bowel syndrome (SBS, or simply short gut) is a malabsorption disorder caused by a lack of functional small intestine. The primary symptom is diarrhea, which can result in dehydration, malnutrition, and weight loss. Other symptoms may include bloating, heartburn, feeling tired, lactose intolerance, and foul-smelling stool. Complications can include anemia and kidney stones. Most cases are due to the surgical removal of a large portion of the small intestine. This is most often required due to Crohn's disease in adults and necrotising enterocolitis in young children. Other causes include damage to the small intestine from other means and being born with an abnormally short intestine. It usually does not develop until less than 2 m (6.6 ft) of the normally 6.1 m (20 ft) small intestine remains.