Intussusception occurs when a portion of intestine slides inside an adjacent portion of intestine. This intestinal telescoping can occur following a bout of intestinal inflammation (e.g.: parvovirus infection in dogs) or other systemic illness; some intussusceptions have no known cause. The enfolding of the intestine narrows the passageway for flow of intestinal contents creating a partial or complete obstruction. Patients with intussusceptions present with lethargy, vomiting, diarrhea, pain, and/or inappetance. Diagnosis may be based on history of illness, physical examination findings (a firm cylindrical mass may be felt in the abdomen), and imaging (e.g.: x-rays, ultrasound). Intussusceptions rarely reverse themselves; treatment of choice for intussusceptions is surgical repair to restore bowel health and prevent recurrence.