1.  Ischemic bowel disease

2.  Intussusception: Usually occurs in the first  5 years of life.
In infants it is spontaneous and reversible.
It is probably related to lymphoid hyperplasia of viral etiology .  Intussusception caused by lymphoid hyperplasia in AIDS have been reported.
In adults intussusception indicates intraluminal mass or tumour (lipoma or leiomyoma) at the point of traction.
A segment of intestine (intussusceptum),   invaginates into immediately  distal segment of intestine (intussuscipiens).
As the segment is further pushed in, there is traction of the mesentery from behind.
Macroscopically, the specimen has a curved 'sausage- like' appearance. The concavity of the specimen is toward the root of the mesentery.
Increasing traction & compression of the mesenteric vessels may lead to infarction. There may be necrosis and sloughing of the  invaginated portion of the bowel.

3.  Meckel's diverticulum

4 main causes of intestinal obstruction :

1. Hernias
2. Intestinal adhesions:  There is localized peritoneal inflammation (peritonitis) following surgery, infection, endometriosis or radiation. Healing of peritonitis  leads to fibrous bridges between viscera. Complications of adhesions include intestinal obstruction, internal herniation within peritoneal cavity and strangulation of viscera. Image link (webpath)

3. Intussusception
4. Volvulus : Volvulus often occurs in small intestine or in the   sigmoid colon and is characterized by complete twising of the bowel loops about its mesenteric base. Complications include obstruction and infarction.

Image link (webpath)