May Be Caused by

 Common

Abdominal abscess

Distended bladder

Fecal impaction

Intestinal obstruction

Intussusception

 Uncommon

Aneurysmal bone cyst of lumbosacral spine

Aneurysmal bone cyst of pelvis

Cystic mesenteric lesion

Dermoid cyst

Duplication cyst

Hydatid cyst

Hydrometrocolpos

Hydrosalpinx

Lymphocele

Meconium

Meningocele

Pyosalpinx

Retroperitoneal hematoma

Retroperitoneal sarcoma

Retroperitoneal teratoma

Sarcoma of lumbosacral spine

Sarcoma of pelvis

Urachal cyst

Urinoma