Ranulas are a type of cyst that affect the major salivary glands. These cysts occur when mucous extravasates into surrounding tissue. There are cervical ranulas and oral ranulas. Cervical ranulas can sometimes appear to be a unilateral, bluish, translucent neck mass.. They can be caused by trauma or blockage of the excretory duct which does not allow the duct to drain mucous properly. Ranulas are most often asymptomatic or have no symptoms, but sometimes patients can have trouble swallowing or chewing and can have trouble breathing. Oral ranulas often cause swelling of the floor of the mouth but is not painful. Females tend to get oral ranulas while males tend to get cervical ranulas. These cysts most often occur in younger adults and older children under the age of twenty. These lesions usually grow quickly but only last about three to six weeks; or until they rupture. This happens spontaneously. Patients who have had a ranula can expect to get one again as they are often chronic in nature. HIV can increase your risk of getting a ranula. Ranulas are often diagnosed by a CT or MRI scan. They appear as a smooth, well-outlined cystic lesion in the oral or neck area. They can sometimes have a slightly increased attenuation. When a ranula is infected is cannot be differentiated from an abcess on a CT. T1 and T2 weighted imaging sequences are utilized in an MRI for a ranula. If a ranula does not heal itself, an excision can be made in order to drain the mucous from the tissue.
All information was taken from the following websites:
http://www.learningradiology.com/archives05/COW%20146-Ranula/ranulacorrect.htm
http://emedicine.medscape.com/article/1076717-overview