Female pharmacist in her pharmacy with a client
kzenon/iStock/Getty Images

The most common type of enema is the type you can buy at a pharmacy to treat constipation. Your doctor may also use an enema to diagnose various types of gastrointestinal diseases. The type of enema you need depends on your circumstances and the recommendation of your doctor.

Saline Enema

Constipation Relief
dina2001/iStock/Getty Images

A saline laxative enema is a popular type of enema available at most pharmacies. It works to relieve constipation by drawing water from the body into the rectum and lower colon to cause a bowel movement. It can also cleanse the bowel prior to a rectal examination. The enema usually comes in a small disposable squeeze bottle with a pre-lubricated syringe for rectal insertion. Although saline enemas are generally safe, water and electrolyte disturbances can occur particularly among people younger than 18 or older than 65 years with gastrointestinal motility disorders, heart disease or renal failure, according to research published in "Alimentary Pharmacology and Therapeutics" in July 2007. If you wonder whether using an enema is okay for you, ask your doctor.

Mineral Oil Enema

People who need to avoid or minimize straining when having a bowel movement use mineral oil, liquid petroleum or castor oil enemas. Women recovering from childbirth or people recovering from certain types of surgery or injury can benefit from mineral oil enemas. The oil attaches to the fecal matter and retains the water content in the stool so it more easily passes through the rectum and out of the body.

Barium Enema

barium enema  demonstrated the normal rectum and cecum
praisaeng/iStock/Getty Images

Barium is a metal used as a contrast for x-ray imaging of the intestines. Gastroenterologists therefore prescribe a barium enema to diagnose diseases and conditions associated with the large and small intestines, such as colon cancer or inflammatory bowel disease. A barium enema is usually done in your doctor's office or the radiology department of a hospital.