A decidual cast is a large piece of tissue that passes through your vaginal canal.

Once the tissue is outside your body, you may notice that it looks like the shape of your uterus. This condition can affect people who menstruate. The decidual cast can cause extreme discomfort as well as vaginal bleeding as it leaves your body.

Generally, symptoms related to this condition go away after the decidual cast exits the body if it’s not related to another condition. There isn’t a single known cause of a decidual cast, but it may be related to hormonal contraception or ectopic pregnancy.

Read on to learn more about decidual casts, including symptoms, when to get help, and risk factors.

Before your body expels the decidual cast, you may experience bleeding, spotting, and abdominal pain or menstrual cramps, which may be severe.

When it’s expelled, a decidual cast will be red or pink. It will be somewhat triangular and close to the size of your uterus. This is because the entire lining of the uterus exited as one piece. The decidual cast will also appear fleshy because it’s made up of tissue.

It’s possible that the decidual cast will also come out in fragments instead of as a single piece of tissue.

Getting technical

The technical term for the symptoms related to a decidual cast moving from inside your uterus to outside your body is “membranous dysmenorrhea.”

How do the symptoms of a decidual cast differ from those of a miscarriage?

The symptoms of miscarriage and a decidual cast can be similar. Both can lead to cramping, pain, vaginal bleeding, and the loss of large pieces of tissue. Contact a doctor if you think you might be pregnant and experience these symptoms.

There’s not a single cause of a decidual cast. You may have this condition for several reasons, including:

Ectopic pregnancy

An ectopic pregnancy is a pregnancy that occurs when an egg is fertilized outside the uterus. This isn’t a viable pregnancy and is considered a medical emergency.

Contact 911 or your local emergency services if you suspect ectopic pregnancy, as it can be life threatening.

Hormonal contraceptives

Hormonal contraceptives, especially those that include a high dose of progesterone, may increase your risk of a decidual cast. These may include oral contraceptives as well as those that can be injected or implanted.

Additionally, you may be at risk of a decidual cast if you’ve recently stopped taking hormonal contraceptives or have been taking them inconsistently.

Other causes for your symptoms

A doctor may consider other conditions with similar symptoms when evaluating your condition, including:

  • pregnancy
  • an ended or miscarried pregnancy
  • intrauterine (within the uterus) masses
  • fibroepithelial polyps, also known as skin tags
  • sarcoma botryoides, a type of tumor that develops within hollow organs
  • rhabdomyosarcoma, a cancer of soft tissue

To determine a decidual cast diagnosis, a doctor will perform a physical examination and discuss your health history. They’ll also ask about any related symptoms you’re experiencing, where you’re feeling them, and for how long you’ve been feeling them.

A pelvic examination isn’t required if you have all the characteristics of a decidual cast. But it may be performed if you don’t see any improvement from medical treatment or if a doctor suspects that you may have secondary dysmenorrhea, or painful periods caused by something other than menstruation itself. An ultrasound may then also be given to differentiate the causes.

If you are at risk for a sexually transmitted infection (STI) or could have a pelvic inflammatory disease (PID), your doctor may need to do a swab.

A doctor may ask whether you might be pregnant or whether you’re taking any hormonal contraceptives.

Before or after you pass a decidual cast, a doctor may conduct some imaging tests. These can help the doctor diagnose the condition. The doctor will also look for other possible conditions, such as ectopic pregnancy or unusual masses in your reproductive system.

You may need to undergo a laparoscopy if all of the noninvasive options still don’t reveal what the cause of your symptoms is.

You may be more at risk of developing a decidual cast if you take hormonal contraception. This can include whether you take it regularly or irregularly. You may also be susceptible to a decidual cast if you have just stopped using it as well.

Most people who experience a decidual cast have no health implications following its passage. There’s no reason to think you’ll experience the condition again even if you’ve had a decidual cast before.

Studies have shown that women have no long-term health impacts after passing a decidual cast.

Studies have shown that many people don’t get medical attention for their decidual cast, often due to feelings of embarrassment or their ability to self-manage symptoms. However, you should contact a doctor right away if you experience painful menstrual cramps and vaginal bleeding that differ from what you usually experience during your monthly period.

Also, contact a doctor if you have a prolonged or heavy period or if it’s causing more discomfort than usual. These could be symptoms of a decidual cast or another condition.

A decidual cast is rare, and there’s nothing you can do to prevent it.

A decidual cast is a possible side effect of some contraceptives. You should be aware of the side effects of any hormonal contraceptives you use.

Be mindful of any unusual symptoms that may occur when you take contraceptives, such as severe cramps and vaginal bleeding. Some other side effects of hormonal contraceptives can include spotting as well as vomiting and nausea.

Expelling a decidual cast can be very painful and may cause you concern, but ultimately the outlook for people with this condition is good.

It’s rare to experience this condition multiple times, and there are no long-term consequences.

You should contact a doctor if you experience symptoms related to a decidual cast. The doctor will examine you to determine the cause of the symptoms and rule out related conditions. You may need additional testing to diagnose the condition.