What is a decidual cast?

Decidual Cast: Definition, Causes, and Clinical Significance

A decidual cast is the spontaneous sloughing of the endometrium as an entire piece while retaining the shape of the uterine cavity, typically associated with hormonal contraception use or discontinuation. 1

Definition and Pathophysiology

• Decidual cast forms when the decidualized endometrium sheds in one piece, maintaining the three-dimensional shape of the uterine cavity 2
• Decidualization is a progesterone-mediated reaction that naturally occurs during the menstrual cycle, but normally the hyperproliferated tissue dissolves and passes during menstruation 3
• When natural dissolution doesn't occur, the intact endometrial lining can be expelled as a cast 3

Common Causes and Associations

• Most commonly associated with initiation or cessation of hormonal contraceptives, particularly those containing progesterone 1, 2
• Reported with various contraceptive methods including:
  • Oral contraceptive pills 4
  • Depo medroxyprogesterone acetate injections 3
  • Desogestrel-containing contraceptives 4
• Can occasionally occur spontaneously without hormonal medication use 2
• Rarely associated with:
  • Extrauterine pregnancy
  • Miscarriage
  • Abortion
  • Pregnancy in anatomical uterine variants (uterus didelphys/bicornis)
  • Following postpartum hemorrhage 2

Clinical Presentation

• Patients typically present with:
  • Abdominal or pelvic pain, often severe 5
  • Vaginal bleeding, which may be heavy 1
  • Passage of tissue per vagina that resembles the shape of the uterine cavity 1, 2
• Can cause genital tract obstruction with symptoms mimicking other obstructive conditions 5
• May be accompanied by severe dysmenorrhea 5

Diagnosis

• Diagnosis is primarily made by:
  • Clinical history of hormonal contraceptive use or recent discontinuation 1, 3
  • Physical examination revealing passage of tissue resembling the uterine cavity 2
  • Histopathological confirmation showing decidualized endometrium 2
• Important to differentiate from other conditions that present with tissue passage:
  • Aborted pregnancy (perform pregnancy test) 2
  • Rhabdomyosarcoma
  • Endometrial polyp 4
  • Pseudogestational sac (which lacks the decidual layer characteristic of true gestational sacs) 6

Complications

• Rarely, decidual casts can become infected 3
• May contain products of conception in cases of unrecognized pregnancy 3
• Can cause significant pain and distress for patients 5
• May lead to genital tract obstruction requiring intervention 5

Management

• Most cases resolve spontaneously without specific intervention 4
• Patient education about this potential side effect should be provided before starting progesterone-containing contraceptives 1
• Imaging may be needed if symptoms suggest obstruction 5
• In severe cases with obstruction, examination under anesthesia may be required 5

Pathological Considerations

• Histologically characterized by decidualized endometrium 2
• Should not be confused with placenta accreta spectrum disorders, which involve abnormal trophoblast invasion into the myometrium 7, 8
• Matrix-metalloproteinases or their regulators may be involved in the pathophysiology 2