Case Report

We report an interesting case of passage of decidual cast tissue. A 16-year-old girl presented to our department with severe abdominal pain & vaginal bleeding. She was prescribed Microgynon 30 micrograms (combined oral contraceptive pill, standard dosage) to take back to back for heavy painful periods. She took those pills for 3 months. After 15 days of her last pill she started to have painful vaginal bleeding associated with severe cramping lower abdominal pain for which she came to the hospital and she passed the decidual cast tissue, and her symptoms settled after the passage of the tissue. She had negative pregnancy test. She was scanned later which revealed normal uterus and ovaries. Following this episode she resumed normal regular periods.

The histopathological examination confirmed the diagnosis.

Histopathology Report

Macroscopy: Cast of uterine cavity 5x6x1 cm.

Microscopy: Partially necrotic endometrium showing marked decidua like change of the stroma but rather inactive dilated glands.

Diagnosis : Decidual change of endometrium.

Figure 1

Figure 1-3: Dedidual cast

Figure 2

Figure 3

Discussion

The lining of the pregnant uterus, other than the area taken up by the placenta, is called the decidua. The appearance of the normal lining of the uterus, by the effect of progesterone, becomes decidualized. When an area of decidua is shed, it is called a decidual cast because it frequently comes out in the shape of the uterine cavity. Decidual casts have a well-known association with ectopic pregnancies (₁). At ultrasonography an ectopic pregnancy with a decidual cast is often mistaken for an intrauterine pregnancy (₂). Clinically expulsion of a decidual cast can mimic a miscarriage. Decidual cast have also been reported in non-pregnant women as a side effect with the use of human menopausal gonadotrophin (HMG), human chorionic gonadotrophin (HCG) and progestogens. It is uncommon to see a decidual cast of the mentioned size, shape and thickness with the use of standard dose combined oral contraceptive pill. Membranous dysmenorrhoea is rare and causes intense cramping pain as a result of the passage of intact endometrial cast through an undilated cervix (₃,₄).

Conclusion

Decidual casts and membranous dysmenorrhoea although rare should be considered in non-pregnant women on HCG, HMG, progestogens or even combined oral contraceptive pills presenting with severe cramping abdominal pain and bleeding with passage of tissue. These casts can be misleading in undiagnosed Ectopic pregnancies then it might be mistaken for intrauterine gestational sac on the ultrasound scan, so it is vital to follow up such cases with serial beta HCG levels.