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Obstetrics Simplified - Diaa M. EI-Mowafi

Hydatidiform (Vesicular) Mole

It is a benign neoplasm of the chorionic villi.

Incidence

1:2000 pregnancies in United States and Europe, but 10 times more in Asia. The incidence is higher toward the beginning and more toward the end of the childbearing period. It is 10 times more in women over 45 years old.

Pathology

  • The uterus is distended by thin walled, translucent, grape-like vesicles of different sizes. These are degenerated chorionic villi filled with fluid.
  • There is no vasculature in the chorionic villi leads to early death and absorption of the embryo.
  • There is trophoblastic proliferation, with mitotic activity affecting both syncytial and cytotrophoblastic layers. This causes excessive secretion of hCG, chorionic thyrotrophin and progesterone. On the other hand, oestrogen production is low due to absence of the foetal supply of precursors.
  • High hCG causes multiple theca lutein cysts in the ovaries in about 50% of cases. It also results in exaggeration of the normal early pregnancy symptoms and signs.

Types

  • Complete mole:
    • The whole conceptus is transformed into a mass of vesicles.
    • No embryo is present.
    • It is the result of fertilisation of anucleated ovum (has no chromosomes) with a sperm which will duplicate giving rise to 46 chromosomes of paternal origin only.
  • Partial mole:
    • A part of trophoblastic tissue only shows molar changes.
    • There is a foetus or at least an amniotic sac.
    • It is the result of fertilisation of an ovum by 2 sperms so the chromosomal number is 69 chromosomes.

DIFFERENTIATION BETWEEN COMPLETE AND PARTIAL MOLE

Feature Complete Mole Partial Mole
Embryonic or foetal tissue Absent Present
Swelling of the villi Diffuse Focal
Trophoblastic hyperplasia Diffuse Focal
Karyotype Paternal 46 XX (96%) or 46 XY (4%) Paternal and maternal 69 XXY or 69 XYY
Malignant Changes 5-10% Rare

DIAGNOSIS

Symptoms

  • Amenorrhoea: usually of short period (2-3 months).
  • Exaggerated symptoms of pregnancy especially vomiting.
  • Vaginal bleeding which is usually dark brown and may be associated with passage of vesicles.
  • Abdominal pain: may be,
    • dull-aching due to rapid distension of the uterus,
    • colicky due to starting expulsion,
    • sudden and severe due to perforating mole.

Signs

  • General examination:
    • Pre-eclampsia develops in 20% of cases, usually before 20 weeks’ gestation.
    • Hyperthyroidism develops in 10% of cases manifested by enlarged thyroid gland, tachycardia and elevated plasma thyroxin level.
    • Breast signs of pregnancy.
  • Abdominal examination:
    • The uterus is larger than the period of amenorrhoea in 50% of cases, corresponds to it in 25% and smaller in 25% with inactive or dead mole.
    • The uterus is doughy in consistency
    • Foetal parts and heart sound cannot be detected except in partial mole.
  • Local examination:
    • Passage of vesicles (sure sign).
    • Bilateral ovarian cysts (5-20 cm) in 50% of cases.

Investigations

  • Urine pregnancy test: is positive in high dilution. 1/200 is highly suggestive, 1/500 is surely diagnostic. In normal pregnancy it is positive in dilutions up to 1/100.
  • Serum β-hCG level: is highly elevated (>100000 mIU/ml).
  • Ultrasonography reveals:
    • The characteristic intrauterine "snow storm" appearance,
    • no identifiable foetus,
    • bilateral ovarian cysts may be detected.
  • X-ray: shows no foetal skeleton.

Complications

  • Haemorrhage.
  • Infection due to absence of the amniotic sac.
  • Perforation of the uterus.
  • Pregnancy induced hypertension
  • Hyperthyroidism.
  • Subsequent development of choriocarcinoma

Treatment

  • As soon as the diagnosis of vesicular mole is established the uterus should be evacuated.
  • The selected method depends on the size of the uterus, whether partial expulsion has already occur or not, the patient's age and fertility desire.
  • Cross- matched blood should be available before starting.

Suction evacuation

  • It is carried out under general anaesthesia, but not that which relax the uterus as halothane as it may induce severe bleeding.
  • An infusion of 20 units oxytocin in 500 m1 of 5% glucose should be maintained throughout the procedure.
  • Dilatation of the cervix is done up to a Hegar's number equal to the period of amenorrhoea in weeks e.g. No. 10 Hegar for 10 weeks’ amenorrhoea. The suction canula used will be of the same size also.
  • A suction canula which may be metal or a disposable plastic (preferred) is introduced into the uterine cavity.
  • The canula is connected to a suction pump adjusted at negative pressure of 300-500 mmHg according to the duration of pregnancy.
  • Although some recommended a gentle sharp curettage to the uterus after evacuation, it is preferable to wait one week for fear of uterine perforation.

Hysterotomy

It may be needed for evacuation of a large mole to minimise and facilitate control of bleeding.

Hysterectomy

It should be considered in women over 40 years who have completed their family for fear of developing choriocarcinoma.

Medical induction

Oxytocins and / or prostaglandins may be used to encourage expulsion of the mole but must always be followed by surgical evacuation.

Follow up

  • As choriocarcinoma may complicate the vesicular mole after its evacuation, detection of serum ß-hCG by radioimmunoassay for 2 years is essential.
  • Detection is done every;
    • 2 weeks after evacuation to ensure regression of b -hCG level then,
    • every month for one year then,
    • every 3 months for another year.
  • Persistent high level indicates remnants of molar tissues which necessitate chemotherapy (methotrexate) with or without curettage. Hysterectomy is indicated if women had enough children.
  • Rising hCG, level after disappearance means developing of choriocarcinoma or a new pregnancy. So combined contraceptive pills should be used for prevention of pregnancy which can be misleading.
  • It is expected that urine pregnancy test is negative 4 weeks after evacuation and serum β-hCG is undetectable 4 months after evacuation.
  • Early features suggesting residual molar tissue include:
    • recurrent or persistent vaginal bleeding,
    • amenorrhoea,
    • failure of uterine involution,
    • persistence of ovarian enlargement.

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