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DIFFERENTIAL DIAGNOSIS OF SONOGRAPHIC FINDINGS

Suyashree Palkar
Consultant Onstetrician and Gynaecologist, Mumbai. Route Hospital, Ballymoney, BT 536BP. Northern Ireland.

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Ultrasound is the most commonly used diagnostic modality in obstetrics and gynaecology today. Still sonographic findings can have their own pitfalls and often not be conclusive in certain cases. Thus an experienced sonologist is of importance.

CASE REPORT

A 31 year old lady was admitted to the gynaecology ward. She was in her first pregnancy and now 12 weeks in gestation according to her first dating scan. She complained of lower abdominal pain and intermittent pv bleeding since the past two weeks. Her menstrual periods had been heavy and painful in the past. She had no urinary complaints. There was no history of contraceptive use in the past and apart from being asthmatic (which was under treatment), She had no other medical complaints. On examination, she was stable suprapubic tenderness was present and speculum exam showed a cervical ectopy but no blood in the vagina. A per vaginal examination was difficult because she was very anxious but it could be gauged that the internal os was closed.

A diagnosis of threatened abortion was made and conservative management started. Her Hb was 11.7 gm%, blood group was O Rh positive and a Mid-stream sample of urine showed no evidence of infection. An ultrasound scan done by the radiologist reported the uterus conatins a viable foetus CRL 57 mms equivalent to an average gestation of 12+ weeks. Liquor volume appears reduced and there is a complex area behind the placenta which could indicate a bleed. In the region of the left cornua there is a 4.8 cm fluid containing lesion which is 32 mm which would be equivalent to a gestation age of 10 weeks? The appearances are those of a viable pregnancy with a non viable ectopic pregnancy.

A repeat scan done in the ward showed a viable intra-uterine pregnancy 12+ weeks. Small echogenic shadow towards the left uterine cornual end measuring 2.5 cms in diameter - diagnosis : Carneous mole. Analgesia and observation was advised.

She still complained of pain in the next 48 hours despite analgesia.

Ultrasound findings done by the same radiologist 48 hours later, showed complex area posterior to the placenta was resolving. The previously demonstrated area was still present but had altered its position, now being situated just to the left of the midline in the pouch of douglas, size remaining the same. The change in position would suggest it to be related to the tube or ovary.

Because of the uncertainty in diagnosis, it was decided that a laparoscopy should be performed. Laparoscopy findings were normal ovaries and tubes. A 2 cm sized fibroid was present near the left cornual region intramurally within the uterus. The patient settled down in the next couple of days with symptomatic treatment and was discharged thereafter.

Fig1 Intra uterine pregnancy

Fig 2. Uterus with foetal adnexal lesion shadow

Fig 3. Uterus with foetal adnexal lesion shadow

DISCUSSION

Masses in relation to the uterus have varying features on ultrasound which can be lead to the correct diagnosis.

A uterine fibroid in a cornual location during pregnancy can be confused with a bicornuate uterus. The incidence of congenital anomalies of the uterus in the randon population is 0.1-0.5%. However a leiomyoma will show increased soundattenuation as well as lack of a central canal and decidual response which would otherwise occur in a bicornuate uterus.[1]

An ectopic pregnancy in the rudimentary horn of the bicornuate uterus or in the interstitial portion of the tube can be diagnosed by an eccentric location of an in utero sac, failure to demonstrate the sac near the internal os on longitudnal scans and incomplete myometrial envelopement of the sac which were the most reliable sonographic criteria.[3] An ectopic pregnancy in the tube can be mistaken for one horn of a bicornuate uterus. The presence of an endometrial canal echo, rather than the echogenic endometrial debris is helpful in the differentiation between the two entities, since none of the patients with anomalous have a well defined echo in the nongravid horn. With the presence of an endometrial decidual response simulating an intra-uterine gestational sac within the anomalous horn, differential diagnosis may be more difficult and additional clinical data may be necessary to differentiate between an ectopic pregnancy and an anomalous uterus.[4]

The appearance of the endometrial reaction and fluid in the non-gravid horn of a bicornuate uterus could in theory, simulate an early twin gestation.[5]

Sometimes patients with normal uteri can simulate findings as in those of uterine anomalies. These are placental membrane and surgical scarring. Intra-uterine membranes of placental origin often change their configuration in response to turbulence in the amniotic fluid resulting from foetal motion seen with real time sonography. True uterine septations are more rigid and not as easily deformed.

Other masses in relation to the uterus in the differential diagnosis can be broad ligament tumours, endometriotic cysts, cystic ovary, and hydrosalpinx.[6]

REFERENCES

1.Pennes DR, Bowerman RA, Silver TM. Congenital uterine anomalies associated with pregnancy. Findings and pitfalls of sonographic diagnosis. Journal of ultrasound Medicine 1985; 4 : 531-39.

2.Jones TB, Fleisher AC, Daniell JF, et al Sonographic characteristic of congenital uterine anomalies and associated pregnancy. JCV 1980; 8 : 435.

3.Reuwen A, Ofer T, Reymond K, et al. Pre-rupture Ultrasound diagnosis of interstitial and rudimentary uterine horn pregnancy. Journal of Reproductive Medicine 1992; 89-92.

4.Marks WM, Filly RA, Callen PW, et al The decidual cast of ectopic pregnancy : a consulting ultrasonic appearance. Radiology 1979; 133 : 451.

5.McArdle CR. Pregnancy in a bicornuate uterus. JCU 1978; 6 : 185.

6.Tindall VR. Jeffcoate’s principles of gynaecology, 5th ed. Tumours of the corpus uteri, pg 426.

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