Incidental Finding on Routine Ultrasound Imaging of the Pelvis

History and Symptoms

This young adult female (22  years old) had no significant complaints and was referred for a routine ultrasound scan of the abdomen to rule out any pathology.  She complained of minor thyroid issues, and an ultrasonography suggested presence of Hashimoto thyroiditis.

Past History

She had a past history of surgery during childhood for a mass in the abdomen. We have deliberately hidden the details of the surgery and histopathologic report for the diagnosis.

Family History

Her parents both had no major surgery or illness. There was no history of diabetes, hypertension, or renal, hepatic, or gastroenterologic complaints in either parent. The patient was the only child and was delivered at full term. Her birth weight was also normal. The child was normal at birth with no reason to suspect any abdominal pathology.

Clinical Examination

Examination revealed a normal liver, spleen, and pelvis. In fact, she had no tenderness anywhere in the abdomen or pelvis. Repeated visits to the surgeon or family physician did not suggest any abdominal pathology. The visits to the doctor were part of the follow-up for the surgery she had earlier. The endocrinologist examined her and decided that other than a case of early Hashimoto thyroiditis, she was perfectly normal. This was confirmed by both hormonal assay and thyroid sonography.

The patient had a history of normal and regular menses and a routine abdominal ultrasound study was advised due to her past history of an abdominal mass for which surgery was performed.

Imaging Studies

Transabdominal ultrasound imaging of the liver, spleen, and both kidneys revealed normal viscera. However, this is what we found on sonography of the pelvis: 

The Uterus

This organ was clearly normal in size (measuring 7.5 x 2.6 x 3.4 cm). The endometrium measured 5 mm in thickness. The patient did not have a  history of coitus. The ovaries clearly revealed abnormalities on both sides.

What's your diagnosis?

Both ovaries show small but well defined, echogenic masses within them. These masses are well defined in outline and measure about 2 to 2.5 cm each. The mass in the left ovary is slightly larger at about 2.5 cm.

What else do you see? The masses in both ovaries are hyperechoic with mild posterior attenuation of the ultrasound beam. This point is important as it may be the only differentiating feature of these masses from 2 other similar types of masses of the ovaries - the hemorrhagic cyst and the endometrioma. In both these latter masses, there is significant posterior acoustic enhancement of the beam as opposed to the posterior acoustic attenuation seen here.
 

Right Ovary

The right ovary is seen in transverse section (to the left) in this ultrasound image. The uterus is seen to the right of the image.

Uterus

Ultrasound image of the uterus in sagittal plane

Both Ovaries

Transverse section ultrasound image showing echogenic masses in both ovaries.

Here are some more ultrasound images of the pelvis of this patient:

This image shows another view of the echogenic mass (arrow) in the right ovary. Note the lack of any posterior acoustic enhancement beyond the mass. Note also the nearby bowel loops producing similar appearances.

Image of both ovaries
The left ovary shows fine fimbriated strands within the ovarian cyst. These suggest presence of hair within the cystic lesion in left ovary.

Another image of both ovaries showing the lesions.
The image of left ovary above shows a view at a slightly different angle showing less of the echogenic mass and an adjacent part of the left ovarian cyst just above the echogenic mass.

Go to the next page to view the final diagnosis.

FINAL DIAGNOSIS: Bilateral dermoid cysts of the ovaries.

Explanation: There is clearly an echogenic mass in each ovary. In addition, the left ovary also shows cystic elements with fine strands passing through it.

This lady had undergone surgery to remove a large dermoid cyst of the left ovary at around 11 years.

This suggests recurrence of the dermoid cyst in the left ovary and formation of a new dermoid cyst in the right ovary.

The main differential diagnosis here are:

1. Echogenic bowel loops lying over the ovaries producing the appearances seen above. However this can be excluded due to the fact that the ovaries are seen separately from the bowel loops on probe pressure.

2. Hemorrhagic cysts of the ovaries: this can be ruled out because hemorrhagic cysts produce acoustic enhancement posteriorly, unlike the masses seen here. Also, the patient had no clinical symptoms of pain or tenderness in the adnexal regions.

3. Endometrioma: this too can be excluded on the basis that the patient had no history to suggest an endometrioma. Besides that, the cysts show posterior acoustic attenuation on sonography.

4. Cystadenofibromas can also be ruled out as the sonographic appearances are different.

5. Last, we ruled out appendicolith because the masses are clearly within the confines of the ovaries and are seen bilaterally.

ULTRASOUND FEATURES OF DERMOID CYSTS

Dermoid cysts are also called mature cystic teratomas and are nearly always benign in nature. They are known to grow very slowly over a long period and rarely reach more than 6 cms.

Sonographically, there are 3 main appearances of mature cystic teratomas or dermoid cysts of the ovaries:

• A cystic mass containing a mural nodule - the Rokitansky nodule. This contains calcified material, bone, teeth, or adipose tissue. This feature was not visualized in this case. This is seen as densely echogenic nodule within a primarily cystic mass.

• Cystic mass with hyperechoic material within it, with posterior acoustic attenuation. This appearance was seen in both ovaries here, suggestive of fatty material within the cyst.

• Presence of hair fibers within the cyst, giving the mature cystic teratoma (dermoid cyst) a finely fimbriated appearance. This feature was seen in the left ovary of the above case.

Very often it is a mixture of the above features in varying degrees that is seen in dermoid cysts of the ovaries.

COMMENTS

This patient had a history of resection of the mature dermoid cyst of the left ovary during her childhood. Thus, the mature cystic teratoma of the left ovary is the result of recurrence of the dermoid cyst on that side. The cystic teratoma of the right ovary has probably newly formed over the past few years.

This patient has been advised conservative treatment and follow-up ultrasound imaging has been advised to monitor the growth of the cystic masses in both ovaries. As ovarian dermoid cysts have very slow growth (less than 2 mm per year) and very low potential for malignancy (for ovarian dermoid cysts less than 6 cm), conservative management is sufficient in this case. Ovarian bilateral dermoid cysts only occur in about 10% of cases. Complications of dermoid cysts such as torsion, malignancy, and rupture are seen in only a small percentage of cases, and only where the mass is very large in size (bigger than 6 cm).

References:

References

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Hamilton CA, Harris JE. Cystic teratoma. Medscape. http://emedicine.medscape.com/article/281850-overview. Updated January 23, 2009. Retrieved May 11, 2011. 

Kadasne R. Ovarian Dermoid Cyst or Cystic Teratomas. http://www.ultrasound-images.com/ovaries.htm#Ovarian_dermoid_cyst_or_Cystic_teratomas. Updated March 26, 2011. Accessed May 11, 2011.

Laberge PY, Levesque S. Short-term morbidity and long-term recurrence rate of ovarian dermoid cysts treated by laparoscopy versus laparotomy. JOGC 2006(September):789-793. http://www.sogc.org/jogc/abstracts/full/200609_gynaecology_1.pdf. Accessed May 11, 2011.

Outwater EK, Siegelman ES, Hunt JL. Ovarian teratomas: Tumor types and imaging characteristics. RadioGraphics 2001;21(1):75-490. http://radiographics.rsna.org/content/21/2/475.full.pdf+htm. Accessed May 6, 2011.

Schwartz, RA, Elston DM. Dermoid cyst follow-up. Medscape. http://emedicine.medscape.com/article/1112963-followup#a2651. Updated March 12, 2010. Accessed May 11, 2011.

Stöppler MC, Shiel Jr. WC. Ovarian cysts. EmedicineHealth.  http://emedicine.medscape.com/. Reviewed August 6, 2010. Accessed May 11, 2011.