Can Doppler Ultrasound Miss Torsion From a Dermoid Cyst?

Yes, a Doppler ultrasound can miss an ovarian torsion caused by a dermoid cyst. A “normal” result showing preserved blood flow should never be used alone to rule out this medical emergency ^[1][2].

While decreased or absent blood flow on an ultrasound is a strong warning sign, research on surgically confirmed cases shows that normal Doppler flow can be seen in 27% to 61% of torsions, depending on the side affected ^[2]. Because a dermoid cyst (a type of ovarian tumor, also called a mature cystic teratoma) makes the ovary heavy and prone to twisting, experiencing severe pelvic pain requires urgent gynecologic evaluation regardless of what the Doppler flow shows ^[3][4].

If you are experiencing symptoms now:
If you have a known dermoid cyst and develop sudden, severe, worsening, or intermittent one-sided pelvic pain, go to the nearest emergency department immediately ^[4]. Do not wait for a scheduled appointment. Symptoms may also include nausea, vomiting, or feeling very unwell ^[4]. Seek emergency care even if your pain temporarily improves or a recent ultrasound was labeled “normal” ^[5].

Why Normal Blood Flow Doesn’t Mean You Are Safe

There are several anatomical reasons why a twisted ovary might still show normal-appearing blood flow on an ultrasound:

• Dual Blood Supply: The ovary receives blood from two different communicating pathways: the ovarian artery and the uterine artery. Because of this, blood can sometimes continue to reach the ovary even if one pathway is twisted ^[6]. However, visible arterial flow does not mean the ovary is adequately functioning or safe from damage.
• Veins Compress Before Arteries: When the ovary twists, the low-pressure veins and lymphatic vessels are usually pinched shut first, while the higher-pressure arteries continue pumping blood in ^[7]. This allows arterial blood flow to remain visible on the Doppler, even though blood cannot drain out—leading to severe swelling and tissue congestion ^[8].
• Partial or Intermittent Torsion: An ovary weighed down by a dermoid cyst can twist and then temporarily untwist (detorse). If the ultrasound is performed during a window when the ovary has partially untwisted, the blood flow may temporarily look normal ^[9][10].

Other Ultrasound Clues

Because Doppler blood flow can be falsely reassuring, radiologists look for other suggestive clues on standard 2D (grayscale) ultrasound. No single sign is required to diagnose torsion, and the absence of these signs does not mean you are safe. However, findings that increase concern include:

• Ovarian Enlargement and Edema: An ovary that is significantly swollen or larger than the other side due to trapped fluid ^[11].
• Peripheralized Follicles: Small fluid-filled sacs (follicles) pushed to the outer edges of the swollen ovary ^[11].
• The “Whirlpool Sign”: A visible twisting of the tissue and blood vessel stalk (the pedicle) that connects to the ovary ^[1].
• Abnormal Position: The heavy dermoid cyst and ovary being displaced from their usual location in the pelvis ^[12][3].
• Free Fluid: Fluid pooling in the pelvis ^[13].

Lab Tests and Ruling Out Other Emergencies

Acute one-sided pelvic pain can also be caused by other emergencies, such as an ectopic pregnancy, appendicitis, or a ruptured cyst ^[7][14]. Emergency doctors will likely run tests—like a pregnancy test or a complete blood count (CBC) to check white blood cells—to investigate these possibilities and gather context ^[4].

However, lab tests are not reliable for ruling out ovarian torsion. While an elevated white blood cell count can sometimes occur, lab tests can also be completely normal or only mildly abnormal in confirmed torsion cases ^[15]. Normal blood work should never delay emergency care if your symptoms suggest a twisted ovary.

Seek Care Based on Symptoms, Not Scans Alone

Because symptoms, physical exams, and imaging all have limitations, there is no single test that can completely rule out a twisted ovary ^[5]. Torsion is definitively confirmed by directly inspecting the ovary during surgery ^[16].

When clinical suspicion remains high despite a “normal” Doppler scan, a gynecologist may recommend an urgent diagnostic laparoscopy (a minimally invasive surgery to look inside the abdomen) ^[17]. This procedure allows the surgeon to confirm the torsion, untwist the ovary to restore blood flow, and potentially remove the cyst, preventing permanent tissue damage ^[17][16].