Diagnosing Uterine Polyps: Scans, Scopes, and Accuracy

Getting an accurate diagnosis for uterine polyps is essential because these small growths can often hide behind the natural folds of the uterine lining. While your doctor may start with a basic ultrasound, that is often just the beginning of the diagnostic journey.

The Limitations of Standard Ultrasound

A transvaginal ultrasound (TVUS) is typically the first step in evaluating abnormal bleeding. During this scan, a probe is placed in the vagina to bounce sound waves off the uterus. However, TVUS has limitations for detecting focal lesions. Because the uterine walls are naturally pressed together, a small polyp can be squeezed flat and look like a general thickening of the lining ^[1].

Research shows that TVUS identifies polyps correctly about 55% to 62% of the time (sensitivity) ^[1][2]. This accuracy depends heavily on the size of the polyp, the skill of the operator, and the timing of your menstrual cycle. Because of this, a “normal” standard ultrasound does not always guarantee the cavity is clear.

The Superiority of Saline Infusion (SIS)

To get a better view, doctors often use Saline Infusion Sonohysterography (SIS). By gently filling the uterine cavity with a sterile saline (saltwater) solution, the walls are pushed apart, allowing the liquid to outline any polyps clearly ^[3].

The accuracy of SIS is significantly higher than a standard ultrasound, with a sensitivity of approximately 87% to 92% in study populations ^[1][2].

• What to expect: A speculum is used to place a very thin tube into your cervix. As the saline enters, you will likely feel cramping, similar to a period. Pain levels vary substantially—some experience mild discomfort, while others find it intensely painful.
• Preparation: For menstruating patients, this is usually scheduled shortly after your period ends when the lining is at its thinnest ^[3]. Discuss pain management (such as taking ibuprofen beforehand, if safe for you) with your doctor. SIS should not be performed if you are pregnant or have an active pelvic infection.

The Role of “Blind” Biopsies

You may be offered a blind endometrial biopsy or a Dilation and Curettage (D&C) to investigate bleeding. In these procedures, a tool is inserted to sample the lining without the doctor being able to see inside the cavity.

These are considered “blind” because they sample the cavity at random. While a blind biopsy is excellent for checking the global health of the uterine lining (and is vital for ruling out widespread cancer or hyperplasia, especially in postmenopausal bleeding), it is not a reliable way to rule out a small, focal growth like a polyp ^[4]. The tool can easily slide right past a small polyp, leading to a false-negative result where the focal polyp remains undetected.

The Gold Standard for Visualization: Hysteroscopy

Hysteroscopy is considered the “gold standard” for evaluating the uterine cavity because it provides direct visualization ^[4].

During a hysteroscopy, a thin, lighted camera (the hysteroscope) is inserted through the cervix into the uterus. This allows the doctor to see the exact size, shape, and location of any growths ^[4]. However, visual appearance alone cannot prove a polyp is benign—only a laboratory analysis (pathology) of the tissue can do that.

• See-and-Treat: The greatest advantage of hysteroscopy is that if a polyp is found, the doctor can often use tiny instruments through the scope to remove it immediately. This ensures the exact tissue causing the problem is tested ^[5][4].
• Risks and Pain: Hysteroscopy can be done in the office or an operating room. Office hysteroscopy can be very uncomfortable or painful for some patients. Discuss local anesthesia or sedation options. While rare, risks include infection, bleeding, cervical injury, or uterine perforation.
• Warning Signs: After any uterine procedure, seek prompt medical care if you experience a high fever, foul-smelling vaginal discharge, severe or worsening pelvic pain, dizziness, or bleeding heavy enough to soak a pad in an hour.

Summary of Diagnostic Accuracy

The following table compares the approximate performance of these tools in study populations. Note: Sensitivity refers to the ability to correctly find a polyp when one is present. Specificity refers to the ability to correctly identify that a patient does NOT have a polyp when the cavity is clear.