Vaginal Wet Mount: Introduction, Principle, Preparation, Result Interpretation, Limitations and Related Videos

Vaginal Wet Mount: Introduction, Principle, Preparation, Result Interpretation, Limitations and Related Videos

Introduction of Vaginal Wet Mount

Vaginal wet mount, also called vaginitis test is very useful for diagnosis  vaginal infections that could be causing vaginitis. Vaginitis encompasses a variety of disorders that cause infection or inflammation of the vagina. The causative agents of vaginitis can include bacteria, yeast, viruses and parasites. Non infectious vaginitis may also occur due to estrogen imbalance (low level)  that causes vaginal dryness as well as a reaction to vaginal products such as soap, bath oils, spermicidal jelly, or douches.

The most common pathogens are as follows-

Bacteria: Gardnarella is a commonly found bacteria in the vagina. Overgrowth results in bacterial vaginosis, Streptococcus or Staphylococcus can also be present but usually do not result in an infection. A bacterial infection can cause a grayish-white discharge with a fishy odor.

Fungi: Candida albicans cause genital itching and a thick, white vaginal discharge with a cottage cheese-like texture.
Viruses:  Human papillomavirus (HPV)
Parasites: Trichomonas vaginalis, Pinworms, scabies, and lice can cause inflammation of the vulva and vagina.
Vaginitis is also sexually transmitted infections (STIs).

Symptoms of vaginitis

Common symptoms of vaginitis are as follows-

  1. vaginal discharge that may have an odor
  2. itching or swelling on the outside of the vagina
  3. burning during urination
  4. pain or discomfort during intercourse

Principle of wet mount

Saline wet mount preparation for vaginal smear analyzing a vaginal discharge specimen for diagnosis the causative agents of vaginitis . It utilizes a physiological saline solution (0.85% NaCl ) as an isotonic media to maintain the cellular structure of the various organisms as well as patient cells that are found in vaginal discharge.

Vaginal Wet Mount  or Vaginal smear Preparation

A wet mount or vaginal smear also called wet preparation uses to find out the causative agents of  vaginal infections that don’t affect the urinary tract. Clinician ( gynecologist) will have you lie down on an exam table with your feet in stirrups, like at a regular gynecologic exam. She/he will insert a speculum into the vagina to help see the area. After that  a sterile cotton swab is inserted into the vagina to obtain a sample of vaginal discharge. The clinician  will transfer the sample onto a slide or leaving on swab. The slide is sent to microbiology section to check  the causative agent of vaginitis.

Requirements for vaginal wet mount test procedure

  • Test slides or vaginal discharge on swab
  • Physiological saline or normal saline
  • Microscope
  • Cover slips
  • Sterile Wooden Applicator Stick
  • Gloves

Wet mount procedure

  1. First wear gloves.
  2. Take a clean and grease free slide ( no need in case of  slides provided by clinician).
  3. Place s sample of the vaginal discharge on a glass slide.
  4. Add one drop of physiological or normal saline
  5. Mix it properly  with sterile wooden applicator stick and apply a cover slip over a uniform suspension  without creating bubbles.
  6. Examine the entire 22- by 22-mm cover slip systematically with the low power objective (10X ) and low light intensity.
  7.  If any suspicious objects encounter, examine with the high dry objective (40X).

Observation of Vaginal smear

Look at under a microscope for bacteria, yeast cells, Trichomonas, pus cells ( dead white blood cell) and clue cells that is a indicator of  bacterial vaginosis.

Result Interpretation of  vaginal smear or vaginal  wet mount 

Bacteria:  The organisms which have size of this range 0.2 – 2.0 × 1 – 10 µm and shape of normally round or rod.

Trichomonas vaginalis:  A moving object usually the size of 10 μm in length and 7 μm in width.

Yeast cells: Oval or round in shape having size of usually 3-5µm  and some with budding

Pus cells:  Dead white blood cells form pus and the pus cells having size of usually  12 to 14 µm with lobes.

Clue cells: Clue cells are epithelial cells of the vagina that get their distinctive stippled appearance by being covered with bacteria.

Uses of wet mount or vaginal smear

It is very useful in vaginal infections to find out –

  • Bacteria
  • Yeast cells
  • Trichomonas
  • Pus cells and
  • Clue cell that is an indicator of  bacterial vaginosis.
  • vaginal pH determination-The normal vaginal pH is 3.8 to 4.5. Bacterial vaginosis, trichomoniasis, and atrophic vaginitis often cause a vaginal pH higher than 4.5.
  • Whiff test. Several drops of a potassium hydroxide (KOH) solution are added to a sample of the vaginal discharge. A strong fishy odor from the mix means bacterial vaginosis is present.
  • KOH mount: A sample of the vaginal discharge is placed on a slide and mixed with a solution of potassium hydroxide (KOH). The KOH kills bacteria and cells from the vagina, leaving only yeast for a yeast infection.
  • It may also be used in a rape investigation to detect presence of sperm.

Limitation of wet mount or vaginal smear

  1. Infections like chlamydia, genital warts, syphilis, herpes simplex, and gonorrhea can also affect the vagina, but the causative agents of theses diseased can not be covered by this wet mount.
  2. Due to lack of stain, it is difficult to get morphological details.
  3. Inappropriate preparation of the smear may hide parasites.
  4. Improper adjustment of the microscope in relation to the objective may create problems.

Key Notes

  1. A properly prepared wet mount should be thin enough to allow newsprint to be visible.
  2. There is a little difference between normal and physiological saline. Physiological saline is  0.85% NaCl where as normal saline 0.9% NaCl.
  3. Oil immersion examination is also preferred in parasitology for the permanent stained smear of parasites.
  4. Intestinal protozoa can not conform on the basis of a wet mount alone and thus permanent stained smears requires to confirm the specific identification of suspected organisms.

Related videos of Vaginal smears

# Vaginal swab Wet preparation under Microscope ||Bacteria ||RBCs ||Pus cells || Epithelial cells as shown below-

#Trichomonas, pus cells, epithelial cells, RBCs in vaginal swab microscopy

#Clue cells under the Microscope as shown below-


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