Sperm washing is the process that prepares a semen sample for an intrauterine insemination (IUI). For an IUI to be performed, the semen sample must be washed free of debris, white blood cells, and prostaglandins, which can cause the uterus to contract. The processing removes dead sperm and concentrates the sperm into a small volume that can easily be handled by the uterus. There are three main methods of sperm washing: the swim-up, density gradient wash, and simple (centrifugation) wash. The type of wash used depends on the individual characteristics of each semen specimen.
This is the most successful method if you're a patient with a normal semen analysis and is not recommended for samples of high viscosity, with high numbers of round cells, or with a high content of debris. In this procedure, the washing media is gently placed over the semen in a conical tube. The specimen is then placed in an incubator for approximately one hour. During this time, the sperm are allowed to swim up into the media, with the purpose of collecting the most motile, normal sperm, free of debris. The supernatant is collected and centrifuged twice with sperm washing media. The final pellet is then re-suspended in approximately 0.5 mls of media. Modified sperm washing media must be used to process the sample.
Density Gradient Wash Method
This wash is used if your samples contain round cells or debris, or have increased viscosity but a relatively normal concentration and motility. The gradient is achieved by layering media of two different densities in a conical tube. The semen is then placed on top of the gradient and the tube is then spun to allow the specimen to proceed through the gradient. The resulting pellet should contain the motile, normal sperm, while the dead sperm and debris are caught up in the gradient media. The pellet is then re-suspended in washing media and centrifuged twice. The final pellet is re-suspended in a final volume of approximately 0.5 mls of media. There are several commercially available kits.
Simple Wash Method
The simple (centrifuge) sperm wash should be performed on a sample that has a decreased concentration and/or motility. A sample containing round cells and debris should not be prepared by this method. Sperm washing media is added to the specimen and centrifuged. The pellet is recovered, re-suspended, and centrifuged again. The final pellet is re-suspended in approximately 0.5 mls of media.
In each of the above cases, the laboratory performs an analysis on both the fresh specimen and washed specimen. This will include an assessment of the count, motility, volume, and viscosity.