Guidelines on the Performance of Surgery in Rodents

Unit for Laboratory Animal Medicine
May 3, 2024 12:00 am

This document is intended to provide guidelines for investigators who perform surgical procedure(s) in rodents such as mice, rats, hamsters, gerbils, guinea pigs, etc.

All surgical procedures, anesthetics, analgesics, antibiotics or other medications used on animals must be approved by the IACUC and described in the animal use protocol. Personnel performing the surgical procedure must be listed on the animal use protocol and appropriately trained in the technique prior to starting any surgeries.  

Any divergence from the recommendations in this document must be described in the animal use protocol prior to implementing the deviation.

  • Responsibility

    1. Principal Investigator and Surgeon
  • Glossary Definitions


    This encompasses both of the following definitions:

    1. Local Anesthesia: Temporarily induces loss of sensation to a specific part of the body. May provide pain relief.
    2. Systemic Anesthesia: Temporarily induces loss of sensation with loss of consciousness. Only provides pain relief due to or during loss of consciousness.


    The quantity to be administered at one time as a specified amount of medication.


    The process of uniquely marking an animal so it can be differentiated from other animals within a group.

    Institutional Animal Care & Use Committee (IACUC)

    Institutional Animal Care & Use Committee. The IACUC is ultimately responsible for approving, requiring modification of, or prohibiting the use of vertebrate animals in research, teaching, and/or testing activities at the University of Michigan. This includes supervision, coordination, training, guidance, and review of every project proposed to include the use of vertebrate animals to ensure that the project has appropriate scientific merit. 

    Post-Operative Record

    A record maintained by investigative personnel that includes:

    • The surgery or procedure and the date it was performed
    • Notation of (at least) daily monitoring for the duration of the post-operative monitoring period as defined in the ULAM rodent or non-rodent mammal surgical guidelines, or as described in the animal use protocol.
    • Any drugs given, including the route, dose, and time/frequency.
    • For animal use protocols that state analgesia will be given "as needed," personnel MUST note that an animal is not painful/no longer needs analgesics BEFORE analgesics are discontinued.
      • The presence or absence of pain MUST be noted each day for the duration of the post-operative monitoring period.
    • The surgical/anesthetic/sedation record and the post-operative record may be combined and kept on a single sheet of paper if preferred.
    • Specific requirements for post-operative monitoring records can be found in these ULAM documents:
  • Procedures

    1. Documentation

    1. Rodent surgery and Post-Operative Records are required for every rodent that has undergone surgery.
    2. An individual rodent surgery and post-operative record must be used for each rodent cage that contains post-operative animals. Multiple animals from the same cage can be contained on the same rodent surgery and post-operative record, as long as the animals have unique identification, and the post-surgical record is completed in a way that allows for individual animal observations to be clearly identified. Each animal must have their own observations recorded daily.
      1. Daily post-operative recordings CANNOT be pre-recorded, i.e., each day’s recording can only be recorded at the time that the post-operative monitoring is occurring.
      2. Alternative post-operative records that include multiple cages on one record may be appropriate if individual animal tracking is still performed and only with approval of a faculty veterinarian.
    3. Rodent surgery and post-operative records must be contained within the animal room or within close proximity to the animals and readably retrievable for review by investigative, IACUC, or veterinary personnel at all times.
    4. Rodent surgery and post-operative records must be kept and maintained until sutures/wound clips are removed or the animal is euthanized.
      1. Denote in the post-operative record if an animal is euthanized or dies within the post-operative period. 
    5. Rodent surgery and post-operative records must remain near the animal for at least 7 days following surgery even if skin incisions are not closed with sutures or wound clips (i.e., surgical glue).
    6. Rodent surgery and post-operative records must include anesthetics and analgesics administered for the surgical procedure and after for post-operative care. The records must also include the frequency of monitoring by any laboratory and veterinary personnel during the post-operative period. Record the following information for both anesthetics and analgesics:
      1. Dose
      2. Frequency of administration
      3. Route of delivery
    7. Rodent surgery and post-operative records for mice and rats must be placed in the assigned folder within the animal room once the post-operative monitoring period is over. Records are stored as outlined in the Guidelines on Medical Records for Investigative Personnel.
    8. Records for animals other than those of the genus Mus or Rattus bred specifically for research must be stored and maintained in accordance with the ULAM Guidelines for Animal Medical Records.

    2. Preparation of the Surgical Area

    1. According to the Guide for the Care and Use of Laboratory Animals: Eighth Edition, "For most survival surgery performed on rodents and other small species...the space should be dedicated to surgery and related activities when used for this purpose, and managed to minimize contamination from other activities conducted in the room at other times." (pg. 144)
      1. The surgical area should be a room or a portion of a room that is easily sanitized and not used for any other purpose during the time of surgery.
      2. Clean and disinfect the surface upon which the surgery will be performed with an approved environmental disinfectant before beginning the surgical procedure.

    3. Preparation of the Surgical Supplies

    1. Use sealed, sterile surgical instruments and supplies, e.g., suture material.
      1. Sterilization, such as steam sterilization (autoclaving), plasma vapor sterilization, ethylene oxide sterilization or vaporized hydrogen peroxide (for heat- or pressure-sensitive items) is required for all surgical instruments, supplies, and implants, unless used directly from sterile packaging from the supplier.
        1. Other methods of sterilization must be described and approved in the IACUC protocol if required for research goals.
      2. Refer to Guidelines for the Storage of Sterile Items
    2. Drapes
      1. Drapes are highly recommended in order to maintain a sterile surgical field.
      2. Extra precautions must be taken in order to maintain appropriate aseptic technique if drapes are not being used. Consult with veterinary personnel to discuss the necessary extra precautions: or 734-936-1037. 
      3. Drapes can be cloth, paper, sterile stockinettes, 3M™ Steri-Drape™ Incise Drapes, or new and unused boxes of GLAD Press'n Seal® wrap.
        1. Sterilize drapes using an autoclave, vaporized hydrogen peroxide or ethylene oxide where appropriate (plastic products).
        2. Drapes can be used for wrapping instrument packs prior to sterilization as well as for creating a sterile field around the incision site.

    4. Preparation of the Animal

    1. Fasting is not required for rodents.
      1. Fasting longer than 6 hours must be scientifically justified in the approved IACUC protocol.
    2. Anesthesia
      1. Use an approved agent appropriate for the species AND the procedure.
        1. See Anesthesia and Analgesia Drug Descriptions for more information on anesthetic and analgesic options.
      2. Maintain the animal in a surgical plane of anesthesia throughout the duration of the procedure
        1. See Anesthesia and Sedation Monitoring Guidelines for more information on determining the surgical plane of anesthesia and monitoring during anesthesia.
    3. Skin Disinfection
      1. Remove an appropriate amount of hair from the surgical site so that there is enough shaved skin around the planned incision to allow for appropriate tissue handling and wound closure without interference by the remaining hair prior to disinfecting the skin.
        1. Animal clippers, razors, depilatory cream (Nair®) or manual plucking can be used to remove hair from the surgical site.
        2. Ensure depilatory creams are:
          1. Not left on the animal’s body longer than appropriate to avoid irritation of the skin.
          2. Completely rinsed from the animal’s body before disinfecting the skin.
      2. Remove all visible debris from surgical site.
      3. Disinfect the surgical site with a recommended skin disinfectant to clean and remove bacteria from the surgical site and prevent the growth of disease-causing organisms.
        1. Perform a minimum of three alternating (inside to outside of prepped surgical area) scrubs of disinfectant (chlorhexidine scrub, iodine scrub, etc.) and rinse (warmed sterile saline, sterile water, or alcohol) after the removal of visible dirt and debris.
        2. 3M™ Avagard™ (Chlorhexidine Gluconate 1% Solution and Ethyl Alcohol 61% w/w) can be used in place of the triplicate application method of scrub and rinse described above.
          1. Dispense 1 pump of Avagard on sterile gauze.
          2. Apply Avagard, working in a circular pattern, inside to outside of prepped area.
          3. Let air dry (typically under 1 minute).
          4. Repeat steps 4.c.iii.2.a-c one more time.
      4. Place a sterile drape, if using, around the surgical site after the skin has been appropriately disinfected while adhering to aseptic technique.

    5. Surgeon Preparation

    1. Wash hands thoroughly using soap and/or a disinfecting solution (e.g., chlorhexidine, iodine-based surgical scrubs, or 3M TM Avaguard TM hand antiseptic).
    2. Required attire for the surgeon during the surgical procedure:
      1. Mask
      2. Individually wrapped sterile gloves, including:
        1. Commercially available sterile surgical gloves
        2. Commercially available sterile exam gloves
        3. Regular exam gloves that are packaged and autoclaved with appropriate quality assurance measures to ensure sterility (autoclave tape, etc.).
      3. Clean scrub top, disposable gown, or lab coat
        1. Follow vivarium PPE procedures when working within the vivarium, i.e., a gown is required and no lab coat.
    3. Don new sterile gloves if aseptic technique is disrupted for any reason (repositioning of the animal, touching anything outside of the sterile surgical field, etc.).
      1. Use of a non-sterile assistant can minimize the need to change sterile gloves within a procedure. 

    6. Performing Multiple Rodent Surgeries in Series

    1. Investigators should begin with at least 2 sets of sterile instruments.
      1. Maintain aseptic technique while cleaning gross debris from instruments followed by sterilizing with a hot bead sterilizer between each animal.
      2. Can use one pack of instruments for up to 5 consecutive surgeries.
        1. Change to a new pack of sterile instruments sooner if unable to properly clean gross debris from instruments between animals.
    2. Use a new sterile suture piece for each animal.
    3. Use a new sterile drape for each animal.
    4. Use new sterile gloves for each animal.
    5. Disinfecting the surgical area between animals is recommended.

    7. Suture Materials & Wound Closure

    1. Surgery in which a body cavity such as the abdomen or thorax has been opened requires a two-layer closure to close the body wall separately from the skin.
    2. Select suture material (absorbable vs. non-absorbable; braided vs. monofilament) that is appropriate to the tissues, procedure, and activity of the animal.
    3. Remove wound clips and skin sutures 7-10 days after placement.

    8. Post-Operative Monitoring & Care

    1. Observe and monitor animals every 15 minutes during recovery from anesthesia until the animal is ambulatory.
      1. House rodents:
        1. In a clean, dry, enclosed space without risk of aspiration.
        2. Individually until completely recovered to avoid cannibalism by cage mates.
      2. Continue monitoring parameters and thermal supplementation throughout the recovery period. See Anesthesia and Sedation Monitoring Guidelines for more information on post-operative monitoring and appropriate thermal support devices.
    2. Administer post-operative medications including analgesics, antibiotics and/or anesthetic reversals during the early recovery period and according to the approved protocol or the advice of a ULAM veterinarian.
    3. Place a yellow acetate with a Surgery Observation Sticker (SOS) over the cage card when the fully recovered animal is returned to the animal room. 
      1. Record on the SOS sticker:
        1. The date of surgery
        2. Circle the closure method used: skin glue, sutures, or wound clips
        3. The “report by” date, i.e., 10 days post-surgery
    4. Remove wound clips and skin sutures by 10 days after surgery unless described otherwise in an IACUC approved protocol or as recommended by a ULAM veterinarian to necessitate incomplete wound healing.
      1. Remove the yellow acetate with SOS sticker once the skin sutures or wound clips have been removed, or 7 days post-surgery if skin glue was used instead of sutures or wound clips.
    5. Investigative personnel must examine all post-surgical animals at least once a day for 7 – 10 days, or until the skin sutures or wound clips are removed and record appropriate information in the rodent surgery and post-operative record.
      1. Examinations include, but not limited to, assessing the animals:
        1. Surgical site.
        2. Overall condition.
        3. Pain level.

    See Procedures section 1 for additional documentation requirements.

    9. Incision Repair

    1. Repair any incision site dehiscence following veterinary personnel consultation or in accordance with the IACUC approved protocol.
    2. Daily post-operative monitoring and record keeping for 7-10 restarts to day 1 following the incision repair.
      1. See Procedures section 8.d. for additional documentation requirements.

    10. Non-Survival Surgery

    1. Non-survival surgeries do not require aseptic techniques or dedicated facilities but should be performed in a clean area, free of clutter, and using acceptable veterinary sanitation practices equivalent to those used in a standard examination/treatment room. Personnel present in the area should observe reasonable cleanliness practices for both themselves and the animals.
  • Appendix A: Rodent Surgery and Post-Operative Record (Notebook Size)

  • Appendix B: Rodent Surgery and Post-Operative Record by Cage

  • Appendix C: Example of Rodent Surgery and Post-Operative Records

  • References

    1. Comparison of Aqueous and Alcohol-based Agents for Presurgical Skin Preparation Methods in Mice. Website at
Species: Rats Mice
Topic: Surgery

If you have questions or comments about this document, contact ULAM Veterinary Staff (

The ULAM Training Core ( or 734-763-8039) can be contacted to provide training in techniques at no charge.

For any concerns regarding animal health after work hours or on holidays/weekends, contact DPS (3-1131) who will contact the on-call veterinarian.