Definition

Contusion: An blunt force injury occurring to soft tissue.

Strain: An injury to muscle and tendon.

Sprain: An injury to ligaments and such structures that surround a joint.

Clinical Signs

Contusion:  Black and Blue discoloration of skin at area of injury. May be painful. May see swelling if there is sufficient pooling of blood in the tissue, also known as a hematoma.

Strain: Pain, swelling from bleeding into muscle, and limited mobility of affected extremity.

Sprain: Pain and rapid swelling of tissue at the site of injury from a pooling of blood. Limited mobility of affected extremity.

*Note: for additional information on recognizing various signs of pain or discomfort refer to: Signs of Pain In Rats.

Etiology

• Contusions are primarily caused by a sudden excessive external pressure. Bleeding occurs into the injured site from the rupture of tiny vessels, and produces the black and blue discoloration of the skin termed bruising.
  The bleeding into the tissues is usually absorbed, and as healing takes place the bruise begins to fade from a blue, to brown, to yellow, before disappearing altogether.
  If a significant amount of bleeding pools in the injured tissue, swelling occurs forming a hematoma. If the hematoma does not absorb on its own, or is not treated, it may clot and form a cyst, or further calcify requiring surgical intervention. With contusions there is no break in the skin, however, tenderness and pain may accompany the injury. If the contusion is to the brain from a head injury, such as in falling from significant height, being dropped, or from other means of excessive pressure to the head, lethargy (sleepiness) or seizures may be seen.

• Strains are injuries that occur when excessive force or stretching is applied to muscle and tendons. This over stretching of the fibers may result in bleeding into muscle tissue, which can cause tenderness and pain.
  This type of injury is generally seen in the rat’s hind extremities from getting a foot caught in wire cage flooring, and then attempting to extricate the foot.

• Sprains occur when there is a tearing of the ligaments or tendons around a joint from a twisting or wrenching type of motion. Function and mobility is lost or lessened. More serious than a strain it results in bleeding into the tissue with rapid swelling, as seen with contusions. Injuries of this type may also occur from getting a foot caught in wire cage flooring.

Because of tenderness or pain that may be associated with any one of these injuries, the rat may try to protect the affected extremity by not wanting to stand or walk on it.

Safety is a primary prevention in all three of these types of injuries. Any one of these can result from drops, falls from heights, or the rat trying to extricate itself or an extremity from a tight area. These injuries can also occur if they are accidentally stepped on while let out to play, or being snapped up by a much larger pet that the owner has forgotten to restrain.

Figure

• Fig. 1: Injury at play and resulting hematoma in 6-week-old male rat

Diagnostics

Examination for severity of swelling and extent of limited mobility.

Radiologic exam may be needed to rule out fractures, or development of calcification in delayed healing.

Possible surgical intervention for unresolved blood blister or hematoma, or for the presence of a calcification, or cyst.

Treatment

Contusions: If head injury seek a veterinarian!
For extremities apply cold compresses for several minutes intermittently, three or four times a day to decrease swelling.
After the first day moist heat application may be alternated with cold compresses to increase absorption in tissues.

Strains: Apply cold compresses for several minutes intermittently, three or four times a day to decrease swelling.
After the first day mild heat may be applied to the injured site to promote absorption.

Sprain: Apply cold compresses for several minutes intermittently, three or four times a day the first day of injury to decrease swelling.
After the first day mild heat or warm (not hot enough to burn!) Epson salt soaks, for 10 minutes at a time 3 to 4 times a day, may be applied to the injured site to promote vasodilation and increase absorption (reducing swelling).

Dosages for the following medications and information for their use can be found here at the Rat Medication Guide.

Ibuprofen, a nonsteroidal anti-inflammatory to control pain and swelling.

Meloxicam, a nonsteroidal anti-inflammatory to control pain and swelling.

Dexamethasone, a corticosteroid for reduction of swelling.

Prednisone, a corticosteroid for reduction of swelling.

If a blood blister or hematoma develops in a small injury of the extremities and attempts with use of warm compresses do not resolve it, incision and drainage may be the treatment of choice.

Should infection develop from the presence of a cyst in the unresolved injury antibiotics and surgical excision may be required. Discuss with a veterinarian.

Nursing Care

• Use of cold compresses to reduce swelling, followed by use of moist heat to increase absorption and healing of tissues.
• Provide pain medication as needed.
• Provide anti-inflammatory agents as needed.
• Provide one level cage to prevent climbing until injury resolved.
• Encourage fluid intake if bleeding is present.
• Consult a vet as soon as possible if the following are observed: increased signs of swelling, presence of infection, lethargy or seizures if a head injury has occurred.

Outcome

• Swelling and injury resolved
• Pain free
• Return of full mobility

Prevention

• Cover wire floored cage. Examples of coverings can include vinyl floor covering, plastic needlepoint canvas, carpeting, towels, self-stick tiles, plastic placemats, fiberboard, and Plexiglas.
• Provide safe environment when outside of cage when other pets are present.
• Remove bedding where threads have unraveled to prevent getting extremities tied up in them.
• Know where your rat is when outside of cage.
• Do safety check of cage. Ask yourself, could they get caught in something and not be able to free themselves without injury? If they chew the strings to the hammock, will they land on a shelf right under it or will there be a considerable fall before landing? Rats can be like 2-year-old toddlers, if it’s there they are going to mess with it without thought to injury, so be observant for them! They put their trust in you to keep them safe.