Rat Health Articles
In Pictures: Mammary tumour surgery - before and after
Introduction
Any tumour removal surgery is accompanied by a risk of natural post-surgical swelling and fluid collection; haematoma or seroma. With larger tumour removals these risks are increased. The position of the tumour (and thus the space left by it) is also an important factor when considering these risks. A tumour removal placed in or around a leg joint is subject to a much higher risk of haematoma/seroma formation than a tumour of the same size placed elsewhere because of the amount of motion involved around the area as a rat moves around. The formation of a haematoma or seroma post-surgery causes a risk of infection and post-surgical complications, for these reasons, any measures which can help avoid fluid collection can be very useful.
Case Details
In the rat pictured the risk of swelling and oedema/seroma were maximised because of the size of the tumour being removed, and it’s position under the forelimb. Due to this maximum risk steps were actively taken to try and prevent swelling and fluid collection.
The wound was closed using a double layer of stitches, one internal set and one external set, both using dissolvable sutures. A double layer of stitches helps to reduce the chances of the rat opening up the surgery site. Tissue glue was not used in this case.
Swelling was countered using an anti-inflammatory drug. These should be given as standard post-surgery as they are also painkillers. What appears to be swelling in the photos is actually just excess skin, ‘left over’ from where it had been forced to stretch around the tumour. Eventually this excess skin receded, ‘springing’ back into place.
The chances of haematoma/seroma formation were lessened by restricting the amount of exercise the rat could have. The route taken was extreme (but was felt necessary due to the very high risk), in that the rat was kept in a very small recovery cage post-surgery for 5 days. This cage was only 12 x 18 x 11 inches, providing enough room for the rat to stretch out horizontally and to turn around comfortably, but not providing any opportunity for climbing or more vigourous exercise. The rat was also given only very short periods of free range exercise during this time; no more than 30 minutes per day. These measures were amazingly successful however and the rat experienced no swelling or fluid collection around the wound!
After the initial 5 days, the rat was transferred to a larger recovery cage and progress monitored. When no fluid build up was observed whilst the rat was in the second recovery cage over 3 days, it was felt that the risk of swelling/fluid collection had passed successfully and the rat was then allowed to return to it’s regular cage.
Further Options
Sometimes measures to counter swelling and fluid collection fail despite the best efforts. When this happens swelling can be aided by giving further anti-inflammatory drugs. Fluid collection can be more difficult to counter, however there are a few measures which may help.
Firstly, the new lump needs checking. It could be something other than a haematoma/seroma. It may be an abscess at the wound site from infection post-surgery, or, in some cases it may be tumour re-growth. These need to be ruled out before assuming that the lump is a haematoma/seroma.
Once confirmed as a haematoma/seroma the approach taken will vary. If the fluid collection is only small, then it will usually resolve itself without any action; this can take anywhere between a few day and up to 4 weeks. If the fluid collection is large, and perhaps growing, then the application of pressure can help. Extra pressure can speed the reabsorption of the fluid and this is usually done with a pressure bandage. Sometimes gently massaging the area several times a day can also help speed reabsorption. Another option would be to have all, or some, of the fluid drained off via a syringe. Draining some of the fluid can sometimes help ‘trigger’ reabsorption, but this method is less reliable as there is also a good chance that the fluid will just reappear after draining.
If the fluid collection shows any signs of being infected, then antibiotics will be required, and if the fluid collection becomes so large as to be a hindrance to the rat, then diuretics may help lessen it’s size without the need for draining.
Article and photo's by Vic