FUR MATS WITH FECES 

THE PROBLEM
Rabbits normal produce two kinds of droppings, formed pellets and caecotrophs. Caecotrophs are soft sticky feces, not pellets. As part of their normal digestive process rabbits eat the caecotrophs (caecotrophy). They do this by taking the caecotrophs directly from their anus. Caecotrophy takes place every day, during a quiet time for the rabbit, such as early in the morning. 

If a rabbit does not eat the caecotrophs, for any reason, it is very likely that some of it will stick in the fur around the anus. Because this type of feces is very sticky, some of the normal pellets stick to it. Rabbit fur is very fine and dense and their skin is very thin and elastic. As the rabbit continues to pass droppings the mat of feces grows; the surface of it becomes somewhat dry and beneath the surface it stays moist. The skin below the mat can become very inflamed, infected, and fragile.

There are several possible reasons why a rabbit might not eat its caecotrophs. The four most common in our experience are:
Stress. Caecotrophy is a "quiet time" activity for rabbits. Any stress that disrupts this quiet time can cause a rabbit to skip eating caecotrophs. Stressors might be simple, one-time events like a loud noise occuring at the time of caecotrophy; they might be obvious changes to the enviroment, like a change in location of the rabbit's hutch, or a new pet that is paying unwanted attention to the rabbit; they might be something subtle, like a change in the feeding schedule. 
Back pain. Back pain due to injury, arthritis or other illness is a common rabbit problem. If it is severe enough a rabbit cannot get into the proper position to perform caecotrophy without significant discomfort.
Obesity. Some rabbits cannot reach their anuses due to obesity.
Personality. Some rabbits have no evidence of stress in their environment and have no sign of a physical problem preventing them from performing caecotrophy, but they still do not do it. They simply appear uninterested in doing it.

TREATMENT
Treatment for fur mats with feces includes clipping and cleaning the affected area, treating any associated skin problem, and diagnosing and managing any problems that led to a failure of the rabbit to perform caecotrophy. 

Fur mats with feces can be very small or very large. They cannot be washed off (attempts to do so usually make the problem worse), they have to be clipped.  Rabbit fur is difficult to clip when it is not matted, and much more difficult when it is matted. The skin under the mat might be inflamed, infected, and very painful to the touch. Rabbit skin is very thin and very elastic, and there are several normal very thin skin folds in the anal area, so it is very easy to accidentally cut the skin while clipping the area. Rabbits often struggle when they are restrained, and because their back legs are very powerful it is very easy for them to injure themselves.

For all of these reasons it is usually very challenging to remove fur mats with feces from rabbits. Sometimes general anesthesia is necessary.