If your kitty has a bout of diarrhea, or if she has trouble grooming herself and develops feces-matted fur on her backside, she’s going to need your help cleaning up. Feces stuck to fur can be a sign of a serious medical ailment. Your cat may have a gastrointestinal infection or a parasitic infestation, or she could be suffering from arthritis or obesity, both of which make self-grooming difficult.
Dilute a little bit of cat shampoo in warm water -- you'll pour it over the cat, not bathe her in it, so you don't need a lot. But use a ratio of 1 part shampoo to 5 parts water, and mix well. Set it aside, then line a sink or plastic basin with a hand towel, which will help your cat get a grip, and fill the basin halfway with lukewarm water.
Put on rubber gloves and old clothes you don’t mind discarding. Long sleeves work best.
Catch your cat when she’s sleepy or in a calm state of mind, such as right after she wakes from a nap, if possible. Talk to her soothingly. Cradle her with your less-dominant hand and gently place her in the water.
Use unscented baby wipes, which won't disintegrate in water, or a clean rag to wipe away wet feces, to moisten dry feces or to gently pull away clumps stuck in the fur. If hair is matted with waste, remove as much as you can without hurting your cat using a fine-tooth comb.
Pour the shampoo mixture over the affected areas of your cat and gently massage with you gloved hand. Use a hand-held sprayer to wash away the soap residue.
Remove your cat from the bath and dry her with a large towel.
Dispose of dirty wipes in a plastic-lined trash can; dispose of the bag since cat fecal matter can become infective after a few days. Disinfect your tub and tools with an antibacterial spray or bleach cleaning solution. Clean your clothes and towels in hot, soapy water, or discard them.