I am sorry your girl is not feeling well. Blood mixed with diarrhea is usually related to a bit of colitis due to a GI upset.
You may be looking at severe food allergies or IBS which is characterized by bouts of constipation and diarrhea:
Purina is full of corn and gluten. Change her food to somthing more natural www.petfooddirect.com
For today add one tablespoon of infant rice cereal to a jar of baby food with no onion powder. That will rest her tummy and clear up the diarrhea.
IBD or pancreatitis are also possiblities:
Pay special attention to this section of the above link
TIPS FOR COLITIS
Colitis is best managed when its cause is known and specific therapy can be instituted. When this is not possible, symptomatic management is often attempted. The following are therapeutic medications and strategies that can be helpful in the treatment of colitis.
Metronidazole: This medication has anti-inflammatory properties in the large intestine as well as ability to kill harmful organisms such as Clostridia and giardia. For more information on this medication, see the link.
Sulfasalazine: This medication consists of a sulfa antibiotic bound to a salicylate anti-inflammatory. The sulfa bond protects the anti-inflammatory medication until it gets to the large intestine thus saving the anti-inflammatory effect for the disease of the large intestine. This is a very effective medication but is typically given three times a day which is an inconvenience. Cats are sensitive to salicylates thus this medication is primarily used in dogs.
Dietary Fiber: The role of fiber in colitis is confusing as there are an assortment of fiber preparations (soluble fibers, insoluble fibers, and mixtures). In general, colitis is felt to be a "fiber-responsive" disease. Fibers are broken down into nutrients for colon cells and also for food for beneficial colon bacteria.
Fructooligosaccharides (FOS): One of the prescription Iams diets as well as the Innovative Veterinary Hi Factor diet emphasizes the addition of FOS to its formulation. FOS's are carbohydrates involving fructose (fruit sugar) units attached to glucose (starch sugar) units. Most carbohydrates are digested by the bacteria of the small intestine leaving only the undigested fibers and other dregs for the teeming masses of the large intestine. FOS's are not fibers but they are digested in the large intestine (not the small intestine) in the same way that fibers are yielding the same biochemicals that fibers do. Why is this good? Tests in healthy cats indicate that this will help remove pathogenic bacteria from the large intestine and promote the growth of helpful bacteria. Think of it as an anti-crime program in the New York City of bacteria. Diets that contain FOS's may be helpful in the management of colitis.
Elimination Diet: Colitis can result from a food intolerance (an example would be lactose intolerance from which numerous people suffer). Intolerances can result from dyes, preservatives, contaminants or even natural proteins in the food. Similarly, colitis can result from an actual food allergy. The solution for these intolerances is the feeding a "pure" diet, ideally a home cooked food made with carbohydrates and proteins that are novel or new to the patient. An 8-10 week diet course is typically needed and no other chews or treats can be offered during the time of the trial. Food allergy cannot be diagnosed by blood test or skin test. At this time, response to elimination diet is the only test for food allergy or intolerance
Since itchy skin is a common manifestation of food allergy or intolerance, more detail on the subject of elmination diet can be obtained on the food allergy page.
Treating for Clostridium: Clostridial organisms are a group of anaerobic bacteria responsible for such unpleasant conditions as tetanus, botulism, and gangrene. There are Clostridial organisms that normally live in the large intestine but they do not cause any trouble unless some stressful event or diet change allows them to over grow. Once they are present in large numbers the toxins that they produce become significant and can cause colitis. (Think of these organisms as the criminal element in the New York City of bacteria. When there is a large scale blackout in the city, large scale looting occurs with these bad eggs leading the way.)
The diagnosis of Clostridial disease is complicated. A fecal smear may show the presence of Clostridial organisms but that does not mean they are producing toxin. Further tests (the "reverse passive latex antigen test" and the "ELISA" test) may be needed but the accuracy of these tests is in dispute. Often a course of a Clostridium-killing antibiotic is used as a test. Such antibiotics include: amoxicillin, tylosin, metronidazole (which has other colitis-helping properties as well), and clindamycin.
Prednisone: Prednisone is the cornerstone of treatment for Inflammatory Bowel Disease and inflammatory bowel disease must be diagnosed by biopsy. Sometimes a trial course of this medication is suggested for colitis. For more information please see the links.
Please let me know how she is doing. I hope she is better very soon.
Sincerest best wishes,