Immune Mediated Thrombocytopenia

immune mediated thrombocytopenia

I recently wrote about the concept of immune disease – those disorders where the immune system goes haywire and attacks normal cells in the body. In a more recent blog, I wrote about one of the important canine immune diseases, immune mediated hemolytic anemia (IMHA). Today’s blog post focuses on a disease similar to IMHA, immune mediated thrombocytopenia (ITP or IMTP).

Defining ITP
The cell targeted by the out of control immune system in ITP is the platelet or blood clotting cell. The platelet is a powerhouse of coagulation. Under the microscope, a platelet is the smallest of the blood cells, yet the sticky platelet provides the first level of defense against hemorrhage. Platelets are in a large part responsible for the formation of a scab when you cut your skin while chopping vegetables or scrape your knee in a bike accident. Dogs, and the rare cat, with ITP can’t form a blood clot if nicked by the groomer because the immune system has destroyed their platelets. The lack of platelets can also result in spontaneous hemorrhage.

Recognizing ITP
You, as the healthcare advocate for your pet, may be the first one to recognize clinical signs of ITP. The hallmark of a low platelet count is little pinpoint hemorrhages on the skin, in the mouth or on the whites of the eyes. Hemorrhage may occur internally making the stool dark like tar or the urine bloody. One of my patients with ITP recently relapsed and came to the ER with a bloody nose. But, not every pet with a low platelet count or bleeding has ITP.

Causes of ITP
There are many other causes of low platelets that must be investigated before a diagnosis of ITP is made. Infectious disease tops the list of potential diagnoses for low platelets. Diseases transmitted by ticks top the list. Ehrlichiosis, Rocky Mountain spotted fever and Anaplasmosis may resemble ITP, but some readily available laboratory testing can quickly identify these diseases. Cancer, especially lymphoma or hemangiosarcoma can cause low platelet counts. Occasionally a reaction to a drug like an antibiotic can cause ITP. When a veterinarian cannot find an underlying cause of a low platelet count and a diagnostic evaluation is unremarkable, by the process of elimination, the diagnosis is ITP.

Treatment of ITP
Even though the blood cell affected in ITP is different than in IMHA, the treatment is similar since the overactive immune system needs to be suppressed to prevent more platelets from being destroyed. The first line therapy involves the use of drugs like prednisone to suppress the immune system. A chemotherapy drug, vincristine, when administered to dogs with ITP increases platelet release from the bone marrow and helps normalize their platelet count faster and shortens hospital stay. Dogs are often hospitalized for several days in case hemorrhage is severe enough to warrant blood transfusion. Most dogs recover from ITP, but some require additional drugs to suppress the immune system long term.

Other diseases affecting the immune system include polyarthritis and a variety of immune mediated skin diseases which will be the topic of a future blog post.

Proteinuria in Pets

proteinuria

When your pet has an annual physical examination, your veterinarian will often request a urine sample. Once you collect the sample, your veterinarian will have the urine analyzed in the laboratory. Urinalysis is a test which assesses nearly 20 different parameters. This blog post will focus on one particular parameter of the urinalysis, protein.

Protein is Not Normal
In a normal dog or cat, very little protein passes through the kidneys and into the urine. When a routine urinalysis identifies an increase in urine protein, a number of tests are performed to determine the source of the protein. If the source is thought to be the kidneys, a follow-up test called a urine protein creatinine ratio is performed. This ratio helps us determine if the protein in the urine is elevated to a level where medical intervention is needed. Multiple assessments of a pet’s protein creatinine ratio may be necessary before a diagnosis of excessive protein in the urine is made. The condition where excessive protein is lost in the urine is called proteinuria.

Causes of Proteinuria
Chronic kidney disease is probably the most common cause of proteinuria, but veterinarians see it in pets with other chronic diseases as well. Diabetes, Lyme disease, and Cushing’s disease have all been associated with increased urine protein levels. But a bladder infection or fever might cause increased protein in the urine. The key to determining the cause of proteinuria is a complete diagnostic evaluation which will include blood tests, blood pressure measurement, and possibly even an ultrasound.

Protein is a Problem
Proteinuria is problematic on several levels. Protein in the urine signals a problem with the kidneys. The leakage of protein though the kidneys damages the kidneys and decreases their ability to remove waste products from the body, leading to kidney failure. Loss of protein in the urine can deplete the protein in the body, putting the patient at risk for swelling of the limbs and blood clots. High blood pressure has also been associated with protein loss in the urine. In both dogs and cats with chronic kidney disease, proteinuria correlates with an increased risk of death from chronic kidney disease when compared to patients without proteinuria.

Treating Proteinuria
Once a diagnosis of proteinuria has been established, any underlying disorders, such as Lyme disease, will be treated. Successful treatment can resolve the proteinuria. If the cause of the proteinuria is chronic kidney disease, then lifelong treatment will be required. Non-drug interventions include a kidney-friendly diet and anti-inflammatory supplements like fish oil. Angiotensin converting enzyme (ACE) inhibitors like enalapril or benazepril, and newer medications like telmisartan (an angiotensive receptor II blocker) are administered to decrease protein loss. If pets have high blood pressure, antihypertensive medications will be prescribed and blood pressure monitored. Some pets with serious protein loss need medications to prevent formation of blood clots.

Help Keep Your Pet Healthy
You are part of your pet’s healthcare team. Your efforts in collecting a urine sample helps veterinarians like me take better care of your pet. Better care means you and your pet can have more healthy and happy years together.

Everyday Medicine: Blood Pressure

pet blood pressure

Everyday Medicine is an intermittent series of blog posts highlighting tests, treatments and procedures common in daily Animal Medical Center practice. Some past examples of this type of blog post include “The Highs and Lows of Blood Sugar” and “The Third Eyelid.” Today’s post focuses on blood pressure.

Blood Pressure Definition
Everyone has had their blood pressure taken at the doctor’s office and we all know high blood pressure, or hypertension, is bad. But what does that Velcro covered cuff really measure? The cuff measures the pressure the circulating blood exerts on the walls of the blood vessel. When your blood pressure is taken, the nurse reports a number over a number. The top number (systolic blood pressure) is the pressure on the vessel walls when the heart pumps and the diastolic blood pressure or bottom number is the pressure when the heart relaxes. The blood pressure monitors veterinarians use in the clinic for dogs and cats usually measure only the top number, or systolic pressure.

Causes of High Blood Pressure
The most common cause of hypertension in both dogs and cats is chronic kidney disease. The International Renal Interest Society recommends all pets with kidney disease have their blood pressure measured as part of a clinical evaluation. Hypertensive pets should be treated with antihypertensive agents to protect their eyes, heart, brain and kidneys from damage due to high blood pressure.

Hyperthyroidism is another known cause of hypertension, most commonly in cats. Successful treatment of hyperthyroidism typically resolves the hypertension without administration of antihypertensive medications.

Causes of Low Blood Pressure
Low blood pressure is a common problem in AMC’s ER patients. Many ER patients have fluid loss. For example, vomiting and diarrhea-producing dehydration decrease the amount of fluid in the blood vessels, as does hemorrhage. Both dehydration and hemorrhage can result in low blood pressure. A severe systemic infection often leads to low blood pressure through a complex series of physiologic events. Since so many emergency situations lead to low blood pressure, an intravenous catheter and administration of intravenous fluids is typically one of the first emergency therapies administered in an animal ER.

If your pet has recently been anesthetized, he probably has a clipped spot on one of his front legs. That spot identifies the location of an intravenous catheter placement. General anesthesia decreases blood pressure. Veterinarians monitor blood pressure during anesthesia and give intravenous fluids during anesthetic procedures to help maintain blood pressure within a normal range.

Pets with hypertension have frequent blood pressure measurements taken while their veterinarians adjust medications to normalize blood pressure. Blood pressure medication must be titrated to the proper amount to prevent low blood pressure or hypotension. Hypotension makes pets weak and may negatively impact their kidney function.

If your pet is making a trip to the veterinarian soon, don’t be surprised if one of the nurses brings out a petite blood pressure cuff and places it around your pet’s wrist, since blood pressure is an important medical test.

Successfully Switching Your Pet to a Prescription Diet

prescription diet

All veterinarians, not just the specialists at the Animal Medical Center, use specially formulated prescription diets to help manage a variety of diseases in pets. For example, low protein diets are used in pets with liver shunts and kidney disease. Pets with arthritis benefit from diets rich in anti-inflammatory nutrients. But, pets don’t always want to give up their favorite brand of food for something you define as “better for them.” Here are some suggestions on how to get your favorite fur baby to accept a new diet.

Go Slow
Many diseases requiring a prescription diet occur in older animals that may be more set in their ways than a young puppy or kitten. Put out a spoonful of the new food on a separate plate from your pet’s regular food. It might take a few days for your pet to sample the new offering, but if she does, gradually increase the amount offered while decreasing the regular food. If your veterinarian recommends a prescription diet, ask if there are different brands or flavors available so you can change up the food while still getting the benefits of a prescription diet. Warm food stimulates the taste buds, so try microwaving the food for few seconds before offering it to your pet.

Keep it Fresh
If you feed canned food, recommended for pets with urinary tract problems or bladder stones because canned food has a high water content beneficial in these diseases. But after an hour or two of sitting in a bowl on the kitchen floor, the food gets crusty as the beneficial water evaporates. There are now bowls with an automatically opening and closing lid. As your pet approaches, the lid opens and allows your pet to consume fresh, soft and tasty food. When your pet finishes eating, the bowl automatically closes. How you store your pet’s food also impacts the taste. For tips on storing pet food to optimize freshness read this information from Hill’s Pet Nutrition.

Tasty Topping
Some pets need a bit of encouragement to try a new diet. Pretend the new food is a treat and use it as a reward. Once your pet readily takes the new “treat,” start putting it in her bowl. Other pets need a jumpstart of tasty food on top of the new food. Tasty bonito tuna flakes or powder make for a low-calorie taste sensation. Consider spicing up the prescription food with some of the new pet food condiments like Petschup or Meowstard or one of the commercially available gravies. Before you add anything to a prescription diet, make sure your veterinarian approves of the choice.

The Other Pet
Inevitably, the pet you want to eat the prescription diet refuses and the pet that doesn’t need it licks the bowl clean. If you have this problem, look into bowls that use radio frequency identification transponders aka your pet’s microchip to unlock a bowl containing the prescription diet. This ensures your healthy pet will not steal the prescription diet intended for your sick pet.

Once you get your pet eating the prescription diet, he will soon be on the road to recovery.

Immune Mediated Disease

immune mediated disease

The body’s immune system is a host defense system in both people and pets. But I bet you don’t often think about your own immune system. There are several reasons the immune system is harder to wrap your head around than other body systems.

  1. You hardly know the immune system is there unless it doesn’t work. The immune system’s job is to protect you against invading organisms that might make you sick. If it is working well, you feel great. If it doesn’t work, you get the flu or the chickenpox.
  2. The immune system is all over your body. The respiratory system seems so obvious. You have a nose, a windpipe and lungs. They control respiration. Bet you can’t describe the location of the cells of your immune system, but they are strewn about in the lymph nodes, spleen, lungs, intestines, and are circulating in your blood stream.
  3. The immune system can cause serious diseases when immune cells start attacking normal cells. These diseases are classified as autoimmune diseases or immune mediated diseases.

Autoimmune Disease
An autoimmune disease is a disease where a hyperactive immune system attacks normal cells as if they were foreign organisms. A diagnosis of autoimmune disease is made when the antibody produced by the abnormal immune function can be identified in the laboratory. Examples of this in people are gluten sensitivity due to an antibody induced by dietary gluten against intestinal cells, or Type 1 diabetes where the immune system makes an antibody that attacks insulin-producing pancreatic cells. Autoimmune diseases are thought to exist in veterinary patients, but tests to confirm the diagnosis are lacking.

Immune Mediated Disease
Immune mediated disease is a disease of unknown cause, but one which is thought to be modulated by an aberrant immune response. Unlike autoimmune diseases, the antibody causing this group of diseases has not been identified. This classification describes several important dog and cat diseases. In dogs and cats, immune mediated hemolytic anemia is an example of an immune mediated disease. Dogs also suffer from immune mediated thrombocytopenia and immune mediated polyarthritis. These diseases target red blood cells, platelets and joints, respectively.

Treatment of Immune Mediated Disease
The key to treatment of immune mediated diseases is to halt the immune reaction underlying the disorder. Veterinarians use immunosuppressive medications to turn off the cells of the immune system. The first line therapy in immune mediated hemolytic anemia, thrombocytopenia and polyarthritis is prednisolone/prednisone, which is a steroid medication. Prednisolone/prednisone receives top billing because it works quickly and is inexpensive. But prednisolone/prednisone is not enough in some cases and a second immunosuppressive agent such as azathioprine, cyclosporine or mycophenylate can be added. Increasing the number of immunosuppressive agents runs the risk of turning off the immune system completely, increasing the risk for a serious infection. Dogs and cats on immunosuppressive agents need close monitoring. Once the immune disease is controlled, the medications are slowly withdrawn and the patient is carefully monitored for relapse.

In future blogs, I will discuss the specifics of some common immune mediated diseases in pets.

Are there supplements to use with cats that have been diagnosed with chronic kidney disease?

CKD

Back in September, I wrote a blog post entitled, “Kidney Disease in Dogs and Cats.” One question I received from this post was about the use of supplements in cats diagnosed with chronic kidney disease. I decided to respond to this question by writing another post since this is an important feline disease and many readers will appreciate the answers to this question.

Chronic Kidney Disease
The inability of feline kidneys to properly filter waste products from the blood, maintain water and electrolyte balance, and even make red blood cells is one of the most common disease processes seen in the geriatric feline. In the early stages of disease, cats compensate well for the decrease in kidney function, but as the disease progresses, more interventions are required to keep your cat with kidney disease feeling well. Many of these interventions provide supplemental nutrients, vitamins, minerals and fluids.

Kidney-Friendly Foods
I am interpreting the reader’s question to be asking about treatments for chronic kidney disease that are not drugs and thus am including food. Practically every pet food company manufactures a kidney-friendly diet. These diets contain less protein than maintenance diets in order to spare the kidneys from working hard to excrete the byproducts of protein metabolism. These diets are also low in phosphorus and supplemented with B vitamins and potassium. Elevated phosphorous has been linked to a shorter survival in cats with kidney disease; consequently, lowering phosphorus is beneficial. Prescription diets developed for management of kidney disease also frequently contain omega-3 fatty acids and antioxidants, which, along with vitamins and minerals, are discussed separately below. The most important feature of feeding your cat with chronic kidney disease a kidney-friendly diet is the diet’s ability to extend survival in cats diagnosed with chronic kidney disease.

Vitamins and Minerals
Because cats with chronic kidney disease make large volumes of urine, they are also excreting large volumes of water soluble vitamins, like B vitamins and potassium. Supplementation of B vitamins, orally or as part of a prescription diet, helps to maintain adequate levels of these important nutrients. Since low potassium levels are so prevalent in cats with chronic kidney disease, several commercial potassium supplements are available in formulations designed to appeal to the most finicky felines. Many of the potassium supplements also contain B vitamins and other ingredients designed to support kidney function. Iron deficiency is a common mineral deficiency in cats with chronic kidney disease. Cats may lose iron due to bleeding ulcers or may not take in enough dietary iron if they have a poor appetite. Oral administration of iron can cause stomach upset, so most often injections are the favored method of iron supplementation in cats.

Omega-3 Fatty Acids and Antioxidants
Inflammation and oxidation play a role in the progression of chronic kidney disease. In dogs, omega-3 fatty acids have beneficial anti-inflammatory effects in chronic kidney disease and are often included in kidney-friendly diets by the addition of fish oil. The impact of omega-3 fatty acids on cats with chronic kidney disease is less clear. Vitamin C, Vitamin E and rosemary are typical natural antioxidants added to kidney-friendly pet food. Omega-3 fatty acids and antioxidants can also be supplemented separately from kidney-friendly diets.

Phosphate Binders
Often, reduction of dietary phosphorus does not correct elevated phosphorus levels. When this occurs, veterinarians often prescribe phosphate binders to trap phosphorus in the intestines where it is excreted in the feces. To be effective, phosphate binders need to be administered with every meal. Several manufacturers have developed feline specific phosphate binders in supplement form.

Supplemental Fluids
When kidneys can no longer regulate water balance, a sick cat may not feel up to drinking adequate amounts of water and will become dehydrated. Even the most squeamish owner can be taught to administer supplemental fluids under the skin (subcutaneous) to keep their cat well hydrated.

With such an array of supplemental nutrients, vitamins and minerals available for cats with chronic kidney disease, cat families should discuss any supplements or diet changes with their cat’s veterinarian to ensure optimal treatment of their cat’s chronic kidney disease.