Differentials - possibilities that should be considered


Differentials - Possibilities That Should Be Considered

Cat walking on hock (heel) on one leg

Question: Hi Dr. Mike, Have 25 pound cat who walks on his heel. Left back leg. Very little support. No pain. Is there a chance massage would help, as he did walk much better after muscle massage?

Send me any info you have.

Thanks very much. Sue

Answer: Sue-

There are a number of possible causes for a cat to walk with the portion of the leg below the hock (heel) low to the ground. However, it is unusual for this to occur on one side only except in the case of injury to the gastrocnemius tendon (the Achilles tendon), the hock joint or the bones, muscles or tendons below this level. When both sides are affected the most common causes are probably diabetic neuropathy, hypokalemia (low potassium levels) and neurologic injuries. It is also almost impossible to rule out the causes of all sorts of odd signs, such as cancer, toxoplasmosis, feline leukemia virus infection, feline immunodeficiency virus infection and feline infectious peritonitis.

No matter what the underlying cause is there is a possibility that massage therapy might be temporarily helpful. Massages help to move trapped fluid around and to increase circulation to the area being massaged, both of which can be helpful. There is some pain relief in just being touched and massage seems to increase this effect. Manipulation of the leg during massage may also be helping to increase the range of motion of a damaged joint, such as a sprain of the tarsal (hock) joint, as well.

If this sign persists, even if it temporarily improves with massage, it would probably be a good idea to try to rule out some of the more common causes of problems, especially diabetic neuropathy in a cat this large.

Mike Richards, DVM 12/1/2001

Leg weakness and gait problems

Question: Dear Dr. Mike,

We have an 11-yr old cat who probably has some Maine Coon Cat blood in her (she is a pound cat so we don't know for sure). She has had a history of spraying in the house since she was a kitten. She's been treated very successfully by the Univ. of Penn. behavioral medicine clinic with drug therapy. Currently she is taking diazepam and amitryptiline to control her spraying; this particular combination/dose has worked well for about 2 yrs.

Within the past few weeks, Beulah has started spraying and defecating outside the box, and the problem is getting worse. We took her back to the clinic for a recheck wondering if her meds needed to be tinkered with. But the vets were extremely concerned about Beulah's gait. Last fall, we noticed a weakness in her hind legs or hips; her hips give out and she has trouble jumping up or going up/down stairs, almost like a stagger. At the time, we took her to our regular vet, who said it was arthritis and nothing could be done. However, the Penn vets think it's more complicated than that. After a neuro consult, they believe it is not an orthopedic problem like dysplasia or arthritis, and not a side effect of the valium, but neurological (e.g. she has some atrophying of the hind leg muscles, flinches when certain parts of her back are touched). They believe it may be a compressed spinal disc. They believe this may have caused the recurrence of elimination problems, either b/c she is stressed out by the pain and decreased mobility, or she is having trouble getting to her litter boxes, or both.

I've read everything on your web site about spinal disc problems in cats and dogs (there's a lot more about dogs than cats but I assume it's generally the same). My questions are:

1. Are there any other possible diagnoses that should be considered? Could low potassium cause the hindquarter symptoms?

2. Blood tests showed normal except for slight thyroid elevation. Could this cause the symptoms?

3. What diagnostic tests will identify the problem fastest? Is it worth it to give her an xray (the vet said this may or may not give a definitive diagnosis)? Would ultrasound or CT scan be better?

4. Assuming it is a disc problem, would cortisone therapy be an option given the lapse of time since onset (I'm really ticked off that my regular vet missed this!).

5. What is the best case scenario if she has surgery? What would happen, or could happen, if she doesn't have surgery? Are there any other treatment options?

Thank you so much for helping me educate myself to make the best choices for a truly beloved cat.


Answer: C-

1) I think that it is possible that problems other than spinal disc disease could be causing your cat's symptoms but low potassium levels probably would have shown up in the blood work (most chemistry panels run at veterinary teaching hospitals include this ion).

2) We have seen rear leg weakness that appeared to improve when hyperthyroidism was treated but not very often. It is a possible problem but not a likely one, in this case.

3)Magnetic resonance imaging is by far the best test for detecting spinal disc disorders. I vaguely recall that cats are a little harder to evaluate due to their size so it would be best to ask the vets at UP, because they probably know for sure if MRI works well for them in cats. Plain X-rays are worth taking as a screening option, even though disc problems that are present may not show up --- because there may be a problem like bone cancer or even vertebral fractures that DO show up.

4) Disc problems in cats are relatively rare (they are reported more often now than in the past, but they are still not really common in cats). It doesn't surprise me that your vet wasn't thinking about this possibility, especially if the neurologic signs are subtle. I could easily see myself overlooking this problem. There is a lot of controversy over whether or not corticosteroids are helpful in disc disease. I think that most veterinary practitioners think they are but there are differing opinions. I would tend to lean towards non-steroidal anti-inflammatories in a dog but they can be problematic in cats -- so I might go for cortisones, even now. Especially if an MRI and surgery are not available options.

5). Surgery is probably best for herniated discs causing spinal problems. The best case scenario is a return to normal or near normal function. In many patients with disc disease there is a slow progression of the disability they cause, eventually leading to loss of use of the rear limbs. This tends to progress even with medical treatment, so surgery is favored when the problem can be identified and localized. I am basing this answer on the problems with dogs, because I honestly can't remember a client of ours opting for surgical repair of a spinal disc problem in a cat.

I wish I could help more with this but my experience is pretty limited.

Mike Richards, DVM 4/20/2000

Fluid accumulation (ascites) in cats

Question: What are the causes of fluid accumulation in cats?

Answer: Pat-

These are causes of fluid accumulation (ascites) in cats:

severe liver disease --- cirrhosis is actually fairly uncommon in cats, but it does occur. If there is a problem in the liver really inhibiting circulation through it, such as liver cancer or really severe liver swelling, this could lead to ascites, too.

pancreatitis -- this has to be pretty severe but it can cause ascites and it might also cause the elevations in white blood cell count, hypoproteinemia and electrolyte disturbances. Usually cats with pancreatitis have vomiting associated with the disorder. Cats with this condition probably in pain from it but don't show that well. Administering pain relievers can help a great deal in making cats feel better and is worth doing on the suspicion of pain, in most cases

heart disease--- the most common heart disease that will cause ascites in cats is cardiomyopathy, but other heart or pericardial problems might cause it. This seems unlikely based on the exam findings but has to be considered.

cancer --- I think that cancer is probably the most common cause of ascites in older cats in our practice but I haven't actually tallied up the cases to be sure of this

FIP -- this is primarily a disease of younger cats, in that the great majority of cases occur in cats less than two years of age, but it can occur in older cats sometimes. Usually, there is an increase in serum protein with FIP due to increases in antibody production (globulins). Personally, I would tend to discount this possibility.

Inflammatory bowel disorders -- sometimes, but not very often, inflammatory bowel disorders (IBD), can lead to ascites. This happens when the intestines get inflamed enough that the leak protein, leading to a loss of protein in the blood stream and this leads to ascites if the protein gets low enough. This can happen with internal parasites in puppies and kittens but that isn't too likely in an adult cat.

It is possible to tell a lot from the appearance of the fluid, sometimes. For instance, if fluid is withdrawn and it turns out to be blood, that would be whole different set of possibilities, such as exposure to rat poison, other bleeding disorders, trauma, etc. If the fluid turned out to be pus, then some sort of septic process would be likely. The fluid associated with FIP is usually yellow and very thick. Other problems produce fluid with different characteristics. Sometimes the fluid contains obvious cancer cells, which makes the search for a diagnosis easier. I am assuming from your note that this was definitely fluid and not blood or pus and that there wasn't anything too remarkable about it.

An ultrasound exam is a good idea. It can help to determine if there are tumors and help to determine what the pancreas and liver look like.

I would take the trip to the internist if the ultrasound exam doesn't show a clear answer for the problem, even if it does involve a trip.

I agree with your vet about getting your cat to eat. I wouldn't worry about the protein content of the a/d diet right at this time. If liver can not process ammonia, the breakdown product of proteins, there will be signs of incoordination, blindness, staggering or seizures. If it does turn out that liver disease is present, the diet can be altered.

Feline infectious peritonitis is still difficult to test for accurately. There is a test whose developers claimed was specific for the FIP coronavirus rather than all coronaviruses of cats, but I don't think that the claims have proven to be accurate. I know of no successful treatment for FIP at this time. It is likely that there are ongoing studies of FIP but I wouldn't go to a lot of trouble to find them, just yet. The odds that FIP is the problem are pretty low. It is not very common in households with three or less cats (you didn't mention how many cats you had but I am assuming not too many). Due to the nature of FIP infection, there isn't a great increase in the risk to the other cats in the house even if this cat does have FIP. So for right now, I'd wait for the cytology and the ultrasound results before worrying more about FIP.

Ultrasound exam can often give a pretty good idea of whether or not liver disease is present. It is usually necessary to do liver biopsy in order to get a definite diagnosis of the type of liver disease present, though. This can sometimes be accomplished by an ultrasound guided needle biopsy and sometimes it is necessary to get a sample for biopsy through surgery. Hepatic lipidosis is the most curable of feline liver diseases and the treatment consists of feeding the cat adequate calories until it is well. Cholangiohepatitis is controllable for long periods, in many cats, using medications. Suppurative cholangiohepatitis is sometimes curable by eliminating the infectious agent if it is a bacteria that is susceptible to antibiotics. It is possible to remove a portion of the liver if there is a cancer that seems to affect only a portion of the liver. To the best of my knowledge no one is doing liver transplants in cats, but it is possible someone is.

The high neutrophil count, with no immature neutrophils reported (no band cells), along with a decrease in lymphocytes, is a typical white blood cell picture for stress or from the administration of corticosteroids. Unfortunately, that doesn't narrow the search for a diagnosis in this case. Low calcium is probably occurring due to the low albumin. Calcium is carried in the blood stream attached (bound) to albumin, so when there is insufficient albumin, the total calcium level drops. Usually the ionized, or free, calcium is normal. Low calcium sometimes occurs in pancreatitis due to the calcium getting trapped in the inflamed tissues in the abdomen, though. The low albumin levels can occur with liver failure, inflammatory bowel disorders, kidney failure and cancers that are causing intestinal or liver problems. Usually low sodium levels are due to vomiting. If you are not seeing vomiting, I am not sure what to make the low sodium and low chloride levels. Rupture of the urinary bladder can lead to low sodium levels but that leads to rapid deterioration in a cat's condition, which doesn't seem to be happening and usually the BUN and creatinine are elevated, too. Low anion gap occurs with low serum albumin so the elevation in anion gap doesn't make much sense to me, unless your cat is pretty dehydrated, which would be scary, since that usually makes the protein level even lower, in reality, than the measured level. Sometimes, when there is fluid accumulation in the abdomen, it will lead to a low volume in the blood stream (since the fluid is coming from there, ultimately), even though the total fluid volume in the body is elevated. This might be causing some of the abnormalities in the electrolytes. Correcting the ascites, might help with this. The diuretic (Lasix Rx) might help in this regard.

I'm sorry, but I can't answer the question about vets in Lexington. I am not personally familiar with anyone practicing in that area. I have sent a couple of patients to the vet school in Knoxville and have been satisfied with the care they received but they were all cats with hyperthyroidism needing radioactive iodine therapy.

Again, I would encourage you to go to the internal medicine specialist if the cytology report and ultrasound exam do not give a clear diagnosis. If there is still confusion after the visit to the internist, it may be a good idea to consider going to the veterinary school.

I would lean towards cancer and pancreatitis as my leading differentials but liver disease has to be included in the differential diagnosis and FIP is possible. Some of the cancers that can lead to the signs you are seeing can have a good prognosis. Intestinal adenocarcinoma causing a partial obstruction of the intestine or intestinal inflammation would be removable surgically, in many cases, and the prognosis after surgery is pretty good, for instance. So you don't have to give up if the diagnosis is cancer.

I hope this helps some.

Mike Richards, DVM 4/18/2000


Question: Dr. Mike, We have a 14 year old tabby female. She has always been an indoor cat. The past 3 or 4 years she has had a problem with occasionally vomiting. Some times the vomit has fur in it but most times not. Changing her food would usually stop the problem for a while, but eventually the problem comes back. Now it seems even changing her food does no good. She seems healthy otherwise and is not losing weight, but the problem bothers us because of our concern for her, and also it is a problem with he mess it creates. The vet just says to change her food. Any ideas?

Answer: I would want to check a fecal exam, check thyroid levels and do a general blood panel on any cat of this age with chronic vomiting. Older cats sometimes become more susceptible to roundworm infection as their immune systems become weaker. I recently did a lot of testing on a cat prior to doing a fecal exam and its vomiting cleared up with deworming. I was sort of embarrassed by the fact that I should have thought of the fecal exam first. If worms aren't present, then more extensive testing is necessary. Hyperthyroidism is just too common a cause of vomiting in older cats to overlook it. Some cats don't lose weight early in this disease. Kidney failure is also pretty common and some cats with chronic renal failure will vomit regularly. If these things were not found to be present with bloodwork, it may be worthwhile to consider treating for inflammatory bowel disease (IBD) or to consider asking for referral to a veterinary specialist with the means to diagnose IBD -- usually done with biopsies taken with endoscopy. There are anecdotal reports that soft moist cat foods are beneficial in cats with IBD -- so if you change foods again before doing any other workup you might want to consider trying one of these foods (Happy Cat is the only brand name I can think of but there are more). I really think it is worth trying to get a diagnosis in most cases of vomiting in cats. Discuss this with your vet again.

Mike Richards, DVM

Staggering, loss of eye control

Question: Last Friday, our cat came staggering out to us unable to balance himself, with is turned to one side, and his eyes out of control wandering all over. He is a 1 1/2 year old neutered male, had been fine up to that point, I can't find anything ,which could have poisoned him. Cannot straighten his head to drink out of the bowl when he tries. My vet seems to think he got into poison, and now is brained damaged, but would he have reconized me today if he was brain damaged. Connie

Answer: Connie - A toxin is possible. It wouldn't be my first thought but that could just be my mindset.

I would worry about feline vestibular disorder (sudden onset of balance problems with abnormal eye movements). This usually lasts less than two to three weeks and clears up with or without medication. Trauma is possible (a head injury). Ear infections and ear tumors are possible (tumors do occur in young cats at times). Feline leukemia, feline infectious peritonitis and feline immunodeficiency virus can sometimes cause central nervous system problems, too.

Mike Richards, DVM

Poor Haircoat

A poor haircoat can be a sign of disease. Diabetes, allergies and hyperthyroidism are common causes of dander or oily haircoats in our practice. It may be worth having your vet check your cat if this problem continues.

For dizziness

Question: My 9 year old cat began to seem slightly dizzy a few weeks ago. Our vet prescribed an antibiotic (Clavamax) and Prednisolone; she suspected vestibular something or other after an xray ruled out any physical injury. Kitty did not improve after the 10-day round of antibiotics and we returned to the vet. Another round of antibiotics were prescribed in addition to a daily 12.5 mg tablet of meclizine, which I understand is used to treat motion sickness in people. A blood test revealed only that the cat was not drinking much water, nothing else abnormal. It's been 3 days since we began the motion sickness medication (it was written for 14 days) and the cat is considerably worse. He is highly disoriented, can barely get around without stumbling, and spends all of his time huddled under the bed. He is eating pretty well, altho' he has lost about a lb. between first and second vet visits ten days apart. He has experienced no injuries that I'm aware of (he did go outside before he got sick) and he does not seem to be in pain. I initially thought that he had had a stroke, but the vet did not find any evidence of that based on her examination of his pupils. Is there anything that you know of that could cause this condition that my vet may have overlooked? Thanks, Sharon

Answer: Sharon - The major causes of dizziness are middle and inner ear infections and problems affecting the cerebellum (part of the brain that controls balance and spatial orientation). An ear infection may respond to antibiotics but sometimes surgery is necessary to relieve pressure in the middle or inner ear. Feline leukemia virus, feline immunodeficiency virus, toxoplasmosis and other infectious diseases can lead to balance problems. Cats do sometimes get infarcts in the brain with similar effects to strokes in humans. Cancer can cause these signs, as well.

If your vet is not able to make a diagnosis and you wish to pursue this further it is reasonable to ask for referral to a veterinary neurologist or internal medicine specialist. If you live close enough to a veterinary school to go there it is possible to get opinions from several experts at once.

Mike Richards, DVM

For Hairloss on abdomen

Question: Dear Dr. Mike:

My 12-year-old spayed female cat has been a healthy cat. However, she has developed hair loss on her stomach and backs of rear legs. Is this old age related? There is no scaliness or patchiness. I would like to treat her with vitamin supplements if that would help. I looked through your wonderful webpage for answers before writing. Thank you for this service. You and your staff are very special people!

Answer: The most common causes of hairloss in the pattern you describe are cystitis or other cause of a "burning" sensation in the vaginal or vulvar area, pychogenic alopecia (behavioral chewing or licking of the haircoat) and occasionally allergies. Sometimes in older cats this behavior shows up with hyperthyroidism.

The cystitis problem should have other signs, such as more frequent urination, staying a long time in the litterbox, or signs like that. This is not always the case, though.

Psychogenic alopecia is self-mutilation of the haircoat, usually brought on by stress or boredom. It is most common in cats who are left alone a lot or cats that are part of multi-cat households of more than 3 or 4 cats and are stressed by the situation. It can occur for any reason that the cat feels as stress, though. So it can be hard to definitely rule out.

Allergies usually respond to treatment with corticosteroids and often have other signs, such as scabbiness in the haircoat or hairloss in other regions. Fleas may be present and initiating the allergic response. The only problem with the "treat to diagnose" approach is that corticosteroids can mask signs of other diseases and it is possible to overlook a primary cause (such as cystitis) because the signs are then masked. A good physical exam is important prior to treatment for possible allergies.

Hyperthyroidism usually has the major sign of eating a lot and losing weight anyway. Cats may be more active than they have been in recent years. They often vocalize a lot with this disease (like walk through the house at night crying for no apparent reason).

Your vet can help sort through these possibilities. It could make your cat a lot more comfortable if a primary cause like cystitis is found and treated.

Mike Richards, DVM

For weight loss

Q: I took my cat to the vet yesterday....he has had rapid weight loss and won't eat or drink.....the vet ran a test for cancer and aids but it showed neg...he gave him some tonic and amoxill for infection....what would cause the rapid loss in weight with no pep at all...I feel like I am losing him....please answer me back...... thank you m.

A: You didn't say how old your cat is and the differentials for weight loss do vary some according to age.

Young kittens with rapid weight loss:

parasitism, feline infectious peritonitis, feline leukemia virus, congenital defects involving the liver or kidneys, malaborption or maldigestion syndromes (not enough digestive enzymes for instance)

Young adult cats with rapid weight loss:

cardiomyopathy (more common in male cats), feline leukemia virus, feline immunodeficiency virus, feline infectious peritonitis, hepatic lipidosis (usually secondary to some other illness), diabetes, kidney or liver disease other than hepatic lipidosis, cancer, other systemic illnesses, parasitism

Rapid Weight Loss in older cats:

cardiomyopathy (usually eating less), diabetes (appetite variable), hyperthyroidism (eating a lot and losing weight anyway), kidney failure (appetite variable), cancer (usually eating less), feline leukemia, feline immunodeficiency virus, feline infectious peritonitis, other systemic illness

Your vet will sort through these possibilities, I'm sure. In many cases it is easy to eliminate a number of the possibilities with a good physical exam and history. Some testing is usually necessary to confirm or rule out the other possible problems.

Michael Richards, DVM

Last edited 08/01/05


Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...