Memorial Day mystery
It's Memorial Day weekend. I'm on call today, so while sticking close to home waiting for the inevitable emergencies, I'm making a diagnostic plan for Flame, a 12-year-old tortoiseshell kitty with a bit of medical history. Four years ago Flame experienced a prolonged episode of poor appetite, intermittent vomiting, and weight loss. We ran lots of tests and found lots of abnormalities, ranging from anemia to liver enzyme elevations, but never made a definitive diagnosis. That would have required a liver biopsy, maybe more.
Understandably, Flame's owners opted for empirical therapy. That means I picked a treatment based on my clinical impression. That means I made my best guess. Happily Flame responded to our ministrations - or maybe Mother Nature healed her in spite of our meddling. Whichever, Flame bounced back to her old self over a few months and I just had to live with the frustration of not knowing what the problem had been.
This fall she returned to see me. She was losing weight again, but this time her appetite was good ... too good. She seemed hungry all the time. Her owners were concerned that whatever ailment had afflicted her years back was recurring, but this time there were no abnormalities on her blood tests, except her thyroid levels. No mystery here, I thought. Flame has hyperthyroidism, one of the most common endocrine disorders in middle-aged cats.
I started her on medication fully expecting her symptoms to abate, but they did not. In spite of a ravenous appetite, Flame is still losing weight and has chronic diarrhea. We have ruled out diabetes, another cause of increased appetite with weight loss. We retested her thyroid. Her medication is controlling that problem. It's time to start looking at gastrointestinal diseases.
The telephone rings. My answering service has two emergency calls for me. I call back one weekend tourist who fed their dog a bone. (Don't do that!) Another message is from someone with a question about their medication. I call back. They are not home. So much for it being an emergency.
Hanging up the phone, my thoughts return to Flame. What are my main differentials for her chronic diarrhea with weight loss? Intestinal parasites (including worms of many types, protozoa like Toxoplasma, and flagellates like Giardia), food sensitivities, bacterial infections, inflammatory bowel disease, intestinal cancer, and exocrine pancreatic insufficiency. Sometimes the nature of the bowel movements can help narrow down the location of the problem. Remember the intestines are divided into different portions with different functions.
The small intestine (SI), which includes duodenum, jejunum. and ileum, begins at the stomach and winds around in a very long, skinny tube. Most absorption of nutrients happens here. The large intestine (LI) is shorter and wider including the cecum and the colon and is more geared toward water resorption and the actual act of defecation. Animals with SI disease may show weight loss, and an increased volume of feces. LI disease may cause straining to defecate, mucousy stools, and decreased volume of stool but increased frequency of defecation. Flame's symptoms are most consistent with SI disease.
Okay, we've got a differential. What's our diagnostic plan? We can start by looking for infectious diseases, i.e., bacteria, worms, protozoa, flagellates, spirochetes. How? With multiple fecal tests, including microscopic flotation studies, wet mounts, rectal cytology, and maybe special stains looking for more obscure organisms. We've already wormed Flame a few times, just in case, but we could do a longer course of a different medication. What about food sensitivities? It sure makes sense to try dietary changes. Some respond to hypoallergenic diets, others to high fiber, while still others respond to ultra-digestible foods. It's trial-and-error. My sense, however, is that Flame has something more serious going on.
I top the list with intestinal cancer, inflammatory bowel disease, or exocrine pancreatic insufficiency (EPI). The first two require intestinal biopsy for definitive diagnosis. The third, EPI, can be diagnosed with specific blood tests. In EPI, the pancreas does not produce enough digestive enzymes. It is uncommon in cats and usually results from chronic pancreatitis. Classic cases have huge, stinky, greasy stools but symptoms can be nonspecific and inconsistent. EPI is treated by supplementing the food with powered pancreatic enzymes to aid digestion and sometimes giving injectable B vitamins.
Inflammatory bowel disease (IBD) is probably the most common cause of chronic diarrhea in cats. It's one of those tricky diseases that you diagnose by ruling out everything else and then taking a biopsy of the intestines. No one knows for sure what causes it but it can sometimes be managed with diet changes alone or in combination with various medications, usually corticosteroids. It's a disease we control but rarely cure. Intestinal cancer is also common in cats. It may be associated with feline leukemia (FeLV) or Feline Immunodeficiency Virus (FIV) and requires biopsy for definitive diagnosis.
Other diagnostic approaches
The fact that I don't palpate any abnormal masses in Flame's tummy does not rule out cancer. Although it may manifest as large solitary growths, intestinal cancer can also replace the normal architecture of the intestines in such a way that there is no discrete, obvious mass, but proper digestion and absorption of nutrients are disrupted. The bowel may feel vaguely thickened on palpation but this is true with IBD too. Radiographs and ultrasounds may be useful, but it is biopsy that gives the final answer.
There goes the phone again. A dog being treated for tick-borne disease is now showing mild neurological abnormalities. I see the dog, run a few tests, try to reassure her owner. The next call is from someone whose dog is lethargic and not eating. They decline my offer to see them on an emergency basis but want to know if they should give benadryl or maybe baby aspirin. Since without an exam and a diagnosis, I have no idea what is wrong, I can't really speculate on appropriate treatment. A home-cooked bland diet and some Pepto Bismol will at least do no harm, I suggest, and reiterate that they should seek medical attention if their pup does not improve.
Now where was I? Oh, yeah. My recommendations for Flame: a variety of fecal studies, EPI blood work, FeLV/FIV test, radiographs, ultrasound, biopsy. What if the owners decline all this? Hhmmmm. We could start with medications for parasites, dietary changes, pancreatic enzymes, and supplemental vitamins. If this doesn't help, move on to corticosteroids. As I just said on the phone, without a definitive diagnosis, it's hard to know the definitive treatment. Sometimes, however, we just have to take our best guess. The phone is ringing again. Someone gave their pug Tylenol. (Don't do that!) I do the math. Luckily it was way below the toxic dose. There goes the phone again. I hate Memorial Day.