Acute Diarrhea

Besides skin issues – chewing and scratching and smelly skin – acute onset diarrhea is probably the most common problem we see in our practice. The diarrhea is sometimes accompanied by vomiting and anorexia, and often times with lethargy. Other cases, however, present with just acute onset diarrhea, and the pet otherwise feels fine and acts fine, including eating and drinking normally with no vomiting.

From a diagnostic standpoint, the history that the owner gives us plays a very large part in how we approach the case. In general, the main questions we want answers to are these:

  • How long has the diarrhea been present?
  • Is the pet still eating and drinking normally?
  • Is there any vomiting?
  • How many times a day is the pet having the diarrhea?
  • Is the pet urgent – i.e., are there accidents in the house? Or conversely, is your pet able to control the BM until he has a chance to go outside?
  • Is there any blood or mucous in the stool?
  • Is the stool watery, or just soft like pudding?
  • What is the pet’s usual diet, and does the pet get any table scraps or other treats?
  • What is the pet’s outdoor environment like? Is he in a controlled, fenced-in yard, or rather does he live on acreage and have access to free standing water and other unwanted variables?

Large Bowel vs. Small Bowel Diarrhea

The main purpose of the above questions is to try to narrow down two questions: 1.) Is the diarrhea coming from the large intestine (LI) or the small intestine (SI)? And 2.) Is the problem acute or chronic? By narrowing the diarrhea down to to its origin – SI or LI, and deciding whether it is acute or chronic, we can narrow our scope of potential problems.

By far the most common diarrhea we deal with in small animal medicine is acute onset, large intestinal (LI) diarrhea. The large intestine is the same thing as the colon, so when we talk about LI diarrhea we’re essentially talking about colitis.

Colitis and LI diarrhea present as the typical case of diarrhea one would think of when you hear the word “diarrhea.” In general, the stool is watery to mucousy, the pet is going frequently in relatively small quantities, he is urgent and often has accidents in the house, and there is sometimes blood in the stool.

On the other hand, SI diarrheas are completely different. SI diarrheas are not urgent at all. The pet usually has a normal frequency and volume of stool, it’s just that the stool comes out unformed. This is the classic cow-paddy, or pudding type of stool.

In veterinary medicine, LI diarrheas outnumber SI diarrheas approximately 20-1. Straight forward LI diarrhea usually means the pet still acts fine and is eating and drinking normally. Occasionally, though, there is a reflex that travels from the colon to the stomach, and makes the pet anorexic or nauseous when the colon is inflamed, as in colitis. In these cases the stomach is normal, but the vomiting is triggered by the inflamed colon reflex. We treat the colon in these cases, and the vomiting almost always clears spontaneously.

Routine Diagnostics for Acute Diarrhea

The workup for any acute colitis case varies, depending primarily on whether the pet acts sick or not. All colitis cases warrant a fecal float and fecal cytology. For those cases wherein the pet is very depressed and/or not eating, blood work to check liver, pancreas and other organ function, as well as cell counts is definitely indicated.

A fecal float is the routine lab test we use to look for intestinal worms. Parasites such as hookworms, roundworms, and whipworms all show up on a fecal float. In a fecal flotation we actually look for the eggs produced by these worms. It’s important to remember that in most cases of intestinal worms, the owner never sees worms passing in the stool.

A fecal cytology is a test in which a thin film of fecal matter is smeared out on a microscope slide, stained, and observed under the microscope. This allows us to view the bacterial flora of the stool. Oftentimes we can identify abnormal bacteria, such as Campylobacter or Clostridium species that are the cause of the diarrhea. Because of the small size of the bacteria we’re searching for it’s imperative that a high-end microscope, capable of 1000x magnification, be used. Ours is a Nikon Eclipse E200, which is an ultra-high resolution scope.

The vast majority of acute colitis cases in pets are of a bacterial origin. Whether it’s Clostridia, Campylobacter, Giardia, or some other microorganism, many of these cases respond to antibiotics. In recalcitrant cases we sometimes will run fecal cultures or advanced diagnostics, such as Polymerase Chain Reaction (PCR) tests to get a diagnose. That is definitely the exception though, as most diarrheas in dogs and cats can be handled relatively easily and without great expense.

Because of the frequency of this problem we strongly recommend discouraging your pets from drinking out of impure water sources, which is the primary source of contaminants. And as difficult as it is to control, always try to keep your pet from eating things off the ground. In Florida, especially, bacteria breed readily and rapidly on dead items on the ground. This is a perfect formula for screaming colitis. In cases of colitis, as in many things, an ounce of prevention is worth a pound of cure.