Monday, February 14, 2011

The controversy of pancreatitis

Chances are that some of you readers out there have had a pet diagnosed with pancreatitis in the past. Typically, the initial clinical signs are a combination of lethargy, vomiting, diarrhea with or without blood, and loss of appetite. Outward signs of pain (groaning, difficulty resting comfortably, and frequent stretching of the hind or forelimbs) are also possible. Your veterinarian may have diagnosed pancreatitis and either sent you home with antibiotics and GI protectants or recommended hospitalization for your pet. Your pet likely recovered, although some cases take a turn for the worse. This is the usual arc of a "pancreatitis" case - lasting anywhere from 48 hours to a week or more. So, what's the real story?

That's the trouble. The "real" story is much, much more complicated.

Pancreatitis is a simple word - pancrea: referring to the pancreas and itis: referring to inflammation. Simply put, pancreatitis means an inflamed pancreas. The pancreas is a crucial organ that lies snugly along the greater curvature of the stomach and along the upper duodenum. It secretes many enzymes that are crucial for food digestion. Without a properly functioning pancreas, dogs, cats, and people cannot digest their food, develop diarrhea, and lose significant amounts of weight (a disease called pancreatic insufficiency). Your pancreas can also be the enemy, as when it becomes extremely inflamed, starts leaking digestive enzymes, and then starts to digest itself and nearby fat (the mesentery that cushions and nourishes the small intestines).

No one really knows what triggers pancreatitis. For many years, it has been associated with dietary indiscretion in dogs - Fluffy got into the trash, or Fluffy was fed a giant, bloody ribeye, or a large, greasy meal from McDonald's. There is also thought to be a hereditary component in Schnauzers, as they are particularly prone to this disease. No direct, causal link has ever been established to prove that these things cause pancreatitis, but we do see many dogs that have gone dumpster diving or been fed possibly offensive foods with suspected pancreatitis. Medications have also been implicated including the diuretic furosemide (Lasix), the immunosuppressant drug azathioprine, sulfa antibiotics, and others. Steroids are a controversial possible cause.

For whatever reason, the pancreas becomes very inflamed. This happens because the digestive enzymes, which are normally secreted into the intestines before activation, become activated within the pancreas and start to autodigest it. As a result, significant inflammation of the pancreas begins. The inflamed pancreas pushes on the stomach and small intestine, causing pain both by the pressure and due to autodigestion. Furthermore, nausea and vomiting occur, followed by diarrhea as a result of the dysfunctional organ.

Many patients present lethargic, with a fever (although fever is not always present), vomiting, diarrhea, and abdominal pain. They are often dehydrated from vomiting and diarrhea. Some present in septic shock, as pancreatitis can be very severe and even life-threatening.

The trick is diagnosing pancreatitis and distinguishing it from other diseases. This might seem like it should be very simple. It is however, the crux of our problem. Pancreatitis is an elusive disease to diagnose with any surety. Therefore, it is often over-diagnosed. Many dogs with vomiting and diarrhea have gastroenteritis, GI foreign bodies, dietary indiscretion unrelated to pancreatitis, or cancer, yet pancreatitis is frequently the diagnosis. It has become a catch-all term for vomiting and diarrhea and seems to be one of the most over-diagnosed diseases I have seen.

So, how is it diagnosed and why is it so tricky? For years, veterinarians looked at the values of amylase and lipase on a chemistry panel. These are enzymes secreted by the pancreas. The problem is, as it turns out, these enzymes are also secreted by the small intestines, kidneys, and other organs. As a result, where once it was thought that elevated amylase/lipase = pancreatitis, now it is understood that this is not necessarily the case. These values can be elevated in other disease processes, and they can also be NORMAL in dogs that have pancreatitis. Other bloodwork findings are very non-specific to pancreatitis and are not helpful in distinguishing.

A test was recently developed called the cPLi (canine pancreatic lipase immunoassay). This test purportedly measures the lipase that is released from the pancreas only, and not the other organs. As a result, if it is elevated, pancreatitis is present. The problem with this test is that there are many false positives, for a variety of reasons. It is useful in that if the test is negative, pancreatitis can likely be ruled out (although not with 100% confidence). It is a good screening test only. If it is negative, you should probably be looking for other causes of vomiting and diarrhea. If it's positive...well, is it a true positive or a false positive?

There is also a test that can be sent out to measure the level of canine pancreatic enzyme. This is the best test we have at the moment, but it has limitations as well. If your veterinarian is very suspicious of pancreatitis, a spec cPLi should be sent to an outside laboratory to measure the value. These can be more helpful in making a definitive diagnosis. Unfortunately, this test is not available at 3am on a Sunday night to us ER veterinarians. This makes our job in differentiating even more difficult.

Xrays can provide clues, but again, a definitive diagnosis cannot be made from just xrays. In suspected cases of pancreatitis, abdominal xrays should ALWAYS be done to rule out some causes of secondary pancreatitis. Since the pancreas is so closely associated with the stomach and small intestines, insults to these organs can cause secondary pancreatic inflammation. Foreign objects stuck in the intestines can cause this, as can cancer and other such diseases. Xrays of classic pancreatitis usually show a loss of detail in the area of the pancreas, mild upper duodenal dilation, and sometimes a mass like effect in the area of the pancreas (right cranial quadrant). These findings are inconsistent and not very specific, unfortunately.

Where does that leave us? There is ultrasound, which - IN THE RIGHT HANDS - can be a very good indicator of pancreatitis. The problem with this is that the everyday practitioner is usually not good enough at ultrasound to see the pancreas. This includes myself. It is an elusive organ, and unless it is really, really enlarged, I can't usually find it. Thus a specialist (i.e. a radiologist) is usually required for that diagnosis. Again, something many owners cannot afford or that is not available to us ER people in the real world (we have an ultrasound, but I am not comfortable finding the pancreas!).

So, where does that leave us? On the bright side, it might be strictly academic. The most important piece of the puzzle is ruling out OTHER, potentially life-threatening problems such as a foreign body in the intestines or cancer. True pancreatitis should be treated like any severe gastroenteritis. IV fluids should be administered. Perfusing the pancreas is crucial to allow it to heal. Anti-emetics such as Cerenia (maropitant) and Zofran (ondansetron) should be used for nausea/vomiting. Metoclopramide (a drug called Reglan that helps promote intestinal motility and stop vomiting) is currently controversial, as it has some negative effects on blood flow to the pancreas. Pain medications should be used in all cases, as some animals are stoic enough that pain can be very hard to detect. These run the gamut from the more minor opioids such as Buprenex to pure mu-agonists such as morphine, hydromorphone, and fentanyl. Patients should have serial blood glucose, electrolyte, and other parameters monitored to make sure they are not worsening.

In some cases, true pancreatitis can progress rapidly to sepsis, DIC, and acute multi-systemic organ failure. It is crucial to treat these cases early and aggressively. Antibiotics were once thought to be warranted, but it has been realized recently that the vast majority of pancreatitis cases are inflammatory but not infectious. No bacterial or viruses are involved. Thus, antibiotics are no longer recommended. I do not use them in my pancreatitis cases, and I have a very high positive outcome.

So, if your vet diagnoses pancreatitis, what should happen? Full bloodwork (a complete blood count/CBC and chemistry panel including amylase/lipase) should be conducted. A spec cPLi should be submitted to an outside laboratory, your pet should undergo xrays of the abdomen to rule out other possible causes of pancreatitis, and an ultrasound referral should be offered (although many owners do not go this route). Early, aggressive intervention in all but the most stable patients should be undertaken to prevent the disease from worsening. IV fluids, anti-emetics, pain control, +/- antibiotics should be administered, and the patient monitored closely. Feeding should be withheld for a period of time (again - clinician preference) to prevent worsening of vomiting.

In most cases, complete recovery will occur, although some cases can become extremely severe and wind up fatal. This is not the majority of cases, thankfully. Possible triggering causes should be identified and avoided in the future (less table scraps, more dog food). Schnauzers should be monitored closely throughout the course of their lives, as they can have low-grade, chronic pancreatitis with occasional flare-ups of more acute disease. Working closely with your veterinarian in cases of pancreatitis is crucial, as well as being an informed, involved owner. Asking questions, doing research, and following veterinarian recommendations can help your pet enormously!

6 comments:

Elizabeth said...

Excellent! Thank you. I just shared this with a list I am on..

Elizabeth said...
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Learning said...

This is a great, easy-to-read synopsis of pancreatitis. Thanks for sharing!

Anonymous said...

I haven't sent out a CPL since on Internal Med rotations during my internship. It just makes no sense to me if you have a radiographic diagnosis. Results don't come back for 2-3 days so it has never (as in not one time) changed the way I treat the patient. And that is my general rule of thumb - if the result won't change my treatment plan, why run the test?

I asked the Internal Med folks the same thing over and over again since by the time we got the test results back, the animal had been discharged from the hospital 90% of the time. The answer was always "so that we know what it was" or "as a baseline". What? Baseline? I've never understood.

Maybe I'm too practical in my approach and not academic enough but truly, why run a diagnostic test when the answer makes no difference in your care, treatment or prognosis?

CEVC said...
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The Homeless Parrot said...

In my opinion and as I was taught, there is no radiographic diagnosis of pancreatitis. There are suspicious findings, but it is not definitive.

I agree with the IM specialists. Having a baseline can be invaluable. It is not perhaps needed in the one-time, acute pancreatitis dog that responds well to therapy, but what about the chronic cases like Schnauzers. It is an excellent monitoring tool to tell if the condition is worsening or improving.

You're right in that it doesn't OFTEN change the course of treatment, as I said in my post - it might be academic. On the other hand, I think owners should be offered every option for a definitive diagnosis, and at this time, the spec cPLi is all we have in the way of that.

Again, this is just my opinion.