Page 604 - Clinical Small Animal Internal Medicine

572 Section 6 Gastrointestinal Disease

filling in our ICU patients (especially patients with sep- A variety of toxins (e.g., mercury, thallium, lead), phar-
VetBooks.ir sis, SIRS, on mechanical ventilation, and those with maceuticals (antibiotics like lasalocid, nitrofurantoin,
salinomycin), pesticides (e.g., organophosphates),
increased risk of aspiration pneumonia) semiquantita-
tively via ultrasonography. If there is sufficient suspicion
hexacarbons) have been reported to cause peripheral
of GI hypomotility (gastric distension), prokinetic drugs organic solvents and other chemicals (e.g., acrylamide,
like prucalopride or erythromycin are administered neuropathies, which might include ileus or other forms
early. If oral medication is not tolerated, rectal adminis- of dysmotility of the GI tract (i.e., megaesophagus, etc.)
tration can be tried. Even though the authors subjectively although these are infrequently seen and poorly
think this type of management decreases the risk of aspi- documented.
ration pneumonia and other complications, there is at
this time no objective evidence that these interventions Diagnostic Tests to Assess Small Intestinal
influence outcome of small animal ICU patients. Motility or Transit Times
Acute pancreatitis causes substantial damage to the GI
tract in people and rodent models. Usually, this is associ- The outcome of SI motor activity depends on the pat-
ated with acute necrosis, ischemia, and bleeding, but terning of contractions in both space and time; that is,
varying degrees of dysmotility have also been docu- where and when do the contractions occur with respect
mented, likely due to cytokines being produced as part of to each other? Methods to assess these relationships
the local inflammatory process. In dogs, the typical clini- must address substantial technical challenges to gather
cal signs associated with acute pancreatitis (vomiting) functionally relevant information.
and the severity of abdominal inflammation in some
patients suggest that GI dysmotility or ileus is commonly Diagnostic Imaging Procedures for Small Intestinal
present. However, no data regarding GI dysmotility in Transit Studies
pancreatitis in small animals are available. Contrast studies of the SI are the most commonly used
There is some evidence that both acute kidney injury method to assess transit time or to search for intestinal
(e.g., in leptospirosis) and chronic kidney disease have an obstruction in small animals. Neat liquid barium sulfate,
inhibitory function on orderly intestinal motility. In ionic or nonionic organic iodine contrast media or, less
other conditions, GI dysmotility is suspected but not frequently, contrast mixed with semisolid food is admin-
proven. One example is diabetes mellitus, where altered istered orally. The recommended dosage for liquid bar-
levels of neuropeptides have been documented in exper- ium is 6–16 mL/kg body weight, with the high end of the
imental animals. However, even in humans, the exact dose range for cats and small dogs and the lower end for
mechanism for small intestinal dysmotility in this endo- large dogs. The protocol for performing a contrast study
crinopathy is not well understood. So far, no consistent of the GI tract in dogs and cats is summarized in Box 53.1.
correlation between changes in enteric neurotransmit- Usually, the final radiograph is taken after 12 hours to
ters, numbers of ICCs (decreased markedly in one check the complete gastric and SI evacuation of contrast.
neuroanatomic human case report) and manometric or Barium‐impregnated polyethylene spheres (see above)
transit observations has been detected. have also been used for SI transit studies. The sensitivity
It is likely that (gastro)intestinal dysmotility is also and specificity of this method, however, is low.
present in other chronic conditions such as IBD, canine Contrast fluoroscopy is used in human medicine to
idiopathic large bowel diarrhea (CILBD), hepatitis/ detect mucosal disease and stenoses that may induce
hepatopathies, etc. Unfortunately, no study investigating secondary changes in motility, transit, and absorption.
GI motility in these conditions in dogs and cats is However, this technique is insensitive for the direct
available. detection of abnormal transit times. Observation times
are limited (radiation exposure) and once the majority of
Iatrogenic and Toxic Causes of Gastrointestinal contrast has entered the small intestine, overlying loops
Ileus of bowel hinder the interpretation. Fluoroscopy has not
Intestinal dysfunction is a common side‐effect when been reported for assessment of small bowel transit in
opioid mu‐ and delta‐agonists are administered as anal- small animals.
gesics. Most commonly, constipation and vomiting are Ultrasonographic assessment of small intestinal motil-
observed. This can occur immediately after the first dose ity is challenging due to observer variability, interference
and persist for the duration of therapy. In most cases, from intraluminal gas and the difficulty of finding objec-
discontinuation of opioid treatment is sufficient to tive measures to assess contractions. Even though two
improve intestinal function. Occasionally, laxatives and studies found that Doppler ultrasound techniques
other therapies may be used additionally to treat (pulsed‐wave and duplex Doppler, respectively) allow
constipation. graphic visualization and qualitative and quantitative