Page 520 - Small Animal Internal Medicine, 6th Edition

492 PART III Digestive System Disorders

Treatment The clinician should treat 3 weeks before deciding that the
Most patients that respond can simply be fed the diet they therapy was ineffective. If therapy appears successful, it is
VetBooks.ir responded to in the dietary trial (assuming it is balanced) for often wise to continue to treat for an additional 1 to 2 weeks
to establish cause and effect. Some animals can then have the
the rest of their lives. Rare patients develop allergies to the
elimination diet and require different elimination diets to be
tained, but others will need repeated or indefinite antibiotic
fed on rotating 2- to 3-week cycles. antibiotic therapy stopped while the dietary therapy is main-
therapy. The clinician should warn the owner that the goal
Prognosis is typically control, not cure. Patients that have nearly con-
The prognosis is usually good. stant diarrhea when not being treated with antibiotics may
need constant antimicrobial therapy (undesirable) or alter-
ANTIBIOTIC-RESPONSIVE SMALL native therapies (e.g., fecal transplantation, probiotics).
INTESTINAL ENTEROPATHY Patients who have episodes every 3 to 4 months might best
be treated when they relapse as opposed to having them on
Etiology antibiotics constantly.
Antibiotic-responsive enteropathy (ARE; also called As of this writing, fecal transplantation is being tried in
antibiotic-responsive diarrhea or dysbiosis) is a syndrome in many dogs with chronic diarrheas, and it might eventually
which there are many E. coli or similar enterics coupled with replace antibiotic therapy as the first line therapy for ARE or
an intestinal host defense that is not capable of maintaining chronic enteropathy (CE). It is too early to know whether
tolerance and subsequently has an abnormal response to this will take place.
these bacteria. Presumably, enterocytes are damaged by
deconjugation of bile acids, fatty acid hydroxylation, genera- Prognosis
tion of alcohols, increased permeability, generation of The prognosis is usually good for control of ARE, but the
inflammatory cytokines, and/or other mechanisms. clinician must be concerned with possible underlying causes.

Clinical Features
ARE can be found in any dog. Clinical signs are principally RELATION OF SMALL INTESTINAL
diarrhea or weight loss (or both), although vomiting and/or DIETARY-RESPONSIVE DIARRHEA AND
hyporexia may also occur. ANTIBIOTIC-RESPONSIVE ENTEROPATHY
Diagnosis Currently, approximately 70% of dogs with chronic diarrhea
Currently available diagnostic tests for ARE have poor sen- are suggested to have dietary-responsive diarrhea, whereas
sitivity and specificity. Quantitative duodenal fluid cultures approximately 15% are suggested to have antibiotic-
are difficult to obtain and interpret. Serum cobalamin and responsive enteropathy. However, it may be more complex
folate concentrations have poor sensitivity and specificity for than that. Although there are some dogs that only respond
this disorder. Duodenal mucosal cytology and histopathol- to dietary therapy and some that only respond to antibiotic
ogy are routinely nondiagnostic for ARE. Most affected dogs therapy, there appears to be a substantial number that
have nonspecific mild to moderate lymphoplasmacytic infil- respond to either therapy (i.e., it just depends upon which is
trates in the intestinal mucosa. done first). Even patients that respond to antibiotic therapy
by itself seem to often respond better when concurrently
Treatment treated with an elimination diet. Further complicating the
Because of the difficulty in diagnosing ARE with laboratory issue is a smaller subset that appears to require simultaneous
tests, a therapeutic trial is reasonable when this disorder is dietary and antibiotic therapy. Therefore recommendations
suspected. Therapy consists of removal of potential causes for therapeutic trials for CE patients should involve a definite
(e.g., blind or stagnant loops of intestine [very rare]) and sequence. Parasites should be eliminated first. After that,
administering antibacterial drugs. Because mixed bacte- dietary trials are appropriate (often starting with a hydro-
rial populations are expected, broad-spectrum oral anti- lyzed diet for 3 weeks and then going to a novel protein diet
biotics effective against aerobic and anaerobic bacteria for 3 weeks if that fails). Cobalamin may be supplemented
are recommended. Tylosin (10-20 mg/kg q24h or divided during this time, even if blood levels have not been mea-
q12h) is often effective. Metronidazole by itself (15 mg/ sured. By itself, cobalamin benefits relatively few CE dogs,
kg q24h) sometimes is sufficient. A combination of met- but it is safe and easy and does help some. If this trial is not
ronidazole (15 mg/kg q24h) and enrofloxacin (7 mg/kg successful, then antibiotics (e.g., tylosin) may be added to
q24h) is effective in some patients not responding to the the elimination diet (preferably another hydrolyzed diet if
previous treatments, but this combination should only be both diets had previously failed) for another 3 weeks. The
used when ARE is strongly suspected and prior therapy hope is that even if antibiotics were necessary for resolution
has failed (it is important to avoid long-term quino- of clinical signs, one will be able to stop the antibacterial
lone therapy to lessen problems with bacterial resistance drugs and maintain clinical remission by feeding the elimi-
to antibiotics). nation diet (i.e., it is often easier to maintain remission than