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Featured Case Study:
Two-year-old spayed, female, mixed-breed dog, Teddi
Daniel
F. Hogan, DVM, DACVIM, Associate Professor of Cardiology, Purdue
University School of Veterinary Medicine and Dennis B. DeNicola, DVM,
PhD, DACVP, Chief Veterinary Educator, IDEXX Laboratories
History
Teddi travels between Indiana, Texas and
Arizona frequently. Vaccinations are current. She had two puppies at
one year and three puppies three months prior to this presentation.
She was spayed after her second litter. Teddi had an episode of
assumed gastritis that resolved six months prior to this presentation.
Interpretive Summary
 Erythron—There is a high-normal red blood cell mass associated with slight
microcytosis (decreased MCV). Moderate numbers of target cells are
present (see Figure 1) and there is a suggestion of microcytosis as
well as hypochromasia on the peripheral blood film. Since there is no
significant anemia or polychromasia present, developing iron
deficiency is unlikely in this case. Because of the lack of
hypercholesterolemia (see below), the likelihood of an upset plasma
phospholipids-to-cholesterol ratio and “lipid loading” onto the
erythrocyte membrane is high. Hepatic dysfunction should be high on
the differential, however, consideration for various nonspecific
metabolic disease, as well as possible splenic disease, should be
included in the differential based solely upon these hematologic
changes. Specifically, investigation into possible hepatic vascular
shunt and insufficiency is warranted since microcytosis not associated
with iron deficiency is a relatively restrictive finding in the dog.
Although the physical examination did not reveal dehydration and the
total protein of the plasma by refractometry does not support
dehydration, consideration for some subclinical dehydration must be
made based upon the finding of a high within-reference-range
erythrocyte mass. This change could also be explained by slight
erythrocytosis associated with a compensatory process if there is any
cardiac insufficiency (bradycardia noted clinically).
Leukon—No significant
quantitative or qualitative leukocyte abnormalities are noted.
Thrombon—The platelet count is minimally outside the reference-range limit, which is well within the third standard of deviation from the clinically normal animal population; this is interpreted to be normal. Platelets are morphologically normal.
Liver panel—Primary
abnormalities are noted in the liver panel. There is evidence of
mild-to-moderate hepatocellular injury with the increased ALT. The
increase in ALKP is extremely minimal and very nonspecific. There is
no other support for cholestatic disease. Hepatic insufficiency is
suggested with the decreased glucose, BUN and cholesterol. However,
since other causes for these abnormalities are possible, additional
specific liver-function testing should be considered. The present
findings of hepatocellular injury and suggested insufficiency, along
with the microcytosis, are strongly supportive of a hepatic vascular
anomaly, which requires confirmation with other diagnostics. See the
results of the liver-function tests.
Acid-base status—The
finding of decreased chloride relative to sodium is supportive of a
metabolic alkalosis with either loss or sequestration of chloride. The
observed clinical sign of intermittent vomiting is most likely
associated with some loss of chloride and is the source of this
electrolyte abnormality. The potential of alkalemia and associated
decreased extracellular potassium should be considered to explain the
hypokalemia. However, decreased intake associated with the anorexia
can also explain the hypokalemia. The high sodium may be related to
subclinical dehydration. The finding of a high within-reference-range
carbon dioxide level in the face of metabolic alkalosis suggests the
possibility of a slight metabolic acidosis (with simple metabolic
alkalosis an increase in total carbon dioxide is commonly seen to
maintain electroneutrality in the face of the decreased chloride). The
slight out-of-reference-range anion gap suggests a possible
titrational metabolic acidosis. Further evaluation of the acid-base
status through blood gas analysis and blood pH determination should be
considered if these electrolyte changes are not corrected during the
course of this disease process.
Protein panel—Although
there are no out-of-reference-range abnormalities, the finding of a
low within-reference-range total protein and albumin in the face of
high within-reference-range erythrocyte mass, and in an animal with
intermittent vomiting and diarrhea, is unusual. The potential of
subclinical dehydration and false-raising of the albumin, resulting in
both a within-reference-range albumin and total protein should be
considered. Any further characterization of protein abnormalities
would require serum protein electrophoresis (SPE). Specific SPE
changes have been reported associated with hepatic insufficiency and,
if other laboratory testing proves inconclusive, evaluation of the SPE
profile in this animal should be considered.
Calcium—The slightly
decreased total calcium value is well within the third standard
deviation outside of the reference range and is considered clinically
insignificant. Some of this change may be related to the low
within-reference-range albumin value. Approximately 50% of total
calcium is albumin-bound and not physiologically functional. If there
were any clinical signs associated with hypocalcemia, measuring an
ionized calcium would be warranted.
Amylase—The minimally
low amylase has absolutely no clinical significance. Decreases in most
enzyme activities in routine serum chemistry profiles have no clinical
significance for day-to-day patient evaluation.
Urinalysis—The finding of a
hyposthenuric urine sample in a dog with potential subclinical
dehydration is of concern and this should be re-evaluated with
repeated urinalysis examinations. No significant abnormalities are
noted in the sediment.
Liver-function tests—The
resting high ammonia level, as well as the pre- and post-bile acid
increases, support the presence of hepatic insufficiency. Further
evaluation should include detailed diagnostic imaging with particular
attention to the possibility of vascular shunt disease, as well as
possible liver biopsy for further characterization of hepatic disease
pending evaluation for vascular shunts.
Diagnostic Imaging
Routine radiology—Standard
radiographic evaluation of the abdomen in this case revealed
microhepatica, which is supportive of possible vascular shunt, but is
not diagnostic for shunt or helpful in characterizing the type of
shunt, if present.
Ultrasonography—Detailed
ultrasonographic evaluation of the abdomen in this case could not
confirm the presence of a vascular shunt; however, there were several
supportive findings beyond the previously observed microhepatica that
suggested vascular shunt.
Mesenteric portogram—A
mesenteric portogram was performed after Teddi was stabilized to help
confirm the presence of a vascular shunt. In this case, a single
extrahepatic vascular shunt was identified.
Diagnosis
Single extrahepatic portosystemic shunt
Clinical Case Outcome
Surgical correction of this single extrahepatic shunt included the
placement of a 3.5-mm ameroid ring around the portosytemic shunt
vessel. The ameroid ring slowly occluded the shunt vessel over
the following six- to eight-week period, which lessened the risk of
hypertension that could be seen after surgery. Teddi recovered from
surgery without complications and was monitored closely in the
intensive care unit for five days postoperatively. Teddi was released
with instructions for restricted activity for two weeks and a recheck
CBC and chemistry profile in twelve weeks. Teddi has responded well
to this procedure.
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(458 KB)
Bile Acids
Don't
forget to treat all pets in the household to prevent potential
reinfestations.
Background: intact
eight-year-old female German shorthaired pointer with the clinical
presentation of two days of acute onset depression, lethargy and
vaginal discharge. The CBC revealed a moderate leukocytosis (WBC =
46,500/µL) and minimal anemia (Hct = 35.6%).
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