Objective—To characterize the texture, mineralogic
features, and chemical features of enteroliths
obtained from horses.
Sample Population—Enteroliths from 13 horses
Procedure—Enteroliths were harvested from 13
horses that underwent ventral midline celiotomy for
treatment of colic or necropsy because of colonic
obstruction and rupture caused by enteroliths. Dietary
and environmental history were determined via questionnaires
or evaluation of medical records. In 7 horses
that underwent surgical treatment for enterolithiasis,
samples of colonic contents were obtained via an
enterotomy in the pelvic flexure. Colonic concentrations
of magnesium (Mg), phosphorus (P), sulfur (S),
sodium (Na), calcium (Ca), and potassium (K) were
determined. Enteroliths were analyzed via electron
microprobe analysis and X-ray diffraction.
Results—Enteroliths varied widely regarding degree
of porosity, presence and distribution of radiating texture,
and composition and size of the central nidus. A
distinct concentric banding was identifiable in all
enteroliths. Struvite was the predominant component
of all enteroliths, although Mg vivianite was identified
in 5 enteroliths, and there were variable quantities of
Na, S, K, and Ca in the struvite within enteroliths.
Despite an abundance of Ca in colonic fluids, Mgphosphate
minerals were preferentially formed, compared
with Ca-phosphates (apatite), in equine
Conclusions and Clinical Relevance—Enteroliths
comprise 2 major Mg phosphates: struvite and Mg
vivianite. There is wide variability in macrotexture and
ionic concentrations between and within enteroliths.
(Am J Vet Res 2001;62:350–358)
Objective—To determine elemental composition of
teeth with and without odontoclastic resorption
lesions (ORL) in cats.
Sample Population—Normal teeth from 22 cadaver
cats and ORL-affected teeth from 21 cats admitted to
the veterinary hospital for dental treatment.
Procedure—An electron microprobe was used to
analyze weight percentages of calcium, phosphorus,
fluorine, sodium, magnesium, sulfur, potassium, and
iron in enamel, dentin, and cementum.
Results—Calcium and phosphorus were the most
abundant elements. Fluorine, sodium, and magnesium
combined were < 5% and sulfur, potassium,
and iron combined were < 0.1% of total elemental
composition. In enamel of normal teeth, a significant
sex-by-jaw location interaction was seen in mean
(± SD) phosphorus content, which was higher in
mandibular teeth of females (17.64 ± 0.41%) but
lower in mandibular teeth of males (16.71 ± 0.83%).
Mean iron content in dentin of normal teeth was significantly
lower in mandibular teeth than maxillary
teeth (0.014 ± 0.005% vs 0.023 ± 0.019%). Mean
enamel sodium content was significantly higher
(0.77 ± 0.046% vs 0.74 ± 0.025) and mean enamel
iron content was significantly lower (0.017 ± 0.008%
vs 0.021 ± 0.005%) in ORL-affected teeth, compared
with normal teeth. In cementum, mean fluorine content
was significantly lower (2.98% ± 0.27 vs 2.99 ±
0.20%) and mean magnesium content was significantly
lower (0.54 ± 0.13% vs 0.60 ± 0.13%) in ORLaffected
teeth, compared with normal teeth.
Conclusions and Clinical Relevance—Results of our
study establish baseline mineral content of enamel,
dentin, and cementum for normal teeth in cats.
Minimal differences in mineral content of enamel and
cementum of normal and ORL-affected teeth were
detected. (Am J Vet Res 2002;63:546–550)
Objective—To elucidate the ultrastructural details of
calcium oxalate-containing urinary calculi from dogs.
Sample Population—38 specimens selected from a
collection of 8,297 oxalate-containing urinary calculi
from dogs: 22 specimens composed of calcium
oxalate (calcium oxalate monohydrate [COM], calcium
oxalate dihydrate [COD], or COM and COD) and
16 specimens composed of calcium oxalate with
amorphous calcium phosphate.
Procedure—Analyses of specimens included use of
plain, reflected, and polarized light microscopy, X-ray
diffractometry, scanning electron microscopy (SEM)
with backscattered electron (BSE) imagery, and electron
Results—Four texture types were observed in calcium
oxalate calculi; 4 texture types of calcium oxalatecalcium
phosphate-mixed calculi were recognized.
Texture types were delineated through differences in
calcium oxalate crystal sizes, which were affected by
urine supersaturation and abundance of crystal nucleation
sites. Segregation of calcium oxalate from calcium
phosphate indicated they do not precipitate under
the same conditions. Deposition of calcium phosphate
between calcium oxalate crystals decreased
the volume of pore spaces within calculi. Porosity
was observed along boundaries between COM and
COD. Minute pores increased the surface area of calculi
exposed to urine, and this increase in liquid-solid
interface promotes interaction of crystals with the
Conclusions and Clinical Relevance—Calcium
oxalate urolithiasis is of major concern, because it is
often a recurrent disease among dogs, principally
treated by surgical removal of calculi, with few effective
dissolution strategies. Understanding the ultrastructure
and mineralogic content of calcium oxalate
and its association with amorphous calcium phosphate
is a step toward the solution of this increasingly
important medical problem. (Am J Vet Res