INTERNAL MEDICINE
No biochemical or haematological changes are spe-
cific indicators although ALP is most consistently ele-
vated (93%).
Sludge within the gall bladder is commonly seen dur-
ing ultrasound examination of the abdomen and is
defined as the presentation of gravity dependent non
shadowing echogenic material within the lumen (Fig. 2).
Figure 2: Gall bladder sludge visualised ultrasonographically
Biliary sludge is a common finding in dogs and there
was no difference in its presence between healthy
dogs, those with hepatobiliary disease and those with
other disease conditions. Biliary sludge is abnormal
in cats and an indicator of disease. Dogs with biliary
sludge have decreased gall bladder motility when
compared to dogs without biliary sludge. A recent ar-
ticle evaluated the progression of biliary sludge in 42
dogs: biliary sludge was classified as mild (50%) mod-
erate (36%), moderate to severe 9% and severe (5%).
This study found that biliary sludge persisted in 88%
of dogs and did not significantly increase or become
more organised in a 12-month period. By the end of
the study 29% of dogs had more sludge filling their
gall bladders and 24% had developed some form of
nondependent (adhered) sludge. All these dogs were
asymptomatic. This is in contrast to humans where
biliary sludge may resolve in 17%, be recurrent in 60%
and persistent in only 8% of patients
This information indicates that biliary sludge may not
be a benign process as previously thought but an
early manifestation changes which will progress to a
GBM which is a slow insidious process. The develop-
ment of biliary sludge is promoted by decreased gall
bladder motility and emptying as well as alterations of
bile characteristics and mucus hypersecretion.
Approximately 13.5% of GBM have bactibilia (bacterial
colonisation). Most pathogens cultured in dogs with
gall bladder diseases are polymicrobial aerobic infec-
tions. In the majority of patients where culture was
positive there was either necrosis or necrosis and rup-
ture of the gall bladder wall. GBM is not a risk factor
for bacterial cholecystitis. Infection is also not a risk
for gall bladder surgery.
Figure 3: Typical ultrasonographic appearance of a gall bladder
mucocoele
A GBM has immobile/adhered bile content with a
range of ultrasonographic presentations, from finely
striated stellate pattern to a Kiwi-fruit appearance and
retracted from the gall bladder (Figure 3) . Progres-
sive expansion of the GBM causes severe gall bladder
distension and may lead to ischaemic necrosis in the
wall. Ultrasonographically gall bladder wall necrosis
will be indicated by a discontinuous gall bladder wall,
echogenic free peritoneal fluid - initially only in the
gall bladder fossa, a thickened or laminated gall blad-
der wall and an echogenic reaction in the gall bladder
fossa.
The common bile duct is normally not visualised, it
should be < 3mm in diameter in the dog. A study has
shown that the ultrasound pattern of a GBM, they
classified 6 patterns, was not associated with clinical
signs and is thus not a valid diagnostic tool for grad-
ing disease.
Cystic mucousal hyperplasia is the most consistent
microscopic change and gall bladder wall necrosis
has been described in 80% of GBM. Varying degrees
of fibrosis, haemorrhage and necrosis are also seen.
The physical appearance of the gall bladder epitheli-
um changes in GBM. In normal gall bladders mucousal
folds are prominent with many sub-epithelial glands.
In GBM cases the epithelial folds were flattened and
consisted of slender fronds of epithelium. Sub-epithe-
lial glands were absent but all epithelial cells however
did appear to be producing mucin.
Associated Conditions
Hyperlipidaemia, hypercholesterolaemia, hyperadren-
ocorticism and hypothyroidism are speculated to pro-
mote the formation of biliary sludge
Cushings Disease
Dogs with hyperadrenocorticism are 29X more likely
to have a GBM and comprise approximately 23% of
the GBM population. In a study with iatrogenic hyper-
cortisolaemia a reversible shift in bile acid composi-
tion towards more cytotoxic, hydrophobic, unconju-
Issue 05 | OCTOBER 2017 | 9