Results
Serum pancreatic (DGGR) lipase concentrations were measured in 205
equids. These included 42 ponies, 39 cobs/crosses, 34 sports horses, 26
warmbloods/crosses, 24 Thoroughbred/crosses, 15 Shetland
ponies/miniature horses, 12 heavy horses and 13 others (including 3
donkeys). There were 117 geldings, 84 females and 4 entire males. The
median age was 13 years (interquartile range [IQR] 9.5; range 0.3-36
years); only 3 horses were younger than 12 months of age. The degree of
pain at admission was categorised as mild in 158 animals, moderate in 40
and severe in 3; one animal showed no signs of pain at the time of
admission (but was painful at the time that referral was organised). The
median heart rate at admission was 52 bpm (IQR 16; range 32-100). The
major findings of FLASH ultrasound scans were unremarkable/normal in 114
animals; distended small intestines were recorded in 37, changes
compatible with colitis in 16, thickened small intestinal walls in 14,
excessive peritoneal fluid in 11, possible colonic displacement in 3,
abdominal mass/neoplasia in 3, haemoperitoneum in 2, gastric distension
in 2, intussusception in one, and liver abnormality in one (n=204).
Gastric reflux (>1 litre) was recorded in 15 horses
(range 1-25 litres). The final diagnosis categories were medical colic
(n=107), surgical colic/euthanased without surgery (n=53), colitis
(n=13), peritonitis (n=15) and other (n=6). The median duration of
illness prior to hospitalisation was 12 hours (range 2->100
hours). The outcomes of the cases were survived (n=147), euthanised
(n=47) and died (n=11).
The median white blood cell count was 7.2 x 109/L (IQR
4.55; range 1.2-35.6 x 109/L) (n=185), neutrophil
count 5.3 x 109/L (IQR 4.2; range 0.4-31.8 x
109/L) (n=185), packed cell volume 36.25% (IQR 16.6;
range 16.0-86.3) (n=196), serum Amyloid A concentration 13.95 mg/L (IQR
923; range 0-9900 mg/L) (n=186), total plasma protein concentration 60.0
g/L (IQR 10; range 26.0-86.0 g/L) (n=199), plasma albumin concentration
36.5 g/L (IQR 6.25; range 16.0-49.0 g/L) (n=186), plasma lactate
concentration 2.0 mmol/l (IQR 19.7; range 0-19.7 mmol/l) (n=144),
peritoneal nucleated cell count 1.4 x 109/L (IQR 3.9;
range 0.3-387.0 x 109/L) (n=122) and peritoneal
lactate concentration 0 mmol/L (IQR 20.7; range 0-20.7 mmol/L) (n=104).
There was a statistically significant association between the systemic
lactate concentration and severity of pain (p = 0.03). There were
statistically significant associations between all of the systemic
haematological/biochemical measurements and the type of colic (p
< 0.01, except WBC (p = 0.03)). There were statistically
significant associations between peritoneal lactate concentration (p =
0.01), blood lactate concentration (p = 0.02), albumin concentration (p
< 0.01) and PCV (p = 0.02), and survival of the colic episode.
The median serum pancreatic lipase concentration in all 205 horses was
17 U/L (IQR 14 – 27; range 1 – 3484). Using the methodology described
by Johnson et al (2019), the lipase concentration was categorised
as normal in 124 animals (60.5%) and elevated in 81 (39.5%) (mildly
elevated in 55 (26.8%), moderately elevated in 14 (6.8%) and severely
elevated in 12 (5.9%)). Serum lipase concentration was less than twice
the upper reference limit (<2x URL) in 178 and >2x
URL in 27 horses. There was no correlation between age and pancreatic
lipase concentration (Spearman’s rank: rho = 0.03; p = 0.68), and no
significant difference between the lipase concentration groups (normal,
mildly, moderately, or markedly elevated) and age (Kruskal-Wallis test;
p = 0.93), or between horses with lipase concentration < or
> 2xURL and age (Kruskal-Wallis tests: p = 0.62). There was
no significant difference in breed and lipase concentration
(Kruskal-Wallis tests p = 0.33 for lipase categories, and Chi-Squared
p=0.39 for < or > 2xURL), or in sex and lipase
concentration (Kruskal-Wallis tests p = 0.52 for lipase categories, and
Chi-squared p=0.33 for < or > 2xURL). There were
no significant associations between any of the haematological or
biochemical findings and the lipase concentration groups.
There was a statistically significant difference in the disease category
and pancreatic lipase concentration categories (Kruskal-Wallis test: p
< 0.001) as well as a significant difference between the
disease category and lipase concentration < or >
2xURL (Chi-squared p<0.01) , with colic cases having higher
lipase concentrations than colitis and peritonitis cases: medical
colics, n = 107, median lipase = 17 U/L (IQR 14 – 30); surgical colics
/euthanased, n = 53, median lipase = 21 U/L (IQR 16 – 32); colitis, n =
24, median lipase = 13 U/L (IQR 11 – 17); peritonitis, n = 15, median
lipase = 15 U/L (IQR 13 – 18); others, n = 6 median lipase = 84 U/L
(IQR 28 – 1094). There were statistically significant differences in
lipase concentrations between these disease categories (Dunn’s post-hoc
test) (Figure 1). Significant differences were present between medical
colic and colitis cases (p < 0.001), surgical colic and
colitis cases (P < 0.001), and surgical colic and peritonitis
cases (p = 0.02). There was no significant association between heart
rate and lipase concentration group (Kruskal-Wallis: p = 0.80) or
between heart rate and lipase concentration < or
> 2xURL (Kruskal-Wallis p=0.24), and no correlation between
heart rate and lipase value (Spearman’s rank: rho = 0.09; p = 0.21).
There was strong evidence of an association between pain severity and
lipase values (Kruskal-Wallis: p = 0.01) and between pain severity and
lipase concentration < or > 2xURL (Chi-squared
p=0.05), with higher lipase concentrations in horses with more severe
pain: mild pain, n = 158, median lipase = 17 U/L(IQR 14 – 25); moderate
pain, n = 40, median lipase = 19 U/L (IQR 15 – 47); severe pain, n = 4,
median lipase = 558 U/L (IQR 22 – 2186). There was no evidence of an
association between outcome (classified as survived, euthanasia or died)
and lipase concentration (Kruskal-Wallis: p = 0.36), however there was a
difference in outcome across lipase concentration groups categorised as
< or > 2xURL (Chi-squared p=0.04). There was no
difference in duration of colic between lipase concentration groups
(Kruskal-Wallis: p = 0.10) or lipase concentration categorised as
< or > 2x URL (Chi-squared p = 0.63).).
Differences were identified in pancreatic lipase concentration category
(Dunn’s post hoc test) for the following FLASH ultrasound findings: no
abnormalities vs colitis, p < 0.001; distended small
intestines vs colitis, p < 0.001; colitis vs colonic
displacement, p = 0.05. The median pancreatic lipase concentration of
horses with different findings on FLASH ultrasonography were as follows:
horses with no significant abnormalities on FLASH ultrasonography
(n=114) had a median pancreatic lipase concentration of 19
U\L (IQR 14 – 32) (98 horses had lipase < 2xURL
and 16 horses > 2xURL); median lipase concentration of
horses with colitis (n = 16) was 12 U/L (IQR 10 – 13) (16 horses had
lipase concentration < 2xURL and none with lipase
concentration > 2xURL); median lipase concentration of
horses with distended small intestines (n = 37) was 19 U\L
(IQR 15 – 32) (29 horses had lipase concentration < 2xURL and
8 had lipase concentration > 2xURL); median lipase
concentration of horses diagnosed with a potential colonic displacement
on FLASH ultrasound (n = 3) was 25 U\L (IQR 22 – 36) (all
3 horses had lipase concentration < 2xURL). Of the 12 horses
with severely increased pancreatic lipase concentration on admission,
3/12 (25.0%) had spontaneous nasogastric reflux (spontaneous
nasogastric reflux was not recorded in any of the other 193 equids),
6/10 (60.0%) had distended and/or thickened small intestine on
abdominal ultrasonography (not performed in 2 cases), 7/12 (58.3%)
survived to hospital discharge, and 5/12 (41.7%) died or were
euthanised (in 2 cases surgery was recommended but the owners opted for
euthanasia for financial reasons). Overall, 15/205 equids (7.3%) had
reflux (> 1 litre) either spontaneously or on passage of
a nasogastric tube recorded at admission. Four of these (26.7%) had
normal pancreatic lipase concentrations, 6 (40.0%) had mildly elevated
concentrations and 5 (33.3%) had severely elevated concentrations. In
total, therefore, 11 of 15 (73%) horses that had gastric reflux
identified at admission to the hospital had elevated serum pancreatic
lipase concentrations. 21 of 51 horses (41%) where FLASH scanning
identified distended small intestines or thickened small intestinal
walls had elevated serum pancreatic lipase concentrations (12 mildly
elevated, 3 moderately elevated and 6 severely elevated). The final
diagnoses in 10 animals with severely increased serum pancreatic lipase
concentrations where a diagnosis was reached included non-specific colic
(n=4), enteritis (n=2), grain overload (n=1), post-foaling colic and
neuropathy (n=1), epiploic foramen entrapment (n=1) and colon torsion
(n=1).
Repeated analyses for pancreatic lipase were performed in 15 animals
(Table 1). In 11 of these horses that had a serum pancreatic lipase
concentration > 21 U/L on admission to the hospital, the
concentration reduced in subsequent samples (following surgical or
medical treatment and resolution of the abdominal pain).