Colic in equine neonates 137 cases (20002010) MACKINNON, 2013

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Colic is a common problem of equine neonates.1,2 It is generally accepted that most neonates referred to a 
hospital for colic can be managed medically2; however, 
this has not been documented in foals < 30 days old. In 
neonates, the most common types of colic that can be 
resolved medically include meconium-associated colic, 
colic caused by enterocolitis (including necrotizing en-
terocolitis), and medical colic of unknown etiology.3,4 
Enterocolitis caused by Clostridium perfringens, Clostrid-
ium difficile, Salmonella spp, rotavirus, and coronavirus 
have all been reported in equine neonates.3,5–8 Colic in 
equine neonates is often complicated by concurrent dis-
ease, which may impact morbidity and mortality rates.2 
The relationship between colic and concurrent disease 
and its impact on survival rate has not been explored 
in equine neonates. It is not unusual for a neonate with 
medical colic to develop a lesion requiring surgical inter-
vention, such as when a foal with enterocolitis develops 
a small intestinal volvulus or intussusception.2,9
Colic in equine neonates: 137 cases (2000–2010)
Melissa C. MacKinnon, DVM, DACVS; Louise L. Southwood, BVSc, PhD, DACVS, DACVECC; 
Megan J. Burke, DVM; Jonathan E. Palmer, VMD, DACVIM
Objective—To document causes of colic in equine neonates, evaluate clinical features of 
neonates managed medically versus surgically, determine short- and long-term survival 
rates for neonates with specific medical and surgical lesions, and assess ability of patients 
to achieve intended use.
Design—Retrospective case series.
Animals—137 client-owned equine neonates (< 30 days old) with a history of colic or signs 
of colic within 1 hour after hospital admission examined between 2000 and 2010.
Procedures—Signalment, history, results of physical examination, laboratory data, ancillary 
diagnostic tests, details of treatment, primary diagnosis, concurrent diseases and short-
term survival rate were obtained from the medical records. Long-term follow-up informa-
tion was obtained through phone survey.
Results—137 neonates with colic were included. The majority (122 [89%]) of neonates 
were managed medically. The 3 most common diagnoses associated with colic were en-
terocolitis (37 [27%]), meconium-associated colic (27 [20%]), and transient medical colic 
(26 [19%]). The most common reason for surgery was small intestinal strangulating ob-
struction, and these neonates were more likely to have severe, continuous pain and were 
less responsive to analgesics. Concurrent diseases were common (87 [64%]) but did not 
significantly impact survival rate. Short-term survival rate was not significantly different 
between medically (75%) and surgically (73%) managed neonates. Long-term survival rate 
was excellent (66/71 [93%]) for horses that survived to hospital discharge. Most neonates 
surviving to maturity were used as intended (49/59 [83%]).
Conclusions and Clinical Relevance—Most neonates examined for signs of colic can be 
managed medically. Short-term survival rate in medically and surgically treated neonates 
was good. Long-term survival rate of foals discharged from the hospital was excellent, with 
most achieving intended use. (J Am Vet Med Assoc 2013;243:1586–1595)
Patients that require surgical management include 
those with SISO, intestinal atresia, uroperitoneum, and 
meconium-associated colic (when medical management 
is unsuccessful).10 The decision to pursue medical ver-
sus surgical treatment when examining an equine neo-
nate with signs of colic can be particularly challenging. 
Features of certain diseases make differentiating between 
medical and surgical lesions difficult because there can be 
considerable overlap in clinical signs, a preponderance 
of serious medical conditions, concurrent diseases, and 
development of a surgical lesion during medical manage-
ment. These are confounded by the need for early surgical 
treatment to ensure a successful outcome and the report-
edly high complication and low survival rates with sur-
gery.2,9,11,12 The importance of timely surgical intervention 
was highlighted by Cable et al12 who suggested a decrease 
in short-term survival rate with longer duration of clinical 
signs before initial evaluation. Most previous reports9,11,12 
on colic in neonates have focused only on foals undergo-
ing abdominal surgery or specific medical conditions6–8,13 
and have not compared clinical features of foals evaluated 
for colic with medical versus surgical lesions.
From the Department of Clinical Studies, New Bolton Center, Univer-
sity of Pennsylvania, Kennett Square, PA 19348. Dr. MacKinnon’s 
present address is Milton Equine Hospital, 10207 Guelph Line RR 
No. 1, Campbellville, ON L0P 1B0, Canada.
Presented in part in poster form at the 10th Equine Colic Research 
Symposium, Indianapolis, July 2011. 
The authors thank Dr. Helen Aceto for statistical advice.
Address correspondence to Dr. MacKinnon (melissa.c.mackinnon@
gmail.com).
ABBREVIATIONS
SISO Small intestinal strangulating obstruction
TCO
2
 Total carbon dioxide
TPP Total plasma protein
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There is a lack of consistency in the literature eval-
uating exploratory celiotomy in foals and young horses. 
Some reports include only patients with gastrointesti-
nal disease,9,14 whereas others include gastrointestinal 
as well as urogenital problems.11,12,15 The definition of 
foal or neonate is also variable, and ages range from 2 
weeks to < 1 year, making comparison between studies 
and application of published results to specific patients 
difficult.
Survival rates for foals and young horses undergo-
ing abdominal surgery are generally considered not as 
favorable as current survival rates for mature horses. 
Overall short-term survival rate (ie, rate of survival 
to hospital discharge) in foals and young horses is re-
ported to be between 61% and 85%,9,11,12,14,15 and overall 
short-term survival rates for neonates specifically vary 
between 25% and 75%.9,11,12,14 Long-term survival rate 
(ie, rate of survival to 6 months to 2 years after surgery) 
in foals and young horses that survived to discharge is 
reported to be between 53% and 69%.9,11,12,15 In neo-
nates surviving to discharge, long-term survival rate 
is reported to be between 33% and 75%.9,11,14 Survival 
rates for adult horses requiring colic surgery have im-
proved substantially over the past 15 to 20 years (short-
term survival rate, 70% to 95%; long-term survival rate 
for horses discharged, 68% to 84%).16–20 However, no 
recent studies have evaluated short- and long-term sur-
vival rates, complications, and ability to be used for in-
tended purpose in neonates with colic.
The objectives of the study reported here were to 
document causes of colic in equine neonates (< 30 days 
old) and the occurrence of concurrent diseases, evalu-
ate clinical features of neonates managed medically ver-
sus surgically, determine the short-and long-term sur-
vival and complication rates for specific medical and 
surgical lesions including reasons for nonsurvival, and 
assess ability to achieve intended use of equine neo-
nates with colic.
Materials and Methods
Medical records of neonates < 30 days old at the 
time of admission to the University of Pennsylvania 
School of Veterinary Medicine New Bolton Center be-
tween January 2000 and August 2010 were reviewed. 
Study inclusion criteria were a history of colic signs 
prior to initial examination or developing signs of colic 
within 1 hour after hospital admission. Neonates were 
excluded if they did not have a history of colic signs, 
developed colic signs > 1 hour after admission, or were 
≥ 30 days old at admission or if the record was not 
available for review. Signs of colic were defined as an 
indication of abdominal discomfort, including rolling, 
flank watching, kicking at the abdomen, tailflagging, 
and painful posture.
Information obtained from the medical record in-
cluded details of signalment (age at admission, breed, 
and sex), history (initial clinical signs, history of colic, 
duration of colic prior to admission, whether the neo-
nate passed meconium, and analgesics administered 
prior to admission), and physical examination at hospi-
tal admission (rectal temperature, heart rate, respiratory 
rate, mucus membrane color and moistness, capillary 
refill time, intestinal borborygmi, abdominal disten-
sion, diarrhea, fecal production, colic signs, and naso-
gastric reflux). Continuous colic signs were defined as 
colic signs that persisted and failed to resolve with anal-
gesic administration. The severity of colic signs (mild, 
moderate, or severe) was recorded from the record. In 
general, mild colic was consistent with occasional or 
transient signs of abdominal discomfort that included 
but were not limited to flank watching, kicking at the 
abdomen, or tail flagging. Moderate colic was consis-
tent with intermittent but recurrent signs of abdominal 
discomfort including flank watching, kicking at the ab-
domen, lying down, and occasional rolling and gener-
ally required analgesic administration. Severe signs of 
colic were continuous and generally not responsive to 
analgesic administration. Persistent rolling was a com-
mon manifestation of severe colic signs. The mucous 
membrane characteristics on physical examination at 
admission were classified as normal or abnormal. Nor-
mal mucous membranes were defined as pink or light 
pink in color, moist, and having a capillary refill time ≤ 
2 seconds. All other mucous membrane characteristics 
were classified as abnormal. Abnormal membranes in-
cluded those that were injected, toxic, pale, tacky, or dry 
and those with prolonged capillary refill time. Intestinal 
borborygmi at hospital admission were characterized as 
normal, decreased, absent, or increased. Intestinal bor-
borygmi were considered normal if the usual variety 
and sounds were ausculted at regular short intervals. 
Decreased borborygmi were defined as intermittent or 
infrequent intestinal sounds. Borborygmi were consid-
ered absent if no sounds were heard on routine auscul-
tation of the abdomen. Increased intestinal borborygmi 
were defined as continuous loud sounds.
Laboratory data evaluated included blood glucose 
and lactate concentrations; PCV; TPP concentration 
including albumin, globulin, and fibrinogen concen-
trations; total WBC count, mature and immature neu-
trophil counts, and lymphocyte counts; toxic changes 
in neutrophils; plasma creatinine concentration; elec-
trolyte and acid-base changes; and IgG concentration. 
Findings from ancillary diagnostic tests including digi-
tal rectal examination, abdominocentesis and peritone-
al fluid analysis, fecal evaluation including Salmonella 
PCR assay and culture and ELISA for C perfringens en-
terotoxin and C difficile A and B toxins, bacteriologic 
culture of blood and antimicrobial susceptibility test-
ing, and abdominal ultrasonographic examination were 
recorded.
Neonates were classified as being managed medi-
cally or surgically. Details of treatments that were 
evaluated included antimicrobial drugs used, IV fluid 
therapy, IV plasma administraiton, parenteral nutrition, 
analgesic drugs used, and enemas performed. When 
neonates were treated surgically, lesion location, type of 
lesion, surgical procedure performed, and any intraop-
erative complications were documented. The need for 
a repeated celiotomy and findings during the repeated 
celiotomies were noted.
The final primary diagnosis associated with the 
signs of colic and any concurrent diseases and compli-
cations were recorded. The final primary diagnosis as-
sociated with the signs of colic used for each case was 
recorded in the medical record. In general, the following 
criteria were used to make the diagnosis. The primary 
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clinical sign for neonates with enterocolitis was diar-
rhea with or without gastroduodenal reflux or intoler-
ance to enteral feeding. Neonates with enterocolitis did 
not have signs or ultrasonographic findings consistent 
with necrosis of the intestinal wall. Neonates with nec-
rotizing enterocolitis had ultrasonographic, surgical, 
or postmortem evidence of pneumatosis intestinalis21 
with or without gastroduodenal reflux (may have con-
tained fresh or digested blood), intolerance to enteral 
feeding, and diarrhea (may have been hemorrhagic). 
When meconium-associated colic was diagnosed, clini-
cal signs were consistent with 1 of 2 clinical situations. 
The first included meconium impaction with persis-
tent signs of colic, abdominal distension, tail flagging, 
straining, frequent attempts to pass feces, decreased to 
absent fecal production, and meconium palpable on 
digital rectal examination, abdominal palpation, visu-
alized on ultrasonographic examination, or both. The 
second included meconium retention with decreased 
to absent fecal production and, after 48 hours of age, 
meconium palpable on digital rectal examination, ab-
dominal palpation, and visualized on ultrasonographic 
examination. The neonates with meconium retention 
in this study had episodic colic responsive to enemas. 
Neonates with clinical signs and diagnostic findings not 
consistent with enterocolitis, necrotizing enterocolitis, 
or meconium-associated colic and, without a confirmed 
diagnosis, were considered to have transient medical 
colic of unknown etiology. The presence of concur-
rent diseases as recorded in the medical record by the 
clinician treating the case was noted. Although the 
diagnosis made by the attending clinician at the time 
of hospitalization was honored, the following criteria 
were generally used by these clinicians. A diagnosis of 
neonatal encephalopathy was made when a foal < 72 
hours of age developed behavioral changes, inadequate 
responsiveness, poor muscle tone, and signs of brain-
stem disease as well as other neurologic signs including 
the occurrence of seizure-like behavior. A diagnosis of 
neonatal nephropathy was made when there was a de-
layed decrease in birth serum creatinine concentration, 
compared with normal age-matched concentrations; 
increases in blood creatinine concentrations; oliguria 
or anuria; or abnormalities seen on urinalysis during 
the first 5 days after birth.
Outcome variables were short- and long-term surviv-
al rates. Short-term survival was defined as survival to dis-
charge from the hospital. When neonates were euthanized 
or died, reasons for death were recorded. Long-term sur-
vival was assessed through phone survey of owner, trainer, 
or referring veterinarian at least 14 months following hos-
pital discharge. Information obtained included details re-
garding duration of follow-up, status (live or dead), colic 
episodes after discharge, long-term complications associ-
ated with reason for hospitalization, whether foal reached 
intended use, and satisfaction with outcome. Only neo-
nates discharged from the hospital were considered for 
analysis of long-term survival. Long-term survivors were 
included if survival information was available until they 
were at least 12 months of age. The circumstances of death 
at any age after discharge from the hospital were recorded. 
Not all data were available for every equine neonate in-
cluded in the study.
Statistical analysis—Continuous data (admission 
rectal temperature, heart and respiratory rates, results 
of hematologic evaluation, and plasma biochemical 
profile) were analyzed via 1-way ANOVA to determine 
the association with short-term survival (alive vs dead 
at hospital discharge), medical versus surgical treat-
ment, and lesion type (transient medical colic, meconi-
um-associated colic, enterocolitis, necrotizing entero-
colitis, SISO, and other). Statistical softwarea was used 
for all analyses. A Bartlett test for homogeneityof vari-
ance was performed. If the data did not have an equal-
ity of variance, a Welch ANOVA was used to analyze 
the data.a When either the 1-way or Welch ANOVA was 
significant for the variables tested, a Bonferroni (Dunn) 
t test for multiple comparisons was performed to de-
termine differences for individual lesion types. When 
multiple comparisons between values were performed, 
the highest P value was reported. The level of signifi-
cance was P < 0.05. Data were tested for normality by 
inspection of skewness and kurtosis for each variable 
and by application of the Shapiro-Wilk test for normal-
ity. Data are presented as mean ± SD for normally dis-
tributed data or median and interquartile range (25th 
and 75th percentile) for nonnormally distributed data.
Categorical data were analyzed via a χ2 test. When 
there were < 5 values/cell, a Fisher exact test was used. 
Data are presented as percentages, and level of signifi-
cance was P < 0.05.
Results
One hundred thirty-seven neonates met the inclu-
sion criteria. The median age was 2 (range, 0 to 28) 
days. The majority of the neonates were Thoroughbreds 
(72/137 [53%]) or Standardbreds (28/137 [20%]). 
There were 76 (55%) colts and 61 (45%) fillies. Most 
neonates were admitted with a history of colic (125/137 
[91%]), and only 12 (9%) neonates developed signs of 
colic during the first hour of hospitalization. One hun-
dred twenty-two (89%) neonates were managed medi-
cally, and 15 (11%) were managed surgically. The medi-
an duration of hospitalization was 5 days, with a range 
of 0 to 35 days.
Primary diagnosis and concurrent disease—There 
were 37 (27%) neonates with enterocolitis, 27 (20%) 
neonates with meconium-associated colic, 26 (19%) 
neonates with transient medical colic of unknown eti-
ology, 22 (16%) neonates with necrotizing enterocoli-
tis, 11 (8%) neonates with an SISO, 2 (2%) neonates 
with septic peritonitis, 2 (1.5%) neonates with overo 
lethal white syndrome, and 10 (7%) neonates with le-
sions categorized as other. The neonates with a SISO 
consisted of 9 neonates with small intestinal volvulus, 
1 neonate with a proximal jejunal intussusception, and 
1 with a segment of jejunum strangulated through a 
mesenteric rent. The 2 neonates with septic peritonitis 
had a perforated gastric ulcer (n = 1) and ruptured ura-
chus (1). Diseases in neonates with lesions categorized 
as other included urinary pain associated with a hema-
toma in the bladder (n = 1), diaphragmatic hernia with 
fractured ribs (1), gastric ulcers (1), inguinal hernia 
(1), lactose intolerance (1), perirectal abscess with sec-
ondary fecal retention (1), dysphagia and aerophagia 
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(1), fecalith with sand colopathy (1), and foreign body 
(sand [1] and bark [1]).
Neonates with a SISO were significantly (P < 0.05) 
more likely to have severe pain (6/11 [55%]) than neo-
nates with transient medical colic (0/26 [8%]), meco-
nium-associated colic (2/27 [7%]), other colic (1/10 
[10%]), enterocolitis (1/37 [3%]) or necrotizing en-
terocolitis (4/22; [18%]). Neonates with SISO were also 
more likely (P < 0.001) to have continuous pain (6/11 
[55%]), compared with neonates with transient medi-
cal colic (0/26 [0%]), meconium-associated colic (1/27 
[4%]), other colic (1/9 [11%]), enterocolitis (2/37 
[5%]), and necrotizing enterocolitis (4/22 [18%]). Few-
er (P < 0.01) neonates with SISO responded to analgesic 
medications (2/9), compared with neonates with tran-
sient medical (7/8), meconium-associated (13/15), oth-
er colic (3/4), and enterocolitis (12/12). In the hospital, 
butorphanol was used as required for analgesia (0.02 to 
0.04 mg/kg [0.009 to 0.018 mg/lb], IM or IV). Abdomi-
nal distension was more frequently (P < 0.05) observed 
in neonates with SISO (10/11 [91%]), meconium-asso-
ciated colic (26/27 [96%]), and necrotizing enteroco-
litis (16/22 [73%]) than in neonates with enterocolitis 
(10/37 [27%]), transient medical colic (11/26 [42%]), 
and other colic (2/10 [20%]). Neonates with SISO (7/9 
[78%]) and necrotizing enterocolitis (14/19 [74%]) 
were more likely to have abnormal oral 
mucous membranes than were neonates 
with transient medical (8/26 [31%]), 
meconium-associated (5/26 [19%]), or 
other colic (2/10 [20%]; P < 0.02) but 
not enterocolitis (20/37 [54%]; P = 0.2).
There was a significant association be-
tween primary diagnosis and age at admis-
sion (P = 0.002), blood glucose (P < 0.001; 
Figure 1) and lactate concentrations (P < 
0.001; Figure 2), TPP (P = 0.008), fibrino-
gen concentration (P = 0.02), nonsegmented 
neutrophils (P = 0.04), sodium (P < 0.001) 
and chloride (P = 0.002) concentrations, 
and TCO
2
 (P = 0.01). Neonates with primary 
diagnoses categorized as other were sig-
nificantly older (median, 12.5 days [range, 
2.8 to 15.0 days]) than neonates with tran-
sient medical colic (1.0 days), meconium- 
associated colic (median, 1.0 day [range, 
1.0 to 2.0 days]), enterocolitis (median, 
2.5 days [range, 2.0 to 3.0]), and necrotiz-
ing enterocolitis (median, 2.0 days [range, 
1.0 to 2.0 days]). Neonates that had more 
severe lesions generally had a lower blood 
glucose and higher blood lactate concen-
tration. Neonates with enterocolitis had a 
higher TPP (6.0 ± 1.0 g/dL), compared with 
neonates with transient medical colic (5.2 
± 0.9 g/dL) and SISO (5.0 ± 0.6 g/dL), and 
had a higher fibrinogen concentration (531 
mg/dL [range, 360 to 508 mg/dL]), com-
pared with neonates with transient medical 
colic (293 mg/dL [range, 239 to 362 mg/
dL]), meconium-associated colic (306 mg/
dL [range, 248 to 396 mg/dL]), and SISO 
(292 mg/dL [range, 257 to 333 mg/dL]). 
Neonates with SISO had a higher plasma sodium concen-
tration (137.6 ± 4.5 mEq/L) than did neonates with meco-
nium-associated colic (130.9 ± 5.6 mEq/L). Neonates with 
septic peritonitis had a significantly lower TCO
2
 (14.2 ± 9.5 
mmol/L) than did neonates with transient medical colic 
(29.7 ± 4.1 mmol/L), meconium-associated colic (31.1 ± 
2.6 mmol/L), other colic (29.3 ± 5.1 mmol/L), and nec-
rotizing enterocolitis (28.0 ± 6.6 mmol/L), and neonates 
with enterocolitis (24.5 ± 6.8 mmol/L) had a lower TCO
2
 
than did neonates with medical and meconium-associated 
colic.
A transcutaneous abdominal ultrasound exami-
nation was performed in 99 of 136 (73%) neonates. 
Sonographically, distended SI with reduced motility 
was observed more frequently (P < 0.01) in neonates 
with SISO (9/10 [90%]), enterocolitis (14/21 [67%]), 
and necrotizing enterocolitis (13/20 [65%]), compared 
with neonates with meconium-associated colic (3/24 
[13%]). Fluid filled large intestine was observed more 
frequently (P < 0.001) in neonates with enterocoli-
tis (11/21 [52%]) and necrotizing enterocolitis (9/20 
[45%]), compared with neonates with SISO (0/9 [0%]) 
and meconium-associated colic (1/24 [4%]). Only neo-
nates with necrotizing enterocolitis were described as 
having thickened large intestine. Most neonates with 
SISO had thickened SI (7/10 [70%]), which was not sig-
Figure 1—Box-and-whisker plots showing the association between blood glucose con-
centration (mg/dL; y-axis) and lesion type (x-axis) for 137 client-owned equine neonates (< 
30 days old) with a history of colic or signs of colic within 1 hour after hospital admission 
on the basis of clinical diagnosis. EC = Enterocolitis. Meconium = Meconium-associated 
colic. Medical = Medical colic. NEC = Necrotizing enterocolitis. Overo = Overo lethal 
white syndrome. For each plot, the box represents the interquartile (25th to 75th per-
centile) range, the horizontal line in the box represents the median, the cross in each box 
represents the mean, the whiskers the minimum and maximum values, and the asterisks 
represent outliers. a–dValues with different letters are significantly (P < 0.05) different.
Figure 2—Box-and-whisker plots showing the association between blood lactate concen-
tration (mmol/L; y-axis) and lesion type (x-axis)for the patients in Figure 1. a–cValues with 
different letters are significantly (P < 0.05) different. See Figure 1 for remainder of key.
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nificantly different from neonates with necrotizing en-
terocolitis (11/20 [55%]) or enterocolitis (7/21 [33%]) 
but significantly (P < 0.05) more frequent than in neo-
nates with transient medical (0/15 [0%]), meconium-
associated (5/24 [21%]) and other (0/7 [0%]) colic.
Identification of an etiologic agent in neonates 
that had fecal analysis performed was not consistent. 
Twenty-nine neonates had enterocolitis with no etio-
logic agent isolated, 3 neonates had enterocolitis with 
C perfringens enterotoxin identified, 2 neonates had 
enterocolitis with C difficle A and B toxins identified, 
2 neonates had enterocolitis with both C perfringens 
enterotoxin and C difficle A and B toxins identified, 
and 1 neonate had enterocolitis with Salmonella spp 
identified. Sixteen neonates had necrotizing enterocoli-
tis with no etiologic agent isolated. Two neonates with 
necrotizing enterocolitis had positive results of culture 
for C difficile A and B toxins, 3 had positive results for 
C perfringens enterotoxin, and 1 had positive results 
for both C difficile and C perfringens toxins. A single 
neonate with transient medical colic, another with me-
conium-associated colic, and one with SISO also had 
positive culture results for C difficile A and B toxins.
Two of the neonates with enterocolitis had con-
current gastrointestinal disease, including one neonate 
with gastric ulceration and another with gastroduode-
nal ulceration syndrome, duodenal stricture, and a per-
forated gastric ulcer with focal peritonitis, which devel-
oped during treatment. One neonate with necrotizing 
enterocolitis had concurrent gastrointestinal disease 
(stricture of the distal jejunum secondary to necrotiz-
ing enterocolitis) and did not survive. One neonate 
with SISO had concurrent enterocolitis on necropsy. 
No neonates with transient medical colic or meconium- 
associated colic had concurrent gastrointestinal disease.
Concurrent systemic disease was present in 87 
of 137 (64%) neonates. Most neonates had 1 (34/87 
[39%]) or 2 (26/87 [30%]) concurrent diseases. The 
proportion of neonates with concurrent disease was 
similar between different primary diagnosis groups. 
The 5 most common concurrent diseases in descend-
ing order were sepsis (42/87 [48%]), neonatal encepha-
lopathy (26/87 [30%]), neonatal nephropathy (24/87 
[28%]), failure of passive transfer of maternal antibod-
ies (19/87 [22%]), and umbilical remnant infection or 
patent urachus (14/87 [16%]).
Medical or surgical management—Nineteen foals 
had what would be considered a surgical lesion: small 
intestinal volvulus (n = 9), meconium-associated colic 
refractory to medical management (3), jejunum incar-
cerated in a mesenteric rent (1), jejunal stricture (1), 
jejunal intussusception (1), diaphragmatic hernia and 
rib fractures (1), fecalith in small colon and large colon 
sand impaction (1), inguinal hernia (1), and ruptured 
urachus with peritonitis (1). Eleven of these foals un-
derwent surgical management. The surgical procedures 
performed in the 11 foals included exploratory celioto-
my (n = 8); exploratory celiotomy and small intestinal 
resection and anastomosis (1); exploratory celiotomy, 
diaphragmatic herniorrhaphy, and fractured rib repair 
(1); and castration with inguinal herniorrhaphy (1). 
None of the surgically managed foals in the study had a 
second exploratory celiotomy. Four foals with types of 
colic usually managed medically underwent explorato-
ry celiotomy. Two had severe necrotizing enterocolitis: 
one with a perforated gastric ulcer with peritonitis and 
the other with enterocolitis. The only intraoperative 
complication occurred during repair of the diaphrag-
matic hernia and rib fractures, in which the foal de-
veloped a tension pneumothorax, which was managed 
with aspiration of the air from the thoracic cavity.
In general, there was little association between signs 
of pain, physical examination findings, laboratory data, 
ultrasonographic findings, and whether the foal under-
went surgery. There was a significant (P = 0.045) associa-
tion between surgery and plasma chloride concentration; 
foals undergoing surgery had a lower plasma chloride 
concentration (92.8 ± 7.0 mmol/L), compared with foals 
managed medically (96.2 ± 6.1 mmol/L). No foals with 
diarrhea (0/43 [0%]) underwent surgery, compared with 
14 of 91 (15%) foals without diarrhea (P = 0.005).
Medical management alone was used in 36 (97%) 
neonates with enterocolitis, 20 (91%) neonates with 
necrotizing enterocolitis, 25 (100%) neonates with 
transient medical colic, and 24 (89%) neonates with 
meconium-associated colic. The type of medical man-
agement (including medical management of postopera-
tive neonates) used for each neonate was decided on 
the basis of clinical judgment and clinician preference. 
Antimicrobial agents were used in 114 of 125 (91%) 
neonates. Ceftiofur (10 mg/kg [4.5 mg/lb], IV q 6 h 
over 20 minutes) was the most commonly administered 
antimicrobial agent (74/114 [65%]). Neonates had re-
stricted access to mares (96/136 [70%]), and a subset of 
neonates were given nothing by mouth (75/136 [55%]) 
for a period of time defined by response to treatment. 
Intravenous fluid therapy for resuscitation or mainte-
nance was administered to 113 of 137 (82%) neonates 
and 85 of the 112 (76%) neonates that received IV fluid 
therapy and dextrose supplementation. Total parenteral 
nutrition was administered to 38 of 134 (28%) neo-
nates and plasma was administered to 66 of 135 (49%). 
An enema was performed in 43 of 135 (32%) neonates. 
A warm soapy water enema was the most common type 
(42/42 [100%]), and an acetylcystine retention enema 
was performed infrequently subsequent to an unpro-
ductive warm soapy water enema in 7 of 42 (17%) pa-
tients. Repeated doses of analgesics were administered 
as required in 49 of 136 (36%) neonates.
Very few complications occurred during hospitaliza-
tion (7/137 [5%]). The complications included IV cathe-
ter–associated jugular thrombophlebitis (enterocolitis [n 
= 1] and meconium-associated colic [1]), skin reaction at 
the IV catheter insertion site (meconium-associated colic 
[1]), rhinitis from dysphagia (meconium-associated col-
ic [1]), transient diarrhea (small intestinal volvulus, [1]), 
laceration over the third metacarpus (enterocolitis [1]), 
and apnea, cardiac arrest, and transient postoperative re-
flux (small intestinal volvulus [1]). 
Short-term outcome—The overall short-term rate 
of survival to discharge from the hospital was (103/137 
[75%]) and was not significantly (P = 1.0) different be-
tween medically (92/122 [75%]) and surgically man-
aged (11/15 [73%]) neonates (Table 1). Severe signs of 
colic at admission were associated with a lower survival 
rate (6/15 [40%]), compared with the survival rate of 
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neonates with either none (42/51 [82%]) or mild (32/37 
[86%]) signs of colic (P = 0.001) but not moderate signs 
(23/34 [68%]; P = 0.07). Absent intestinal borborygmi 
was associated with a lower (P = 0.01) survival rate (2/7 
[29%]), compared with decreased (32/43 [74%]), nor-
mal (44/51 [86%]), or increased (21/26 [81%]) borbo-
rygmi. Neonates with abnormal oral mucous membranes 
had a lower (P < 0.001) survival rate (33/60 [55%]) than 
did neonates with normal oral mucous membranes 
(69/71 [97%]). Neonates with abdominal distension had 
a lower (P = 0.05) survival rate (53/77 [69%]) than did 
neonates with no abdominal distension (50/60 [83%]). 
Nonsurviving neonates had a significantly lower admis-
sion rectal temperature (P < 0.001), blood glucose con-
centration (P < 0.001), TPP (P = 0.001), and TCO2 (P = 
0.039) and higher blood lactate (P < 0.001) and plasma 
creatinine (P= 0.048) concentrations, compared with 
surviving neonates (Table 2).
Neonates with necrotizing enterocolitis and SISO 
were significantly less likely to survive to discharge than 
were those with enterocolitis, transient medical colic, 
meconium-associated colic, and other colic (Table 1). 
Foals with concurrent disease did not have a significantly 
(P = 0.06) lower survival rate (63/87 [72%]), compared 
with foals without concurrent disease (40/46 [87%]).
Four neonates that had surgical management were 
euthanized under general anesthesia because of a grave 
prognosis. The 4 neonates had severe necrotizing en-
terocolitis (n = 2), extensive nonviable small intestine 
owing to small intestinal volvulus (1), and a perforated 
gastric ulcer with peritonitis (1). All of the foals that 
were treated surgically and allowed to recover from 
general anesthesia survived to discharge (11/11).
Thirty neonates managed medically did not survive 
to discharge. Four neonates died, 8 were euthanized 
because of financial constraints (3 prior to treatment, 
3 when surgery was required, and 2 when they failed 
to respond to treatment), 4 because of both financial 
constraints and poor prognosis, and 14 owing to poor 
prognosis and failure to respond to medical manage-
ment. Because of the frequent occurrence of concurrent 
disease, the true contribution of the cause of the colic 
signs to the negative outcome could not be assessed.
Long-term outcome—Attempts were made to con-
tact 103 owners, trainers, or referring veterinarians by 
telephone or email to obtain long-term outcome in-
formation on neonates that were discharged from the 
hospital alive. Information on long-term outcome was 
obtained for 71 of 103 (69%) neonates. Of the 71 neo-
nates, 66 (93%) were alive and 5 (7%) were not alive at 
12 months of age. The median duration after discharge 
of long-term outcome information in the 66 neonates 
that were alive at 12 months of age was 33 months, with 
a range from 12 to 141 months. Three other deaths were 
reported after 12 months. There was only 1 complica-
tion after discharge associated with the exploratory ce-
liotomy, which was a small incisional hernia, and this 
did not affect outcome.
There were several causes of death in the 8 non-
survivors. Two nonsurvivors were euthanized 2 months 
after discharge: one due to a genetic renal defect (pri-
mary diagnosis during hospitalization foreign material 
enteropathy) and the other due to Salmonella-associated 
enterocolitis (primary diagnosis during hospitalization 
entercolitis with no etiologic agent isolated). Three non-
survivors were euthanized or died at approximately 6 
months of age. One was euthanized because of severe 
Rhodococcus equi pneumonia that was nonresponsive 
to treatment (primary diagnosis during hospitalization, 
meconium-associated colic), 1 was found dead in the 
field and necropsy confirmed an aneurysm (primary 
diagnosis during hospitalization, meconium-associated 
colic; surgical intervention, exploratory celiotomy), and 
1 was found dead in the field and a postmortem exami-
nation was not performed (primary diagnosis during 
hospitalization, gastric ulceration). Two nonsurvivors 
Diagnosis Surgical Medical Overall
Medical (n = 26) NA 22/26 (85) 22/26 (85)a
Meconium-associated colic 3/3 (100) 24/24 (100) 27/27 (100)a
 (n = 27)
Enterocolitis (n = 37) 1/1 (100) 31/36 (86) 32/37 (86)a
Necrotizing enterocolitis 0/2 (0)* 8/20 (40) 8/22 (36)b
 (n = 22)
SISO (n = 11) 4/5 (80)* 0/6 (0) 4/11 (36)b
Septic peritonitis (n = 2) 0/1 (0)* 0/1 (0) 0/2 (0)
Overo lethal white syndrome NA 0/2 (0) 0/2 (0)
 (n = 2)
Other (n = 10) 3/3 (100) 7/7 (100) 10/10 (100)a
All cases (n = 137) 11/15 (73)* 92/122 (75) 103/137 (75)
Data are the proportion (percentage) surviving.
*Nonsurvivors were neonates euthanized during surgery 
because of a grave prognosis; all foals that recovered from surgery 
survived to hospital discharge.
NA = Not applicable.
a,bValues with different superscript letters differed significantly 
(P < 0.05) between clinical diagnoses. 
Table 1—Short-term survival rate of 137 client-owned equine neonates 
(< 30 days old) with a history of colic or signs of colic within 1 hour 
after hospital admission grouped on the basis of clinical diagnosis.
 Nonsurvivors (n = 34) Survivors (n = 103) 
 Median Median
Admission data Mean ± SD (interquartile range) Mean ± SD (interquartile range)
Rectal temperature (°C) 38.38 ± 3.8 37.89 (37.3–38.61) 38.50 ± 2.0 38.61 (38.33–38.89)
Blood glucose (mg/dL) 91.4 ± 50.1 88.0 (42–133.5) 139.5 ± 34.4 140.6 (118.5–157.25)
Blood lactate (mmol/L) 8.2 ± 5.2 7.3 (2.3–12.6) 3.1 ± 2.6 2.4 (1.5–3.4)
TPP (g/dL) 5.1 ± 0.9 5.1 (4.6–5.5) 5.7 ± 0.9 5.6 (5.0–6.2)
Plasma creatinine (mg/dL) 5.0 ± 7.4 2.6 (1.7–5.4) 2.3 ± 2.6 1.6 (1.3–2.5)
TCO2 (mmol/L) 25.2 ± 7.3 26.3 (20.6–30.1) 28.4 ± 5.6 30.1 (26.8–32.0)
Table 2—Admission data that were significantly (P < 0.05) different between neonates that did and did 
not survive to hospital discharge.
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were euthanized at 3 years of age. One was euthanized 
as a result of severe equine protozoal myeloencephali-
tis (primary diagnosis during hospitalization, necrotiz-
ing enterocolitis), and the other was euthanized on the 
racetrack after sustaining a catastrophic musculoskeletal 
injury (primary diagnosis during hospitalization, meco-
nium-associated colic; surgical intervention, exploratory 
celiotomy). The remaining nonsurvivor was euthanized 
at 10 years old after having 3 successive colic surgeries 
(primary diagnosis during hospitalization, meconium-
associated colic). None of the neonates appeared to have 
died or were euthanized as a direct result of colic as a 
neonate; however, some of the reasons for death or eu-
thanasia may be loosely linked to illness as a neonate.
Survival to 12 months of age in neonates discharged 
from the hospital can also be examined for each primary 
diagnosis. Twenty of 21 (95%) neonates with entercolitis 
survived to 12 months of age. Of 19 neonates with meco-
nium-associated colic, 17 survived to 12 months of age. 
All 15 neonates with transient medical colic survived to 
12 months of age. All 4 neonates with necrotizing en-
terocolitis survived to 12 months of age. Eight of the 9 
neonates that underwent surgical treatment and were 
available for follow-up survived to 12 months of age.
Only 1 of 71 (1.4%) foals was reported to have an 
episode of colic during the first year of age. This animal 
had an episode 1 month and a second 13 months af-
ter discharge, but both episodes of colic were mild and 
responded to medical management in the field. Three 
other foals were reported to have episodes of colic af-
ter 12 months of age. Two had 1 episode each approxi-
mately 18 months after discharge, both of which were 
mild and responded to medical management in the 
field. The remaining horse was euthanized at 10 years 
old and did not have any colic episodes prior to the 
episode that lead to the animal undergoing the first ex-
ploratory celiotomy at 10 years of age.
The intended uses of the 71 neonates with avail-
able follow-up information in this study included race-
horse (48 [68%]), other athletic endeavors (15 [21%]), 
pleasure (6 [8%]), and breeding (2 [3%]). Of 59 ani-
mals, 49 (83%) were used as intended and 10 (17%) 
were not. Twelve were sold as yearlings, so it remains 
unknown whether they were used as intended. For the 
10 that did not perform at their intended use, 5 died or 
were euthanized prior to performance, 4 had soundness 
issues during training and never raced, and 1 did not 
meet expectations while training and never raced. Of 
the 49 animals that performed their intended use, 47 
(96%) performed at the expected age. Of the 2 horses 
that did not, one was small in stature, started late as a 
2 year old, and then raced well, and the other had time 
off as a 2 year old to mature and then raced but did not 
meet expectations.All owners or trainers were satisfied 
with the outcome from the initial hospital admission.
Discussion
In this retrospective study of 137 neonates (< 30 
days old) referred for treatment of colic over a 10-year 
period, the vast majority of patients (86%) had what 
are generally considered medically treatable condi-
tions: entercolitis (27%), meconium-associated colic 
(20%), transient medical colic of unknown etiology 
(19%), and necrotizing entercolitis (16%). The overall 
short-term survival rate was 75%, and this was not 
significantly different between medically (75%) and 
surgically (73%) managed neonates. The most com-
mon reason for surgery was SISO, and these patients 
were more likely to have severe, continuous pain and 
were less responsive to analgesics. Our results support 
the anecdotal belief that most neonates referred to a 
specialty hospital for colic do not require surgery. In 
our hospital, a previous study16 found that approxi-
mately 42% of mature nongeriatric (ie, 4 to 15 years 
of age) horses admitted for colic undergo exploratory 
celiotomy, which is higher than the 11% of neonates in 
the present study. Geriatric horses (≥ 16 years of age) 
were even more likely to have a lesion requiring surgi-
cal correction (53%).16
In the present study, concurrent diseases were com-
mon (63% of neonates being treated with colic had at 
least 1 concurrent disease). However, the overall impact 
of concurrent disease on rate of survival to discharge 
was not as high as expected (72% and 87% for neonates 
with and without concurrent disease, respectively). The 
types of concurrent diseases were not unexpected and 
were common diseases of neonates; the most frequent 
ones included sepsis, neonatal encephalopathy, neona-
tal nephropathy, failure of passive transfer of maternal 
antibodies, and umbilical remnant infection or patent 
urachus. Whereas the overall impact of concurrent 
disease on survival rate was not significant, we would 
still caution that serious concurrent diseases can im-
pact survival. The presence of concurrent diseases can 
increase the cost of hospitalization and may impact the 
decision for euthanasia. The mere presence of a concur-
rent disease should not influence the decision to pur-
sue treatment of neonates with colic. However, owing 
to the high occurrence of concurrent diseases, neonates 
examined because of colic should be examined thor-
oughly and monitored closely during treatment.
The decision to perform an exploratory celiotomy 
versus pursuing further medical management can be 
challenging in neonates with colic.2,10 In this retrospec-
tive study, the only factor significantly associated with 
surgical intervention was a lower plasma chloride con-
centration, compared with neonates managed medical-
ly. This is likely because chloride is sequestered in the 
upper gastrointestinal tract in neonates with a proximal 
obstruction, which was the most common reason for 
surgery. Unfortunately, the overlap in values between 
the 2 groups and the small absolute difference of the 
means makes chloride concentration clinically unhelp-
ful in predicting whether medical or surgical treatment 
is appropriate for an individual patient. A small num-
ber of neonates underwent surgery (n = 15), and it is 
possible that with larger numbers, more significant fac-
tors may be identified. Concurrent diseases can have an 
important impact on the manifestation of colic signs, 
and neonates with severe surgical lesions may display 
mild rather than severe persistent signs of colic.10 Not 
all of the neonates undergoing surgery had a classic 
surgical lesion, and some of the neonates with surgical 
lesions were euthanized without surgery. Therefore, to 
clarify the decision for surgical intervention, the neo-
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nates with SISO were considered. The neonates with 
SISO were significantly more likely to have severe pain, 
continuous pain, and less response to analgesics than 
neonates with other diagnoses. These characteristics of 
the colic signs combined with distended small intestine 
visualized ultrasonographically and the presence of ab-
dominal distension are all supportive of the need for an 
exploratory celiotomy.
The situation of a neonate with a medical colic de-
veloping a surgical lesion was not common in this study. 
However, this retrospective study represents only the 
subset of neonates for each primary diagnosis with a his-
tory of colic signs or that developed colic signs within 
the first hour after initial evaluation. Only 1 of 122 man-
aged medically neonates developed a secondary surgical 
lesion. Necrotizing enterocolitis was diagnosed, and this 
neonate was euthanized 48 hours after admission be-
cause of failure to respond to medical management and 
owner financial constraints. At necropsy, the necrotizing 
enterocolitis was confirmed and a distal jejunal stricture 
was diagnosed and judged to be secondary to the nec-
rotizing enterocolitis. A second neonate being managed 
medically that died of respiratory arrest 12 hours after 
admission had both small intestinal volvulus and entero-
colitis diagnosed on necropsy.
Whereas abdominal radiographic examination has 
been traditionally used to evaluate foals with colic, it 
was not used in the present study. After 2000, abdomi-
nal ultrasonography has been used instead of plain 
radiography to evaluate neonatal colic patients and is 
also frequently used to evaluate adult horses with colic 
in our clinic. Pneumatosis intestinalis is diagnostic for 
necrotizing enterocolitis when the clinical findings are 
also supportive of the diagnosis.21 No other ultrasono-
graphic findings were identified in this study as being 
definitive for a specific diagnosis, which was expected, 
given that there is considerable overlap in the ultraso-
nographic findings for different diagnoses.22
The overall short-term survival rate for neonates 
treated for colic was good in this retrospective study, 
with 75% surviving to discharge. Whether they were 
treated medically or surgically did not impact short-
term survival rate. Neonates with necrotizing entero-
colitis and SISO were overall less likely to survive to 
discharge than were neonates with any other cause 
of colic. Several clinical features were associated with 
nonsurvival. The nonsurviving neonates had a signifi-
cantly lower admission rectal temperature, blood glu-
cose concentration, TPP concentration, and TCO
2
 and 
higher blood lactate and plasma creatinine concentra-
tions, compared with surviving foals. Survival rate was 
also significantly lower in neonates with severe signs of 
colic at admission, absence of fecal production, absent 
intestinal borborygmi, abnormal oral mucous mem-
branes, and abdominal distension. These clinical fea-
tures reflect the degree of cardiovascular compromise 
and lesion severity. In adult horses, PCV and heart rate 
are consistently associated with survival rate23–26 but 
were not in the neonates of the present study. Heart 
rate is more variable in neonates than in adults and is 
influenced to a greater degree by restraint. The PCV 
was variable in the neonates because of some having 
concurrent neonatal isoerythrolysis and the recognized 
change in neonatal PCV with age.27 Blood glucose con-
centration is also typically higher in adult horses24 that 
do not survive, whereas lower blood glucose concentra-
tion was associated with nonsurvival in the neonates of 
the present study. Hypoglycemia in neonates can be due 
to lack of nursing or increased metabolic demands and 
reduced gluconeogenesis from concurrent diseases.27 
The frequent occurrence of concurrent disease may 
also confound survival statistics, although the mere oc-
currence of such disease did not significantly influence 
survival rate. Future studies evaluating factors associ-
ated with survival for the individual causes of colic are 
likely to be more useful for providing prognosticindi-
cators for clients.
Surgical intervention was not associated with a de-
creased short-term survival rate in neonates in this ret-
rospective study, compared with medical management. 
The short-term survival rate was 73% for neonates that 
underwent surgical intervention, and if only the true 
surgical lesions are considered, short-term survival 
rate was 83%. The short-term survival rate was 100% 
for the neonates that recovered from general anesthe-
sia. The neonates euthanized under general anesthesia 
were all euthanized because of severe disease and grave 
prognosis. No neonates underwent a second explor-
atory celiotomy. The short-term survival rates in this 
study are similar to or better than those reported by 
others (61% to 85%).9,11,12,14,15 The excellent short-term 
survival rate (100%) in neonates that recovered from 
general anesthesia may be associated with early referral 
and timely surgical intervention, but owing to the small 
number of cases, this cannot be proven. The reported 
long-term survival rate after exploratory celiotomy in 
neonates discharged from the hospital ranges from 35% 
to 75%.9,11,12,15 The rate of long-term survival (to at least 
12 months of age) in this study for foals with surgi-
cal treatment was 89%, and the reason for nonsurvival 
was unrelated to colic. An insufficient number of pa-
tients underwent surgical intervention to explore the 
association between survival and strangulating lesions, 
resection and anastomosis, and lesion location. Despite 
the small number of surgical cases in this retrospective 
study, the concerns regarding exploratory celiotomies 
in neonates should be reconsidered.
Although the potential for adhesions following ab-
dominal surgery is always a concern in neonates with 
colic, we could not objectively evaluate the occurrence 
of adhesions in this retrospective study. All of the surgi-
cally managed neonates that were recovered from gen-
eral anesthesia were discharged alive from the hospital. 
Even though long-term follow-up did not include in-
formation from all of the discharged neonates treated 
surgically, the 2 patients that did not survive were re-
ported to have died or were euthanized because of non-
gastrointestinal causes (equine protozol myeloenceph-
alitis and catastrophic musculoskeletal injury). Details 
of the presence or absence of gastrointestinal adhesions 
at postmortem examination were not available because 
those postmortem examinations were not performed at 
our hospital. Only one surgically managed neonate was 
reported by the owner to have a single episode of mild 
colic 18 months after discharge from the hospital. The 
medically managed neonates that were euthanized dur-
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ing hospitalization, primarily those with necrotizing 
enterocolitis, did not have adhesions on postmortem 
examination. It would have been useful to have more 
surgically managed neonates, especially those under-
going resection and anastomosis; however, we limited 
our search to neonates admitted during or after the year 
2000 because it is our subjective opinion that colic pa-
tient management has improved since the 1990s. Al-
though the study included small numbers, the results 
clearly show that neonates can do well with colic sur-
gery and we attribute much of this to early surgical in-
tervention when necessary and the perceived improve-
ment in colic patient management. Whereas the impact 
of postoperative intraperitoneal adhesions was not ap-
parent in this study, we recommend early surgical inter-
vention when indicated, meticulous surgical technique 
(ie, efficient, atraumatic, and aseptic), and intraopera-
tive adhesion prevention modalities including lavage 
with balanced electrolyte solution, carboxmethylcellu-
lose solution, and fucoidanb).
In this retrospective study, there were 2 clinical 
manifestations of enterocolitis, with an intestinal nec-
rotizing component being the differentiating feature.21 
The short-term survival rate was significantly lower 
for neonates with necrotizing enterocolitis (36%) than 
that for neonates with enterocolitis (86%). There was 
no association between survival and identification of 
C perfringens enterotoxin, C difficile A and B toxins, or 
positive results of PCR assay and culture for Salmonella 
spp. Medical management was used in most neonates 
with enterocolitis and necrotizing enterocolitis. It is im-
portant to attempt to differentiate between enterocolitis 
and necrotizing enterocolitis so that a more accurate 
prognosis can be given to the owner.
Meconium-associated colic cases had an excel-
lent prognosis for short-term survival, as all neonates 
survived to discharge from the hospital. These results 
are supportive of a previous report28 that appropriate 
medical management is successful in resolving almost 
all cases of meconium-associated colic.
The final main group of medically managed neo-
nates with colic signs did not fit the diagnostic criteria 
of enterocolitis, necrotizing enterocolitis, meconium-
associated colic, or any other definable disease. The 
etiology of the colic signs in these cases was unknown. 
The colic signs were transient and generally responded 
to medical management. Therefore, they were catego-
rized as transient medical colic of unknown etiology. 
These neonates were grouped on the basis of clinical 
features and response to treatment for signs related to 
colic. Because the etiology was unknown, it is possible 
that these cases should not all be considered equal and 
grouped together. Four foals with transient medical 
colic died or were euthanized due to their concurrent 
diseases. There was a good prognosis for short-term 
survival in this group of neonates (short-term survival 
rate, 88%). Further research to define the pathogenesis 
of the transient medical colic in neonates is warranted.
Long-term survival rate for neonates discharged 
from hospital was excellent. The reasons for nonsurviv-
al were unrelated to the diagnosis during hospitaliza-
tion for all but 1 neonate. This neonate was treated for 
enterocolitis (etiology unconfirmed) and was healthy 
for 2 months before developing salmonellosis associ-
ated with enterocolitis, which lead to euthanasia. It is 
unlikely that the first enterocolitis episode was respon-
sible for the second one, considering that the neonate 
had a negative result of a fecal PCR assay for Salmo-
nella spp during the first episode and was healthy for 8 
weeks between episodes. A different neonate was found 
dead in the field at 6 months of age, and a postmor-
tem examination was not performed. The neonate did 
not have any episodes of colic after discharge prior to 
death. In that case, it is impossible to definitively con-
clude whether the reason for death was related to the 
reason for hospitalization because a postmortem exam-
ination was not performed. On the basis of our results, 
admission to a referral hospital for colic as a neonate 
does not appear to predispose to colic episodes later in 
life. When the neonates survived to maturity, they were 
likely to be used as intended and reasons for not doing 
so were not related to colic.
The results of this study suggested that most neonates 
referred to a hospital for colic signs can be managed medi-
cally and the need for surgical intervention is less com-
mon than it is in adult horses. However, it is important to 
consider that the medical conditions can often be serious 
and require intensive management. Concurrent diseases 
in neonates being treated for colic are common. Impor-
tantly, the mere presence of concurrent disease did not 
significantly impact survival. Neonates with SISO lesions 
were significantly more likely to have severe pain and con-
tinuous pain and were less responsive to analgesics. The 
overall short-term survival rate for neonates being treated 
for colic was good to excellent and was not affected by 
whether they were managedmedically or surgically. Neo-
nates with necrotizing enterocolitis and SISO were overall 
less likely to survive to discharge. If neonates were dis-
charged from the hospital, rate of survival to 12 months of 
age appeared to be excellent, and if surviving to maturity, 
the neonates were likely to be used as intended. Owners 
should not be discouraged from performing an explorato-
ry celiotomy when indicated in neonates.
a. SAS, version 4.3, SAS Institute Inc, Cary, NC.
b. Peridan, Bioniche Animal Health USA Inc, Athens, Ga.
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From this month’s AJVR 
Collection and characterization of semen 
from green iguanas (Iguana iguana)
Dawn M. Zimmerman et al
Objective—To determine an efficient method for the collection of semen samples by means of 
electroejaculation, characterize spermatozoa quality and quantity, and determine the effect of refrig-
erated storage on motility of spermatozoa obtained from green iguanas (Iguana iguana).
Animals—18 adult green iguanas.
Procedures—Green iguanas were anesthetized, and semen samples were obtained by means of 
electroejaculation. Up to 3 series of electrostimulations were performed; the procedure was stopped 
after a semen sample was obtained. Various semen sample variables were evaluated.
Results—Semen samples were obtained from 16 iguanas; most (n = 10) iguanas produced a semen 
sample after the second series of electrostimulations. Median semen sample volume was 0.05 mL. 
Mean spermatozoa concentration was 269.0 X 106 spermatozoa/mL. Median percentage of motile 
spermatozoa was 78%. The only morphological abnormality of spermatozoa was bent tails (mean 
percentage in a semen sample, 5.7%). Spermatozoa motility decreased significantly during refrigera-
tion (4°C); median percentage motility after 24, 48, and 72 hours of refrigeration was 60%, 33%, 
and 0%, respectively.
Conclusions and Clinical Relevance—Results of this study suggested electroejaculation can be 
performed to collect semen samples from green iguanas, characteristics of iguana semen samples 
are similar to those for semen samples obtained from other reptiles, and motility of iguana sper-
matozoa decreases during refrigeration within 48 to 72 hours. (Am J Vet Res 2013;74:1536–1541)
See the midmonth issues 
of JAVMA 
for the expanded 
table of contents 
for the AJVR 
or log on to 
avmajournals.avma.org 
for access 
to all the abstracts.
December 2013