Meconium Impaction in Newborn Foals
By Patrick M. McCue, DVM, Ph.D.,
Diplomate American College of Theriogenologists
Meconium is the term used to describe the first feces or stool produced by a newborn foal. In most
instances, the meconium is passed within the first three hours of life without difficulty. However,
some foals cannot pass the meconium and an impaction or blockage of the intestinal tract occurs
which results in severe abdominal pain. The EZ Pass enema is designed to assist foals in passing
the retained meconium in foals with impactions refractory to standard medical treatments
Meconium
Meconium is comprised of digested amnionic fluid, gastrointestinal secretions, bile, and cellular
debris that accumulate in the intestinal tract of the late-term fetus.1 It is usually dark greenish
brown or black in color, firm pellets to pasty in consistency and is generally passed within the first 3
to 4 hours after birth.2,3 The average time to initial passage of meconium in 22 foals born at
Colorado State University was 53 ± 35 minutes. Two additional foals did not begin to pass
meconium for 5 hours, 33 minutes and 7 hours, 20 minutes, respectively. Once the meconium has
completely passed, the feces of a newborn foal should change in character to a softer consistency
and a lighter yellow-orange color of 'milk stool'.
Colt foals reportedly have a higher incidence of meconium impactions than filly foals, possibly due to
a narrower pelvic canal.4,5 Meconium impaction has been reported to be the most common cause of
colic or abdominal discomfort in the newborn foal, with 1.5 % of all foals affected.6 A foal is
considered to have a meconium impaction or retained meconium if frequent failed attempts to pass
meconium occur within the first 12 to 36 hours of life.
Failure to pass the first feces typically results in significant abdominal pain.7 A foal may also pass a
small amount of meconium and still develop a meconium impaction. Therefore, continued monitoring
of bowel movements over the first 24-36 hours of life is warranted. Retention of fecal material may
be within the small colon at the pelvic inlet (low impaction) or higher up within the transverse or
right dorsal colon (high impaction).2,3
Predisposing factors for meconium impaction include maternal malnutrition, delayed colostrum
intake and subsequent loss of the laxative effect of colostrum, dystocia, prematurity, prolonged
gestation, low birth weight, intestinal disease, dehydration and hypomotility of the colon.6
Clinical Signs of Meconium Impaction:
Mild clinical signs are usually apparent within 6 to 24 hours after birth.2 More severe signs occur as
the duration and abdominal distention increases. Impactions of the colon may be associated with
more pronounced pain than impactions of the rectum.
Clinical signs include:
Failure to pass meconium
Progressively increasing abdominal pain or colic manifested by rolling on the ground, kicking at the
abdomen and swishing of the tail
Depression
Frequent and persistent posturing, squatting and straining to defecate (Figures 1 and 2)
|ying down frequently
Reluctance to suckle consistently due to repeated abdominal pain; bouts of colic may occur following
nursing
The urachus of some foals may re-open due as a result of straining to defecate
Figure 1. Foal with meconium impaction straining to defecate.
Figure 2. Foal with meconium impaction straining to defecate
Diagnosis:
Clinical signs
Digital rectal examination with a well-lubricated finger (rectal impactions)
Deep abdominal palpation
Abdominal ultrasonography
Contrast radiography incorporating a barium enema8
Differential Diagnosis of Abdominal Pain in Newborn Foals:
Enterocolitis
Colonic atresia
Colon torsion
Lethal White Foal Syndrome
Uroperitoneum (ruptured urinary bladder)
Small intestinal volvulus or intussusception
Diaphragmatic hernia with bowel strangulation
Other abdominal abnormalities
Treatment:
1.Enema
Two types of enemas are routinely used in neonatal foals to assist with passage of meconium.
Perhaps the most common is administration of 100 to 133 mls (approximately 3.5 to 4.5 oz) of a
commercial sodium phosphate enema (Fleet®, C.B. Fleet Co, Inc, Lynchburg, VA, or generic
equivalent).2,3,9 The foal is restrained either standing or in lateral recumbency. The protective
shield is removed from the enema bottle and the pre-lubricated tip is carefully inserted into the
rectum. The bottle is slowly and gently squeezed to evacuate the contents into the rectum. A
sodium phosphate enema should not be administered more than twice to a newborn foal within the
first 24 hours of life due to the risk of hyperphosphatemia.2,5,6
An alternative is to administer an enema consisting of 500 to 1,000 mls (approximately 1 to 2 pints)
of warm soapy (i.e. Ivory® Liquid, Proctor and Gamble, Cincinnati, OH) water.1,9 The soapy water
enema is infused into the rectum slowly by gravity flow through a soft flexible Foley catheter.
Breeding farms may choose to routinely give all newborn foals an enema within the first 1-2 hours
after birth or may selectively administer enemas only to foals that do not pass meconium on their
own. Either type of management strategy is acceptable. Foals that do not successfully pass
meconium in the first few hours of life should be treated because of the potential for significant
complications, including colic, patent urachus, failure to nurse adequately (and secondary decreased
passive transfer of immunoglobulins), and colonic and/or rectal edema and inflammation.
Translocation of bacteria through the inflamed colonic epithelium and the urachus (if patent) can
lead to sepsis.
If administration of 1 to 2 sodium phosphate or soapy water enemas is not successful in resolving a
meconium impaction, administration of an acetylcysteine enema (see below) is indicated. Routine
sodium phosphate or soapy water enemas may not be successful in alleviating a high meconium
impaction.
2.Acetylcysteine (4 %) Retention Enema
Meconium impactions refractory to traditional sodium phosphate or soapy water enemas were
historically treated surgically.10,11,12 In 1990, Madigan and Goetzman first introduced the concept
of treating foals with acetylcysteine for meconium impactions.13 Since that time, medical
management of refractory cases of meconium impactions with acetylcysteine has largely eliminated
the need for surgical intervention.5
A commercial acetylcysteine retention enema (EZ-PassTM; Animal Reproduction Systems, Chino,
CA) is now available. It is recommended that this be administered to newborn foals under the
advice or supervision of a veterinarian.
Acetylcysteine has been reported to cleave disulfide bonds in the mucoprotein molecules of
meconium, decrease the tenacity of the meconium and thus make the outer surface of the
meconium slippery. Increasing the pH of the acetylcysteine solution with sodium bicarbonate
increases its inherent mucolytic activity. It has been reported that the maximal effect of
acetylcysteine is realized after 30-45 minutes.5
In a retrospective study of 41 cases of refractory meconium impactions treated with acetylcysteine,
the average time to resolution was 11 ± 16 hours (range 1 to 96 hours) and an average of 1.5
enemas were used (range 1 to 3).5 No complications were reported with the use of 4 %
acetylcysteine retention enemas for treatment of refractory meconium impaction.
For administration, the foal must be restrained, either by laying him/her down on the ground or by
sedation. A soft, flexible Foley catheter is inserted 1 to 2 inches into the rectum and the balloon cuff
is gently inflated with no more than 30 mls of air. A volume of 125 mls (approximately 4.2 ounces)
of a 4 % acetylcysteine solution is slowly infused into the rectum through the Foley catheter (Figure
3). The clamp placed on the catheter is closed and the acetylcysteine solution is allowed to remain
in the rectum for 15 to 45 minutes (Figure 4).3,5 After waiting for the appropriate amount of time,
the clamp is opened, the cuff of the catheter deflated and the catheter removed. The foal may then
be allowed to stand or move freely (Figure 5). As noted previously, it is recommended that the foal
be monitored for complete passage of the retained meconium and that observations be continued
for the next 24-36 hours. The presence of yellow 'milk stool' indicates that meconium has passed
completely (Figure 6)
Figure 3. Administration of an acetylcysteine enema through a Foley catheter
Figure 4. Foal with Foley catheter in place after receiving acetylcysteine enema
Figure 5. Foal defecating following an acetylcysteine enema
Figure 6. Foal with normal 'milk scours' after complete passage of meconium.
Ancillary Therapy:
1.Allow foal to nurse colostrum or provide colostrum via bottle or stomach tube. Colostrum is a
valuable source of antibodies required for passive transfer and has a strong laxative effect. Foals
with colic associated with meconium impactions may not nurse as vigorously and may be at risk of
failure of passive transfer.
2.Analgesics such as flunixin meglumine or butorphanol tartrate as needed. Caution should be used
with administration of non-steroidal anti-inflammatory medications.
3.Intravenous fluids as needed.
4.Mineral oil (60 to 120 mls or approximately 2 to 4 ounces) administered by nasogastric intubation
to foals greater than 24 hours of age.
5.Foals with severe prolonged meconium impactions may be predisposed to sepsis. Consequently,
administration of plasma and/or systemic antibiotics may be indicated.
6.Rarely, a severe refractory case of meconium impaction may require surgical
intervention.10,11,12
7.Manual removal of meconium impacted in the rectum is not recommended due to the potential for
injury to the rectal mucosa.3
Summary:
Meconium impactions are one of the most common causes of colic in neonatal foals. It is
recommended that foals be administered a sodium phosphate or warm soapy water enema within
the first 3 hours after birth either routinely or if they have not yet passed meconium. Administration
of an acetylcysteine retention enema is recommended for foals with refractory cases of meconium
impaction.
References:
1.Rossdale PD, Ricketts SW. The practice of equine stud medicine. The Williams & Wilkins
Company: Baltimore, 1974, pp. 250-251.
2.Madigan JE. Manual of equine neonatal medicine. Live Oak Publishing: Woodland, CA, 1997, pp.
117-120.
3.Knottenbelt DC, Holdstock N, Madigan JE. Equine Neonatology, Medicine and Surgery. Saunders:
Edinburgh. 2004; pp 249-252.
4.Martens RJ. Pediatrics. In: Equine Medicine and Surgery, 3rd edition. Mannsman RL, ES McAllister
(eds). American Veterinary Publications, Santa Barbara, 1982; pp. 333-334.
5.Pusterla N, Magdesian KG, Maleski K, Spier SJ, Madigan JE. Retrospective evaluation of the use of
acetylcysteine enemas in the treatment of meconium retention in foals: 44 cases (1987-2002).
Equine Veterinary Education 2004;16:133-136.
6.Semrad SD, Shaftoe S. Gastrointestinal diseases of the neonatal foal. In: Robinson NE (ed),
Current Therapy in Equine Medicine (3rd Edition), WB Saunders: Philadelphia, 1992, pp 445-455.
7.Bernard W. Colic in the foal. Equine Veterinary Education 2004;16:319-323.
8.Fischer AT, TY Yarbrough. Retrograde contrast radiography of the distal portions of the intestinal
tract in foals. J Am Vet Med Assoc 1995;207:734-737.
9.Ryan CA, LC Sanchez. Nondiarrheal disorders of the gastrointestinal tract in neonatal foals. Vet
Clin Equine 2005;21:313-332.
10.Cran HR. Laparotomy in a case of retention of the meconium in a foal. Vet Rec 1980;107:47.
11.Hughes FE, HD Moll, DE Slone. Outcome of surgical correction of meconium impactions in 8 foals.
J Equine Vet Sci 1996;16:172-175.
12.Vatistas NJ, JR Snyder, WD Wilson, C Drake, S Hildebrand. Surgical treatment for colic in the foal
(67 cases): 1980-1992. Equine Vet J 1996;28:139-145.
13.Madigan JE, BW Goetzman. Use of acetylcysteine solution enema for meconium retention in the
neonatal foal. Proc Am Assoc Equine Pract 1990;36:117-119.