ABSTRACT. Meconium impaction is a common condition that affects the equine neonate and often requires immediate veterinary attention. This article highlights the role of the veterinary nurse in assisting the veterinary surgeon with the diagnosis of this condition through the use of digital palpation, radiography and ultrasonography, and providing treatments such as enemas, analgesic medications and fluid therapy Occasionally, despite the best efforts of the vet and the veterinary nurse, the neonate may require hospital referral for intensive care and/or surgical intervention.

Meconium is the foal’s first faeces, formed in utero and passed after birth. It is a dark, sticky and tarry material comprised of sloughed intestinal secretions, ingested amniotic fluid, cellular debris and mucous (Figure 1).

Figure 1: The normal appearance of meconium, evacuated from a newborn foal a few hours after birth

Meconium impaction, also known as meconium retention in more severe cases, is one of the most common causes of colic in the newborn foal. This condition affects foals that fail to evacuate their first faeces, and the foal develops a painful colonic obstruction. This occurs within the first 12 hours of birth. Most impactions are located in the pelvic inlet of the small colon but can also be situated in the dorsal or transverse colon.

The causes of meconium impaction are still poorly understood, although it is thought that the intrinsic consistency of the material, and the narrowed pelvic inlet of foals, especially in colts, mainly contribute to the condition. Premature neonates with impaired gastrointestinal function may also experience the condition owing to prolonged recumbency and dehydration. It is believed too that late- term foals are prone to this condition.

Meconium impaction can also be a symptom of more serious acquired disorders that result in ileus – for example, septicaemia and neonatal encephalopathy; or congenital conditions such as atresia coli or atresia ani. However, these serious conditions are beyond the scope of this article.

In order to recognise abnormalities in the equine neonate, it is important to be familiar with a foal’s normal post-partum behaviour.

A healthy foal will attempt to stand almost immediately after birth and will nurse from the mare – ingesting colostrum within the first two hours of birth. The ingested colostrum acts as a laxative, when the fluid stretches and expands the stomach, the gastro-colonic reflex is stimulated. This action causes increased motility of the colon, thus triggering the evacuation of the meconium. Evacuation occurs approximately two to three hours after birth, with most of the meconium evacuated within the first 12 hours of birth.

If the foal fails to pass meconium by 12 hours old, it would be described as having ‘retained meconium’. Because the dense consistency of meconium is markedly different from the normal soft, milk faeces that follow, a normal foal will even exhibit some straining whilst passing meconium. This is not to be interpreted as a sign of meconium impaction.

The clinical examination

A normal foal’s temperature ranges between 37.3°C and 38.8°C. Although heart rate and respiration rate can vary greatly depending on the demeanor of the foal, a normal foal’s resting heart rate should remain between 70 to 90 beats per minute, and respiration rate between 16 and 40 breaths per minute.

The mucous membranes should be pink and moist, and capillary refill time less than two seconds. On auscultation, active gut sounds should be audible in all four gastrointestinal quadrants. With meconium retention, a foal’s temperature may not vary but respiratory and heart rates may increase along with increased discomfort. Gut sounds are often audible, but can subside with gas and fluid build up if the foal continues to nurse without evacuating the meconium.

Early signs of meconium retention in foals can be restlessness, tail-swishing, frequently posturing to urinate, straining and frequent attempts to pacify themselves by short stints at nursing. More marked signs of a foal with meconium retention are often described by owners as a colicky’ foal (Figure 2).

Figure 2: A foal showing classic signs of colic

These signs include flank-watching, rolling, twisting, tucking legs up, lying on the back, marked abdominal distention and being ‘off suck’. Depending on the severity of the meconium retention, one or all of the foal’s vital parameters may be elevated. Although in primary meconium impaction, the foal’s temperature usually remains normal, its heart rate can rise above 100 beats per minute and respiration rate above 40 breaths per minute.

The mucous membranes become congested and tacky, predominantly as a result of dehydration from not nursing adequately. The foal's gut sounds can become less audible and more gaseous sounding. It is important to note that these signs are not uniquely associated with meconium retention (Figure 3).

Figure 3: Lateral abdominal radiographs of a newborn foal with a severely gas distended large colon. This is characteristic of a distal colon obstruction

Further diagnostics

It is imperative that if meconium impaction is suspected, a vet should be called to examine the foal. A careful digital rectal examination can be carried out by gently placing a gloved and well- lubricated finger into the foal's rectum to determine the presence of a firm faecal mass. The absence of palpable meconium in the rectum does not rule out the condition, as the obstruction may be more proximally positioned in the intestine.

Radiography can be a useful diagnostic tool. A lateral radiograph of the foal’s abdomen may reveal granular spherical masses in the distal intestine. The use of ultrasonography, however, is a more reliable method of visualising the impaction
, as the obstruction is almost always visible using this modality.

Haematology and biochemistry analysis – including lactate and glucose – may not be useful in definitively diagnosing meconium retention because a foal with the condition often has normal values. Even so, blood analysis should initially be performed to provide a baseline should the foal’s condition deteriorate, and to monitor its hydration status. It could also be used to help rule out more serious underlying pathologies. Most importantly, IgG levels must be checked to determine the status of the foal’s transfer of passive immunities.


Whether the meconium retention is mild or severe, the foal should be monitored frequently to ensure its vital parameters do not deteriorate. The patient should be monitored for signs of dehydration or abdominal distension. Most cases of meconium retention respond well to  enemas as they are an excellent means in treating the condition at the source.

Sodium phosphate enemas, such as the commercially available ‘Fleet’ enema, are easy to use, as well as convenient and inexpensive. They work by drawing water into the colon thereby resulting in a bowel movement. Their administration can be repeated, but care must be taken to not administer too many so as to cause hyperphosphotaemia (Figure 4).

Figure 4: A newborn foal passing meconium after being administered a sodium phosphate enema

A maximum of two to three Fleet enemas should be given in a 24-hour period. If commercial preparations are not available, a warm soapy enema made with a mild un-perfumed liquid soap mixed in 200ml of water, may be used instead. These preparations are routinely administered to all newborn foals in most commercial thoroughbred stud farms.

Acetylcysteine retention enemas should only be used when meconium retention has been diagnosed, and not prophylactically. Acetylcysteine breaks down disulfide bonds, thereby dissolving the meconium. Administration takes about Vi hour to perform. Sedation may be required for this procedure (Table 1).

The foal can be sedated with butorphanol tartrate (0.05-0.1 mg/kg IV) and/or diazepam (0.11-0.22 mg/kg IV). Acetylcysteine enemas are thought to be more effective because they manually break down the impacted faecal balls into a pasty consistency which is easily evacuated.

The neonates ability to fight infection relies entirely on passive transfer of antibodies from ingested colostrum. Therefore, a foal which fails to nurse colostrum adequately is at markedly increased risk of opportunistic infection. IgG can be measured in clinic with a SNAP test or can be sent away to a commercial laboratory for analysis. If the IgG level in the blood is below 400 mg/dl, one or two litres of poly- immune plasma can be administered.

Antibiotic cover is also routinely given when foals are being treated for meconium retention. Pain relief medications, such as hyoscine butylbromide (Buscopan, Boehringer) at 0.3 mg/kg IV, flunixin meglumine (Finadyne, MSD Animal Health) at 0.25-1.1 mg/kg IV, SID or BID, or butorphanol tartrate (Torbugesic, Pfizer) at 0.05-0.1 mg/kg IM or IV, can be administered in modest doses to keep the foal comfortable whilst passing the impaction.

As with any species, if dehydration is suspected, NSAIDS should not be administered as this may result in acute renal failure. Assessment of the foal’s PCV and lactate can help determine the hydration status of the foal. Fluid boluses may be required and administered as directed by the attending veterinary surgeon.

Possible complications

There are some common secondary complications that occur in foals with meconium retention.

A foal will strain quite vigorously in an attempt to pass meconium, thus increasing the pressure within the abdomen and reopening the urachus.

This is identified by urine dribbling from the navel. Conversely, urine can be forced subcutaneously at the junction of the urachal closure and umbilical stump, evidenced by an oedematous sheath.

While the foal is passing the impaction, it may be necessary to place a Foley catheter into the bladder and monitor urine output to avoid either of these pathologies progressing. As the foal recovers from meconium retention, it is likely to have normal urinary function, but must be monitored closely after the urinary catheter is removed. Occasionally, these foals do not return to normal urinary function and require surgery for an umbilical resection.

Another possible complication occurs when the meconium compromises the intestine which triggers bacterial translocation across the gut causing septicaemia. This may present as dullness, hyperaemia, fever and even cyanotic mucous membranes. These cases usually require specialised intensive care for 24-hour monitoring, broad-spectrum antibiotics, evaluation of haematology and biochemistry parameters and fluid therapy.

Finally, in rare cases a foal may be unable to pass the meconium, the pain becomes uncontrollable or the abdomen continues to distend and compromises respiration. In these instances, it may be necessary to refer the patient to a surgical facility. Although surgical intervention is an option, the chance of post-surgical complications is high.

It is well documented that the administration of acetylcysteine enemas is now the treatment of choice and has probably prevented the need for surgery in many cases. 


Cecily Burbidge RVT(Ontario) RVN

Cecily graduated from the University of Guelph's Veterinary Technology programme and worked at the University in Ontario, until she moved to the UK. She was employed in the neonatal unit at Rossdale's Equine Hospital, Newmarket, for two years. After her wedding in 2011. Cecily moved to Scotland and is presently employed at the University of Glasgow, Weipers Centre Equine Hospital.

To cite this article use either

DOI: 10.1111/j.2045-0648.2012.00176.x or Veterinary Nursing Journal Vol 27 pp 194-197

Veterinary Nursing Journal • VOL 27 • May 2012 •