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Basics ⬇

Outline

BASICS

Definition!!navigator!!

  • Meconium refers to the fetal feces made up of cellular debris, amniotic fluid, intestinal secretions, and bile
  • Meconium is normally passed within 3 h of birth, and is considered retained if the foal has not passed all meconium by 12 h after birth
  • Most meconium impactions are in the small colon at the pelvic inlet, but they also occur in the right dorsal colon or transverse colon

Pathophysiology!!navigator!!

Delayed passage of meconium can create an obstruction in the distal small colon, resulting in discomfort and accumulation of gas orad to the obstruction. Colic pain and abdominal distention can lead to additional systemic effects secondary to hypoglycemia, ileus, and dehydration.

Systems Affected!!navigator!!

GI

Genetics!!navigator!!

N/A

Incidence/Prevalence!!navigator!!

Meconium impaction is the most common cause of colic in neonatal foals. No specific incidence rate has been reported.

Geographic Distribution!!navigator!!

N/A

Signalment!!navigator!!

  • All breeds
  • Possible higher incidence in colts
  • Neonatal foals, usually 6–36 h of age

Signs!!navigator!!

  • Abdominal pain (colic)—tail flagging, kicking at abdomen, rolling
  • Straining to defecate; tenesmus—resulting in mild rectal prolapse and/or reopening of the urachus
  • Failure to pass meconium. The foal may pass some meconium but retain enough meconium to cause an impaction
  • Depression and decreased nursing
  • More severe or advanced impactions can cause abdominal distention and severe signs of colic
  • Initial signs are usually within 6–24 h of birth

Causes!!navigator!!

  • Narrow pelvic canal (more common in colts)
  • Delayed colostrum ingestion
  • Systemic disease, such as hypoxia or sepsis, can result in decreased intestinal motility
  • Dehydration, prolonged recumbency, and drugs that slow GI motility may also contribute

Risk Factors!!navigator!!

See Causes.

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Atresia coli—similar signs initially, but no meconium staining is seen after repeated enemas
  • Intestinal aganglionosis (lethal white foal syndrome)—in white foals, offspring of overo Paint breeding; usually no meconium production
  • Other GI causes of neonatal colic—enterocolitis, small intestinal volvulus, intussusception
  • Uroperitoneum—foal may posture and strain in a similar manner; free fluid in abdomen and electrolyte abnormalities help to confirm uroabdomen. Excessive straining from meconium impaction causes bladder tears in some foals, and may also cause the umbilicus to reopen due to excessive abdominal pressure

CBC/Biochemistry/Urinalysis!!navigator!!

  • No consistent abnormalities
  • Dehydration/hemoconcentration and hypoglycemia will occur in foals that have not been nursing adequately

Other Laboratory Tests!!navigator!!

Foals with inadequate colostrum ingestion will have a low IgG concentration.

Imaging!!navigator!!

  • Abdominal radiography—gas-filled large and small colon with radiodense fecal material in distal small colon; barium enema can help to confirm the site of obstruction and barium also acts as an osmotic agent in the enema
  • Abdominal ultrasonography—dense fecal material in the small colon; can rule out enteritis, uroabdomen, or other causes of colic/abdominal distention

Other Diagnostic Procedures!!navigator!!

  • Abdominal palpation—identify abdominal distention; firm fecal material/meconium may be recognized on deep abdominal palpation when there is not significant gas distention
  • Digital rectal examination—use a well-lubricated, gloved finger; hard feces may be identified in the rectum; rule out atresia ani

Treatment ⬆ ⬇

Outline

TREATMENT

Appropriate Healthcare!!navigator!!

  • Foals with mild meconium impaction may be treated with enemas at the farm. Foals with more severe impactions or with concurrent medical problems should be admitted for inpatient medical care
  • Enemas—administration of soapy water or sodium phosphate enemas is usually effective; 200–300 mL of warm, soapy water can be administered gently by gravity or very gentle syringe pressure via a red rubber catheter advanced only into the caudal rectum. Acetylcysteine retention enemas are used for impactions that are refractory to soapy water or sodium phosphate enemas. Acetylcysteine (4%) will cleave disulfide bonds in the mucoprotein of the meconium, causing the surface to become slippery. Acetylcysteine retention enemas are administered via Foley catheter with an inflated bulb. Gravity flow is used to administer 100–200 mL of solution, and it is retained for approximately 30–40 min. Enemas will cause some rectal irritation, and continued straining due to irritation should not be confused with persistent meconium impaction. Use of phosphate enemas should be limited in order to avoid hyperphosphatemia
  • Oral laxatives—mineral oil can be administered via nasogastric tube in order to encourage passage of feces. Colostrum also appears to have a laxative effect. In more refractory cases of impaction, osmotic agents such as sodium sulfate can be given via nasogastric tube; however, these can be irritating to the GI tract, and may place the foal at risk of sepsis secondary to bacterial translocation. Mineral oil and other laxatives should not be used in foals <24 h of age

Nursing Care!!navigator!!

The foal should be encouraged to rise and nurse every hour as long as enteral nutrition is tolerated. IV fluids are needed in more severe cases to hydrate the foal and prevent/treat hypoglycemia. Foals that have not nursed well or that have meconium retention secondary to lack of colostrum intake should be treated with hyperimmune plasma if indicated by low IgG.

Activity!!navigator!!

Stall rest is useful for monitoring feces and colic signs, although strict rest is not necessary.

Diet!!navigator!!

  • Nutrition—if the foal is colicky and has a continued obstruction, supplementation with IV fluids and dextrose or with parenteral nutrition should be initiated
  • Foals can be supplemented with mare's milk via feeding tube if not nursing adequately. Feed small volumes initially as the meconium retention can lead to colic and reflux

Client Education!!navigator!!

Clients should be instructed to monitor for passage of meconium and recognize normal neonatal feces. Any decrease in nursing or lethargy should prompt an examination by a veterinarian.

Surgical Considerations!!navigator!!

Surgical treatment—very rarely necessary; ventral midline celiotomy with guided enema and bowel massage is usually sufficient to resolve the impaction. Severe cases may require enterotomy to remove hard meconium or other obstructive material.

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

  • NSAIDs such as flunixin meglumine (0.5–1.1 mg/kg IV or PO every 12–24 h) or ketoprofen (1.1–2.2 mg/kg IV every 12–24 h) can be given for analgesia
  • Sedation and analgesia are often needed for administration of the enema—xylazine (0.5–1.1 mg/kg IV), butorphanol (0.02–0.1 mg/kg IV), or diazepam (0.1 mg/kg IV)

Precautions!!navigator!!

  • NSAIDs should be used with caution in neonates, especially if there are signs of dehydration or renal compromise
  • The foal should be monitored closely for changes in condition—analgesics and sedation may mask a more serious underlying condition

Possible Interactions!!navigator!!

N/A

Alternative Drugs!!navigator!!

Midazolam (0.1–0.2 mg/kg) can be used instead of diazepam. Butorphanol is preferred over an NSAID for pain control, especially if the foal is less than 24 h of age.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Progression of colic signs and abdominal distention—take serial measurements of the abdomen by marking a site on the dorsum and ventrum and using a tape measure or string to assess for increasing abdominal circumference
  • Passage of fecal material—pasty yellow “milk” feces are passed after all meconium has been passed

Prevention/Avoidance!!navigator!!

  • Ensure adequate colostrum intake
  • Routine administration of a warm soapy water enema is recommended if the foal has not passed its meconium within 3 h of birth

Possible Complications!!navigator!!

  • Frequent enemas can cause rectal irritation and further signs of straining
  • Rectal tear from overzealous enemas
  • Secondary ileus
  • Bacterial translocation and sepsis from irritated GI mucosa
  • Foals that require surgical correction of the impaction are at risk of abdominal adhesions

Expected Course and Prognosis!!navigator!!

Meconium impactions have a very good prognosis, and rarely require surgery. Generally, 1 or 2 enemas will resolve mild meconium impactions.

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

Neonatal hypoxia and sepsis can contribute to meconium retention.

Age-Related Factors!!navigator!!

This is a condition of neonatal foals.

Abbreviations!!navigator!!

  • GI = gastrointestinal
  • IgG = immunoglobulin G
  • NSAID = nonsteroidal anti-inflammatory drug

Suggested Reading ⬆ ⬇

Pusterla N, Magdesian KG, Maleski K, et al. Retrospective evaluation of the use of acetylcysteine enemas in the treatment of meconium retention in foals: 44 cases (1987-2002). Equine Vet Educ 2004;16:133–136.

Ryan CA, Sanchez LC. Nondiarrheal disorders of the gastrointestinal tract in neonatal foals. Vet Clin North Am Equine Pract 2005;21:313–332.

Author(s) ⬆

Author: Margaret C. Mudge

Consulting Editor: Margaret C. Mudge