Colic in the Neonatal Foal

Abdominal pain is a common problem in neonates. It is may be difficult to distinguish cases that require surgery from those that can be treated medically, therefore a thorough history and physical exam utilizing ultrasound of the abdomen must be performed, along with laboratory evaluation.

I. Clinical Signs

1. Restlessness, attempts to defecate, swishing of the tail, walking around the stall, tail elevation and straining.
2. Advanced signs of abdominal pain are lying down and gettingup repeatedly, dorsal recumbency, rolling.
3. May appear to be attempting to urinate frequently.
4. Abdominal distention may or may not be present.
5. Fever in cases of infectious enteritis.
6. Bruxism, salivation, dorsal recumbency, diarrhea, interrupted nursing in cases of gastrointestinal ulceration.

II. Differential Diagnosis

III. Diagnostic Approach [3]

1. Complete history, considerations:

1. Breed (overo-overo: agangliosis) and sex (colts more predisposed to meconium retention than fillies).
2. Age of the foal at presentation and at the onset of clinical signs.
3. Urination and defecation (frequency and characteristics).
4. Diet: mare's milk or milk replacers, amount and frequency of feedings if supplementing.
5. Peripartum events and farm history of current or past enteritis.

2. Physical exam, including:

1. Observation of the patient. Gastric distention can cause dilation of the caudal rib cage. Severe distention may indicate a colonic disorder.
2. Auscultation and percussion of the abdomen. Absence of borborygmi sounds indicates ileus; the presence of high pitched resonant sounds (ping) indicates gas distention.
3. External palpation of the abdomen. Urinary bladder and occasionally colonic impactions and masses can be felt.
4. Ballottement of the abdomen may help differentiating gas from fluid abdominal distention.
5. Rectal digital palpation can reveal rectal impaction with meconium.
6. Measurement of abdominal circumference. Serial determinations are helpful to monitor progression or regression of abdominal distention.
7. Nasogastric intubation to determine the presence of reflux and/or gas. Reflux suggests intestinal obstruction or ileus, although its absence does not rule it out. In every case of abdominal pain, NGT must be passed for diagnostic and/or therapeutic purposes.

3. Clinicopathologic data

1. Acute bacterial enteritis (leukopenia with left shift, toxic neutrophils, hyperfibrinogemia). (See Diarrhea).
2. Chemistry panel and blood gases - Ruptured bladder (marked hyperkalemia), or metabolic acidosis with electrolyte imbalances in diarrhea cases.
3. Lactate levels elevated in severely compromised cases.

4. Abdominal Radiography and Ultrasound (See Ultrasonography of the Fetus and the Neonate & Thoracic and Abdominal Radiography) may assist with a specific diagnosis

1. Volvulus of small intestine
2. Large colon torsion
3. Meconium impaction (high)
4. Diaphragmatic hernia
5. Gastroduodenal ulcers and subsequent pyloric stenosis and delayed gastric emptying.
6. Enteritis

5. Abdominal ultrasonography is considered valuable (See Ultrasonography of the Fetus and the Neonate).
6. Abdominocentesis should be performed carefully in the recumbent or standing foal. Perform a sterile prep and block the skin. Some prefer using a needle (20 ga) while others have used bitch catheter or teat cannula. Sedation may be required. Nucleated cell counts are lower in foals than in adults (greater than 1500/μl are considered elevated) [4]. Normal peritoneal fluid protein concentration ranges from 0.3 to 1.8g/dl [4]. Cytologic examination may reveal bacteria, ingesta, or degenerated cells. If peritonitis suspected, culture of the fluid is indicated. Peritoneal tap is often normal in cases of enteritis. In foals with suspected uroperitoneum, the creatinine concentration of peritoneal fluid and serum must be obtained (See Ruptured Bladder & Uroperitoneum).
7. Fecal analysis (flotation, culture, microscopic evaluation) is indicated in cases of diarrhea, especially if stools are bloody. Pathogens associated with diarrhea and colic are Salmonella spp. and Clostridium spp. (See Diarrhea)
8. Gastroscopy should be used to detect gastric ulceration, pyloric stenosis, colonoscopy to detect malformations of rectum and small colon.
9. Exploratory celiotomy indicated if surgical condition is identified or in unidentified cause of persistent or severe pain/distention. Surgical considerations (see references for detailed descriptions).

1. Correct fluid, electrolytes and blood gas abnormalities before surgery if possible.
2. Avoid damaging umbilicus and associated vessels. [If suspect umbilical infections or involvement (patent urachus) then remove at time of surgery].
3. Use wound protectors whenever possible
4. Use copious abdominal lavage (warm Lactated or buffered Ringers solution ± antibiotics as foals are more prone to get adhesions.
5. Minimize tissue handling - Intestine is easily irritated and damaged.
6. Recent reports suggests prevention of ischemiainduced small intestinal adhesions in foals using flunixin meglumine and Penicillin and gentamicin treatment [5]; others have suggested treat with IV DMSO at 20 mg/kg diluted in 500 ml saline.

IV. Specific Conditions With Severe Pain Manifestations

1. Enteritis

1. Auxiliary lab tests: CBC, fibrinogen, electrolytes, blood gases and paracentesis are indicated.
2. Blood may have low white blood cell count (degenerative left shift) and peritoneal fluid analysis is usually normal.
3. Clostridium enteritis requires immediate therapy (See Diarrhea).
4. Ultrasound reveals fluid-filled hypermotile small and large intestine.

2. Duodenal-pyloric stenosis
   Clinical signs (See Gastroduodenal Ulcers).

1. Advanced stages of gastric ulcers.
2. Persistent bruxism, salivation and/or regurgitation, endoscopic and radiographic evidence of gastric outflow obstruction.
3. Progressive debilitation and unresponsive to medical therapy.

3. Diagnosis

1. History and clinical signs
2. Upper G.I. barium study - Delayed gastric emptying.

1. Normal 2 hour gastric emptying time after 12 hour fast using 5 ml/kg of a 30% weight/volume barium suspension [6].
2. Gastric endoscopy.

4. Surgery

1. Improved outcome if done before severe debilitation and peritonitis develop. May develop into racing and performance horses based on a report [7].
2. Gastrojejunostomy - Most common procedure.
3. Gastroduodenostomy - Ideal, but more difficult.
4. Must continue ulcer therapy after surgery.
5. Often have secondary hepatitis problem (retrograde infection) or blind loop syndrome.
6. Recent report showed 50% survival rate long term on 16 foals with gastrojejunostomy [7].

5. Small or Large Intestinal Strangulation
   Clinical signs

1. Depression, anorexia, milk stained face.
2. Elevated respiratory and heart rates ± increased temperature.
3. ± Abdominal distension and tympany.
4. Progressive systemic deterioration.
5. May occasionally see milk regurgitation.
6. Persistent pain, even with most analgesics.

6. Diagnosis - Large bowel problems often have slower onset.

1. Clinical signs.
2. Abdominal US, thoracic radiographs can be very useful.
3. Differential diagnosis

1. Intussusception (jejunal-jejunal, ileo-cecal, etc).
2. Diaphragmatic hernia - Thoracic radiographs show distended loop of intestine (usually small).
3. Intra-abdominal hernias (mesenteric rents, etc).
4. Strangulated scrotal hernia - See below.
5. Thromboembolism (large or small bowel) usually seen after a previous surgery.
6. Volvulus of large intestine.

V. Therapy

1. Treat cause if determined.
2. Stabilize with fluids and pain relief.
3. Prevent/treat sepsis

1. Plasma (failure of passive transfer or high risk foal) (See Plasma Therapy).
2. Antimicrobial therapy (high risk foal) (See Guidelines for Drug Use in Equine Neonates):

1. Broad spectrum
2. Anaerobe coverage (if suspected)

4. Analgesia [8,9]

1. NSAIDs, important to maintain adequate hydration. Use low doses due to potential side effects — GI ulceration and nephrotoxicity.

1. Dipyrone (10-20 mg/kg IV or IM), off the market in the US.
2. Ketoprofen (less ulcerogenic) 2.2 mg/kg IV.
3. Flunixin-meglumine (0.25-1.5 mg/kg IV or IM), lower dose used to prevent deleterious effects of endotoxemia.
4. Phenylbutazone (2.2 mg/kg PO or IV) more ulcerogenic.
5. COX-2 specific blockers have not been extensively studied in neonates.
6. Opiate agonists

i. Butorphanol tartrate (0.02-0.1 mg/kg IV or IM). It has been shown to decrease intestinal motility in adults although still the most convenient opioid currently available.
ii. Morphine can be used in foals at a dose of 0.1-0.2 mg/kg IM.
iii. Fentanyl is a highly potent opioid and is most commonly used for musculoskeletal conditions (available as a patch 100 μg/hr release)

2. Tramadol has not been extensively studied in neonatal foals. It has been used to eliminate moderate to severe pain in adult horses at a dose of 1-2 mg/kg IV, IM [9].
3. Anticholinergics: Buscopan (N-butylscopolamine bromide) can be used as a spasmolytic in cases of inflamed bowel or meconium impaction. It has minimal side-effects (mild tachycardia) and can be given at a dose of 0.2-0.3 mg/kg IV q12 hrs.
4. Alpha 2 adrenergic agonists: Xylazine hydrochloride (0.2-0.5 mg/kg IV). More potent in neonates than in adults which will decrease GI motility, can cause marked depression, bradycardia. Whenever possible avoid its use in compromised foals ≤2 weeks old.
5. Prevent/treat gastrointestinal ulceration [10] (See Gastroduodenal Ulcers)

1. Proton pump inhibitors b Mucosal protectants
2. Histamine type 2 receptor antagonists
3. Antacids