7 Equine Pelvic Flexure Impactions

• Impactions are the second most common cause of colic in horses

Common Impaction Sites:

• Pelvic flexure impactions are the most common
• Small colon and cecum are other sites
• Small intestinal impactions (ileal) are rare

Pelvic Flexure Impactions

• History includes decreased water intake, partial anorexia, and decreased fecal production
• Risk factors are decreased water intake (cold/frozen or "new tasting" water), bad teeth, and winter

Colic Workup for Pelvic Flexure Impactions:

• Mild to moderate pain is present
• Heart rate may be normal to mildly increased (30-60 bpm)
• Temperature is usually normal, but can have fevers with prolonged or small colon impactions
• Mucous membranes are usually pink, but may be tacky with increased CRT
• Gut sounds are decreased to absent
• Rectal exam reveals a firm impaction of the pelvic flexure without gas distension; many hard, mucus-covered fecal balls may be present in the small colon
• Nasogastric intubation yields no reflux
• Abdominocentesis results are normal, but indicated in severe or unresolved impactions
• Blood work ranges from normal to evidence of dehydration
• In long-duration impactions, the bowel wall can thin, with possible endotoxemia signs like fever, abnormal mucous membranes, and neutropenia

Treatment for Pelvic Flexure/Colonic Impactions:

• Many impactions are treatable medically, referral may not be needed
• Analgesia with flunixin meglumine is important to determine if the horse can be medically managed; if pain persists within 12-24 hours, consider referral
• Stop feed and encourage the horse to drink water (warm), force-feed salt, and provide mild exercise; green grass can be offered as a laxative if impactions are resolving

Oral Therapy:

• Water (with or without electrolytes) aids in correcting dehydration; continue oral fluids if no reflux is present (2-4 L every few hours)
• Mineral oil may be administered
• Cathartics (e.g., Epsom salts (MgSO4), sodium sulfate, or dioctyl sodium sulfosuccinate (DSS)) draw water into the bowel but can irritate the gut

Additional Treatments

• Intravenous fluid therapy is indicated for long-standing or unresolved impactions, or if nasogastric reflux develops; can be done twice maintenance, though not practical in a field setting
• Surgery is indicated if pain cannot be controlled, the impaction is long duration, and signs of cardiovascular compromise appear

Sand Impactions

• Horses with sandy soil access may develop large colon impactions
• Examine feces for sand presence (in a glove) and use radiographs to identify sand in the colon; psyllium hydrophilic mucilloid may help pass sand

Small Colon Impactions

• Risk factors include similar factors to pelvic flexure impactions, plus diarrhea (Salmonella); less common than pelvic flexure impactions

Clinical Signs of Small Colon Impactions

• Similar to pelvic flexure impactions with fever, abdominal distension, endotoxemia, and diarrhea
• Rectal exam reveals a tubular small colon
• Treatment may be medical or surgical, with about 50% requiring surgery

Cecal Impactions

• Two syndromes exist: excessive accumulation of feed material and secondary to a concurrent illness/problem
• Medical treatment can be attempted, but surgery should be strongly considered due to a tendency to rupture

Large Colon Displacements

• To be covered in surgery with comments about left dorsal displacement (LDD, nephrosplenic entrapment)
• LDD involves the large colon on the lateral aspect of the spleen or entrapped between the spleen and the left kidney

Clinical Signs of LDD

• Similar to gas colic with mild to moderate abdominal pain, mild to moderate increase in HR, and decreased gut sounds; no fever or nasogastric reflux; signs of endotoxemia or changes on laboratory work are absent
• Diagnosis is by rectal exam and ultrasound

LDD Treatment

• Medical (analgesics, fluids) treatment can be administered.
• Phenylephrine (alpha agonist) is used to cause vasoconstriction and decrease spleen size. Exercise the horse post administration
• Use phenylephrine carefully with older horses due to the risk of fatal hemorrhage

Anterior Enteritis (Proximal Enteritis, Duodentitis-Proximal Jejunitis)

• Proximal enteritis is an inflammatory condition of the upper small intestine leading to pain (gastric and small intestinal distention) and gastric reflux

Clinical Signs of Anterior Enteritis

• Mild to severe colic, depression
• HR moderately increased (60-80 bpm)
• Temperature normal to elevated (101-103 F)
• Rectal exam may reveal small intestinal distention with possible thickened mesentery; confirm with ultrasound
• Gut sounds decreased to none
• Nasogastric reflux may be present with a range of 4-20 L of red-brown, foul-smelling fluid
• Bloodwork variations include leukopenia, normal, leukocytosis, dehydration, and electrolyte abnormalities
• Abdominocentesis is frequently abnormal
• Diagnosis is based on clinical exam and colic resolution after gastric decompression, very similar to strangulating obstruction of the SMI.

Key Differences Between Proximal Enteritis and Strangulating Lesion:

• Pain: Proximal enteritis resolves with NG reflux, while strangulating lesions continue to be painful
• Reflux Characteristics: Proximal enteritis often has red/brown, foul-smelling reflux
• Fever: Proximal enteritis can often result in a fever
• Leukocytosis: Proximal enteritis can often result in a high WBC count
• Rectal Exam: Proximal enteritis distention is no longer palpable after NG refluxing, but bowel and mesentery may feel thickened. Strangulating lesions still present distention of SI loops
• Abdominocentesis: Not helpful to differentiate; can be abnormal in both. TP can be high and WBC normal in AE.

Pathophysiology of Anterior Enteritis:

• Unknown etiology; may involve infectious agents (Salmonella spp., Clostridium spp.) or mycotoxins
• Hallmarks include secretion of electrolytes, protein, and water into the small intestine lumen, and ileus

Anterior Enteritis Treatment

• Gastric decompression should be performed frequently; reflux amount varies (4-80 L/day)

Fluid therapy:

• Includes correcting dehydration, replacing ongoing losses, and maintenance fluids; IV fluids may be required in large amounts
• Protein/oncotic pressure replacement may be necessary if protein and albumin levels fall (TP < 4.0 gm/dl albumin < 2.0 gm/dl)
• Anti-endotoxin therapy examples: low dose flunixin, polymyxin
• Anti-inflammatory/analgesic drugs, utilizing flunixin meglumine (NSAID) for anti-inflammatory, analgesic and anti-endotoxic effects; clinicians may use DMSO as a free radical scavenger
• Antibiotics may be indicated with low WBC, fever, and elevated liver enzymes; use broad-spectrum antibiotics
• Provide nutrition with partial parental nutrition to horses that are NPO for 3-4 days, through glucose and amino-acid solutions
• Pro-motility agents work best in normal gut and may include lidocaine and metaclopramide
• Once reflux stops, slowly reintroduce water and feed, and consider anti-ulcer drugs