Gastrointestinal: Diseases Associated with Colic

Equine colic, characterized by abdominal pain, is a multifaceted condition encompassing a spectrum of etiologies. Understanding the diverse diseases associated with colic, organized by anatomic location, is paramount for veterinary practitioners tasked with diagnosing and managing these complex cases. By delineating the various anatomical sites implicated in colic pathology, clinicians can adopt a systematic approach to evaluation and treatment, ultimately optimizing patient outcomes.

Stomach

Gastric Dilatation and Gastric Rupture Gastric dilatation in horses typically results from excessive gas accumulation or intestinal obstruction, often attributed to the consumption of fermentable feedstuffs like grains, lush grass, or beet pulp. The overproduction of volatile fatty acids is presumed to impede gastric emptying. Left untreated, gastric dilatation can swiftly progress to gastric rupture, particularly when caused by overeating. Mechanical obstruction, typically originating from the small intestine, can lead to gastric dilatation due to fluid accumulation from the obstructed small intestine, resulting in gastric reflux upon nasogastric tube passage. Colonic displacements, especially right dorsal displacement of the colon, may also induce gastric dilatation by obstructing duodenal outflow. Additionally, horses with proximal enteritis-jejunitis may exhibit gastric dilatation alongside fluid accumulation and gastric reflux.

Rupture of the stomach, often along its greater curvature, is a fatal complication of gastric dilatation. Mechanical obstruction, ileus, trauma, or overload are common underlying causes, with mechanical obstruction accounting for the majority of cases. Clinical signs of gastric dilatation include severe abdominal pain, tachycardia, retching, and pale mucous membranes. Once the stomach ruptures, acute signs are typically replaced by depression and toxemia, with a poor prognosis for survival.

Gastric Impaction While uncommon, gastric impaction can cause colic in horses and is linked to various feedstuffs and contributing factors such as diseased teeth or rapid eating. Clinical signs include severe abdominal pain, often leading to a surgical diagnosis due to the lack of other distinctive findings. Treatment usually involves repeated intragastric administration of carbonated drinks or saline/water infusion if identified surgically. Post-surgical care may include massaging the stomach to break down the impaction and gradual reintroduction of feeding. Prognosis is favorable if diagnosed early or if surgical intervention is prompt and successful.

Small intestines

Ileal Impaction Ileal impaction, commonly observed in regions like the southeastern US, Germany, and the Netherlands, often results from infection with the intestinal tapeworm Anoplocephala perfoliata or feeding Coastal Bermuda hay without recent anthelmintic administration. Clinical signs range from mild to severe abdominal pain, reduced intestinal sounds, gastric reflux, and tachycardia. Diagnosis may be challenging due to subsequent distention of the jejunum, complicating identification via rectal examination. Treatment involves fluids and mineral oil if identified early, with surgery indicated in severe cases. Complications may arise postoperatively, including intra-abdominal adhesions.

Intra-abdominal Adhesions Fibrous adhesions within the small intestine are typically a consequence of prior abdominal surgery, chronic distention, peritonitis, or larval parasite migration. Clinical signs vary from mild recurrent colic to severe pain, often manifesting within 60 days of surgery. Surgical treatment involves transection of the adhesion, potential resection of affected intestine, and anastomosis. Prognosis is guarded due to the likelihood of recurrence and poor long-term outcomes.

Ascarid Impaction Young horses, particularly those with inadequate parasite control, may develop small intestinal impactions due to anthelmintic administration targeting Parascaris equorum. Clinical signs include abdominal pain, toxemia, and possible gastric reflux containing ascarids. Treatment may involve medical management or surgical intervention, with a guarded prognosis, especially post-surgery.

Proximal Enteritis-Jejunitis A poorly understood disease affecting the proximal small intestine, proximal enteritis-jejunitis, is associated with regions like the southeastern and northeastern US, England, and Europe. Suspected involvement of Clostridium difficile toxins leads to various lesions, including hyperemia and necrosis. Clinical signs include abdominal pain progressing to depression, moderate to severe small intestinal distention, and increased protein concentration in peritoneal fluid. Treatment options range from medical to surgical, with survival rates reported at 44%, often complicated by acute laminitis.

Intussusception Jejuno-jejunal, ileal-ileal, or ileocecal intussusceptions are common, particularly in horses under three years old. Clinical signs range from acute to chronic abdominal pain, often necessitating surgical intervention for reduction and potential resection. Prognosis depends on the timing of surgery and extent of damage, with adhesion formation posing additional risks.

Small Intestinal Volvulus Volvulus occurs when the small intestine rotates >180° on its mesenteric axis, resulting in vascular compromise. Clinical signs include acute pain, increased heart rate, gastric reflux, dehydration, and elevated PCV and plasma protein concentrations. Surgical correction is necessary, with prognosis influenced by timing and extent of resection.

Pedunculated Lipomas Common in older horses, pedunculated lipomas suspend from the mesentery, occluding intestinal lumens and impeding blood supply. Clinical signs include depression, severe pain, and distended loops of small intestine palpable on rectal examination. Surgery is indicated, with prognosis dependent on promptness of intervention.

Internal incarcerations, most commonly occurring at mesenteric rents and the epiploic foramen, pose significant challenges in equine veterinary medicine. Mesenteric rents represent defects in the small-intestinal mesentery, allowing segments of the small intestine to become incarcerated, often leading to volvulus. Such incidents are not age-specific and can affect horses across all age groups.

The epiploic foramen, a natural opening bound by anatomical structures such as the caudate lobe of the liver and the caudal vena cava, is another critical site for internal incarcerations. Incarcerations through this foramen typically involve the distal jejunum and ileum, sometimes causing tearing of the omentum during the process. While older horses, particularly those over seven years of age, are more frequently affected, cases have been documented in younger animals. Notably, this condition is often linked to windsucking or cribbing behavior.

Clinical manifestations of internal incarcerations may initially be nonspecific, resembling proximal enteritis or pedunculated lipomas. Definitive diagnosis frequently necessitates surgical intervention due to the challenges in clinical assessment. Moreover, the position of the affected intestine within the omental bursa may render peritoneal fluid analysis inconclusive.

Surgical intervention remains the primary treatment modality for horses afflicted with mesenteric rents or epiploic foramen entrapments. The procedure involves the exteriorization of the affected intestinal segment, followed by viability assessment and potential resection and anastomosis if deemed necessary. Prognosis is closely tied to the timeliness of surgical intervention, with early procedures yielding favorable outcomes. However, diagnostic challenges arising from vague clinical signs may delay surgical decisions, negatively impacting prognosis. Laparoscopic techniques, aimed at evaluating and closing affected spaces with mesh, offer promising advancements in treatment methodology.

Inguinal Hernia Associated with Colic in Horses

Inguinal hernias, frequently precipitated by stallion breeding, trauma, or strenuous exercise, constitute another significant cause of equine colic. Predominantly observed in certain breeds such as Tennessee Walking Horses, American Saddlebreds, and Standardbreds, inguinal hernias often manifest as acute colic episodes.

Characteristic clinical findings include swelling and firmness of the affected testis, with palpable intestinal loops within the inguinal canal in acute cases. Reduction attempts may be feasible in early presentations but become futile once intestinal edema sets in. Rectal examinations typically reveal distended loops of small intestine, further aiding diagnosis.

Surgical intervention via a ventral midline celiotomy and inguinal approach remains the cornerstone of treatment. This often entails testicular removal and resection of the affected intestine. Prognosis varies among breeds, with Standardbred horses generally exhibiting more favorable outcomes compared to Tennessee Walking Horses, attributed partly to delayed surgical decisions in the latter.

Cecum and Large Intestine

Impaction of the cecum and large intestine constitutes a significant colic etiology in horses, often precipitated by anatomical predispositions and dietary factors. Common impaction sites include the pelvic flexure region of the left colon, the junctions of various colonic segments, and the cecum itself.

Several predisposing factors contribute to impaction formation, including coarse feed, dental issues, and inadequate water intake. Breed predispositions have also been noted, with Morgan, Arabian, and Appaloosa breeds being overrepresented in clinical studies.

Clinical presentations of cecal and large-colon impactions may vary, with affected horses often exhibiting mild colic signs initially. Diagnosis relies on rectal examination findings, with impacted masses palpable in characteristic anatomical locations. Management strategies encompass both medical and surgical approaches, with aggressive fluid therapy playing a central role in treatment protocols.

Enteral fluid therapy has garnered increasing interest as a cost-effective alternative to intravenous fluid therapy, yielding promising results in clinical practice. Surgical intervention may be warranted in cases resistant to medical management, with procedures such as enterotomies facilitating impaction resolution.

Prognosis varies depending on multiple factors, with survival rates ranging from excellent to guarded based on the severity of clinical presentation and response to treatment.

Enterolithiasis, Right Dorsal Colitis, Volvulus, and Descending Colon Abnormalities Associated with Colic in Horses

Enterolithiasis, right dorsal colitis, volvulus, and descending colon abnormalities represent additional complexities in equine colic cases, each necessitating tailored diagnostic and therapeutic approaches. Enterolithiasis, characterized by magnesium ammonium phosphate crystal concretions, often requires surgical intervention for resolution. Right dorsal colitis, frequently linked to NSAID administration, poses diagnostic and therapeutic challenges, with discontinuation of NSAIDs and dietary modifications forming the cornerstone of management.

Volvulus, marked by the twisting of the colon, mandates surgical correction to alleviate obstruction and restore intestinal integrity. Similarly, abnormalities involving the descending colon, such as impactions and foreign body obstructions, require prompt recognition and intervention to mitigate potential complications.