Canine Intussusception Study Guide

Overview and Clinical Importance

Intussusception is the invagination (or telescoping) of one segment of the gastrointestinal tract into the lumen of an adjacent segment. The invaginated segment is termed the intussusceptum, while the enveloping outer segment is called the intussuscipiens. This condition represents a surgical emergency in veterinary medicine because it leads to intestinal obstruction, compromised blood supply, tissue necrosis, and potentially life-threatening peritonitis if left untreated.

Intussusception is a common cause of bowel obstruction in small animals and is most frequently encountered in young dogs (less than 1 year of age). The condition requires rapid recognition and surgical intervention for optimal patient outcomes. Understanding the etiology, clinical presentation, diagnostic approach, and surgical management is essential for NAVLE success.

Etiology and Pathophysiology

Mechanism of Intussusception

Intussusception occurs when there is abnormal intestinal motility characterized by a segment of hypermotile bowel adjacent to a segment with decreased motility (ileus). The hypermotile segment telescopes into the adjacent relaxed segment, typically in the direction of normal peristalsis (normograde or direct intussusception). Retrograde intussusception can occur but is less common.

The pathophysiology progresses as follows: initial invagination causes partial obstruction, which may progress to complete obstruction. The mesentery becomes trapped between the intussusceptum and intussuscipiens, leading to venous congestion and edema of the invaginated segment. Progressive constriction eventually compromises arterial blood flow, causing ischemia and necrosis. Fibrinous adhesions form between serosal surfaces, and if left untreated, bowel perforation and peritonitis develop.

Predisposing Factors and Underlying Causes

Any condition causing intestinal inflammation (enteritis) or altered motility can predispose to intussusception. In approximately 67% of cases, no identifiable cause is found (idiopathic). The most common predisposing factors include:

Signalment and Breed Predispositions

Approximately 75% of dogs with intussusception are less than 1 year of age. Large breed dogs may be more commonly affected, although intussusception can occur in any breed. German Shepherds are particularly predisposed to gastroesophageal intussusception. When intussusception occurs in older dogs (greater than 3-4 years), neoplasia should be suspected as an underlying cause.

Types and Anatomical Locations

The most common location for intussusception in dogs is the ileocolic junction (ileum into colon/cecum), accounting for approximately 43-50% of cases. Jejunojejunal intussusception is the second most common type.

Clinical Signs and Presentation

Clinical signs vary based on the location of intussusception, degree of obstruction (partial vs. complete), duration, and presence of vascular compromise. Signs may be acute or chronic/intermittent.

Acute Presentation

• Vomiting - often persistent; may be bilious or contain blood
• Diarrhea - frequently bloody (hematochezia) or mucoid; "currant jelly" appearance
• Abdominal pain - may present as hunched posture, reluctance to move
• Depression and lethargy
• Anorexia
• Dehydration - tachycardia, prolonged CRT, pale mucous membranes

Chronic Presentation

• Intermittent, intractable diarrhea
• Weight loss and emaciation
• Hypoalbuminemia - intussusception is one of the two major causes of protein-losing enteropathy in dogs less than 12 months of age (along with parasites)
• Intermittent episodes of obstruction that spontaneously resolve

Physical Examination Findings

• Palpable abdominal mass - reported in approximately 53% of cases; firm, tubular, "sausage-shaped" structure
• Abdominal distension
• Tenesmus (especially with ileocolic intussusception)
• Rectal prolapse of intussuscepted segment - distinguish from true rectal prolapse by attempting to pass a probe alongside the prolapsed tissue (impossible with intussusception, possible with rectal prolapse)
• Signs of shock in severe cases: tachycardia, weak pulses, prolonged CRT, hypothermia

Diagnosis

Laboratory Findings

Laboratory abnormalities are often nonspecific and reflect the underlying cause and degree of illness:

• CBC: Leukocytosis or leukopenia (if concurrent parvovirus), stress leukogram, hemoconcentration from dehydration
• Serum biochemistry: Electrolyte abnormalities (hypokalemia, hypochloremia), azotemia (prerenal), hypoalbuminemia in chronic cases, elevated lactate
• Fecal examination: To rule out parasites as underlying cause; parvovirus ELISA testing

Diagnostic Imaging

Abdominal Radiography

Plain radiographs have limited sensitivity (approximately 48%) for detecting intussusception. Findings may include:

• Signs of intestinal obstruction: dilated, gas/fluid-filled intestinal loops
• Soft tissue density mass effect in abdomen
• Decreased serosal detail (if peritonitis present)
• "Gravel sign" - granular appearance from trapped ingesta

Contrast (barium) studies may show a "coiled spring" appearance as contrast outlines the intussusception, but have largely been replaced by ultrasound.

Abdominal Ultrasonography - Gold Standard

Ultrasound has 98-100% sensitivity and 88-100% specificity for diagnosing intussusception. It is the imaging modality of choice.

Board Tip - Memory Aid: "TARGET your diagnosis with ultrasound!" The TARGET SIGN is pathognomonic for intussusception. Think of it like looking at a dartboard (target) from above - you see concentric rings. On longitudinal view, you see "stacked pancakes" or parallel lines.

Doppler Ultrasound for Reducibility Prediction

Color Doppler assessment of blood flow to the intussusceptum can help predict reducibility and bowel viability. Absence of blood flow suggests non-viability and the need for resection rather than manual reduction.

Treatment

Preoperative Stabilization

Intussusception is a surgical emergency. However, patient stabilization prior to anesthesia is essential:

• IV fluid therapy: Correct dehydration and electrolyte imbalances (crystalloids; colloids if hypoalbuminemic)
• Broad-spectrum antibiotics: For bacterial translocation risk (ampicillin/sulbactam, or cefazolin plus metronidazole)
• Analgesia: Opioids (methadone, hydromorphone) - also help slow intestinal motility
• Antiemetics: Maropitant (1 mg/kg IV or SC q24h)
• Address underlying cause: Continue parvovirus treatment if applicable

Surgical Options

Surgical Decision Making

Assessment of bowel viability is critical. Signs of viable bowel include: pink color, presence of peristalsis, pulsatile mesenteric vessels, and return of color after decompression. Non-viable bowel appears dark purple/black, lacks peristalsis, and has no mesenteric pulses - these segments require resection.

Postoperative Care

• Continued IV fluid therapy: Until eating normally
• Analgesia: Opioids (also provide GI motility benefits)
• Antiemetics: As needed
• Antibiotics: Depending on contamination level
• Early enteral nutrition: Small, frequent meals of highly digestible food within 12-24 hours if tolerated
• Treat underlying cause: Deworming, continue parvovirus treatment, address dietary issues
• Monitor for recurrence: Most recurrences occur within 72 hours to 3 weeks postoperatively

Prognosis and Complications

Prognosis

With appropriate surgical treatment, prognosis is generally good. Survival rates with surgical correction range from 70-90% depending on underlying cause and timing of intervention. Factors affecting prognosis include:

• Duration of intussusception (better if treated early)
• Underlying cause (parvovirus carries higher mortality)
• Presence/absence of peritonitis
• Amount of bowel resected
• Prevention of recurrence

Complications

Board Tip - Recurrence Prevention: "TRAP" prevents recurrence: Treat the underlying cause (deworm, treat enteritis) Resect non-viable bowel (don't just reduce if damaged) Assess for enteroplication (selective cases) Prevent parasites/parvovirus with routine preventive care

Differential Diagnosis

When a young dog presents with vomiting, bloody diarrhea, and abdominal pain, consider:

• Parvoviral enteritis - can be concurrent with intussusception
• Intestinal foreign body obstruction
• Hemorrhagic gastroenteritis (HGE)
• Intestinal volvulus/mesenteric torsion
• Severe parasitism
• Intestinal neoplasia (especially in older dogs)
• Rectal prolapse - distinguish from prolapsed intussusception