Feline 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 portion is called the intussusceptum, while the receiving segment is the intussuscipiens. This condition represents a surgical emergency in cats and is an important differential diagnosis for acute abdominal conditions on the NAVLE.

While intussusception is less common in cats than in dogs, it carries significant morbidity and mortality if not promptly diagnosed and treated. The condition most commonly affects young cats under one year of age, with approximately 80% of cases occurring in animals less than 12 months old. The ileo-colic junction is the most frequently affected site, though intussusception can occur anywhere along the gastrointestinal tract.

Etiology and Predisposing Factors

Intussusception occurs when increased motility (hyperperistalsis) of an intestinal segment drives it toward a relaxed following segment. The exact cause is often unclear, but several predisposing factors have been identified.

Common Underlying Causes

Breed Predispositions

While intussusception can occur in any cat breed, certain breeds have been reported to have increased susceptibility:

• Siamese cats - historically associated with higher frequency of intussusception
• Maine Coon cats - significant overrepresentation in recent studies (up to 76% of cases in one study)
• Burmese cats - reported predisposition in literature
• Oriental cats - including related breeds

Pathophysiology

Understanding the pathophysiology of intussusception is essential for recognizing the urgency of this condition and predicting clinical progression.

Mechanism of Formation

Intussusception develops when a segment of bowel with hyperperistalsis encounters an adjacent segment with ileus or reduced motility. The hypermotile segment telescopes into the relaxed segment, typically in a normograde direction (following normal peristalsis), though retrograde intussusception can occasionally occur.

Pathophysiological Sequence

• Initial Invagination: The intussusceptum (invaginating bowel) enters the intussuscipiens (receiving bowel), pulling mesentery and blood vessels with it
• Venous Congestion (Early Stage): Constriction of mesenteric vessels between the inner and outer intussusceptum causes venous return obstruction while arterial flow continues
• Edema and Swelling: The affected bowel becomes swollen and congested, with serosal surfaces beginning to adhere through fibrinous exudation
• Arterial Compromise (Late Stage): Progressive constriction eventually obstructs arterial flow, leading to ischemia and necrosis of the affected intestinal wall
• Local Peritonitis: Bacterial translocation and tissue devitalization cause localized peritonitis
• Perforation Risk: If untreated, necrotic bowel may perforate, leading to septic peritonitis and rapid clinical deterioration

Consequences of Obstruction

Intussusception causes partial or complete intestinal obstruction. The severity of clinical signs depends on: degree of obstruction (partial vs. complete), location of intussusception (proximal obstructions cause more severe vomiting), duration of obstruction, and presence of vascular compromise.

Clinical Signs and Presentation

Clinical signs of intussusception in cats can be vague and nonspecific, often mimicking other gastrointestinal disorders. The presentation varies depending on the location, degree of obstruction, and duration of the condition.

Common Clinical Signs

Physical Examination Findings

Palpable Abdominal Mass: A firm, cylindrical or sausage-shaped mass is palpable in approximately 50-53% of cases. This mass represents the intussusception and should be differentiated from feces and foreign bodies. Careful palpation is essential as it may elicit pain.

Rectal Prolapse: In ileocaecocolic intussusceptions, the invaginated segment may prolapse through the anus. Rectal palpation is essential to differentiate true rectal prolapse from prolapsed intussusception - with intussusception, a probe can be passed alongside the prolapsed tissue.

Diagnosis

A combination of clinical suspicion, physical examination findings, and diagnostic imaging is required for accurate diagnosis of intussusception.

Laboratory Findings

Laboratory abnormalities are often nonspecific but help assess the patient's overall condition:

• Complete Blood Count: May be normal; leukopenia with viral infections (panleukopenia); leukocytosis with bacterial infection or peritonitis
• Serum Biochemistry: Hypokalemia, hypochloremia, hyponatremia; hypoalbuminemia in chronic cases; azotemia with severe dehydration
• Fecal Examination: Check for intestinal parasites; may reveal blood or mucus

Diagnostic Imaging

Abdominal Radiography

Survey radiographs may reveal signs of intestinal obstruction but are often nonspecific. Findings may include: gas and fluid-filled dilated loops of bowel proximal to obstruction, poor abdominal detail with peritonitis, and soft tissue mass in the region of the intussusception. Contrast studies (barium series) may help outline the intussusception but have largely been replaced by ultrasonography.

Abdominal Ultrasonography (Diagnostic Modality of Choice)

Ultrasonography is highly reliable for diagnosing intussusception in cats with sensitivity and specificity approaching 100% in experienced hands. The characteristic ultrasonographic appearance includes:

Additional Diagnostic Considerations

• Doppler Ultrasonography: Presence of blood flow in mesenteric vessels correlates with successful manual reduction (75% success rate); absence suggests irreducible intussusception
• Exploratory Laparotomy: Some cases are only confirmed at surgery, particularly when imaging is equivocal

Treatment

Intussusception is a surgical emergency. Treatment involves patient stabilization followed by surgical intervention. Clinical deterioration can be rapid and fatal without prompt treatment.

Preoperative Stabilization

Before surgical intervention, patients require stabilization:

• Intravenous Fluid Therapy: Aggressive crystalloid resuscitation (shock rate: 45-60 mL/kg/hour in cats); correct dehydration and electrolyte imbalances
• Electrolyte Correction: Particularly hypokalemia, hypochloremia; monitor and correct acid-base abnormalities
• Analgesia: Opioids (buprenorphine 0.01-0.02 mg/kg IV/IM; methadone 0.1-0.3 mg/kg IV/IM) provide pain relief and slow bowel motility
• Broad-Spectrum Antibiotics: Target gram-negative aerobes and anaerobes; ampicillin-sulbactam or cefazolin with metronidazole are commonly used

Surgical Management

Surgical Approach

• Perform ventral midline celiotomy for complete abdominal exploration
• Examine entire gastrointestinal tract - multiple intussusceptions can occur simultaneously
• Attempt manual reduction by applying gentle traction on intussusceptum while applying pressure on intussuscipiens
• Assess bowel viability: color (pink = viable; dark red/black = compromised), peristaltic activity, patency of mesenteric vessels
• Perform resection and anastomosis if bowel is non-viable, irreducible, perforated, or mass lesion present
• Consider enteroplication to prevent recurrence (controversial in cats)

Postoperative Care

• Pain Management: Continue opioid analgesia (also helps slow bowel motility)
• IV Fluids: Continue until patient is eating and drinking normally
• Antibiotics: Continue broad-spectrum coverage for 5-7 days
• NPO Period: Withhold food for 12-24 hours post-surgery; reintroduce small, easily digestible meals
• Activity Restriction: Limit activity for 10-14 days post-surgery
• Address Underlying Cause: Deworming, nutritional management, treat primary disease

Prognosis

Prognosis for cats with intussusception is generally good with prompt surgical intervention. However, several factors influence outcome:

Survival rates: Long-term survival rates of 70-80% are reported for cats undergoing surgical treatment. Recurrence typically occurs within the first few weeks post-surgery and requires immediate attention.

Memory Aids and Board Tips

Intussusception Mnemonic: TARGET

T - Telescoping of bowel (intussusceptum into intussuscipiens)

A - Abdominal mass palpable (sausage-shaped, cylindrical)

R - Rings on ultrasound (concentric hyperechoic/hypoechoic)

G - GI signs: vomiting, anorexia, +/- bloody diarrhea

E - Emergency surgery required

T - Typically young animals (less than 1 year)

Key Breed Association: MSSS

Maine Coon, Siamese, Sphynx, and BurmeSe are predisposed breeds (remember: Maine Coon has highest overrepresentation in studies)

Exam Focus: When you see a young cat (especially Maine Coon or Siamese) presenting with vomiting, abdominal pain, and a palpable cylindrical abdominal mass, immediately think INTUSSUSCEPTION. The target sign on transverse ultrasound is diagnostic. Treatment is surgical emergency - stabilize, then operate!