Definition

Pyloric stenosis or chronic hypertrophic pyloric gastropathy is an obstructive narrowing of the pyloric canal resulting from varying degrees of muscular hypertrophy or mucosal hyperplasia.

Pathophysiology

• Can result from a congenital lesion composed primarily of hypertrophy of the smooth muscle or be one of three types of acquired form-primarily circular muscle hypertrophy (type 1), a combination of muscular hypertrophy and mucosal hyperplasia (type 2), or primarily mucosal hyperplasia (type 3).
• The cause is unknown; proposed factors include increased gastrin concentrations (which have a trophic effect on the muscle and mucosa) or changes in the myenteric plexus that lead to chronic antral distension and its associated effects.

Systems Affected

• Gastrointestinal-chronic intermittent vomiting; regurgitation has also been reported.
• Musculoskeletal-weight loss.
• Respiratory-possible aspiration pneumonia.

Genetics

Inheritance pattern unknown

Incidence/Prevalence

Uncommon

Geographic Distribution

N/A

Signalment

Signs

Causes

• Congenital or acquired
• May be influenced by infiltrative mural diseases
• Chronic elevations in gastrin concentrations
• Neuroendocrine factors may play a role

Risk Factors

Chronic stress, inflammatory disorders, chronic gastritis, gastric ulcers, and genetic predispositions influence the disease process in humans and may play a role in small animals.

Differential Diagnosis

• Gastric neoplasia
• Gastric foreign body
• Granulomatous fungal disease (e.g., pythiosis)
• Eosinophilic granuloma
• Motility disorders
• Cranial abdominal mass-pancreatic or duodenal

CBC/Biochemistry/Urinalysis

• Findings vary, depending on the degree and chronicity of obstruction.
• Hypochloremic metabolic alkalosis (characteristic of pyloric outflow obstruction) or metabolic acidosis (or mixed acid-base imbalance).
• Hypokalemia.
• Anemia-if concurrent GI ulceration.
• Prerenal azotemia-if dehydration present.

Other Laboratory Tests

N/A

Imaging

Diagnostic Procedures

Endoscopy-allows evaluation of the mucosa for ulceration, hyperplasia, and mass lesions; specimens can be obtained for histopathologic evaluation.

Pathologic Findings

• Include focal to multifocal mucosal polyps, diffuse mucosal thickening, and pyloric wall thickening, with variable degree of pyloric narrowing.
• Changes range from hypertrophy of the circular smooth muscle to hyperplasia of the mucosa and associated glandular structures; a wide spectrum of inflammatory cell infiltration exists.

Appropriate Health Care

• Depends on severity of clinical signs.
• Patients should be evaluated and surgery scheduled at the earliest convenience.

Nursing Care

• Appropriate parenteral fluids to correct any electrolyte imbalances and metabolic alkalosis or acidosis.
• Isotonic saline (with potassium supplementation) is the fluid of choice for hypochloremic metabolic alkalosis.
• Consideration of postoperative nutritional support is important.
• In severe cases treated with gastroduodenostomy or gastrojejunostomy, surgical placement of a jejunostomy tube for enteral nutrition may be advantageous.

Activity

Restrict

Diet

Highly digestible, low-fat-until surgical intervention is feasible.

Client Education

• Surgical treatment is highly successful.
• If clinical signs recur postoperatively, more aggressive surgical procedures may be indicated.

Surgical Considerations

• Surgical intervention is the treatment of choice.
• Goals involve establishing a diagnosis with histopathologic samples, excising abnormal tissue, and restoring GI function with the least-invasive procedure.
• Surgical procedures depend on the extent of obstruction-pyloromyotomy (Fredet-Ramstedt), pyloroplasty (Heineke-Mikulicz or antral advancement flap), gastroduodenostomy (Billroth 1), gastrojejunostomy (Billroth 2).

Drug(s) Of Choice

• Antiemetics and motility modifiers are generally ineffective.
• H₂-antagonists and proton pump inhibitors may provide symptomatic relief.

Contraindications

• Evidence of complete pyloric obstruction precludes the use of promotility drugs.
• Avoid anticholinergic agents because of their inhibitory effects on GI motility.

Precautions

N/A

Possible Interactions

N/A

Alternative Drug(s)

N/A

Patient Monitoring

Postoperatively for recurrence of clinical signs because of poor choice of surgical procedure.

Prevention/Avoidance

N/A

Possible Complications

Postoperative surgical complications include recurrence of clinical signs, gastric ulceration, pancreatitis, bile duct obstruction, and incisional dehiscence with peritonitis.

Expected Course and Prognosis

• 85% of dogs show good-to-excellent results with resolution of clinical signs upon proper surgical intervention.
• Poor prognosis if gastric neoplasia (especially adenocarcinoma) is an underlying cause.

Associated Conditions

Gastric ulceration

Age-Related Factors

Intermittent vomiting in young brachycephalic breeds upon weaning is suggestive of congenital stenosis.

Zoonotic Potential

None

Pregnancy/Fertility/Breeding

High gastrin concentrations in pregnant females may predispose to development of the syndrome.

Synonyms

• Chronic hypertrophic antral gastropathy
• Hypertrophic gastritis
• Acquired antral pyloric hypertrophy
• Congenital pyloric stenosis

Abbreviation

GI = gastrointestinal