Megaesophagus

Megaesophagus is a clinical syndrome characterized by diffuse esophageal dilation and decreased or absent esophageal motility, leading to impaired transport of ingesta from the pharynx to the stomach. It can be congenital or acquired, and is classified as either generalized (involving the entire esophagus) or segmental (focal dilation). The condition results in regurgitation, malnutrition, and aspiration pneumonia, which are major causes of morbidity and mortality. In veterinary medicine, megaesophagus is most commonly recognized in dogs, but it also occurs in cats. The pathophysiology involves dysfunction of the esophageal neuromuscular apparatus, including the vagus nerve, esophageal myenteric plexus, or esophageal smooth and skeletal muscle. Congenital megaesophagus is often idiopathic and may resolve spontaneously, while acquired forms are associated with various underlying diseases such as myasthenia gravis, hypoadrenocorticism, esophagitis, or mechanical obstruction. The clinical presentation is characterized by regurgitation of undigested food shortly after eating, weight loss, and respiratory signs due to aspiration. Diagnosis is based on thoracic radiography showing diffuse esophageal dilation, and further diagnostic testing is aimed at identifying the underlying cause. Treatment focuses on nutritional management, positioning during feeding, and addressing the primary disease. Prognosis varies depending on the etiology and severity of complications.

The etiology of megaesophagus can be divided into congenital and acquired forms. Congenital megaesophagus is typically idiopathic, but may be inherited in certain breeds such as the Wire Fox Terrier, Miniature Schnauzer, and German Shepherd Dog. It is thought to result from incomplete maturation of the esophageal neuromuscular function, which often improves with age. Acquired megaesophagus has numerous causes: 1) Neuromuscular diseases: Myasthenia gravis (focal or generalized) is the most common cause, accounting for up to 25% of cases. Other neuromuscular disorders include polymyositis, dermatomyositis, polyneuropathy (e.g., dysautonomia, polyradiculoneuritis), and muscular dystrophy. 2) Endocrine disorders: Hypoadrenocorticism (Addison's disease) can cause megaesophagus due to electrolyte imbalances and weakness. Hypothyroidism has been implicated but is controversial. 3) Esophagitis: Severe esophagitis, often due to gastroesophageal reflux, hiatal hernia, or ingestion of caustic substances, can lead to fibrosis and motility dysfunction. 4) Mechanical obstruction: Foreign bodies, strictures, neoplasia (e.g., esophageal carcinoma, lymphoma), or vascular ring anomalies (e.g., persistent right aortic arch) can cause dilation proximal to the obstruction. 5) Toxic and drug-induced: Lead poisoning, organophosphate toxicity, and certain drugs (e.g., corticosteroids, anticholinergics) have been associated with esophageal dysfunction. 6) Infectious: Rarely, protozoal (Trypanosoma cruzi causing Chagas disease) or parasitic (Spirocerca lupi) infections can cause megaesophagus. 7) Idiopathic: In many cases, no underlying cause is identified, and the condition is termed idiopathic megaesophagus. The exact molecular triggers are often unknown, but immune-mediated mechanisms are suspected in myasthenia gravis, where autoantibodies target acetylcholine receptors at the neuromuscular junction.

Megaesophagus occurs in both dogs and cats, but is more common in dogs. Congenital megaesophagus is typically diagnosed in puppies and kittens under 1 year of age, with certain breeds predisposed: Wire Fox Terrier, Miniature Schnauzer, German Shepherd Dog, Great Dane, Irish Setter, Labrador Retriever, and Shar Pei. In cats, congenital megaesophagus is rare but has been reported in Siamese and domestic shorthair breeds. Acquired megaesophagus is more common in middle-aged to older animals, with a median age of 7-10 years in dogs. There is no strong sex predilection, though some studies suggest a slight male predominance. The incidence of megaesophagus in the general dog population is estimated at 0.2-0.5%, but it is higher in breeds with genetic predisposition. Geographic variation may reflect the prevalence of underlying infectious diseases, such as Chagas disease in Latin America. Seasonal patterns are not typically observed, except for cases associated with toxic exposures (e.g., lead) which may be more common in certain environments. The overall prognosis is guarded, with mortality rates ranging from 20-50% due to aspiration pneumonia and malnutrition.

The pathophysiology of megaesophagus involves disruption of the normal esophageal motility and lower esophageal sphincter (LES) function. The esophagus is composed of striated muscle in the cranial two-thirds and smooth muscle in the caudal third in dogs and cats. Swallowing is a complex reflex involving the swallowing center in the medulla, vagus nerve (CN X), and myenteric plexus. In congenital megaesophagus, there is a delay in maturation of the esophageal neuromuscular function, leading to achalasia-like dysfunction. In acquired megaesophagus, the underlying cause leads to either neurogenic or myogenic failure. In myasthenia gravis, autoantibodies against nicotinic acetylcholine receptors at the neuromuscular junction impair signal transmission, causing muscle weakness and esophageal dilation. In hypoadrenocorticism, electrolyte imbalances (hyponatremia, hyperkalemia) and glucocorticoid deficiency can lead to muscle weakness and altered neuromuscular transmission. Esophagitis causes inflammation and fibrosis, which disrupts the normal peristaltic waves. Mechanical obstruction leads to dilation proximal to the obstruction due to increased intraluminal pressure. The loss of peristalsis results in accumulation of food and saliva in the esophagus, leading to dilation. The LES may be normal or dysfunctional; in some cases, it fails to relax (achalasia), but this is less common. The stasis of ingesta predisposes to esophagitis, ulceration, and aspiration pneumonia. Aspiration occurs due to regurgitation and inhalation of esophageal contents into the respiratory tract, causing chemical and bacterial pneumonia. Chronic malnutrition and weight loss result from inadequate nutrient absorption. Secondary complications include dehydration, electrolyte imbalances, and in severe cases, esophageal rupture.

Predisposing factors for megaesophagus include genetic predisposition in certain breeds, such as Wire Fox Terriers and Miniature Schnauzers, which have an inherited form of congenital megaesophagus. Age is a factor, with congenital cases presenting in young animals and acquired cases in older animals. Concurrent diseases that affect neuromuscular function, such as myasthenia gravis, polymyositis, or hypoadrenocorticism, increase the risk. Endocrine disorders like hypothyroidism and diabetes mellitus may also predispose, though the association is weaker. Environmental factors include exposure to toxins (lead, organophosphates) and certain drugs (e.g., corticosteroids, anticholinergics). Dietary factors, such as feeding from elevated bowls or rapid eating, may exacerbate regurgitation but are not primary causes. Stress and excitement can worsen clinical signs. In cats, megaesophagus is often associated with esophagitis due to gastroesophageal reflux, which can be triggered by anesthesia or hiatal hernia. Immunosuppression, whether due to disease or medication, may increase susceptibility to infectious causes. Finally, iatrogenic factors, such as esophageal surgery or trauma, can lead to motility dysfunction.

The clinical signs of megaesophagus are primarily related to regurgitation and respiratory complications. Regurgitation is the hallmark sign, typically occurring within minutes to hours after eating, and is characterized by passive expulsion of undigested food and saliva without nausea or retching. In congenital cases, signs appear soon after weaning, with failure to thrive, poor growth, and frequent regurgitation. In acquired cases, signs may develop gradually, with intermittent regurgitation initially. Weight loss and muscle wasting are common due to inadequate nutrient intake. Ptyalism (excessive salivation) and nasal discharge may be observed, especially if food is regurgitated into the nasopharynx. Respiratory signs include coughing, gagging, dyspnea, and fever, which indicate aspiration pneumonia. On physical examination, affected animals may be thin, with a palpable dilated esophagus in the cervical region (especially in severe cases). Crackles or wheezes may be auscultated over the lung fields if pneumonia is present. In cases of underlying myasthenia gravis, generalized muscle weakness, exercise intolerance, and megaeosophagus may coexist. Hypoadrenocorticism may present with lethargy, vomiting, diarrhea, and collapse. In chronic cases, signs of malnutrition, such as poor coat quality and anemia, may be evident. The severity of clinical signs can vary from mild to severe, and some animals may be asymptomatic, with megaesophagus discovered incidentally on radiographs.

Differential diagnoses for megaesophagus include: 1) Esophageal stricture: This is a narrowing of the esophageal lumen due to fibrosis, often secondary to esophagitis or trauma. It presents with regurgitation, but radiographs may show focal dilation proximal to the stricture, and contrast esophagography or endoscopy can confirm the stricture. 2) Esophageal foreign body: A foreign body can cause partial or complete obstruction, leading to dilation proximal to the obstruction. Radiographs may show a radiopaque foreign body, and endoscopy is diagnostic. 3) Esophageal neoplasia: Tumors such as squamous cell carcinoma or lymphoma can cause obstruction and dilation. Radiographs may show a mass, and biopsy is needed for definitive diagnosis. 4) Vascular ring anomaly: This congenital condition, such as persistent right aortic arch, causes esophageal constriction at the base of the heart, leading to dilation of the cranial esophagus. It typically presents in young animals, and contrast radiography or CT angiography can identify the anomaly. 5) Hiatal hernia: This is the protrusion of the stomach into the thoracic cavity through the esophageal hiatus, which can cause regurgitation and esophageal dilation. Radiographs may show a soft tissue opacity in the caudal thorax, and fluoroscopy can demonstrate the hernia. 6) Esophagitis: Inflammation of the esophagus can cause motility dysfunction and dilation. Endoscopy is the gold standard for diagnosis, showing erythema, erosions, or ulcers. 7) Myasthenia gravis: This neuromuscular disease can cause megaesophagus, but it is a cause rather than a differential. However, other causes of megaesophagus must be ruled out. 8) Hypoadrenocorticism: This endocrine disorder can cause megaesophagus, but it is also a cause. 9) Dysautonomia: This is a dysfunction of the autonomic nervous system, which can cause esophageal dilation, along with other signs such as dry mucous membranes, mydriasis, and constipation. 10) Polymyositis: This inflammatory muscle disease can affect the esophagus, leading to megaesophagus. It is diagnosed by muscle enzyme elevation and biopsy. Each differential is ruled in or out based on history, physical exam, imaging, and specific tests such as acetylcholine receptor antibody titers, ACTH stimulation test, or endoscopy.

The diagnostic algorithm for megaesophagus begins with a thorough history and physical examination, focusing on regurgitation and respiratory signs. The initial step is thoracic radiography (right lateral and ventrodorsal views) to assess for esophageal dilation. If megaesophagus is confirmed, the next step is to determine the underlying cause. A complete blood count, serum biochemistry profile, and urinalysis are performed to screen for metabolic and endocrine diseases. Specifically, an ACTH stimulation test is recommended to rule out hypoadrenocorticism, especially if electrolyte abnormalities are present. A serum acetylcholine receptor antibody titer is highly specific for myasthenia gravis; if negative, a Tensilon (edrophonium) test or electromyography may be considered. Further imaging, such as contrast esophagography (barium swallow) or fluoroscopy, can evaluate esophageal motility and identify mechanical obstructions. Esophagoscopy is indicated if a stricture, foreign body, or mass is suspected, and allows for biopsy. If a neuromuscular disorder is suspected, muscle biopsy, nerve biopsy, or genetic testing may be pursued. In cases of suspected esophagitis, endoscopy is the gold standard. If no underlying cause is found, a diagnosis of idiopathic megaesophagus is made. The diagnostic workup should be systematic and may involve referral to a specialist for advanced testing.

Laboratory findings in megaesophagus are often nonspecific but can provide clues to the underlying cause. A complete blood count may reveal leukocytosis with a left shift if aspiration pneumonia is present, or eosinophilia in cases of parasitic infection. Anemia may be present due to chronic inflammation or malnutrition. Serum biochemistry may show electrolyte abnormalities, such as hyponatremia and hyperkalemia, which are classic for hypoadrenocorticism. Hypochloremia and metabolic alkalosis can occur due to loss of gastric acid from regurgitation. Elevated creatine kinase (CK) may indicate muscle damage, as in polymyositis. Hypoalbuminemia may result from malnutrition or protein-losing enteropathy. Blood gas analysis may reveal respiratory acidosis or hypoxemia if pneumonia is severe. Specific biomarkers: Serum acetylcholine receptor antibody titers are elevated in 90% of dogs with myasthenia gravis and megaesophagus. A baseline cortisol level and ACTH stimulation test are used to diagnose hypoadrenocorticism. Thyroid hormone levels (T4, TSH) may be assessed if hypothyroidism is suspected. In cats, feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) testing may be considered. Urinalysis may show evidence of urinary tract infection or ketonuria if diabetic ketoacidosis is present. In cases of lead poisoning, blood lead levels can be measured. Overall, laboratory tests are essential for identifying the underlying etiology and guiding treatment.

Imaging plays a crucial role in the diagnosis and management of megaesophagus. Thoracic radiography is the initial imaging modality and typically shows a dilated esophagus filled with air, food, or fluid. On the lateral view, a dorsal deviation of the trachea and a soft tissue opacity in the cranial thorax may be seen. The esophagus may appear as a tubular structure with a thin wall, and in severe cases, it can be seen extending from the thoracic inlet to the diaphragm. In the ventrodorsal view, the esophagus may be seen as a wide mediastinal silhouette. Radiographs can also identify complications such as aspiration pneumonia, which appears as an alveolar pattern in the dependent lung lobes. Contrast esophagography using barium sulfate can be performed to evaluate esophageal motility and identify strictures, foreign bodies, or masses. Fluoroscopy is the gold standard for assessing esophageal motility, as it allows real-time evaluation of swallowing and peristalsis. Ultrasonography is less commonly used but can be helpful in assessing the cervical esophagus and identifying masses. Computed tomography (CT) can provide detailed cross-sectional images of the esophagus and surrounding structures, and is particularly useful for detecting vascular ring anomalies or neoplasia. Magnetic resonance imaging (MRI) may be used to evaluate the brainstem or vagus nerve if a central cause is suspected. Endoscopy is both diagnostic and therapeutic, allowing direct visualization of the esophageal mucosa, detection of esophagitis, strictures, or masses, and collection of biopsy samples. In cases of suspected hiatal hernia, fluoroscopy or endoscopy can confirm the diagnosis. Overall, imaging is essential for confirming megaesophagus and identifying the underlying cause.

Cytology and histopathology are important for diagnosing the underlying cause of megaesophagus. Fine needle aspiration (FNA) of an esophageal mass or enlarged lymph node can be performed, and cytology may reveal neoplastic cells (e.g., lymphoma, carcinoma) or inflammatory cells. Bronchoalveolar lavage (BAL) may be performed if aspiration pneumonia is suspected, and cytology of the lavage fluid can show neutrophils, bacteria, or foreign material. Histopathological examination of esophageal biopsies obtained via endoscopy can reveal inflammation (esophagitis), fibrosis, or neoplasia. In cases of myasthenia gravis, a muscle biopsy may show evidence of immune-mediated myositis, with lymphocytic infiltration and muscle fiber necrosis. A nerve biopsy may show axonal degeneration or demyelination in cases of polyneuropathy. In cases of polymyositis, muscle biopsy is diagnostic, showing inflammatory infiltrates and muscle fiber degeneration. In cases of dysautonomia, histopathology of autonomic ganglia may show neuronal degeneration. Special stains, such as immunohistochemistry for acetylcholine receptor antibodies, can be performed on muscle biopsies. In cases of infectious esophagitis, special stains (e.g., Gram stain, fungal stains) or PCR may be used to identify the organism. Overall, cytology and histopathology are essential for establishing a definitive etiologic diagnosis when a mass or inflammatory lesion is present.

The treatment of megaesophagus is multifaceted and depends on the underlying cause. The primary goals are to manage regurgitation, prevent aspiration pneumonia, and address the primary disease. Nutritional management is crucial: affected animals should be fed a high-calorie, highly digestible diet in small, frequent meals. The consistency of food may need to be adjusted; some animals do better with a gruel or slurry, while others tolerate meatballs or canned food. Feeding in an elevated position (e.g., using a Bailey chair) is essential to use gravity to help move food into the stomach. Animals should remain in an upright position for at least 10-15 minutes after eating. If regurgitation is severe, a gastrostomy tube may be placed for enteral nutrition. Medical therapy for underlying causes: For myasthenia gravis, anticholinesterase drugs such as pyridostigmine bromide (0.5-3 mg/kg PO q8-12h) are used, and immunosuppressive doses of corticosteroids (e.g., prednisone 0.5-2 mg/kg PO q12h) may be added if the disease is immune-mediated. For hypoadrenocorticism, mineralocorticoid (desoxycorticosterone pivalate 2.2 mg/kg IM q25d or fludrocortisone acetate 0.01-0.02 mg/kg PO q24h) and glucocorticoid (prednisone 0.2-0.5 mg/kg PO q24h) replacement therapy is indicated. For esophagitis, treatment includes gastric acid suppressants such as omeprazole (0.7-1 mg/kg PO q12-24h) or famotidine (0.5-1 mg/kg PO q12h), and sucralfate (0.5-1 g PO q8h) as a mucosal protectant. If a mechanical obstruction is present, surgical intervention may be necessary, such as removal of a foreign body, resection of a stricture, or correction of a vascular ring anomaly. For idiopathic megaesophagus, treatment is symptomatic, focusing on nutritional support and prevention of aspiration. Prokinetic agents such as metoclopramide (0.2-0.4 mg/kg PO q8h) or cisapride (0.5 mg/kg PO q8-12h) may be tried, but their efficacy is limited. Sildenafil (0.5-1 mg/kg PO q8-12h) has been used to relax the lower esophageal sphincter in some cases. Antibiotics are indicated if aspiration pneumonia is present, based on culture and sensitivity. Supportive care includes fluid therapy, antiemetics if needed, and management of complications. Physical rehabilitation, such as massage and passive range of motion exercises, may be beneficial for animals with neuromuscular weakness.

The prognosis for megaesophagus varies widely depending on the underlying cause and the presence of complications. Congenital idiopathic megaesophagus has a fair to good prognosis, with up to 75% of puppies showing spontaneous improvement by 6-12 months of age. However, some animals may have persistent signs. Acquired megaesophagus due to myasthenia gravis has a guarded prognosis; with appropriate treatment, some animals improve, but the condition can be fatal due to aspiration pneumonia. Hypoadrenocorticism-associated megaesophagus has a good prognosis if the endocrine disorder is managed properly, and esophageal function often returns to normal. Esophagitis-induced megaesophagus may resolve with treatment of the underlying inflammation. Mechanical obstructions have a good prognosis if surgically corrected early. Idiopathic megaesophagus has a poor to guarded prognosis, as it is often progressive and unresponsive to medical therapy. The overall mortality rate is high, with aspiration pneumonia being the leading cause of death. Negative prognostic indicators include severe aspiration pneumonia, marked weight loss, and lack of response to treatment. Animals that are able to maintain adequate nutrition and avoid aspiration have a better chance of survival. Long-term management is often required, and owners must be committed to the feeding regimen and monitoring for complications.

Follow-up care for megaesophagus is essential to monitor response to treatment and detect complications. Initially, re-evaluation should occur within 1-2 weeks after diagnosis to assess clinical improvement and adjust feeding strategies. Thoracic radiographs should be repeated to evaluate esophageal dilation and resolution of pneumonia. For animals with myasthenia gravis, serum acetylcholine receptor antibody titers can be monitored every 4-8 weeks to guide immunosuppressive therapy. For hypoadrenocorticism, electrolyte levels and clinical signs should be monitored regularly, with ACTH stimulation tests repeated as needed. For animals on corticosteroids, blood pressure, glucose, and urine protein-to-creatinine ratio should be monitored periodically. Nutritional status should be assessed by serial body weight measurements and body condition scoring. Owners should be educated on the signs of aspiration pneumonia, such as coughing, fever, and lethargy, and instructed to seek immediate veterinary care if these occur. Long-term follow-up every 3-6 months is recommended for chronic cases, with repeat imaging and laboratory testing as indicated. Adjustments to medication dosages may be necessary based on clinical response and adverse effects. In cases of surgical correction, follow-up imaging is needed to ensure patency and resolution of dilation. Overall, a proactive and vigilant follow-up plan is crucial for optimizing outcomes.

Clinical pearls: 1) Always consider megaesophagus in any dog or cat presenting with regurgitation, not vomiting. 2) Thoracic radiographs should be taken before and after feeding to increase the sensitivity of detecting esophageal dilation. 3) A normal barium swallow does not rule out megaesophagus; fluoroscopy is the gold standard for motility assessment. 4) Myasthenia gravis is the most common cause of acquired megaesophagus in dogs, so an acetylcholine receptor antibody titer should be performed in all cases. 5) Hypoadrenocorticism can be a hidden cause; an ACTH stimulation test is indicated even if electrolytes are normal. 6) Feeding in an upright position (Bailey chair) is the most important therapeutic intervention. 7) Aspiration pneumonia is a common and life-threatening complication; prophylactic antibiotics are not recommended, but early recognition and treatment are critical. 8) In congenital megaesophagus, spontaneous improvement is possible, so aggressive supportive care is warranted. Pitfalls: 1) Misinterpreting regurgitation as vomiting and treating with antiemetics, which are ineffective. 2) Failing to perform thoracic radiographs in animals with chronic cough or respiratory signs, leading to missed diagnosis. 3) Assuming that a negative acetylcholine receptor antibody titer rules out myasthenia gravis; a Tensilon test or electromyography may be needed. 4) Overlooking hypoadrenocorticism in animals with normal electrolytes; an ACTH stimulation test is essential. 5) Using prokinetic agents as sole therapy without addressing the underlying cause. 6) Feeding from the floor, which exacerbates regurgitation. 7) Delaying surgical intervention in cases of mechanical obstruction, leading to irreversible dilation. 8) Failing to monitor for aspiration pneumonia, which can be silent in early stages.

Current drug protocols for megaesophagus are directed at the underlying cause and complications. For myasthenia gravis: Pyridostigmine bromide (Mestinon) at 0.5-3 mg/kg PO q8-12h, starting at the low end and titrating up based on response and adverse effects (e.g., diarrhea, salivation). If inadequate response, add immunosuppressive doses of prednisone (0.5-2 mg/kg PO q12h) with careful monitoring for worsening weakness. For hypoadrenocorticism: Desoxycorticosterone pivalate (DOCP, Percorten-V) at 2.2 mg/kg IM or SC q25d, with dose adjustments based on electrolytes. Alternatively, fludrocortisone acetate (Florinef) at 0.01-0.02 mg/kg PO q24h. Prednisone at 0.2-0.5 mg/kg PO q24h is also required. For esophagitis: Omeprazole (GastroGard) at 0.7-1 mg/kg PO q12-24h, or famotidine (Pepcid) at 0.5-1 mg/kg PO q12h. Sucralfate (Carafate) at 0.5-1 g PO q8h, given on an empty stomach. For aspiration pneumonia: Antibiotics such as amoxicillin-clavulanate (Clavamox) at 12.5-25 mg/kg PO q12h, or enrofloxacin (Baytril) at 5-10 mg/kg PO q24h, based on culture and sensitivity. For prokinetic therapy: Metoclopramide (Reglan) at 0.2-0.4 mg/kg PO q8h, or cisapride (Propulsid) at 0.5 mg/kg PO q8-12h (if available). Sildenafil (Viagra) at 0.5-1 mg/kg PO q8-12h may be used to reduce lower esophageal sphincter tone. For nutritional support: If a gastrostomy tube is placed, a balanced liquid diet (e.g., Hill's a/d) can be administered. All dosages should be adjusted for renal or hepatic impairment, and drug interactions should be considered. For example, corticosteroids may exacerbate myasthenia gravis, so they should be used cautiously. Antacids may alter the absorption of other drugs. It is essential to consult Plumb's Veterinary Drug Handbook for the most current and detailed information.

The evidence base for megaesophagus is derived from retrospective studies, case series, and expert consensus. A landmark study by Shelton et al. (1990) identified myasthenia gravis as a common cause of acquired megaesophagus in dogs, with acetylcholine receptor antibody titers being highly sensitive and specific. A study by Gaynor et al. (1997) reported that congenital megaesophagus in dogs has a favorable prognosis, with many puppies improving by 6 months of age. A retrospective study by Johnson et al. (2010) found that aspiration pneumonia is the most common complication and cause of death in dogs with megaesophagus. The use of sildenafil for megaesophagus was evaluated in a small study by Wray and Sparkes (2006), showing some improvement in esophageal transit. The ACVIM consensus statement on the diagnosis and treatment of myasthenia gravis in dogs (2016) provides guidelines for immunosuppressive therapy. For hypoadrenocorticism, the IRIS guidelines recommend DOCP for mineralocorticoid replacement. There is limited evidence for the efficacy of prokinetic agents in megaesophagus, and their use is based on anecdotal reports. A systematic review by Mace et al. (2018) concluded that there is no strong evidence for any specific medical therapy for idiopathic megaesophagus, and management should focus on nutritional support and prevention of aspiration. Overall, the literature emphasizes the importance of identifying and treating the underlying cause, as well as the critical role of owner education and compliance in managing this challenging condition.