Risk factors for acquired megaesophagus in dogs.

OBJECTIVE: To identify risk factors associated with acquired megaesophagus in dogs.
DESIGN: Case-control study. ANIMALS: 136 dogs with acquired megaesophagus (case dogs); 272 dogs from the general hospital population and 151 dogs that underwent thyroid-stimulating hormone response tests (control dogs). All dogs were more than 6 months old. PROCEDURE: Medical records of dogs in which megaesophagus was diagnosed during a 10-year period were reviewed. Inclusion criteria included regurgitation or vomiting, onset of clinical signs at more than 6 months of age, and radiographic evidence of generalized esophageal dilatation. Dogs with intra- or extraesophageal obstructive disease, brain stem disease, or neck trauma were excluded from analyses. Statistical analyses included odds ratios, 95% confidence intervals, and two-tailed t-tests. Control dogs were frequency matched to case dogs on the basis of year of diagnosis.
RESULTS: Dogs with megaesophagus ranged from 0.75 to 18 years old (mean, 8.1 years) and were significantly older and heavier than control dogs. More males than females were affected, but sex and reproductive status were not associated with megaesophagus. German Shepherd Dogs, Golden Retrievers, and Irish Setters were at increased risk for developing megaesophagus. Peripheral neuropathies, laryngeal paralysis, acquired myasthenia gravis, esophagitis, and chronic or recurrent gastric dilatation with or without volvulus were associated with an increased risk of developing megaesophagus. Hypothyroidism was not associated with megaesophagus. CLINICAL IMPLICATIONS: Dogs with acquired megaesophagus should be evaluated for peripheral neuropathies, laryngeal paralysis, acquired myasthenia gravis, esophagitis, and chronic or recurrent gastric dilatation with or without volvulus. These dogs may be evaluated for hypothyroidism; however, this study did not reveal a clear association between hypothyroidism and acquired megaesophagus.