Dysautonomia in dogs: a retrospective study.

Dysautonomia was diagnosed in 11 young (median age, 14-months), predominantly medium- to large-breed dogs from 1988 to 1995. Clinical signs caused by autonomic dysfunction of the urinary, alimentary, and ocular systems were most common. Dysuria, mydriasis, absence of pupillary light reflexes, decreased tear production, dry mucous membranes, weight loss, and decreased anal tone were present in over 75% of affected dogs. Ocular pharmacological testing with a dilute (0.1%) solution of pilocarpine was used to demonstrate iris sphincter receptor function in all dogs. A low-dose (0.0375 mg/kg s.c.) bethanechol test and pharmacological testing with phenylephrine and epinephrine also demonstrated cholinergic and adrenergic receptor function in 4 dogs. All dogs died or were euthanized as a results of autonomic dysfunction. Neuronal depletion, with associated gliosis and minimal inflammation were noted histologically in the autonomic ganglia of each dog. The pelvic, ciliary, celiac, cranial cervical, and cranial and caudal mesenteric ganglia were affected in all dogs. The cause of autonomic failure in these dogs was not determined.