Achalasia‐Like Disease with Esophageal Pressurization in a Myasthenic Dog

An 8-year-old, intact male Pug was examined for a 7-day history of progressive weakness, progressive decline in food intake, dysuria, and dysphonia. The dysuria was described as an inability to void when being walked as the dog could not lift its leg and did not urinate although there was evidence of urine leakage in the dog’s blankets. When initially examined, the dog was alert with a BCS of 5/9. The physical examination did not reveal abnormalities. Results of hematology, serum biochemistry, and urinalysis as well as abdominal ultrasound did not reveal abnormalities. Upon owners’ request, the dog was discharged without further work-up, and gabapentin (5 mg/kg, PO q12h) were prescribed for suspected lumbosacral pain. Because of increasing weakness over the next 2 days, the dog was presented at an emergency clinic, where urinary retention caused by lumbosacral disease was suspected and treated with a single dose of dexamethasone (10 mg IM). Three days later, the dog was again examined for anorexia and progressive weakness. Physical examination revealed an alert dog able to walk 2–3 m with a stiff gate and kyphotic posture before finally lying down. Laboratory work revealed a CK (111 U/L; reference range, 51–191) within reference range and no abnormalities were detected on urinalysis. A bacterial culture of urine showed no growth. Thoracic radiographs revealed moderate esophageal dilatation and a markedly dilated stomach (Fig 1). Results of a neurologic examination were consistent with a neuromuscular junction disorder, and an edrophonium chloride challenge (0.2 mg/kg IV) showed a dramatic positive response. At the time of electromyographic testing, an upper gastrointestinal endoscopy was also performed because of concerns about steroid-induced gastric ulceration. Before anesthesia, esophageal high-resolution manometry (HRM) was used to evaluate esophageal function (Fig 2). A manometric catheter was lubricated with 2% lidocaine gel and carefully inserted intranasally. It was passed through the nasopharynx into the esophagus and finally positioned so that it recorded the pressure profile of the entire esophagus from the pharynx to the stomach. Real-time pressure imaging enabled accurate placement, and 3–4 pressure sensors were positioned intragastrically to rule out artifacts caused by breathing-related movements of the esophagogastric junction. HRM examination revealed an abnormal swallowing mechanism: after normal upper esophageal sphincter (UES) relaxation (UES residual pressure 0.4 mmHg [ 10.5 to 0.3 mmHg], UES relaxation time to nadir 138 mmHg (58–140 mmHg), relaxation duration 300 ms [145–305 ms]) the aborally propagating peristaltic waves of the tubular esophagus, as well as lower esophageal sphincter (LES) relaxations [LES baseline pressure 37.3 mmHg (14.6–45.1 mmHg), LES residual pressure 27 mmHg (1.9–19.1 mmHg)] were completely absent throughout the study. The peristaltic waves were discontinued by simultaneous contractions of the tubular esophagus beginning at a point just past the first third of the tubular esophagus (Fig 3). The subsequent esophagogastroduodenoscopy did not reveal abnormalities except for a dilated and flaccid esophagus. Biopsies were taken from the middle and lower esophagus, stomach, and duodenum. Histopathologically, all esophageal, gastric, and duodenal biopsies did not reveal abnormalities. Electromyographic examination of the limbs and epaxial muscles did not reveal abnormalities. Supramaximal repetitive nerve stimulation of the tibial and ulnar nerve at a frequency of 3 Hz produced a decrement of 30% (reference <10%). At this point, myasthenia gravis (MG) was suspected on the basis of clinical, electromyographic, and pharmacologic testing results. After treatment with pyridostigmin (1.5 mg/kg PO, q8h), the dog had progressive improvement of all clinical findings. By the time the AChR titer came back negative (0.22 nmol/L; normal <0.6 nmol/L) on day 14, the dog had already fully recovered. Upon recheck on day 21, the dog’s owners had already stopped pyridostigmin 4 days From the Clinic for Small Animal Internal Medicine (Kempf, Kook), and the Division of Neurology, Clinic for Small Animal Surgery (Beckmann), Vetsuisse Faculty, University of Zurich, Zurich, Switzerland (Beckmann). Corresponding author: Dr Peter Hendrik Kook, Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 260, Zurich 8057, Switzerland; e-mail: peterhen drikkook@gmail.com. Submitted June 20, 2013; Revised January 2, 2014; Accepted January 14, 2014. Copyright © 2014 by the American College of Veterinary Internal Medicine DOI: 10.1111/jvim.12329 Abbreviations: