American Journal of Roentgenology · 2000 · 105 citations · 19 references
When findings of achalasia are present on barium studies, a narrowed distal esophageal segment longer than 3.5 cm with little or no proximal dilatation in a patient with recent onset of dysphagia should be considered highly suggestive of secondary achalasia, even in the absence of other suspicious radiographic findings.
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ROBERT R. CASSELLA, ARNOLD L. BROWS, George P. Sayre et al. · Annals of Surgery · 1964 · 278 citations · Full text
Comparison of pseudoachalasia and achalasia
Peter J. Kahrilas, S.M.A. Kishk, J. F. Helm et al. · The American Journal of Medicine · 1987 · 250 citations
James C. Reynolds, Henry P. Parkman · Gastroenterology Clinics of North America · 1989 · 181 citations