Retrograde cricopharyngeus dysfunction (R-CPD), also known as inability to belch syndrome—a narrative review

Retrograde cricopharyngeus dysfunction (R-CPD), also known as ‘inability to belch syndrome’, is an under-recognized disorder wherein the upper esophageal sphincter (UES) fails to open following gaseous reflux. First described in 1987, R-CPD was rediscovered in 2019 along with the first effective treatment, endoscopic botulinum toxin (Botox) injection into the cricopharyngeus (CP). Since then, there has been an explosion of literature on R-CPD. The objectives of this review were to discuss the physiology of belching and R-CPD along with the epidemiology, diagnostic criteria, and clinical experience in managing R-CPD.