idity of
tissues, and spasm of the cricopharyngeus muscle, are etiologic
factors. Cicatricial stenosis below the level of the inferior
constrictor is a contributory cause in some cases.

_Prognosis_.--After the pouch is formed, it steadily increases in
size, since the swallowed food first fills and distends the sac before
the overflow passes down the esophagus. When a pendulous sac becomes
filled with food, it presses on the subdiverticular esophagus, and
produces compression stenosis; so that there exists a "vicious
circle." The enlargement of the sac produces increasing stenosis with
consequent further distension of the pouch. This explains the
clinically observed fact, that unless treated, pulsion diverticula
increase progressively in size, and consequently in distressing
symptoms. The sac becomes so large in some cases as to contribute to
the occurrence of cerebral apoplexy by interference with venous
return. Practically all cases can be cured by radical operation. The
operative mortality varies with the age, state of nutrition, and
general health of the patient. In general it may be said to have a
mortality of at least 10 per cent, largely due to the fact that most
cases are poor surgical subjects. Recurrences after radical operation
are due to a persistence of the original causes, i.e., bolting of
food; stenosis, spasmodic or organic, of the esophageal lumen; and
weakness in the support of the esophageal wall, which, unsupported,
has little strength of its own.

_Symptoms_.--Dysphagia, regurgitation, a gurgling sound and subjective
bubbling sensation on swallowing, sour odor to the breath, and cough,
are the chief symptoms. With larger pouches, emaciation, pressure
sensation in the neck and upper mediastinum, and the presence of a
mass in the neck when the sac is filled, are present. Tracheal
compression by the filled pouch may produce dyspnea. The sac may be
emptied by pressure on the neck, this means of relief being often
discovered by the patient. The sac sometimes spontaneously empties
itself by contraction of its enveloping muscular layer, and one of the
most annoying symptoms is the paroxysm of coughing, waking the
patient, when during the relaxation of sleep the sac empties itself
into the pharynx and some of its contents are aspirated into the
larynx. There are no pathognomonic symptoms. Those recited are common
to other forms of esophageal stenosis, and are urgent indications for
diagnostic esophagosco