Achalasia

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Achalasia, a failure of the lower esophageal sphincter to relax, has an estimated incidence, in the United States, of 1 per 100,000 population per year [147]. Males and females are equally affected. The character istic plain film findings include a widened mediastinum with an air-fluid level in the upright position. The increased mediastinal density may wander from the right in the upper chest to the left in the retrocardiac region. On barium studies, a beaklike deformity of the submerged segment (subdiaphragmatic) is a classic finding. Although the more proximal esophagus is classically atonic, a significant percentage of patients show esophageal contractions, so-called vigorous achalasia.

Various therapies have been used over time to treat achalasia. Surgery, systemic medications, and various endoscopic techniques all have their advantages and disadvantages. Nitrates and calcium channel blockers work as smooth muscle relaxants with some relief of symptoms [especially isosorbide dinitrate (Isordil)]. These are of use early in the course of the disease [147].

More recently, direct injection of botulinum toxin (botox) has been proposed as a therapeutic measure. However, the treatment's effect is not permanent, and multiple procedures are necessary to ensure long-standing relief. Botox still plays a role in the frail and elderly, who are not good candidates for surgery and/or pneumatic dilatation.

Surgical therapy, initially through a laparotomy, but also performed via thoracotomy is a long-standing therapeutic option. More recently, it has become possible to perform the procedure laparoscopically. Heller, in 1914, first described the performance of two longitudinal myotomies on opposite sides of the distal esophagus [148]. As a consequence of the myotomy, many patients have gastroesophageal reflux, and therefore many surgeons perform an antireflux procedure at the same time. A Nissen fundoplication may close the gastroesophageal junction too tightly, and therefore an anterior (Dor) or a posterior (Toupet) fundoplication is used to control the reflux. The former is used in elderly patients and those with a megaesophagus (>7cm diameter), while the latter is reserved for less severe dilatation, especially in younger patients [148].

The last treatment option is that of pneumatic dilatation. The esophagus must reach a diameter of at least 3 cm to partially disrupt the circular muscle fibers of the lower esophageal sphincter [147]. Endoscopes and standard bougies do not reach this size, and therefore balloon dilatation is necessary. Many different dilators have been used over the years, but only two are currently available in the United States. These are the Rigiflex and Witzel dilators. Both utilize polyethylene balloons, with the former positioned fluoroscopically over a guide wire and the latter mounted on an endoscope [147].

The efficacy of all these therapies is difficult to determine. Relief of symptoms is a subjective criterion, while completeness of esophageal emptying is objective [149]. However the correlation between the two criteria is not always good [150-152]. Therefore, de Oliveira and colleagues proposed a timed barium swallow to evaluate the patient's response to therapy [149]. In this procedure, the patient drinks medium density barium in the upright position until satiated. Films of the esophagus are then taken at 0, 2, and 5 minutes postingestion, being careful to maintain the same magnification factors for all views.

Measurements yield the percentage of emptying over time. This exam can be repeated to measure the response post-therapy.

Following myotomy, the herniation of the mucosa through the incised circular muscle fibers of the lower esophageal sphincter may cause the formation of pseudodiverticula [153] (Fig. 2.58). This condition has been reported to progress to a giant epiphrenic diverticulum measuring 8 cm in greatest diameter [154]. A similar deformity may be seen following pneumatic dilatation as well [155]. Because of the decreased effectiveness of the lower esophageal sphincter, it is not surprising that gastroesophageal reflux is a complication of both myotomy and pneumatic dilatation. Barrett's metaplasia and even carcinoma have been reported [156].

Immediately following pneumatic dilatation, there may be improved emptying of the esophagus. However, edema and hemorrhage in the wall as well as spasm of the lower esophageal sphincter may actually lead to decreased emptying. Therefore the immediate post-procedure study is a poor predictor of the patient's ultimate response [157]. Imme-

Figure 2.58. Heller myotomy. Single-contrast esophagram of a patient who had undergone a Heller myotomy. Paired bulges from the distal esophagus represent pseudodiverticula through the operative muscle defects.

diate post-procedure studies should be performed only to exclude an esophageal tear (which may be clinically silent).

Patients at highest risk for having a perforation are those with blood on the dilator, tachycardia, and chest pain more than 4 hours after the procedure [158]. The Rigiflex dilator is associated with a significantly lower rate of perforation than the Witzel dilator [159].

The radiographic findings of esophageal injury vary with the depth of the mural disruption. More limited injuries, confined to the mucosa, may present as a linear extraluminal collection of contrast paralleling the esophageal lumen [160] (Fig. 2.59). A somewhat deeper injury may present as a double-barreled appearance to the esophagus similar to that seen in an aortic dissection, or communicating hematoma [160] or thermal injury of the esophagus [161]. The mucosal stripe separating the two lumina is readily evident as a thin lucency between the two contrast collections. Alternatively, if the intramural hematoma is non-communicating (the mucosal flap has sealed over), a smooth filling defect in the esophageal wall is noted [162]. A through-and-through

Figure 2.59. Achalasia pneumatic dilatation tear. Immediate post-pneumatic dilatation esophagogram shows a well-contained extraluminal collection of contrast representing a mucosal tear.

disruption would present with one or more of the following: pneumo-mediastinum, subcutaneous air, pleural fluid, and extravasation of air beyond the normal confines of the esophagus. The latter may include air in the lesser sac from perforation of the "submerged" subdiaphragmatic portion of the esophagus [163]. Perforation of the segment can be confirmed on conventional contrast studies and/or CT imaging. Incomplete tears are usually managed conservatively with operative intervention needed for full-thickness disruption [164].

These complications, including frank perforation, resolve with no serious long-term sequelae [158] (Fig. 2.60). However, as many as half of all patients studied over a 5-year period continue to have symptoms [155].

Another unusual complication is an intradiaphragmatic abscess. One such abscess was noted following a 3-week relatively asymptomatic period following pneumatic dilation. Both conventional and CT pre-operative studies failed to identify the exact site of this abscess, which had to be drained operatively [165].

Figure 2.60. Post-pneumatic dilatation esophageal deformity. Repeat study of the same patient in Figure 2.59, many months later, reveals a bilobed out-pouching of contrast at the distal esophagus, similar to, but smaller than that seen following a Heller myotomy.

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