Laboratory and instrumental investigations

Radiographic studies

For patients in whom a diagnosis is uncertain, a plain chest radiograph may be the first available study. The classically described finding on upright chest X-ray is an absent gastric air-bubble. This finding, present in nearly all normal individuals, is absent in approximately half of patients with acha-lasia.73,74 Additional findings include a widened mediastinum from esophageal dilatation, a posterior mediastinal air-fluid level from retained food/secretions and lung parenchymal abnormalities from chronic aspiration.67,73,75

Barium swallow, however, is the definitive radiographic study, and, in a review of the European experience with achalasia, it is the most commonly performed test.76 On barium swallow, classic achalasia typically shows esophageal dilatation with distal narrowing at the gastro-esophageal (GE) junction, the 'bird's beak' deformity (Figure 5.1). Also, retained food/secretions, absent peristalsis, tortuosity of the esophagus and, occasionally, an epiphrenic diverticulum can be seen.67,73,75 Because a barium swallow is performed under fluoroscopy it is a dynamic study, and may also reveal back-and-forth sloshing of the barium boluses when the patient is in the supine position, owing to the esophageal dilatation and the ineffective peristalsis.67,75,77 However, the diagnostic accuracy of barium swallow is approximately 85%, which can be due to a very early stage

Bird Beak Barium
Figure 5.1 'Bird's beak' appearance characteristic of esophageal achalasia on esophogram (courtesy of Hans Bjorknas, Gastrolabs, Finland).

Laboratory and instrumental investigations 65

of achalasia not showing the classic signs, due to a tumor of the GE junction mimicking achalasia or due to a peptic stricture.67,73,76

Computed tomography (CT) has no real role in the diagnosis of achalasia.67 The findings are consistent with those already seen on plain X-ray or barium swallow, such as a dilated esophagus, esophageal air-fluid levels, and possibly displacement of mediastinal structures by a dilated esophagus. Furthermore, masses that may cause pseudoachalasia are infrequently identified on a

CT scan.78,79

With the desire to limit radiation exposure, particularly in children, alternative means of diagnosis are sought. Radionuclide bolus transport has been evaluated as one such alternative, with achalasia diagnosed when esophageal emptying time is prolonged. When evaluating patients with mano-metrically diagnosed achalasia using radionuclide transport, Stacher et al found that sensitivity for this evaluation was 68%, with a specificity of 95%.80 Their criteria were an esophageal emptying time of > 20 s (the time for 95% of the bolus to enter the stomach), compared to a normal median time of 7.3 s (range 5.5-12.0 s). Because radionu-clide bolus transport is a functional study with relatively low sensitivity (other esophageal motility disorders also show prolonged transit time), this study may be best suited for follow-up of patients after treatment, or in the few cases in which achalasia is suspected, despite normal LES pressure on manometry.67,73,80

catheter is slowly withdrawn until the sensor is measuring LES pressure. Under quiet respirations, resting LES pressure is measured at mid-respiration. Swallow-induced LES relaxation is measured with the patient taking several wet swallows using small volumes of liquid. The catheter is further withdrawn until the distal sensor is a few centimeters above the LES and the proximal sensors are spaced throughout the esophageal body. Esophageal peristalsis and wave progression are assessed during several more wet swallows.

Because achalasia affects the smooth muscles of the esophagus, the manometric findings involve the mid- and distal esophagus, sparing the proximal regions of predominantly striated muscle. The two manometric abnormalities found in all patients with achalasia are aperistalsis of the eso-phageal body and abnormal LES relaxation.1,67-69 Simultaneous, low-amplitude contractions (< 40 mmHg) throughout the esophageal body are characteristic of the aperistalsis seen after wet swallows. Abnormal LES relaxation is characterized by either absent/incomplete relaxation (70-80% of patients) or normal relaxation of short, and therefore ineffective, duration - typically less than 6 s each (20-30% of patients).69, 81 This latter finding commonly accompanies early stage acha-lasia.68 Manometric findings associated with achalasia, but not required for diagnosis, include elevated resting LES pressure and resting esophageal body pressure exceeding baseline gastric pressure.1 Table 5.2 summarizes normal and abnormal manometric findings.

Manometry

The gold standard for accurate diagnosis of acha-lasia remains esophageal manometry, using either a perfused-catheter or a solid-state system. The minimum information collected from manometry will include resting LES pressure, relaxed LES pressure and peristaltic function of the esophageal body. Depending on local protocol, upper esophageal sphincter (UES) pressure may also be assessed. Fluoroscopy may be used to assist in positioning of the sensors. Manometry is usually performed with a catheter containing multiple, evenly spaced sensors, which is passed by the oral or nasal route into the stomach. Resting gastric pressures are measured to provide a baseline. The

Endoscopy

Despite radiographic and manometric evidence typical of achalasia, pseudoachalasia secondary to a tumor at the GE junction must be ruled out.67,73 Findings consistent with achalasia may include a dilated, atonic esophageal body; mucosal thickening and/or erythema; and a puckered LES which fails to open with insufflation, but which is easily passed with the endoscope. If there is visual evidence of extrinsic compression or the endoscope fails to pass through the GE junction with gentle pressure, then a tumor must be excluded. Biopsies should be taken from suspicious areas seen above the GE junction or seen on retroflexion from within the stomach.

Table 5.2

Normal and abnormal manometric findings (from references 1, 67 and 68)

Basal LES pressure

Swallow-induced LES relaxation

Peristaltic wave progression

Distal wave amplitude

Normal

10-45 mmHg

complete (less than 8 mmHg above gastric baseline, or 95% of LES baseline)

2-8 cm/s from UES to LES

30-180 mmHg

Achalasia

>45 mmHg (up to 40% of patients have normal values)

incomplete (more than 8 mmHg above gastric baseline, or 35% of LES baseline) Complete but of short duration (<6 s)

simultaneous

<40 mmHg

LES, lower esophageal sphincter; UES, upper esophageal sphincter

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