Esophageal Manometry
Esophageal manometry allows accurate assessment of LES pressure and relaxation, as well as peristaltic activity including contraction amplitude, duration, and velocity. However, esophageal manometry is generally not indicated in the evaluation of the patient with uncomplicated GERD because most of these patients have a normal resting LES pressure. It is an integral component of pH testing to define the LES location accurately, a task poorly performed by endoscopy, fluoroscopy, or the pH pull-through technique. Esophageal manometry is an essential test in the preoperative evaluation of patients for antireflux surgery. A normal LES pressure does not preclude surgery for the reasons discussed, yet occasionally an alternative diagnosis such as achalasia or scleroderma is made, which may change the clinical approach. Most importantly, the presence of ineffective peristalsis characterized by either low-amplitude (<30>
Radiolabeled technetium-99m sulfur colloid scintiscanning is useful as a semiquantitative test for detecting GER. After instilling 300 mL of radioisotope in saline through a nasogastric tube into the stomach, gamma counts over the esophagus are obtained in the supine position before and after provocation with abdominal compression. Although test specificity approaches 90%, the sensitivity is quite variable, from 14% to 90%.
The acid perfusion (Bernstein) test is useful for detecting the relationship of symptoms to esophageal acidification. The study is done with the patient upright with a nasogastric tube positioned in the midesophagus. Initially, normal saline is infused at 120 drops/min for 5 to 15 minutes, followed by an infusion of 0.1 N hydrochloric acid. If symptoms develop with acid infusion, saline is reinfused to assess symptom relief. Symptoms during acid infusion, but not saline infusion, constitute a positive test. The sensitivity of the Bernstein test for GERD ranges from 32% to 100%, and its specificity ranges from 40% to 100%. In clinical practice, 24-hour esophageal pH testing has generally replaced both these tests.
Ambulatory esophageal bilirubin monitoring
Bile reflux can be measured using ambulatory esophageal bilirubin monitoring (Bilitec: Medtronics, Minneapolis, MN), which uses the spectrophotometric property of bilirubin, the most common pigment in bile. As in pH testing, a fiberoptic light source is introduced into the esophagus with a data collection system worn on a waist belt. A spectrophotometer measures the wavelength absorption at 450 nm (bilirubin) and at 565 nm (reference) every 8 seconds. An integrated microcomputer calculates the difference of the absorbances, which is directly proportional to the bilirubin concentration in the sample. This allows a pH-independent assessment of duodenogastroesophageal reflux, which is preferable to the older method employing an esophageal pH of more than 7. 70 In the future, ambulatory measurements of esophageal impedance, which measures the electrical activity of liquid and gas moving up and down the esophagus, combined with pH monitoring may be the preferred technique for measuring nonacidic reflux.
DIFFERENTIAL DIAGNOSIS
Symptoms associated with GERD may be mimicked by other esophageal and extraesophageal diseases including achalasia, Zenker diverticulum, gastroparesis, gallstones, peptic ulcer disease, functional dyspepsia, and angina pectoris. These disorders usually can be identified by failure to respond to aggressive antisecretory therapy and by diagnostic tests such as endoscopy, barium esophagram, esophageal manometry, ultrasound, nuclear emptying studies, and various cardiac tests. Although GERD is the most common cause of esophagitis, other causes (esophagitis, infections, or radiation esophagitis) need to be considered in cases that are difficult to manage cases and in older or immunocompromised patients.
