Radiology and endoscopy for acid reflux GERD

Radiology and endoscopy:

Barium swallow is considered an inappropriate initial test for evaluation of patients with only heartburn. It has a low sensitivity and specificity for diagnosis of GERD. Moreover, barium reflux can be demonstrated in up to 20% of healthy subjects , Up to 50% of patients with GERD will have normal endoscopies. The sensitivity of upper endoscopy in patients with typical GERD symptoms is approximately 30–50% . Nevertheless, upper endoscopy is indicated in patients who have symptoms suggestive of complicated disease or those at risk for Barrett’s esophagus. The indications for upper endoscopy in patients with GERD are listed in. Considering that the majority of patients with GERD have a normal endoscopy, a variety of novel endoscopic methods such as chromoendoscopy or narrow band imaging have been evaluated in an attempt to detect subtle mucosal abnormalities that cannot be seen with conventional white light endoscopy. (Yoshikawa I,2005)

Yoshikawa and colleagues have demonstrated more unstained streaks in the distal esophagus in patients with GERD than in the controls when they used chromoendoscopy with Lugol’s iodine solution . In a separate study, narrow band imaging (NBI) was used to evaluate patients with erosive esophagitis (ERD) and NERD compared to normal subjects. Patients with GERD were noted to have an increased number, tortuosities and dilation of intrapapillary capillary vessels when compared to the control subjects . In a similar study, Fock et al. demonstrated that microerosions, mucosal islands and increased vascularity at the squamous columnar junction were more commonly detected in NERD patients when compared to normal subjects . However, the role of these novel techniques to improve mucosal visualization remains to be further elucidated. Histological findings have been addressed in patients with NERD. Potential markers of esophageal mucosal damage observable by light or electron microscopy are included in. (Tobey NA, et al ,2004) Dilation of intracellular spaces (DIS) was proposed as one of the earliest signs of acid damage to the esophagus. As a result, the permeability of the mucosal epithelium to noxious agents such as acid or possibly other stimuli is increased. Hence, it was suggested that this is a plausible mechanism in the occurrence of reflux symptoms such as heartburn in patients without mucosal breaks (Tobey NA, et al ,2004)

Various controlled studies have shown that DIS was more prevalent in patients with NERD than in control subjects, and most importantly, intercellular space dilation has been shown to improve after treatment with acid suppression. In the CHEER study, patients with reflux disease underwent extensive histopathological evaluation before and after treatment with either esomeprazole or ranitidine. Intercellular space dilation was observed more commonly in patients with GERD at the squamo-columnar junction (SCJ). The proportion of reflux disease patients with intercellular space dilation decreased from 76 to 53% after 4 weeks of therapy with a proton pump inhibitor (PPI) and from 80 to 69% after treatment with a histamine-2 receptor antagonist (H2RA) (Armstrong D, et al ,2003)

Despite the diagnostic potential of histopathology, in particular the presence of intercellular space dilation, the widespread use of histology in clinical practice is hampered by the need for electron or light microscopy and the lack of standardization of biopsy techniques. Proton pump inhibitor test The PPI test is defined as a short trial of acid suppression with a PPI to determine if the patient has symptomrelief. If there is a significant improvement in symptoms, the patient is considered to have GERD. This is a simple and non-invasive diagnostic tool for GERD. Variable doses of the proton pump inhibitor have been used for the PPI test: 40–80 mg daily of Omeprazole, 30–60 mg daily for lansoprazole and 40 mg daily for rabeprazole for a treatment duration of 1–4 weeks in patients with symptoms suggestive of GERD or non-cardiac chest pain (NCCP). The sensitivity of this tool for diagnosing GERD in patients with classical GERD symptoms and those with NCCP is 80 and 78%, respectively. (Gasiorowska A,, et al , 2008)

A study by Fass et al. compared the omeprazole test with 24-h pH monitoring for diagnosing GERD in patients with proven erosive esophagitis on endoscopy. The omeprazole test was shown to be as accurate as ambulatory 24-h esophageal pH monitoring when taking into account patients with a positive symptom index, and patients with abnormal acid exposure in either the supine or erect position despite a normal total acid contact time .The reliability of the PPI test in patients with NERD has yet to be determined. However, it should be noted that a positive response to the PPI test does not always equate to a diagnosis of GERD; likewise, a negative response does not necessarily exclude the diagnosis. Manometry and esophageal impedance/pH monitoring Esophageal manometry has no role in the diagnosis of GERD. However, manometry is indicated primarily in patients with GERD who are potential candidates for antireflux surgery to exclude achalasia or ineffective peristalsis. Furthermore, it provides the best means of ensuring optimal positioning of a pH electrode for ambulatory pH or impedance monitoring. Before the advent of impedance monitoring, ambulatory 24-h pH monitoring was regarded as the gold standard for diagnosing GERD. The sensitivity of the test ranges from 79 to 96%, and the specificity ranges from 85 to 100%.(Fass R,, et al , 2000)

However, studies have shown that up to 25% of patients with erosive esophagitis and 50% of patients with NERD have a normal 24-h pHmonitoring study . With the advent of the wireless pH capsule, which increases the pH monitoring for up to 48 h, the sensitivity of the test has been shown to be greater because it reduces the day-to-day variability, and it reduces the potential for false-negative results . Impedance monitoring is generally combined with pH monitoring to allow for the characterization of the refluxate into categories of acid, weakly acid and weakly alkaline reflux. Weakly acidic reflux has been defined as a reflux event associated with a concomitant drop in esophageal pH to between 4 and 7 and weakly alkaline reflux as an impedance detected reflux event not associated with a pH drop below 7.( Des Varannes SB, et al , 2005)

The improved diagnostic sensitivity of using combined impedance and pH monitoring over pH testing alone was demonstrated by a recent study examining symptom associations between acid and non-acid reflux events in 60 GERD subjects off proton pump inhibitor therapy. Bredenoord et al. demonstrated that the proportion of patients with a positive symptom-association probability (SAP) was greater with combined pH-impedance testing compared with pH testing alone (77 versus 68%, p\0.05).( Lichtenstein DR, et al , 2007) Upper endoscopy has been advocated to be the investigation of choice by many experts for patients who continue to have symptoms despite acid suppression therapy .Nonetheless, the value of upper endoscopy in this patient population has been shown to be limited by a recent study by Poh et al. In the study, erosive esophagitis was shown to be less prevalent in the PPI treatment failure group (6.7%) compared to the no treatment group (30.8%; p\0.05). ( Poh CH, et al , 2010)