Evaluation of Gastroesophageal Reflux by Transabdominal Ultrasound in Adults: Focused on Subdiaphragmatic Esophageal Length, His angle, Moment of Reflux

 

Ki-Tae Park¹, Youn-Sin Jeong¹, Youl-Hun Seoung*²

¹Department of Radiology, Hanaro Clinic, Daejeon, 34411, Republic of Korea

²Department of Radiology Science, Cheongju University, Republic of Korea

 

ABSTRACT:

Background/Objectives: The purpose of this retrospective study was to evaluate factors affecting the diagnosis of gastroesophageal reflux (GER) using transabdominal ultrasound. Methods/Statistical analysis: The patient group comprised of 18 adults with upper endoscopy results of Los Angeles (LA)-classifications A or above, while the control group included of 68 adults with normal upper endoscopy. The ultrasonography was used to measure the subdiaphragmatic esophageal length, gastroesophageal angle (His angle) and real-time ultrasonography at the moment of reflux. Findings: The subdiaphragmatic esophageal length was 29.2±3.6 ㎜ in the control group, and 22.7±3.2 ㎜ in the patient group. The results showed statistically significant difference between the two groups. The cut-off value for the subdiaphragmatic esophageal length was 25.1 ㎜. Sensitivity and specificity were 88.9% and 86.9% respectively. The gastroesophageal angle measured 121.9±12.3° in the control group and 141.5±8.8° in the patient group. The cut-off value of 134.6° showed a sensitivity of 83.3% and specificity of 83.8%. There were statistically significant differences (p = 0.001) during real-time ultrasonography with reflux in 77.8% of the patient group and 10.3% in the control group. The real-time ultrasonography showed a sensitivity of 77.8%, specificity of 89.7%, positive predictive value of 66.7% and negative predictive value 93.8%. Improvements/Applications: This study suggests that the transabdominal ultrasound used in measuring the subdiaphragmatic part of the esophageal length, His angle and real-time ultrasonography to be good predictive factors in diagnosing GER disease. Therefore, a medical examination with a noninvasive procedure such as transabdominal ultrasound may be a useful procedure in predicting gastroesophageal disorders.

 

 

1. INTRODUCTION:

Gastroesophageal reflux (GER) disease is a disorder in which gastric acid is refluxed into the esophagus causing clinical symptoms or morphological changes in the esophagus¹. The amount of time gastric reflux is exposed is directly related to the symptoms and severity of GER disease. However, reflux is only considered a disease when it causes frequent or severe symptoms or when it produces injury².

 

 

Many symptoms such as heartburn and regurgitation may affect the quality of life in most otherwise healthy individuals. While showing chronic and recurrent symptoms, common complications of GER disease are potentially severe which include esophagitis, strictures, and Barrett’s esophagus³.

 

Although there are typical symptoms presenting in patients with GER disease, the majority of patients present non-burning chest pain and other atypical symptoms, also referred to as extra-esophageal manifestations of reflux disease. While there is no single test sufficient in diagnosing GER disease, these extra-esophageal manifestations are difficult to express in Korean, and therefore is difficult to diagnose GER disease in the outpatient clinic⁴.

Therefore, a noninvasive, simple and safe technique such as transabdominal ultrasound (US) may be a useful tool⁵. The purpose of our study was to analyze US images in measuring the subdiaphragmatic part of the esophageal length, gastroesophageal angle (His angle) and the real-time ultrasonography of the moment of reflux in diagnosing GER disease.

 

2. LITERATURE REVIEW:

2.1. Materials:

This study was carried out from October 2015 to April 2017 at a radiology clinic in Daejon, Korea. An upper endoscopy and transabdominal ultrasound was performed on 86 adults aged 27 to 79. The average age in men was 54 and 55.5 in women. A total of 36 men and 50 women participated in the study. The patient group comprised of 18 adults (12 male, 6 female) with upper endoscopy results of Los Angeles (LA)-classifications A or above, while the control group included of 68 adults (24 male, 44 female) with normal upper endoscopy.

 

2.2. Methods:

Examinations were performed using US in a real-time system (RS80, Samsung, Korea) with a 1- and 7-MHz curved array transducer (CA1-7A S-Vue, Samsung, Korea) by an experienced sonographer with 15 years of clinical sonographic experience. Both groups were positioned lying supine after fasting for at least 6 hours. The US probe was placed on the epigastric region, and the beam was directed cephalad to visualize the gastroesophageal junction through the window of the left lobe of the liver⁶. (Fig 1)

 

 

Figure 1. Ultrasound showing the intra-abdominal esophageal segment from the subxiphoid oblique view during inspiration, E; esophagus, H; heart, L; left lobe of liver, S; stomach

 

The subdiaphragmatic esophageal length was measured on the longitudinal scan from the lower side of the diaphragm to the triangular pad of gastric folds at the cardia of the stomach. (Figure 2)

 

 

Figure 2. Viewing and measuring the length of the subdiaphragmatic part of the esophagus in ultrasound examination, Arrow; diaphragmatic sphincter, Triangle; triangle pad, Dotted line; subdiaphragmatic part of esophagus

 

The triangular pad representing the radiation away from the cardiac orifice was considered the point of entrance of esophagus into the stomach⁷. In the longitudinal sonogram, the His angle was delimited within the tangent line passed from the fornix of the stomach and the line of the anterior wall of the esophagus⁸. (Figure 3)

 

Figure 3. Viewing and measuring His angle (@) in ultrasound examination

 

The presence of gastroesophageal reflux in the US examination was estimated by real-time ultrasonography viewing to and fro of the air bubble passing through the cardia of stomach to the diaphragm⁹. (Figure 4)

 

Figure 4. Real-time ultrasonography viewing to and fro of the air bubble (arrow) passing through cardia of stomach to the diaphragm, A: abdominal aorta, E: esophagus, H: heart, L: liver, S: stomach

 

Two physicians measured the subdiaphragmatic esophageal length and His angle while a radiologist analyzed the real-time ultrasonography during the moment of reflux. A radiologist and family medicine physician with over 1 year of US experience also cross-examined and drew the average length of the results.

 

2.3. Statistical Analysis:

The SPSS statistical package, version 23.0 (SPSS Inc., Chicago, IL, USA) was used for statistical analysis. The reliability of the subdiaphragmatic esophageal length and His angle measured by two observers was evaluated using Cohen's kappa coefficient (k). A k value greater than 0.8 was defined as almost agreement. The average of subdiaphragmatic esophageal length and His angle among the patient and control groups were drawn using the independent t-test. Differences were considered significant when the p value was less than 0.05. The ROC (receiver operating characteristic) curves were created using the cut-off values evaluated on the US findings. The subdiaphragmatic esophageal length and His angle values that would yield the best sensitivity and specificity values for the detection of reflux were chosen as cut-off points for US¹⁰. The chi-squared test was used to compare real-time ultrasonography during the moment of reflux and actual gastroesophageal reflux disorders. Sensitivity, specificity, positive predictive values (PPV), and negative predictive values (NPV) of real-time ultrasonography was analyzed by cross tabulation.

 

3. RESULTS:

The results of this study showed that the subdiaphragmatic esophageal length was 29.2±3.6 mm in the control group, while the patient group measured 22.7±3.2 mm. The results showed statistically significant difference between the two groups as seen Table 1. When the cut-off value for the subdiaphragmatic esophageal length was set as 25.1 mm, the presence of reflux was detected with a sensitivity of 88.9% and specificity of 86.9%. The His angle was measured 121.9±12.3° in the control group and 141.5±8.8° in the patient group. The results showed statistically significant difference between the two groups as seen Table 2. When the cut-off value for the His angle was set as 134.6° the sensitivity and specificity for the detection of reflux on US was 83.3% and 83.8% respectively. The results were statistically significant between the two groups. The k-value of the subdiaphragmatic esophageal length and His angle were both greater than 0.8 confirming almost perfect agreement. We found US features of the moment of reflux in 77.8% of the patient group and 10.3% in the control group. There were significantly statistical differences (p = 0.001) between the reflux on the real-time ultrasonography and actual gastroesophageal reflux disorders. The presence of reflux in real-time ultrasonography showed a sensitivity of 77.8%, specificity of 89.7%. The PPV was 66.7% and NPV 93.8% as seen Table 3.

 

Table 1: Length of subdiaphragmatic part of the esophagus in ultrasound examination

Groups	N	Length (㎜)	p values
Control subjects	68	29.2±3.6	0.001
Patient subjects	18	22.7±3.2
Total	86

 

Table 2: Gastroesophageal angle among the two groups

Groups	N	Angle	p values
Control subjects	68	121.9±12.3°	0.001
Patient subjects	18	141.5±8.8°
Total	86

 

 

Table 3: Cross tabulation analysis of the presence of gastroesophageal reflux in ultrasound and the evidence of reflux on endoscopy

Presence of reflux in ultrasound			Endoscopy		Total
			Control group	Patient group
Reflux in ultrasound	No reflux	Count	61	4	65
		% within Reflux in US	93.8%**	6.2%	100.0%
		% within Endoscopy	89.7%‡	22.2%	75.6%
	reflux	Count	7	14	21
		% within Reflux in US	33.3%	66.7%*	100.0%
		% within Endoscopy	10.3%	77.8%†	24.4%
Total	Count		68	18	86
	% within Reflux in US		79.1%	20.9%	100.0%
	% within Endoscopy		100.0%	100.0%	100.0%

^† Sensitivity, ^‡ Specificity, * Positive predictive value, ^** Negative predictive value

 

4. DISCUSSIONS:

Most patients with GER disease rely on oral medications while a stop in such medications may lead to relapse of the disorder. The treatment of this chronic disorder is actually focused on improving the quality of life in such patients. Currently in Korea, there is an increase in GER disease patients without symptoms due to an increase in annual general health check-ups¹⁰. While the majority of patients with GER disease is treated medically and requires either a barium examination or endoscopy, there is no consensus on which diagnostic test should be performed in their evaluation¹⁰. In previous studies, upper endoscopy showed a diagnostic accuracy with sensitivity and specificity of 62%~68%, 96%. An esophageal pH monitor showed 30%~96% while the Bernstein test showed results of 32%~100%, 40%~100%. This shows that not one test is available in the diagnosis of GER disease^12,13. Endoscopic assessment of the esophagus for the presence or absence of GER disease as well as the assessment of its severity is crucial to formulate decision about the patient’s management and prognosis¹⁴.

 

The LA classification system of GER disease is by far the most widely used system to describe the endoscopic appearance of reflux esophagitis and grade its severity¹⁵. One limitation of the LA classification system is that it excludes minimal mucosal changes that are associated with reflux disease¹⁴. Also, the 24-hour pH monitoring is known to be the most accurate test in diagnosing GER disease, however it is an expensive and uncomfortable test and false negative results are not uncommon while positive results do not always correlate with clinical findings. Another factor that may contribute to GERD is the reflux of bile. However, it is difficult to prove such reflux and is not primarily used as a standard test in diagnosis^16,17. The Bernstein test does not prove reflux but reproduces pain when the lower esophagus is irritated with an acid solution in patients with GER disease. A false positive reading may be seen in up to 15% of people¹⁸.

 

Whereas over 75% patients present and express typical symptoms of GER disease overseas, Korean patients mostly express atypical symptoms making it difficult to diagnose in Korea⁴. Therefore we conducted this study to evaluate a noninvasive and approachable parameter derived from ultrasound to evaluate patients with GER disease.

 

Three parameters were evaluated and limitations were corrected in our study to help diagnose GER disease. First, a shorter subdiaphragmatic length increased the possibility of GER disease¹⁹. When using the cutoff value of 25.1mm for the subdiaphragmatic esophageal length, the sensitivity and specificity were 88.9% and 86.8% respectively. However, using a transabdominal US in measuring the length of the subdiaphragmatic esophageal length was affected by respiration, and made accurate measurements difficult²⁰. Also, the triangular pad used as a landmark had a possibility of being perceived differently among observers. In order to reduce such limitations, the average lengths among the two observers were used and all measurements were held after inspiration.

 

Secondly, a larger His angle increased the possibility of GERD²¹. When using the cutoff value of 134.6°, the sensitivity and specificity were 83.3% and 83.8% respectively. However, the measurement of His angle was influenced by the inflated amount of gas in the stomach and needed careful attention when measuring. A curve was formed when the beam was directed cephalad to visualize the gastroesophageal junction through the window of the left lobe of the liver, making it difficult to decide which line should be used as a landmark in measuring the His angle. In order to reduce such errors, when an angle showed to be different, the angle of lesser degrees was chosen. Also in order to reduce the difference among observers, 10 images were measured beforehand showing a reliable k result of over 0.8.

 

Lastly, US has an advantage over CT and MRI when observing live gas reflux from stomach to the esophagus. In our study, confirmation of the presence of reflux flow of air bubble in real-time ultrasonography showed high sensitivity, specificity, PPV, and NPV. If US examinations showed no reflux during real-time ultrasonography, there was a low possibility of having a GER disease on endoscopy. However, when US examinations showed reflux of gas, if endoscopy results showed no mucosal damage, according to the LA classification GER disease was not diagnosed. Therefore, a reflux of gas on ultrasound did not conclude mucosal damage of the esophagus or GER disease.  In our study, a total of 10 patients showed a short subdiaphragmatic esophageal length of less than 25.1 mm and an obtuse angle of over 134.6°.  Nine were in the patient group and 1 in the control group. The 1 patient included in the control group showed a reflux of gas during real-time ultrasonography but did not show any mucosal damage, and was thus classified in the control group.

 

Although our study showed good parameters in diagnosing GER disease with US, the following limitations should be considered when interpreting our findings. As this study was retrospective in design and included a small study population the results might not be adequately generalizable. There was a limitation in extracting patients with adequate visualization of the subdiaphragm and real-time ultrasonography while performing an upper endoscopy on the same day. Also, patients with obesity or with extreme gaseous distention, measurements through US was not possible.

 

5. CONCLUSIONS:

This study suggests that the transabdominal US used in measuring the subdiaphragmatic esophageal length, His angle and real-time ultrasonography of the moment of reflux were good predictive factors in diagnosing GER disease. Our study concluded that a shorter subdiaphragmatic esophageal length of 25.1 mm and obtuse His angle of 134.6° accompanied by real-time ultrasonography viewed to and fro of the air bubble during the moment of reflux on abdominal US were good predictive values in diagnosing GER disease. Therefore, a medical examination with a noninvasive procedure such as transabdominal US might be an accurate and standardized procedure in predicting gastroesophageal disorders.

 

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Received on 13.02.2019           Modified on 14.05.2019

Accepted on 20.06.2019         © RJPT All right reserved