Measurement of hiatal surface area and other hiatus oesophageal diameters at computed tomography imaging in patients with gastroesophageal reflux disease and its relationship with hiatal hernia.

BACKGROUND: The oesophageal hiatus is a long and oblique opening in the diaphragm where the thoracic section of the oesophagus passes into the abdomen. Enlarged hiatal surface and insufficiency are considered to be associated with gastroesophageal reflux disease (GERD) and hiatal hernia (HH). In this study, we aimed to retrospectively evaluate the relationship and the presence of GERD with HH by performing hiatal surface area (HSA) and other hiatal measurements at the thorax and abdominal computed tomography (CT) images in cases without any intra-abdominal or oesophageal surgery history. PATIENTS AND METHODS: A total of 192 patients of GERD+ and 173 cases with GERD- as a control group were included in the study. In CT examinations of 365 patients included in the study, measurements and comments were made by an experienced radiologist in abdominal radiology. In CT scans, the following were evaluated for each case; HSA, hiatus anterior-posterior (A-P) diameter, hiatus transverse diameter, and HH types. The HSA measurement was made with the freehand region of interest in the picture archiving and communication system.
RESULTS: A total of 365 cases were included in this study; there was a significant difference between the median HSA, A-P diameter, and transverse diameter measurements between GERD- and GERD+ groups (P < 0.001). A statistically significant difference was found between the presence of GERD and HH types (P < 0.001).
CONCLUSIONS: CT imaging helps investigate the presence of HH at GERD+ patients. In addition, pre-operative valuable data can be obtained from the detection of HH types and HSA measurements in cases with HH.

INTRODUCTION

The oesophageal hiatus is a long and oblique opening in the diaphragm where the thoracic section of the oesophagus passes into the abdomen. The edges of the hiatus are adjacent to the diaphragmatic crura and may show some variations between individuals.[12] Besides, the oesophageal hiatus has a sphincter mechanism independent of the lower oesophageal sphincter.[3] Enlarged hiatal surface area (HSA) and insufficiency are considered associated with gastroesophageal reflux disease (GERD) and hiatal hernia (HH).[45] Further, in most patients with HHs, GERD is detected compared to patients without hernia.[46] In symptomatic GERD cases referred to laparoscopic anti-reflux surgery, pre-operative measurement of oesophageal hiatus defect and HSA has been recommended to prevent HH recurrence and intra-thoracic wrap migration.[78]

When the stomach extends partially or totally to the thorax regardless of swallowing, this finding is called a common medical condition, the HH. HH is classified into three types: type 1 sliding, type 2 para-oesophageal and type 3 mixed.[91011] Type 1 sliding HH is defined when the stomach and oesophagogastric junction (EGJ) are above the diaphragmatic hiatus and EGJ is above the gastric fundus. Type 2 para-oesophageal HH is defined when EGJ is at the diaphragmatic hiatus level and the part of the stomach by more than 2 cm is above the diaphragm next to the oesophagus. Type 3 mixed HH can be roughly considered the total of sliding and para-oesophageal hernia [Figure 1].

Figure 1

In the picture representing hiatal hernia types, blue arrows indicate the oesophagogastric junction; (a) normal oesophagus and stomach, (b) type 1 sliding hiatal hernia, (c) type 2 para-oesophageal hiatal hernia, (d) type 3 mixed hiatal hernia

Hiatal defect size and volumetric measurements in pre-operative computed tomography (CT) are helpful and determinative at the operative technique concerning the need for a relaxing incision on the diaphragm or rescue gastropexy. Therefore, knowing this information preoperatively helps decide and determine surgical complexity and operative approach.[12] Until a few years ago, data published in the literature on HSA mostly used calculations based on gross measurements obtained during surgery or cadaver.[111314] In one study, assuming that the hiatus was shaped like a circle slice, it indirectly determined HSA by using linear measurements during surgery.[15]

In this study, we aimed to retrospectively evaluate the relationship and presence of GERD with HH by performing HSA and other hiatal measurements at the thorax and abdominal CT images in cases without any intra-abdominal and oesophageal surgery history.

PATIENTS AND METHODS

Patient selection

This retrospective study was evaluated and approved by the local ethics committee. Between September 2018 and February 2020, all thorax and abdominal computed tomography scans performed at the department of radiology were retrospectively analysed. Abdominal and/or oesophageal surgical history, cirrhosis and portal hypertension, known congenital anomaly-genetic disease, mediastinal fibrosis, body mass index (BMI) ≥35 and age younger than 18 were the exclusion criteria. Finally, 192 cases of GERD+ and 173 cases with GERD− as a control group were included in the study. GERD+ patients included in the study had clinical diagnoses and upper gastrointestinal endoscopy results, and medication treatments were available. In the CT images of 365 patients included, measurements were made by an experienced radiologist in abdominal radiology.

Computed tomography protocol and measurements

Images of all cases were obtained using 40 slices CT scanner (Siemens, SOMATOM Sensation 40). CT parameters of the thorax and abdominal tomography scanning included 0.4 s portal rotation time, 120 kVp, 200 mA, 1.25 mm section thickness and 512 × 512 matrix size. All CT images were reconfigured using the “picture archiving and communication system” (PACS) INFINITT: 3.0.11.4 (BN11) program and analysed. Analysis and measurements for each case were performed in axial, sagittal and coronal planes, respectively. Besides, additional data were obtained by providing three-dimensional post-processing, including maximum density projections and multi-plane image reformatting in all cases.

In CT scans, the following were evaluated for each case; HSA, hiatus anterior–posterior (A-P) diameter, hiatus transverse diameter, and HH types [Figure 2]. The HSA measurement was made with the freehand region of interest in PACS, as it provides convenience and gives more accurate results.

Figure 2

On the axial computed tomographic section view of the case without hiatal hernia; (a) the white arrows show the hiatus oesophagus and (b) the red arrows show the HSA measurement made at this level using the freehand region of interest method

Statistical analysis

Statistical analysis was performed using SPSS software (IBM SPSS version 22.0, IBM, Armonk, NY, USA). Descriptive statistical methods (median, frequency, percentage, minimum and maximum) were used to define the study data. Kolmogorov–Smirnov test assessed the normality of quantitative data distribution. Pearson’s Chi-square test was used to compare categorical variables, and Fisher’s exact test was applied if the number of subgroups was low. Spearman’s correlation analysis was used to evaluate the relationship between the parameters. Kruskal–Wallis test was applied to compare HSA and other diameter CT scan measurements between different groups (GERD+, GERD − and HH types). According to the results of the analysis, a P < 0.05 was considered statistically significant.

RESULTS

Of the 365 cases involved in this study, 179 were male and 186 were female. The youngest case was 18 years old and the oldest case was 94 years old, both males. In females, the youngest case was 19 years old and the oldest case was 89 years old. The mean age in all cases was 50.88 ± 17.11, 50.43 ± 17.32 for males and 51.32 ± 16.95 for females.

In addition to gender, there was no statistically significant difference between GERD− and GERD+ groups and BMI measurements (P = 0.68, P = 0.76). Hiatus measurements were compared in both groups; median HSA was measured as 4.89 cm2 in GERD− group and 19.11 cm2 in GERD+ group. In GERD − cases, the median A-P diameter was measured as 7.07 mm and the median transverse diameter was 7.58 mm. In GERD+ patients, it was measured as 15.48 mm and 16.55 mm, respectively. There was a significant difference between the median HSA, A-P diameter and transverse diameter measurements between the two groups (P < 0.001). Demographic data and CT measurements associated with GERD are summarized in Table 1.

Table 1

Demographics, measurements of mean hiatal surface area and other diameters

	n	Mean age	Mean BMI±SD	Median HSA (cm2)	Median A-P diameter (mm)	Median transverse diameter (mm)
GERD−	173	43.85±14.88	28.1±5.1	4.89 (2.45-12.80)	7.07 (4.48-13.06)	7.58 (5.29-14.19)
GERD+	192	57.22±16.54	26.2±4.8	19.11 (2.92-87.76)	15.48 (4.8437.18)	16.55 (5.26-42.52)

BMI: Body mass index, SD: Standard deviation, HSA: Hiatal surface area, GERD: Gastroesophageal reflux disease, A-P: Anterior-posterior

When the relationship between gender and GERD and between gender and HH types was evaluated using the Chi-square test, no statistically significant difference was found (P = 0.65, P = 0.99). The distribution and frequency of HH types by gender are shown in Table 2.

Table 2

Distribution of hiatal hernia types by gender

	HH types				Total
	None	Type 1	Type 2	Type 3
Gender
Male
n	88	59	21	11	179
Percentage HH	48.6	49.6	48.8	50.0	49.0
Female
n	93	60	22	11	186
Percentage HH	51.4	50.4	51.2	50.0	51.0
Total
n	181	119	43	22	365
Percentage HH	100.0	100.0	100.0	100.0	100.0

HH: Hiatal hernia

The distribution of age, HSA and diameter measurements by gender were evaluated, respectively [Table 3]. There was no statistically significant difference between gender and age, HSA, A-P diameter and transverse diameter measurements (P > 0.05).

Table 3

Distribution of age, hiatal surface area and diameter measurements by gender

	n	Minimum age	Maximum age	Mean±SD
Male
Age	179	18	94	50.43±17.326
HSA (cm2)	179	2.45	84.54	12.7269±12.77487
A-P (mm)	179	4.48	37.18	11.5668±6.03150
Transverse (mm)	179	5.26	42.52	12.4156±6.81297
Female
Age	186	18	89	51.32±16.952
HSA (cm2)	186	2.52	87.76	12.0263±12.24114
A-P (mm)	186	5.01	36.52	11.4291±6.34350
Transverse (mm)	186	5.34	37.81	12.1834±6.64914

SD: Standard deviation, HSA: Hiatal surface area, A-P: Anterior-posterior

According to the Spearman’s correlation, there was a moderate positive correlation between age and HH types, HSA, A-P diameter and transverse diameter (ρ: 0.391–0.430). Thirteen of the GERD− cases had type 1 HH, whereas type 2 and type 3 HH were not. In GERD+ patients, 106 type 1 HH, 43 type 2 HH and 22 type 3 HH were present. A statistically significant difference was found between the presence of GERD and HH types (P < 0.001). The relationship between GERD− and GERD+ groups and HH types and the distribution of cases are shown in Table 4.

Table 4

Relationship between gastroesophageal reflux disease and hiatal hernia types

	HH types				Total
	None	Type 1	Type 2	Type 3
GERD
−
n	160	13	0	0	173
Percentage HH	88.4	10.9	0.0	0.0	47.4
+
n	21	106	43	22	192
Percentage HH	11.6	89.1	100.0	100.0	52.6
Total
n	181	119	43	22	365
Percentage HH	100.0	100.0	100.0	100.0	100.0

HH: Hiatal hernia, GERD: Gastroesophageal reflux disease

DISCUSSION

The oesophageal hiatus is an opening limited by the tissue that is continuous with the diaphragmatic crura in the diaphragm. The pathological expansion of the hiatus has clinical consequences. The size of the hiatus affects the surgeon’s choice of the hernia repair method, predicting the long-term success rate.[816] In addition, some studies have shown that there may be a significant relationship between low hiatus area, decreased the lower esophageal sphincter pressure and increased acid reflux in patients with GERD.[714]

Koch et al. showed that the hiatal area size was negatively correlated with low oesophageal sphincter (LES) pressure and positively correlated with acid reflux as observed by pH monitoring.[8] Similarly, Batirel et al. showed a negative correlation of the size of the hiatal area obtained from surgical measurements and the LES pressure, as well as a positive correlation between acid reflux and HSA obtained by pH monitoring.[7] A previous similar study also showed that GERD is associated with larger HH sizes measured by high-resolution manometry and pH monitoring.[17]

Granderath et al. described a method for the quantitative estimation of HSA using surgical measurements and suggested that the type of surgical repair is based on the size of the hiatal defect. Patients with HSA ≤4 cm2 were operated with sutures only, and patients with HSA >8 cm2 mesh were placed.[15] Similarly, another study has shown a relationship between the benefits of HSA-based surgical technique selection and the long-term success rate of repair surgery with the size of the hiatus.[16] Shamiyeh et al. found mean HSA by working with cadavers. Considering post-mortem changes, a formula was used to calculate HSA.[13]

HH can be easily identified on a CT scan as a soft tissue structure that extends in front of and to the right or opposite of the aorta.[18] Ouyang et al. reported that subjects with larger HSA and mixed-type hernias in GERD+ cases had larger hiatus than subjects without a hernia. However, in patients with GERD+ without hernia, it was not detected a significantly larger hiatus oesophagus than the control group.[4] Moten et al. compared preoperative CT images with intraoperative measured HSA values in patients undergoing laparoscopic HH repair and found that the calculated HSA value on CT was more accurate.[19] Kumar et al. evaluated the HH morphology by CT and found a significant increase in HSA in patients with different HH types compared to the control group.[20] Boru et al. compared the preoperative CT and intraoperative HSA measurements in obese patients with ‘bariatric surgery + posterior cruroplasty history’ and showed that CT gave more accurate results. The difficulty of evaluation of intra-operative hiatus oesophagus and insufficient measurement technique made HSA measurement difficult. In the same study, a significant decrease in HSA dimensions was observed in 1st -year control the thorax and abdominal CT.[21]

We used PACS software in this study since it is accessible, easy to use and measurements can be made in a short time. Furthermore, unlike some studies, we evaluated the non-obese group that was previously evaluated in a few publications.[41920] This study has one of the largest case numbers in the literature.[42021] Besides, our study has the second largest number of cases in the literature regarding the evaluation of hiatus oesophagus measurements with CT imaging.[4] We determined the relationship between GERD and HH with more data by measuring other diameters besides HSA. Finally, we compared the relationship between gender and GERD and HH types, respectively.

Limitations of our study include the lack of special algorithms and CT evaluation and measurements by a radiologist. Second limitation is the lack of pH monitoring measurements in GERD+ cases. Furthermore, taking measurements without using a workstation can be considered another limitation. We think that with the new studies, this problem can be overcome and the measurements can be standardised with PACS software.

CONCLUSIONS

CT imaging helps investigate the presence of HH in GERD+ patients. In addition, preoperative valuable data can be obtained from the detection of HH types and HSA measurements in cases with HH.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.