PATHOPHYSIOLOGY OF HEARTBURN AND DYSPEPSIA

Question 1

What are the three esophageal defense mechanisms that protect the esophageal mucosa from acid damage?

(Ba cơ chế phòng vệ thực quản bảo vệ niêm mạc thực quản khỏi tổn thương axit là:)

Answer 1

The three esophageal defense mechanisms are:

Antireflux barriers: Rào cản chống trào ngược
Esophageal acid clearance: Lưu thông axit thực quản
Tissue resistance: Kháng cự mô học

Question 2

What are the components of the antireflux barrier?

Answer 2

The anti-reflux barrier includes the intrinsic lower esophageal sphincter (LES), the diaphragmatic crura, the intra-abdominal location of the LES, the phrenoesophageal ligaments, and the acute angle of His.

(Rào cản chống trào ngược bao gồm cơ quan hạ thực quản (LES) nội tại, chân cột cơ hoành mạc, vị trí bụng trong của LES, mạc cơ hoành - thực quản, và góc His sắc.)

Question 3

What is the function of the lower esophageal sphincter (LES)?

Answer 3

The LES is contracted at rest but relaxes on swallowing to permit the flow of food, liquids, and saliva into the stomach.

Lower esophageal sphincter (LES): The LES is a muscular ring at the lower end of the esophagus that acts as a barrier, preventing stomach acid and contents from flowing back into the esophagus.
(Cơ quanh niêm mạc hạ thực quản (LES): LES là một vòng cơ quan hạ thực quản ở đáy thực quản, hoạt động như một rào cản, ngăn axit dạ dày và nội dung không cho vào lại thực quản.)

Question 4

What are transient relaxations of the LES?

Answer 4

Transient relaxations of the LES occur when there is no swallowing or esophageal peristalsis, allowing retrograde movement of stomach contents into the esophagus.
Những lần thư giãn tạm thời của cơ quan hạ thực quản xảy ra khi không có sự nuốt hoặc chuyển động chuyển hóa thực quản, cho phép nội dung dạ dày di chuyển ngược vào thực quản.

Question 5

What is the role of the crural diaphragm in the antireflux barrier?

Answer 5

The crural diaphragm provides an extrinsic squeeze to the LES, contributing to resting pressure and augmenting LES contractile function during periods of increased abdominal pressure, such as with coughing, sneezing, or bending over.
(Vai trò của cơ hoành mạc trong rào cản chống trào ngược là cung cấp một lực ép bên ngoài cho cơ quan hạ thực quản (LES), góp phần vào áp lực nghỉ ngơi và tăng cường chức năng co bóp của LES trong những khoảng thời gian có áp lực bụng gia tăng, như khi ho, hắt hơi hoặc cúi xuống)

Question 6

What does the angle of His contribute to in the antireflux barrier

Answer 6

The angle of His creates a flap valve effect that contributes to the anti-reflux barrier.

Question 7

What are the physiologic mechanisms that help protect the esophageal mucosa from damage during reflux of acidic gastric material?

Answer 7

The physiologic mechanisms that protect the esophageal mucosa during reflux include esophageal acid clearance, neutralization of residual acid by saliva and esophageal gland secretions, clearance of refluxed material by peristalsis and gravity, tight junctions in esophageal mucosa, and buffering and extruding of hydrogen ions by epithelial cells.
(Cơ chế sinh lý giúp bảo vệ niêm mạc thực quản khỏi tổn thương trong quá trình trào ngược chất acid dạ dày gồm có lưu thông axit thực quản, trung hòa axit dư bằng nước bọt và tiết ra từ tuyến thực quản, loại bỏ chất trào ngược bằng chuyển động chuyển hóa và lực hấp dẫn, các điểm nối chặt chẽ trong niêm mạc thực quản, cũng như cơ chế cân bằng và xóa bỏ ion hydrogen bằng tế bào biểu mô.)

Question 8

How does esophageal acid clearance occur?

Answer 8

An esophageal acid clearance occurs when peristalsis moves refluxed material into the stomach. (Lưu thông axit thực quản xảy ra khi chuyển động chuyển hóa đẩy chất trào ngược vào dạ dày.)

Question 9

What role does saliva and esophageal gland secretions play in protecting the esophageal mucosa

Answer 9

,Saliva and esophageal gland secretions neutralize residual acid from refluxed gastric material.

Question 10

How does gravity help clear the esophagus during reflux?

Answer 10

,Gravity assists in clearing the esophagus by helping refluxed material move back into the stomach.

Question 11

How do tight junctions in esophageal mucosa and the intercellular space matrix contribute to protecting the esophageal mucosa

Answer 11

,Tight junctions in esophageal mucosa and the intercellular space matrix reduce epithelial damage from hydrogen ions during reflux.

Question 12

What is the role of epithelial cells in protecting the esophageal mucosa

Answer 12

,Epithelial cells are capable of buffering and extruding hydrogen ions that penetrate the cell membrane during reflux.

Question 13

How does tissue resistance contribute to protecting the esophageal mucosa

Answer 13

,Tissue resistance is aided by the esophageal blood supply, which delivers oxygen, nutrients, and bicarbonate, and removes hydrogen and carbon dioxide, thereby maintaining normal tissue acid-base balance.

Question 14

Why are symptoms and esophageal damage uncommon despite the common occurrence of gastroesophageal reflux

Answer 14

,Symptoms and esophageal damage are uncommon because of the protective effects of the esophageal defense mechanisms described above.

Question 15

What is heartburn likely related to

Answer 15

,Heartburn is likely related to stimulation of esophageal mucosal chemoreceptors.

Question 16

What are the potential causes of heartburn symptoms

Answer 16

,Heartburn symptoms can be caused by acid reflux, weakly acidic reflux, bile reflux, and mechanical stimulation of the esophagus.

Question 17

Why do some reflux episodes produce symptoms while most do not

Answer 17

,The reasons why some reflux episodes produce symptoms while most do not are unclear, but possible contributing factors include mucosal disruption, decreased acid clearance, inflammation, reduced salivary bicarbonate concentration, volume of refluxate, frequency of heartburn, and interaction of pepsin with acid.

Question 18

What is one theory for the occurrence of heartburn symptoms with smaller boluses of acid

Answer 18

,One theory is that the esophagus becomes hypersensitive from repeated acid exposure, causing symptoms to occur with smaller boluses of acid.

Question 19

What can lead to increased acid exposure in the esophagus

Answer 19

,Any disruption in the esophageal defense mechanisms can lead to increased acid exposure.

Question 20

What is a major stimulus for transient LES relaxation episodes

Answer 20

,Distention of the proximal stomach by either food or gas is a major stimulus for transient LES relaxation episodes.

Question 21

How can decreased LES pressure be overcome in some patients

Answer 21

,Some patients may have decreased LES pressure that can be overcome by an abrupt increase in intra-abdominal pressure from coughing, straining, or bending over.

Question 22

What happens in a hiatal hernia and how does it affect GERD

Answer 22

,A hiatal hernia occurs when the upper part of the stomach pushes upward through the diaphragm. It impairs LES function and esophageal acid clearance, displaces the LES from the crural diaphragm, reduces LES pressure, and results in more frequent transient relaxations of the LES, all of which contribute to increased reflux. Its presence is a recognized contributing factor in patients with Barrett’s esophagus and esophageal cancer.

Question 23

What are some situations that can lead to prolonged exposure of esophageal tissue to refluxed material

Answer 23

,Prolonged exposure of esophageal tissue to refluxed material can occur in a lying or sleeping position, with decreased salivation, or with peristaltic dysfunction. Large volumes of refluxate from delayed gastric emptying or overeating can also increase esophageal acid exposure.

Question 24

What can happen to the tight intercellular junctions of the esophageal mucosa due to prolonged exposure to refluxed material

Answer 24

,The resulting damage to the tight intercellular junctions of the esophageal mucosa can lead to increased cellular permeability to hydrogen ions, with subsequent cellular injury. This increased permeability partly explains the development of heartburn in the absence of overt esophagitis.

Question 25

What is an important determinant of the degree of esophageal damage from reflux

Answer 25

,The composition of the refluxate is an important determinant of the degree of esophageal damage. Pepsin and/or bile salts combined with acid produce greater injury than that seen with acid alone.

Question 26

How does Helicobacter pylori infection affect gastric acidity and the development of heartburn and GERD

Answer 26

,Helicobacter pylori infection lowers gastric acidity, thereby possibly protecting against the development of heartburn, GERD, and related complications.

Question 27

What are some factors that can decrease LES pressure and lead to increased reflux

Answer 27

,Foods (e.g., fat, chocolate, peppermint) and medications (e.g., theophylline, morphine, calcium channel blockers, diazepam) can decrease LES pressure, leading to increased reflux.

Question 28

Which foods irritate inflamed esophageal mucosa and may contribute to heartburn

Answer 28

,Citrus, tomato-based, and spicy foods irritate inflamed esophageal mucosa and may contribute to heartburn.

Question 29

How does tobacco smoke contribute to heartburn

Answer 29

,Tobacco smoke contributes to heartburn by relaxing LES pressure and decreasing salivation.

Question 30

What factors can increase intra-abdominal pressure above the LES pressure and lead to reflux

Answer 30

,Bending over, straining to defecate, lifting heavy objects, and performing isometric exercises may increase intra-abdominal pressure above the LES pressure, leading to reflux.

Question 31

What is the association between obesity and GERD

Answer 31

,Obesity increases intra-abdominal pressure, and epidemiologic studies suggest that the prevalence of GERD is considerably higher in obese patients. Central obesity, as measured by waist-to-hip ratio, may be a better predictor for the development of GERD than body mass index (BMI).

Question 32

What factors are associated with increased esophageal acid exposure and symptoms

Answer 32

,Daytime naps are associated with increased esophageal acid exposure and symptoms compared with nocturnal sleep. Sleeping on the right side is also associated with increased reflux.

Question 33

What role may genetics play in the development of GERD

Answer 33

,Genetics may play a role in the development of GERD, as family clustering of GERD along with its complications has been reported.

Question 34

What are some common causes of dyspepsia

Answer 34

,Dyspepsia may be caused by PUD, GERD, celiac disease (rarely), gastric or esophageal malignancy (rarely), or other GI disorders.

Certain medications (e.g., iron, antibiotics, narcotics, digoxin, estrogens and oral contraceptives, theophylline, levodopa, nonsteroidal anti-inflammatory drugs [NSAIDs]) commonly cause dyspepsia through direct gastric mucosal injury, changes in GI function, exacerbation of reflux, or other mechanisms.

Question 35

What is the pathophysiology of functional dyspepsia

Answer 35

,The pathophysiology of functional dyspepsia is unclear but may include delayed gastric emptying, impaired gastric accommodation to food intake, hypersensitivity to gastric distention, altered duodenal sensitivity, abnormal intestinal motility, or central nervous system dysfunction. One or more of these disturbances can occur in individual patients. The cause of symptoms in patients with functional dyspepsia has not been established, but population studies have suggested a genetic predisposition, infectious factors, and psychological components. H. pylori infection may play a role in functional dyspepsia, as evidenced by a small improvement in symptoms after eradication of the infection. Psychosocial factors are an important contributor to symptom severity. Patients with functional dyspepsia also may have anxiety disorders, depression, somatoform disorders, or a recent or remote history of physical or sexual abuse. The exact mechanism is unknown, but some studies have suggested a relationship between psychosocial factors and visceral hypersensitivity.