Digestion – A Comprehensive Overview

I. Structure and Function

• Digestive Tract (DT): This is a long muscular tube that runs from the mouth to the anus. It’s responsible for breaking down food and absorbing nutrients.

• Oral Cavity: The initial segment of the DT, starting at the mouth and ending at the esophagus.

• Thoracic DT: This section passes through the chest cavity, making a slight curve around the Aorta and the left Pulmonary Artery.

• Abdominal DT: A short segment, concluding at the cardia, forming the “angle of His”.

• Peristalsis: This is a wave-like muscular contraction that propels food along the DT.

• Functional Dysmotility: A condition where abnormal peristaltic waves (specifically, a third wave) occur, leading to food stagnation.

II. Diagnostic Techniques

• Ultrasound:

• Frequency: 2-15MHz.

• Principle: Uses high-frequency sound waves emitted from a transducer. The reflected waves are captured and processed to create an image.

• Scanning Device: Gantry.

• Processing Unit: Translates data into visual images.

• Density Units:

• Water: 1g/cm3 = 0H

• Uniform Air: 0.003g/cm3 = -1000H

• Solid Bone: 1.7g/cm3 = 17000H

• Magnetic Resonance Imaging (MRI):

• Principle: Relies on the magnetic properties of hydrogen atoms (H+) when exposed to radio waves.

• Magnets: Two types: permanent and superconducting.

• Units of Measurement: Tesla (T) or Gauss (G) (1T=10,000G).

• Magnetic Fields >=1T: Produce high-quality images in shorter scan times.

• Radiography (X-ray):

• Indications: Assessing DT structure, morphology, and mobility.

• Methods:

• Barium Swallow: Uses 500ml of water-soluble barium contrast agent.

• Upright Position: For capturing the stomach in a vertical position.

• Four Gutmann Films: Taken while the patient is prone.

• Additional Views: Supine with head tilted back, and double-contrast studies (combining barium and air).

• Air-Contrast Study: Recommended when barium studies are inconclusive. It involves insufflating air into the stomach. Indications include peritonitis.

III. Digestive Disorders

• Achalasia:

• Cause: Diminished number of nerve cells in the DT.

• Radiographic Findings: DT dilation without peristalsis, associated with hiatal hernia or carcinoma.

• Esophagitis:

• Presentation: Thickened walls, possible ulceration.

• Complications: Fibrosis, stricture, Barrett’s esophagus.

• Esophageal Stricture:

• Classification:

• Benign: Straight, smooth edges, gradual transition between the narrowed segment and healthy tissue.

• Malignant: Thread-like, irregular edges, abrupt transition between the affected area and healthy tissue.

• Causes:

• Gastroesophageal reflux disease (GERD).

• Other inflammatory processes leading to chemical burns.

• Radiation therapy.

• Cancer.

• Congenital abnormalities.

• Esophageal Diverticula:

• Types: Zenker’s diverticula, commonly located in the cervical region, and other diverticula, often found in the middle third of the esophagus.

• Esophageal Varices: Caused by portal hypertension.

• Hiatal Hernia:

• Diaphragm: Has three openings: esophageal, aortic, and inferior vena cava. Two posterolateral clefts (Bochdalek) and one retrosternal cleft (Morgagni).

• Classification:

• Acquired: Pass through the esophageal opening, including sliding hiatal hernia and paraesophageal hiatal hernia. Symptoms include reflux.

• Congenital:

• Bochdalek: Hernia through a cleft between the diaphragm and abdominal wall.

• Morgagni: Hernia through a cleft between the diaphragm and sternum.

• Causes:

• Trauma, chronic increased abdominal pressure (vomiting, coughing, straining, pregnancy, obesity).

• Congenital defects.

• Risk Factors: Obesity, pregnancy, persistent coughing, chronic constipation, connective tissue disorders.

IV. Endoscopic Techniques

• Esophagogastroduodenoscopy (EGD):

• Rigid Endoscopy:

• Flexible Endoscopy:

• Nasogastric Endoscopy:

V. Stomach and Duodenum

• Structure:

• Fundus: A dome-shaped area at the top of the stomach, adjacent to the left diaphragm.

• Body: The main portion of the stomach, connected to the fundus.

• Antrum: The lower, wider part of the stomach.

• Duodenal Bulb: A triangular-shaped portion at the beginning of the duodenum.

• Greater Curvature, Lesser Curvature: Curves running along both sides of the stomach from the fundus to the antrum.

• Duodenal Bulb: It’s also called the “ampulla” or “cap,” located between the pylorus and the first part of the duodenum. It can be compressed by an enlarged gallbladder.

• Duodenum: A C-shaped structure embracing the head of the pancreas. It has four segments:

• First Part: Connects to the duodenal bulb.

• Second Part: Runs along the right side of the superior mesenteric vessels.

• Third Part: Curves towards the left side.

• Fourth Part: Ascends to the left, ending at the duodenojejunal flexure (angle of Treitz).

VI. Diseases of the Stomach and Duodenum

• Gastritis: Includes gastritis with mucosal hypertrophy (fundus and body > 10 mm, antrum and pylorus > 5 mm, duodenum > 3 mm).

• Peptic Ulcer Disease:

• Curvature Ulcer: Barium fills the ulcer cavity.

• Ulcers May Cause Traction on the Greater Curvature or Converging Mucosal Folds Towards the Base of the Ulcer.

• Penetrating Ulcer (Haudek’s Sign): Demonstrates an air-fluid level on X-ray.

• Anterior-Posterior Ulcers: Barium collects on the stomach wall, potentially with surrounding edema.

• Greater Curvature Ulcer, Prepyloric Area: High risk of malignancy, often larger in size.

• Pyloric Ulcer: Barium pooling in the pyloric canal or an “L-shaped” configuration of the pylorus.

• Prepyloric Ulcer: Resembles greater curvature ulcers, easily mistaken for peristalsis or mucosal folds.

• Duodenal Bulb Ulcer (Non-complicated): Barium pooling commonly located in the center of the duodenal bulb. Surrounding edema or converging folds may be present. The bulb is not distorted. If situated on the duodenal bulb margin, a one-sided indentation may be seen.

• Old Duodenal Bulb Ulcer: Barium pooling may be visible due to scarring. The duodenal bulb demonstrates fibrous changes:

• Snail-like shape.

• “Bird’s beak” appearance.

• Coleman’s deformity, etc.

• Indirect Duodenal Bulb Ulcer: The bulb does not retain barium. A one-sided indentation is present. The bulb is displaced posteriorly. Pyloric stenosis exists.

• Gastric Cancer (Mass Type): X-ray findings: barium filling defect, irregular borders, no change on subsequent films. Complete antral replacement by the tumor results in a “cut-off” stomach appearance.

• Gastric Cancer (Linitis Plastica):

• Localized Rigidity: Lack of peristalsis along the involved greater curvature on films.

• Rigidity of a Gastric Region: “Ring” appearance.

• Body Rigidity: Creates a “double-bubble” stomach (symmetrical narrowing in the middle, forming an X shape).

• Antral Rigidity: “Goose neck” configuration.

• Gastric Cancer (Ulcerative and Ulcer-Carcinomatous): X-ray appearance: “lens” or “root-like.”

• Loss of mucosal folds surrounding the ulcer or a change in their direction.

• Irregular or flat ulcer base.

• Cancer of the Upper Stomach:

• Irregular filling defect in the fundus, more noticeable in the supine position with head tilted back.

• Alterations in the angle of His.

• Infiltration of the cardia, leading to narrowing with irregular margins.

• Hammer’s sign: Barium flow through the cardia resembles water flowing through a crevice.

• Causes of Pyloric Stenosis:

• Fibrous scarring from duodenal ulcer disease.

• Cancer.

• Pyloric muscle hypertrophy.

Note:

• This information is for general knowledge and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment.

• Consult a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.

Expansion:

• This article could be enhanced with illustrative images, additional details on treatments, and preventive measures for digestive diseases.

• Dividing the content into distinct sections could improve readability and comprehension.