Imaging of the Intestines

Introduction

Imaging modalities

The common radiologic modalities used to evaluate the intestines are the following:

• Radiography ( X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests)
• Ultrasonography (US)
• CT
• Fluoroscopy Fluoroscopy Production of an image when x-rays strike a fluorescent screen. X-rays

Preparation and orientation Orientation Awareness of oneself in relation to time, place and person. Psychiatric Assessment

Prior to interpretation of any image, the physician should take certain preparatory steps. The same systematic approach should be followed every time:

• Confirm the name of the patient, date, and time on all images.
• Obtain knowledge of the patient’s medical history and physical exam.
• Confirm the appropriate exam and technique for the suspected or confirmed pathology at hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy.
• Compare any available images of the same area taken in the same modality.

Determine the orientation Orientation Awareness of oneself in relation to time, place and person. Psychiatric Assessment of the image:

• Right or left marker on X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests
• In the United States, standard exam views place a marker (dot) to the patient’s right.
• For CT/MRI, on axial Axial Computed Tomography (CT) view, the image is sliced and viewed from inferior to superior (as if you are looking from the patient’s feet up).

Radiography (X-ray)

Overview

• Medical indications:
  • Emergency care
    • Acute abdominal pain Abdominal Pain Acute Abdomen
    • Not passing bowel movements or gas
    • Foreign body Foreign Body Foreign Body Aspiration ingestion
    • Suspected bowel perforation Bowel perforation Perforated viscus or GI perforation represents a condition in which the integrity of the GI wall is lost with subsequent leakage of enteric contents into the peritoneal cavity, resulting in peritonitis. The causes of perforated viscus include trauma, bowel ischemia, infections, or ulcerative conditions, all of which ultimately lead to a full-thickness disruption of the intestinal wall. Perforated Viscus
    • Suspected gastric outlet obstruction Gastric Outlet Obstruction Hypertrophic Pyloric Stenosis
  • Routine care
    • Signs and symptoms of abdominal infection
    • Monitoring renal calculi Renal calculi Stones in the kidney, usually formed in the urine-collecting area of the kidney (kidney pelvis). Their sizes vary and most contains calcium oxalate. Imaging of the Urinary System burden 
    • Suspected mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast
    • History of ingested foreign object
    • Verification of correct placement of IVs, lines, and tubes 
    • Postoperative evaluation
• Advantages:
  • Low cost 
  • Low radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma dose 
  • Ubiquitous availability
  • Fast
• Disadvantages:
  • Poor resolution of soft tissue Soft Tissue Soft Tissue Abscess
  • Exposure to ionizing radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma
  • The patient must hold still for the image.

Exam technique

General positioning:

• Rotation Rotation Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. X-rays:
  • There should be no rotation Rotation Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. X-rays.
  • Pedicles of the spine Spine The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column: Anatomy should be symmetric. 
• Visualization:
  • Bowel gas should be completely radiolucent Radiolucent An object of low density that is permeable to X-rays (looks black) X-rays.
  • Peritoneal fat planes should be visible laterally.

Positioning for specific views:

• Anteroposterior (AP):
  • The board is against the patient’s back. 
  • The X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests beams in the anterior to posterior direction through the patient.
  • Can be completed supine or upright
  • Upright positioning is better for evaluating bowel obstruction Bowel obstruction Any impairment, arrest, or reversal of the normal flow of intestinal contents toward the anal canal. Ascaris/Ascariasis and free air.
• Lateral decubitus:
  • The patient is supine.
  • The board is against the patient’s side.
  • Usually, the left side is down on the table (allows for better visualization of free air).

Penetration Penetration X-rays is the degree to which radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma has passed through body, resulting in a darker or lighter image.

• Under-penetration: The film appears whiter, and features are less apparent.
• Over-penetration: The film appears darker, and features are less apparent.

Interpretation and evaluation

Systematic inside-out approach Inside-Out Approach Imaging of the Lungs and Pleura (central to peripheral):

• Look at the bowel gas pattern.
• Look for solid organ silhouettes Solid Organ Silhouettes Imaging of the Urinary System (e.g., liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy, spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy, kidney).
• Look peripherally for normal fat planes.
• Look for evidence of free intraperitoneal Intraperitoneal Peritoneum: Anatomy air.
• Evaluate soft tissues for abnormal calcifications (e.g., stones, masses in pediatrics).
• Look at the lung bases Bases Usually a hydroxide of lithium, sodium, potassium, rubidium or cesium, but also the carbonates of these metals, ammonia, and the amines. Acid-Base Balance for evidence of consolidation Consolidation Pulmonary Function Tests, effusion, and pneumothoraces.
• Evaluate osseous structures (e.g., vertebral body Vertebral body Main portion of the vertebra which bears majority of the weight. Vertebral Column: Anatomy height, iliac bones, femurs).
• Once an abnormality is noted, use a patterned approach to come up with differential diagnoses.

Normal findings

AP view:

• Bowel gas:
  • Should be present in the small and large bowels
  • Should not distend the small bowel Small bowel The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine: Anatomy beyond 3 cm
  • Should not distend the cecum Cecum The blind sac or outpouching area of the large intestine that is below the entrance of the small intestine. It has a worm-like extension, the vermiform appendix. Colon, Cecum, and Appendix: Anatomy beyond 10 cm
  • Should be uniform throughout the abdomen
  • The small bowel Small bowel The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine: Anatomy should have valvulae conniventes, while the large bowel has haustra Haustra Colon, Cecum, and Appendix: Anatomy.
• Organs:
  • The liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy should be visible under the right hemidiaphragm and uniform, with no free air.
  • The stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach: Anatomy and the colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix: Anatomy should be visible, with air in the lumen under the left hemidiaphragm. 
  • Renal outlines, if visible, should be in the RUQ and LUQ.
• Fat planes: peripheral fat planes with normal appearance
• Lung bases Bases Usually a hydroxide of lithium, sodium, potassium, rubidium or cesium, but also the carbonates of these metals, ammonia, and the amines. Acid-Base Balance
  • Should be clear with minimal lung markings
  • Costophrenic angles should be sharp.
• Bones:
  • Pedicles should be present and bilaterally symmetric.
  • Vertebral body Vertebral body Main portion of the vertebra which bears majority of the weight. Vertebral Column: Anatomy heights should be gradually bigger as they move inferiorly.
  • Spinous processes should be located on the midline.

Ultrasonography

Overview

• Medical indications:
  • Emergency care: concern for appendicitis Appendicitis Appendicitis is the acute inflammation of the vermiform appendix and the most common abdominal surgical emergency globally. The condition has a lifetime risk of 8%. Characteristic features include periumbilical abdominal pain that migrates to the right lower quadrant, fever, anorexia, nausea, and vomiting. Appendicitis
  • Routine care: none
• Advantages:
  • Low cost 
  • No radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma dose 
  • Widespread availability
  • Fast
• Disadvantages:
  • Poor resolution 
  • Narrow field of view
  • The patient must hold still for the image.
  • Technician dependent

Exam technique

• Positioning:
  • Patient:
    • Access to the RLQ
    • Maximize contact between the patient’s skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions and the ultrasound probe Probe A device placed on the patient’s body to visualize a target Ultrasound (Sonography).
  • Visualization: The appendix Appendix A worm-like blind tube extension from the cecum. Colon, Cecum, and Appendix: Anatomy should be the most superficial to the probe Probe A device placed on the patient’s body to visualize a target Ultrasound (Sonography) without other organs and/or bowel interposing, although the appendix Appendix A worm-like blind tube extension from the cecum. Colon, Cecum, and Appendix: Anatomy is found in a variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables location within the abdomen.
• Depth and gain: determines the field of view and echogenicity characteristics of the tissue

Interpretation and evaluation

• Size: A normal appendix Appendix A worm-like blind tube extension from the cecum. Colon, Cecum, and Appendix: Anatomy should not exceed 6 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma in diameter.
• Echogenicity: homogenous without echogenic/shadowing or endoluminal foci
• Position: typically in the RLQ of the abdomen
• Normal organ wall thickness:
  • Stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach: Anatomy: 4–6 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma
  • Small bowel Small bowel The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine: Anatomy: 3–4 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma
  • Appendix Appendix A worm-like blind tube extension from the cecum. Colon, Cecum, and Appendix: Anatomy: up to 2 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma
  • Large bowel: 2–3 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma

Normal findings

Computed Tomography

Overview

• Medical indications:
  • Follow-up of suspicious X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests/US findings
    • Appendicitis Appendicitis Appendicitis is the acute inflammation of the vermiform appendix and the most common abdominal surgical emergency globally. The condition has a lifetime risk of 8%. Characteristic features include periumbilical abdominal pain that migrates to the right lower quadrant, fever, anorexia, nausea, and vomiting. Appendicitis
    • Suspected bowel obstruction Bowel obstruction Any impairment, arrest, or reversal of the normal flow of intestinal contents toward the anal canal. Ascaris/Ascariasis
    • Radiograph suspicion of free intraperitoneal Intraperitoneal Peritoneum: Anatomy air
    • Suspicious soft-tissue calcifications (e.g., tumor Tumor Inflammation, calculi, etc ETC The electron transport chain (ETC) sends electrons through a series of proteins, which generate an electrochemical proton gradient that produces energy in the form of adenosine triphosphate (ATP). Electron Transport Chain (ETC).)
  • Malignancy Malignancy Hemothorax
    • Suspicious calcifications ( neuroblastoma Neuroblastoma Neuroblastoma is a malignancy that arises from the neural crest cell derivatives along the sympathetic chain (neuroblasts) and is most commonly located in the adrenal medulla. The tumor often presents in childhood with a flank mass that crosses the midline. Neuroblastoma)
    • Staging Staging Methods which attempt to express in replicable terms the extent of the neoplasm in the patient. Grading, Staging, and Metastasis malignancy Malignancy Hemothorax for metastatic disease
  • Major trauma
    • Evaluation of abdominal viscera
    • Evaluation for hemorrhage with or without active extravasation on delayed images
    • Concern for subtle pathology not seen on US
• Advantages:
  • Excellent anatomical detail resolution 
  • Structures can be seen in 3 dimensions.
• Disadvantages:
  • Involves high radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma dose
  • The patient must hold still for the exam.
  • Expensive to perform

Exam technique

Standard CT scanning Standard CT scanning Imaging of the Liver and Biliary Tract:

• The patient lies supine on the table. 
• The table is moved into the CT scanner, which rotates around the patient.
• The patient is instructed to hold their breath and remain still for the duration of the scan (seconds).
• Exams can be done with or without IV or oral contrast.
• Timing of IV contrast dye can help direct the radiology inquiry of certain areas of pathology:
  • A CT with IV contrast is typically performed in the portal venous phase, initially with another set of images at a delayed time point to evaluate for active extravasation.

Interpretation and evaluation

Interpretation should follow a systematic and reproducible pattern.

• Review the patient’s history and physical exam.
• Achieve the ideal evaluation with a soft-tissue window/level (W:400 L:50).
• Compare to any available recent imaging of the interested area.
• Orient the image:
  • Axial Axial Computed Tomography (CT) images are seen as if looking from the patient’s feet up.
  • Sagittal Sagittal Computed Tomography (CT) and coronal Coronal Computed Tomography (CT) images are used to supplement the diagnosis.
• Identify landmark anatomical structures.
• Observe for “continuity” of parenchyma while scrolling through image slices.

Normal findings

Normal CT findings:

• The small bowel Small bowel The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine: Anatomy diameter should be uniform, without segments of dilatation.
• The duodenum Duodenum The shortest and widest portion of the small intestine adjacent to the pylorus of the stomach. It is named for having the length equal to about the width of 12 fingers. Small Intestine: Anatomy, jejunum Jejunum The middle portion of the small intestine, between duodenum and ileum. It represents about 2/5 of the remaining portion of the small intestine below duodenum. Small Intestine: Anatomy, and ileum Ileum The distal and narrowest portion of the small intestine, between the jejunum and the ileocecal valve of the large intestine. Small Intestine: Anatomy should each be in its expected location, with typical fold pattern.
  • Valvulae conniventes decrease distally in the small bowel Small bowel The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine: Anatomy.
  • Haustra Haustra Colon, Cecum, and Appendix: Anatomy are present in the colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix: Anatomy.
• The bowel wall thickness should be < 3 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma when properly distended.
• Homogenous bowel wall enhancement

Abnormal Findings on X-ray, US, and CT

Appendicitis Appendicitis Appendicitis is the acute inflammation of the vermiform appendix and the most common abdominal surgical emergency globally. The condition has a lifetime risk of 8%. Characteristic features include periumbilical abdominal pain that migrates to the right lower quadrant, fever, anorexia, nausea, and vomiting. Appendicitis

US:

• Noncompressible, dilated appendix Appendix A worm-like blind tube extension from the cecum. Colon, Cecum, and Appendix: Anatomy (> 6 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma)
• Thickened walls with no peristalsis Peristalsis A movement, caused by sequential muscle contraction, that pushes the contents of the intestines or other tubular organs in one direction. Gastrointestinal Motility
• With or without a fecalith (also called appendicolith)
  • Hyperechoic Hyperechoic A structure that produces a high-amplitude echo (lighter grays and white) Ultrasound (Sonography) structure within the lumen
  • Posterior shadowing 
• Fluid collection around the appendix Appendix A worm-like blind tube extension from the cecum. Colon, Cecum, and Appendix: Anatomy suggests a periappendiceal abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease or contained perforation Perforation A pathological hole in an organ, blood vessel or other soft part of the body, occurring in the absence of external force. Esophagitis.
• Limitations Limitations Conflict of Interest: inability of the sound to penetrate air in the bowel loops ( anechoic Anechoic A structure that produces no echo at all (looks completely black) Ultrasound (Sonography) images may obscure underlying pathology)

CT:

• Appendiceal dilatation (> 6 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma)
• Wall thickening
• Fat stranding around the appendix Appendix A worm-like blind tube extension from the cecum. Colon, Cecum, and Appendix: Anatomy
• With or without mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast (phlegmon or abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease)
• With or without adjacent free intraperitoneal Intraperitoneal Peritoneum: Anatomy air
• With or without fecalith (also called appendicolith) that appears as a hyperdense structure within the lumen

Intestinal obstruction Intestinal obstruction Any impairment, arrest, or reversal of the normal flow of intestinal contents toward the anal canal. Ascaris/Ascariasis and volvulus Volvulus A volvulus is the twisting or axial rotation of a portion of the bowel around its mesentery. The most common site of volvulus in adults is the colon; most frequently the sigmoid volvulus. Patients typically present with symptoms of bowel obstruction such as abdominal pain, distension, vomiting, and constipation/obstipation. Volvulus

Radiography:

• Dilated small bowel Small bowel The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine: Anatomy: centrally located dilated loops with circumferential circular opacity Opacity Imaging of the Lungs and Pleura within it (valvulae conniventes)
• Dilated large bowel: peripherally located dilated loop with incomplete circular opacity Opacity Imaging of the Lungs and Pleura within it (haustration)
• Presence of air in the rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal: Anatomy signifies a partial obstruction
• Absence of air in the rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal: Anatomy signifies a complete obstruction
• 3 or more air-fluid levels indicate obstruction, especially if at varying craniocaudal levels in the same loop of bowel.
• Sigmoid volvulus Sigmoid volvulus Volvulus: coffee Coffee A beverage made from ground coffee beans (seeds) infused in hot water. It generally contains caffeine and theophylline unless it is decaffeinated. Constipation bean sign, arises from the left iliac fossa and extends toward the RLQ
• Cecal volvulus Cecal volvulus Volvulus: arises from the right iliac fossa and extends toward the LUQ

CT:

• Increased sensitivity for detecting bowel ischemia Bowel ischemia Mesenteric ischemia is a rare, life-threatening condition caused by inadequate blood flow through the mesenteric vessels, which results in ischemia and necrosis of the intestinal wall. Mesenteric ischemia can be either acute or chronic. Mesenteric Ischemia/infarction via bowel wall enhancement
• Can detect portal venous gas

Pneumoperitoneum Pneumoperitoneum A condition with trapped gas or air in the peritoneal cavity, usually secondary to perforation of the internal organs such as the lung and the gastrointestinal tract, or to recent surgery. Pneumoperitoneum may be purposely introduced to aid radiological examination. Perforated Viscus

Radiography:

• Air under the diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm: Anatomy in upright X-rays X-rays X-rays are high-energy particles of electromagnetic radiation used in the medical field for the generation of anatomical images. X-rays are projected through the body of a patient and onto a film, and this technique is called conventional or projectional radiography. X-rays
• Free air adjacent to the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy in left lateral decubitus view
• Cupola or mustache sign: air trapped underneath the central tendon Central tendon Diaphragm: Anatomy of the diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm: Anatomy in supine abdominal X-rays Abdominal X-Rays X-rays
• Rigler sign:
  • Outlining of both sides of the bowel wall by gas
  • May be confused with adjacent dilated bowel loops (CT to differentiate)
• Lucent liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy sign: reduced liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy radiodensity in supine X-rays X-rays X-rays are high-energy particles of electromagnetic radiation used in the medical field for the generation of anatomical images. X-rays are projected through the body of a patient and onto a film, and this technique is called conventional or projectional radiography. X-rays due to the accumulation of air anterior to the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy
• Football sign: outlining of the whole abdomen by gas
• Silver sign (also called falciform ligament Falciform Ligament Liver: Anatomy sign): outlining of the falciform ligament Falciform Ligament Liver: Anatomy of the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy

CT:

• Best seen using the lung window Lung Window Computed Tomography (CT)
• Extraluminal air
• Irregular shape (it does not take on a bowel loop shape)
• Usually detected under the anterior abdominal wall Abdominal wall The outer margins of the abdomen, extending from the osteocartilaginous thoracic cage to the pelvis. Though its major part is muscular, the abdominal wall consists of at least seven layers: the skin, subcutaneous fat, deep fascia; abdominal muscles, transversalis fascia, extraperitoneal fat, and the parietal peritoneum. Surgical Anatomy of the Abdomen (anti-dependent abdomen)

Pneumatosis intestinalis Pneumatosis intestinalis A condition characterized by the presence of multiple gas-filled cysts in the intestinal wall, the submucosa and/or subserosa of the intestine. The majority of the cysts are found in the jejunum and the ileum. Necrotizing Enterocolitis

• Radiography: gas ( radiolucency Radiolucency Chondrosarcoma) taking the shape of the bowel walls (curvilinear)
• CT:
  • Radiolucency Radiolucency Chondrosarcoma within the bowel wall
  • Patterns of radiolucency Radiolucency Chondrosarcoma
    • Linear
    • Bubble shaped
    • Curvilinear
  • Scrutinize the portal venous system for air.

Pneumobilia and portal venous gas

CT:

• Pneumobilia
  • Linear, branching lucencies 
  • Centrally located in the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy
  • Result of incompetence of the sphincter of Oddi
• Portal venous gas
  • Linear, branching lucencies 
  • Peripherally located in the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy
  • Result of air from the proximal portal venous system

Fluoroscopy

Overview

• Medical indications:
  • Emergency care:
    • Acute abdominal pain Abdominal Pain Acute Abdomen
    • Not passing bowel movements or gas
    • Foreign body Foreign Body Foreign Body Aspiration ingestion
    • Suspected gastric outlet obstruction Gastric Outlet Obstruction Hypertrophic Pyloric Stenosis
    • Evaluation for malrotation Malrotation Pediatric Gastrointestinal Abnormalities with volvulus Volvulus A volvulus is the twisting or axial rotation of a portion of the bowel around its mesentery. The most common site of volvulus in adults is the colon; most frequently the sigmoid volvulus. Patients typically present with symptoms of bowel obstruction such as abdominal pain, distension, vomiting, and constipation/obstipation. Volvulus
    • Reflux assessment 
  • Routine care: postoperative evaluation 
• Advantages:
  • Low cost 
  • Low radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma dose (although it can become high with prolonged study time)
  • Ubiquitous availability
  • Fast
  • Dynamic imaging
• Disadvantages:
  • Poor resolution of soft tissue Soft Tissue Soft Tissue Abscess
  • Exposure to ionizing radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma
  • The patient must hold still for the image.

Exam technique

• Positioning:
  • Rotation Rotation Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. X-rays: There should be no rotation Rotation Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. X-rays unless specified in a particular study protocol.
  • Visualization:
    • Bowel gas should be completely radiolucent Radiolucent An object of low density that is permeable to X-rays (looks black) X-rays.
    • Peritoneal fat planes should be visible laterally.
• Positioning for specific views:
  • AP:
    • The board is against the patient’s back.
    • The X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests beams in a floor-to-ceiling direction through the patient.
    • Can be completed supine or upright
• Penetration Penetration X-rays: degree to which radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma has passed through the body, resulting in darker or lighter image
  • Under-penetration: The film appears whiter, and features are less apparent.
  • Over-penetration: The film appears darker, and features are less apparent.

Interpretation and evaluation

Systematic inside-out approach Inside-Out Approach Imaging of the Lungs and Pleura (central to peripheral):

• Look at the bowel gas pattern.
• Look for solid organ silhouettes Solid Organ Silhouettes Imaging of the Urinary System (e.g., liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy, spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy, kidney).
• Look peripherally for normal fat planes.
• Look for evidence of free intraperitoneal Intraperitoneal Peritoneum: Anatomy air.
• Evaluate soft tissues for abnormal calcifications (e.g., stones, masses in pediatrics).
• Look at the lung bases Bases Usually a hydroxide of lithium, sodium, potassium, rubidium or cesium, but also the carbonates of these metals, ammonia, and the amines. Acid-Base Balance for evidence of consolidation Consolidation Pulmonary Function Tests, effusion, and pneumothoraces.
• Evaluate osseous structures (e.g., vertebral body Vertebral body Main portion of the vertebra which bears majority of the weight. Vertebral Column: Anatomy height, iliac bones, femurs).
• Once an abnormality is noted, use a patterned approach to come up with differential diagnoses.

Dynamic approach:

• Watch the flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure of contrast through the bowel for any abnormalities (e.g., obstruction, stenosis Stenosis Hypoplastic Left Heart Syndrome (HLHS), extravasation).
• Evaluate muscle contraction.
• Evaluate mucosal fold patterns.

Common GI fluoroscopy Fluoroscopy Production of an image when x-rays strike a fluorescent screen. X-rays exams:

• Barium swallow: used for esophageal evaluation
• Upper GI series: used for esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus: Anatomy, stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach: Anatomy, and duodenum Duodenum The shortest and widest portion of the small intestine adjacent to the pylorus of the stomach. It is named for having the length equal to about the width of 12 fingers. Small Intestine: Anatomy evaluation
• Small bowel Small bowel The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine: Anatomy follow-through: used for stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach: Anatomy and small intestine Small intestine The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine: Anatomy evaluation
• Gastrostomy tube study 
• Barium enema Barium enema X-ray examination of lower gastrointestinal tract. Imaging is done while a barium compound (e.g., barium sulfate) fills the large intestine via the rectum as a contrast material. Diarrhea
  • Barium is injected rectally for a single- or double-contrast evaluation of the large bowel.
  • Often used to evaluate the colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix: Anatomy in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship who cannot tolerate a colonoscopy Colonoscopy Endoscopic examination, therapy or surgery of the luminal surface of the colon. Colorectal Cancer Screening
  • CT colonography CT colonography A non-invasive imaging method that uses computed tomographic data combined with specialized imaging software to examine the colon. Colorectal Cancer Screening is a better alternative than a barium enema Barium enema X-ray examination of lower gastrointestinal tract. Imaging is done while a barium compound (e.g., barium sulfate) fills the large intestine via the rectum as a contrast material. Diarrhea.
  • It is usually used to evaluate for colonic structural abnormalities.

Normal findings

AP view:

• Bowel gas:
  • Should be present in the small and large bowels
  • Should not distend the small bowel Small bowel The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine: Anatomy beyond 3 cm
  • Should not distend the cecum Cecum The blind sac or outpouching area of the large intestine that is below the entrance of the small intestine. It has a worm-like extension, the vermiform appendix. Colon, Cecum, and Appendix: Anatomy beyond 10 cm
  • Should be uniform throughout the abdomen
  • The small bowel Small bowel The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine: Anatomy should have valvulae conniventes, while the large bowel has haustra Haustra Colon, Cecum, and Appendix: Anatomy.
• Organs:
  • The liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy should be visible under the right hemidiaphragm and uniform, with no free air.
  • The stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach: Anatomy and colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix: Anatomy should be visible, with air in the lumen under the left hemidiaphragm. 
  • Renal outlines, if visible, should be in the RUQ and LUQ.
• Fat planes: peripheral fat planes with normal appearance
• Lung bases Bases Usually a hydroxide of lithium, sodium, potassium, rubidium or cesium, but also the carbonates of these metals, ammonia, and the amines. Acid-Base Balance
  • Should be clear with minimal lung markings
  • Costophrenic angles should be sharp.

Pathologic findings in different types of GI fluoroscopy Fluoroscopy Production of an image when x-rays strike a fluorescent screen. X-rays

Esophageal pathologies found via Barium swallow:

• Structural esophageal abnormalities
  • Filling defects
    • A 1-side compression Compression Blunt Chest Trauma (with or without irregular margins)
    • Acute margins on each end
    • Proximal dilatation
  • Diverticula (e.g., Zenker’s diverticulum Diverticulum A pouch or sac opening from the colon. Diverticular Disease): outpouching of contrast from the lumen
  • Hiatal hernias: gastric folds extending above the diaphragmatic hiatus
• Esophageal motility Esophageal Motility Gastrointestinal Motility abnormalities
  • Achalasia Achalasia Achalasia is a primary esophageal motility disorder that develops from the degeneration of the myenteric plexus. This condition results in impaired lower esophageal sphincter relaxation and absence of normal esophageal peristalsis. Patients typically present with dysphagia to solids and liquids along with regurgitation. Achalasia
    • Bird beak sign: tapering of the esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus: Anatomy
    • Dilated esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus: Anatomy
  • Diffuse esophageal spasm Diffuse esophageal spasm A hypermotility disorder of the esophagus that is characterized by spastic non-peristaltic responses to swallowing; chest pain; and dysphagia. Dysphagia (typically in older individuals)
    • Corkscrew esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus: Anatomy
    • Uncoordinated esophageal contractions
• Transluminal esophageal rupture Esophageal rupture Esophageal rupture or perforation is a transmural defect that occurs in the esophagus, exposing the mediastinum to GI content. The most common cause of esophageal perforation is iatrogenic trauma by instrumentation or surgical procedures. Esophageal Perforation: contrast material visualized in the mediastinum Mediastinum The mediastinum is the thoracic area between the 2 pleural cavities. The mediastinum contains vital structures of the circulatory, respiratory, digestive, and nervous systems including the heart and esophagus, and major thoracic vessels. Mediastinum and Great Vessels: Anatomy

Gastric pathologies found via upper GI series:

• Masses (e.g., carcinoma or bezoar)
  • Filling defects
  • Best seen on single-contrast examination
• Gastric and duodenal ulcers
  • Outpouching of contrast due to break in the mucosal lining
  • Best seen on double-contrast examination

Small bowel Small bowel The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine: Anatomy pathologies found via upper GI series:

• Crohn’s disease
  • Intraluminal filling defects
  • Fistulas 
  • Lack of bowel movement due to adhesions
  • Narrowing of the lumen
• Celiac disease Celiac disease Celiac disease (also known as celiac sprue or gluten enteropathy) is an autoimmune reaction to gliadin, which is a component of gluten. Celiac disease is closely associated with HLA-DQ2 and HLA-DQ8. The immune response is localized to the proximal small intestine and causes the characteristic histologic findings of villous atrophy, crypt hyperplasia, and intraepithelial lymphocytosis. Celiac Disease: reversal of fold patterns between the jejunum Jejunum The middle portion of the small intestine, between duodenum and ileum. It represents about 2/5 of the remaining portion of the small intestine below duodenum. Small Intestine: Anatomy and ileum Ileum The distal and narrowest portion of the small intestine, between the jejunum and the ileocecal valve of the large intestine. Small Intestine: Anatomy
• Small bowel Small bowel The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine: Anatomy distortion Distortion Defense Mechanisms: mesenteric reaction from desmoid or carcinoid tumor Tumor Inflammation

Large bowel pathologies found via Barium enema Barium enema X-ray examination of lower gastrointestinal tract. Imaging is done while a barium compound (e.g., barium sulfate) fills the large intestine via the rectum as a contrast material. Diarrhea:

• Diverticula
  • Outpouching of contrast from the lumen
  • Multiple
  • Mostly in the sigmoid Sigmoid A segment of the colon between the rectum and the descending colon. Volvulus colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix: Anatomy
• Colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix: Anatomy cancer
  • Narrowing of the lumen
  • Filling defects (apple core appearance)
  • Irregular borders
• Polyps
  • Filling defects
  • Smooth margins
• Fistulas: contrast-filled abnormal tract