Plain Abdominal X-ray Pattern Recognition

Normal Plain and contrasted radiographic GIT

Pattern Recognition

INTRODUCTION

The abdomen is composed of the abdominal and pelvic cavities and is often divided into nine anatomic regions.

NINE ANATOMICAL REGIONS

• Right hypochondriac
• Epigastric
• Left hypochondriac
• Right lumbar
• Umbilical
• Left lumbar
• Right iliac
• Hypogastric
• Left iliac

ABDOMINAL QUADRANTS

• It may also be described in terms of quadrants:
• Right-upper quadrant (RUQ)
• Right-lower quadrant (RLQ)
• Left-upper quadrant (LUQ)

Left-lower quadrant (LLQ)

ABDOMINAL ORGANS

The abdominal cavity contains organs of the digestive system (stomach and intestines), the hepatobiliary system (liver, gallbladder, and pancreas), the urinary system (kidneys and ureters), and the circulatory system (spleen).

The pelvic cavity contains the bladder, portions of the intestines,and the reproductive organs.

GASTROINTESTINAL SYSTEM ORGANS

A major portion of the gastrointestinal (GI) system is the alimentary tract, which serves to digest and absorb food.

Extend from the mouth to Anus the alimentary tract consists of the mouth, pharynx, esophagus, stomach, small bowel, large bowel, and rectum.

IMAGING CONSIDERATIONS

• Radiography

Abdominal radiography is often performed for survey purposes, without contrast agents.

The usual starting point is a supine radiograph taken to include the kidneys, ureters, and bladder (“KUB”).

The frequency of abnormal findings on a conventional abdominal radiograph is fairly low and nonspecific, but it is of most value for patients complaining of severe abdominal tenderness and to rule out bowel obstructions and perforations

Anteroposterior (AP) projections of the abdomen are generally taken in the supine position.

An AP radiograph allows examination of air distribution within the bowels and of the size of the viscera, serves to evaluate vascular and other types of calcifications and body or soft tissue trauma, and, finally, serves as a preliminary radiograph for other procedures.

As with other body areas, evaluation of the abdomen should be done systematically.

This should include inspection of the renal outlines, ureters, psoas muscles, spleen, liver, gallbladder, and peritoneal fat stripes.

Radiographic findings

In a normal abdomen, varying amounts of gas and fecal material are always present in an unprepared patient.

The liver,kidney, spleen, and psoas muscle shadows are variably outlined because of the lucent layer of fat surrounding them.

Properitoneal fat stripes are visible as radiolucencies extending laterally from the costal margins down to the iliac crests.

Plain Abdominal X-ray Pattern Recognition

The aorta and pancreas are not normally seen unless they are calcified, as might be expected in an older patient in the case of the aorta or in a patient with chronic calcific pancreatitis.

AIR-FLUID LEVEL

Few, if any, air–fluid levels are present in the normal patient who is radiographed in the erect position. Limited fluid levels in the small bowel and large bowel, however, may be considered normal.

Fluid levels are abnormal when they are seen in dilated bowel loops or when they are numerous.

In infants and children,gas may be scattered throughout the bowel,but in adults gas is normally seen only in the stomach and colon.

BOWEL GAS(FREE AIR)

Small bowel gas in an adult, therefore, may indicate a pathologic process.

In some patients, gas may be recognizable only on erect radiographs because of the presence of intraluminal fluid.

Free air should not be visible in the peritoneal cavity and is indicative of a bowel perforation or other pathologic entities that introduce air into the peritoneum.

Plain Abdominal X-ray Pattern Recognition

Erect abdominal radiographs must include the diaphragm to assess for free air, and in instances in which the patient is unable to stand, a left lateral decubitus abdomen should be obtained.

Note: In Gastrointestinal System, Some contents of the abdomen can be seen without contrast media.

However, most of the GI tract cannot be examined directly.

Small bowel on plain x-ray

• The small bowel lies centrally.
• There should be no more than 3 short air-fluid levels on an erect film.
• There should only be small amounts of gas in the small bowel.

After being swallowed, air reaches the colon within 30 minutes.

The jejunum is recognised by valvulae conniventes, folds which traverse the full width of the bowel.

The distal ileum is smoother in appearance.

Large bowel

The large bowel lies peripherally. There may be longer fluid levels and the maximum diameter is variable.

The large bowel often contains faeces & has a speckled appearance due to gas trapped in the faeces.

• The haustra may be outlined by gas.

It is quite common to see gas outlining much of the large bowel normally.

The haustra can be recognised by the fact that they do not cross the full width of the bowel and they are not regular.

Other soft tissues seen on a plain films

• The bladder may be seen as a soft tissue density arising from the pelvic floor.

The stomach is normally outlined with air below the left hemidiaphragm.

CONTRASTED INVESTIGATION OF THE GIT

Radiographic investigation of the GI system is commonly a combination of fluoroscopy and radiography.

Fluoroscopic examination of the GI system requires positive and negative contrast agents for visualization of body parts.

Barium sulfate is generally used as the positive contrast agent but is contraindicated in cases of GI tract perforation etc.

ORGAN TO BE INVESTIGATED

ESOPHAGUS

Most upper GI studies begin with the patient in the erect position to evaluate air and fluid levels in the alimentary tract.

An esophageal or barium swallow study may be performed to demonstrate anomalies and abnormalities of the esophagus.

Transport of the food or liquid bolus through swallowing is the sole function of the esophagus and is accomplished by gravity and peristalsis.

STOMACH

One common radiologic procedure of the GI tract is an “upper GI,” in which barium sulfate flows from the esophagus and into the stomach and small bowel.

Once the barium reaches the stomach, the evaluation of the stomach contour, position, and rugae and the peristaltic changes occurring as the stomach fills and empties.

Plain Abdominal X-ray Pattern Recognition

In many instances, a gas-producing substance (carbon dioxide crystals) is used with barium sulfate to produce a double-contrast examination.

The purpose is to expand the stomach and promote coating of the stomach mucosa.

SMALL BOWEL

In some instances, the barium sulfate mixture may be followed as it progresses through the small intestines.

Radiographs are exposed at set intervals to determine GI motility and to demonstrate abnormalities within the small bowel.

Once the contrast agent reaches the ileocecal valve, the small bowel study is complete, typically within 2 to 3 hours.

LARGE BOWEL

The lower GI tract is examined by administering a barium enema through the rectum. This examination demonstrate abnormalities of the large bowel and intraluminal neoplasm's.

The barium enema is performed in a single-contrast fashion with only barium or as a double-contrast study using barium sulfate in combination with a negative contrast agent.

Plain Abdominal X-ray Pattern Recognition

The negative contrast agent distends the lumen, allowing improved visualization of the mucosal lining, especially small polyps and intraluminal tumors.

After evacuation of the barium sulfate mixture, the radiographer will obtain a “postevacuation” radiograph to visualize colon contraction and to demonstrate the mucosa.

CONGENITAL AND HEREDITARY

ANOMALIES

Esophageal Atresia

Atresia is a congenital absence or closure of a normal body orifice or tubular organ.

Esophageal atresia is a rare congenital anomaly in which the esophagus fails to develop past some point, resulting in discontinuation of the esophagus.

Plain Abdominal X-ray Pattern Recognition

The symptoms of esophageal atresia are visible soon after birth and include excessive salivation, choking, gagging, dyspnea, and cyanosis.

Diagnosis of this congenital anomaly may be established by inability to pass an NG tube into the stomach.

Plain Abdominal X-ray Pattern Recognition

If a radiopaque NG tube is used, the terminal end of the pouch may be demonstrated radiographically with a chest radiograph without the use of a contrast agent.

BOWEL ATRESIA

Ileal atresia, a congenital discontinuation of the ileum, is the most frequent type of bowel atresia, followed by duodenal atresia.

This anomaly manifests a few days after birth.

The most common signs and symptoms of ileal atresia are abdominal distention and the inability of the infant to pass stool. Eventually the infant regurgitates feedings.

HYPERTROPHIC PYLORIC STENOSIS

Hypertrophic pyloric stenosis (HPS) is a congenital anomaly of the stomach in which the pyloric canal leading out of the stomach is greatly narrowed because of hypertrophy and hyperplasia of the pyloric sphincter.

Its exact cause is unknown, but it seems to be genetically related.

Plain Abdominal X-ray Pattern Recognition

HPS is typically suggested by projectile bile-free emesis in a previously healthy infant around 2 to 6 weeks of age.

Affected infants often become dehydrated and fail to gain weight.

It is most commonly confused with pylorospasm, which, in contrast, is an incomplete obstruction to fluid flow into the duodenal bulb resulting from spasmodic changes in pyloric muscle tone.

Abdominal radiography may show gastric distention with HPS.

On occasion, a mass impression of the thickened pyloric muscle on an air-filled gastric antrum may be noted.

Sonography has become the standard and highly accurate method for diagnosing HPS without the need for radiation exposure.

It allows imaging of the pyloric muscle and channel, and the constant imaging of an elongated, thickwalled pylorus indicative of HPS.

Measurements of pyloric channel length, pyloric diameter, and muscle thickness are often used for diagnosis.

HIRSCHSPRUNG DISEASE (CONGENITAL

AGANGLIONIC MEGACOLON)

Refers to the absence of neurons (Meissner and Auerbach autonomic plexus) in the bowel wall, typically in the sigmoid colon.

A malformation of the parasympathetic nervous system results in the absence of neurons in the bowel wall preventing the normal relaxation of the colon and subsequent peristalsis.

This anomaly results in gross dilatation of the colon to the point of narrowing and constriction.

Plain Abdominal X-ray Pattern Recognition

This generally becomes apparent shortly after birth, when the affected infant passes little meconium and the abdomen becomes distended.

As the patient ages, the continued effects are severe constipation and recurrent fecal impactions.

It is important to diagnose this disease early because it can progress to toxic megacolon if left untreated.

MECKEL DIVERTICULUM

Meckel diverticulum is a congenital diverticulum of the distal ileum.

This saclike anomaly is located within 6 feet of the ileocecal valve and is a remnant of a duct connecting the small bowel to the umbilicus in the fetus.

Children with Meckel diverticulum often develop an ulcer in the adjacent bowel, and a common sign is repeated episodes of bleeding from the ulcerated site.

Plain Abdominal X-ray Pattern Recognition

Symptoms in adolescents and adults include cramping, vomiting, and bowel obstruction. The symptoms mimic those of appendicitis except for the location of the pain.

Diagnosis of Meckel diverticulum is difficult, as it may not be visible on a radiograph of the small bowel.

However, nuclear medicine Meckel scans are useful in diagnosing this anomaly by identifying ectopic gastric mucosa.

Plain Abdominal X-ray Pattern Recognition

This is accomplished through injection of Tc-99m pertechnetate, which is taken up by the mucus-secreting cells of the gastric mucosa.