The Role Of Radiological Imaging Biology Essay

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Abdominal pain and gastrointestinal symptoms, such as vomiting or diarrhea, are common chief complaints in young children presenting in emergency departments. It is the emergency physician's role to differentiate between a self-limited process such as viral gastroenteritis or constipation and more serious life threatening surgical emergencies, such as appendicitis or bowel obstruction or infections that require specific treatment (such as streptococcal pharyngitis or pneumonia). Approximately 25% of all children will be brought to medical attention for abdominal pain by the age of 15 years; however, only 5% of the patients will likely require hospitalisation, and fewer yet, will require surgical intervention[1-2].

Common causes of Acute Abdominal pain in children according to age [3]:

Neonate: Necrotizing enterocolitis, Volvulus, Testicular torsion,Colic, Dietary protein allergy, Adhesions

2 months-2 years: Gastroenteritis, Viral illness, Trauma (including inflicted injury),Incarcerated hernia, Intussusception, Meckel's diverticulum, Urinary tract infection, Foreign body ingestion, Sickle cell syndrome vasoocclusive crisis, Dietary protein allergy, Tumour, Hirschsprung disease, Adhesions, Hemolytic uremic syndrome, Toxin, Hepatitis

2-5 years: Gastroenteritis, Viral illness, Trauma (including inflicted injury), Pharyngitis,

Constipation, Urinary tract infection, Pneumonia, Appendicitis, Intussusception, Meckel's diverticulum, Foreign body ingestion, Sickle cell syndrome vasoocclusive crisis, Henoch Schönlein purpura, Ovarian torsion, Intraabdominal abscess, Tumor, Adhesions, Haemolytic uremic syndrome, Hepatitis, Toxin, Primary bacterial peritonitis

>5 years : Gastroenteritis, Viral illness, Appendicitis, Trauma, Constipation, Pharyngitis,

Pneumonia, Urinary tract infection, Diabetic ketoacidosis, Sickle cell syndrome vasoocclusive crisis, Henoch Schönlein purpura, Inflammatory bowel disease, Ovarian torsion, Ruptured ovarian cyst, Testicular torsion, Intra-abdominal abscess, Cholecystitis, Pancreatitis, Urolithiasis, Hepatitis, Meckel's diverticulum, Perforated ulcer, Adhesions, Hemolytic uremic syndrome,

Myocarditis, pericarditis, Primary bacterial peritonitis, Familial Mediterranean fever

The challenge to the clinician caring for a child with abdominal pain comes in determining which child warrants further work-up. A good history and physical examination cannot be overstated. The initial evaluation of the patient may help guide subsequent investigation, including imaging. There are three questions that the clinician must address in regards to imaging:

•€ Does this child require imaging for diagnosis?

•€ Does this child require imaging to exclude a diagnosis?

•€ Which imaging technique is most likely to give the information needed to direct clinical



Imaging usually starts with a supine abdominal X-ray. A review of this should provide answers to the following questions [5]:

1. Is gas present throughout large and small bowel?

2. Is there gaseous distension? Is it both large and small bowel or is it confined to one?

3. Is the caecum visible in the right iliac fossa or right abdomen?

4. Are the large and small bowel correctly sited in the abdomen?

5. Is there organomegaly - liver, spleen, kidneys?

6. Is there a mass lesion? If so, what is the suspected organ of origin?

7. Is there air in the hernial orifices?

8. Is there any calcification within the organs, mass or peritoneum?

9. Are the psoas outlines visible? Loss of psoas outline is a soft sign of intra-abdominal


10. Are the properitoneal fat stripes displaced?

11. Are the lung bases clear?

12. Are the bones and disc spaces normal?

If there is doubt about free air or a need to identify fluid levels, an erect or a decubitus film may be indicated.

Ultrasound of the abdomen is extremely helpful in both establishing and excluding pathology.

Abdominal ultrasound should include both examination of the organs and bowel, the latter requiring the use of a high-frequency linear-array probe. The questions to be addressed with ultrasound are [5]:

1. Are the liver, kidneys, spleen, gallbladder and pelvic organs present, correctly sited, are normal in size and echo texture?

2. Is there free fluid?

3. Are there mesenteric nodes?

4. Is there free fluid, either in the subdiaphragmatic areas, pelvis, paracolic gutter or between bowel loops?

5. Is there a mass? What is the likely organ of origin? Is it solid, cystic, or does it have a mixed echo texture? Are the margins well or poorly defined? Is there calcification?

6. Is the bowel wall of normal thickness?

7. Is intestinal peristalsis normal, excessive or absent?

Computed tomography is required in selected circumstances but should be agreed on an individual basis. The examination should be individually tailored with the area of coverage, slice thickness and pitch, and milliampere level adjusted to answer the clinical questions. A CT scan with or without contrast is done. Magnetic resonance imaging is seldom required as a primary imaging technique but supplements CT and ultrasound in selected cases. Some of the common causes of abdominal pain are described here with their radiological findings:


Constipation is a common clinical problem in children. There is usually a history of longstanding constipation, poor fluid intake, passage of hard stools. Radiologic studies are unnecessary in the diagnosis and management of constipation in young children. A plain X-ray of the abdomen can confirm that the colon has a significant amount of stool present.


Appendicitis is the cause of pain in 2.3% of all the children with abdominal pain seen in the emergency departments. It is the most frequent condition requiring emergency abdominal surgery in childhood [4]. The diagnosis of appendicitis is clinical, but if examination is not clear then radiological examination needs to be done.

The classic presentation, consisting of generalized abdominal pain migrating to the right lower quadrant, associated with nausea, vomiting, and fever, is seen less often in the paediatric patient [6].

The most common findings of appendicitis in children are right lower quadrant pain,

abdominal tenderness, guarding, and vomiting [7].

The Radiological examination may include plain X-ray which is not useful and might show a faecolith in the right iliac fossa in 10 % percent of the patients.

Ultrasonography is noninvasive, rapid, and can be performed at the bedside. The normal appendix in paediatric patients is visualized readily by ultrasonography because there is usually less abdominal wall fat than in adults. Graded compression of the appendix is used to determine the presence or absence of inflammation. An inflamed appendix is usually aperistaltic, difficult to compress, and measures >6 mm in diameter. Presence of periappendiceal fluid collection may indicate an early perforation but can simply be a result of inflammation. The drawback of the ultrasound is that it is operator dependant. Experienced ultrasonographers can achieve sensitivities of 85% to 90% and specificities of 95% to 100% in acute appendicitis [8].

In recent years, CT has become the test of choice for paediatric surgeons when ultrasonography fails to give a definitive diagnosis [8]. Every variation, from triple-contrast (intravenous, oral, and rectal) CT scanning to noncontrast, unenhanced CT, has been used [8]. CT offers the advantage of greater accuracy, the ability to identify alternative diagnoses, and in some studies, lower negative laparotomy rates [8]. The sensitivity and specificity of CT is > 95% [11].

Although CT appears to be better than ultrasonography in making the diagnosis of appendicitis in children [8], it is slower, requires contrast and exposes the young child to significant radiation.


Intussusception occurs commonly between the ages of 3 months and 5 years. 60% of cases occur in the first year and the peak incidence at the age of 6 to 11 months. The disorder, which appears predominantly in males, believed to occur more often in the spring and autumn. Commonly there is intermittent colicky abdominal pain, vomiting, and bloody mucous stools. Intussusception occurs when a segment of bowel, the intussusceptum, prolapses and invaginates into another segment, the intussuscipiens.

Four types are described: ileocolic; ileo-ileo colic; colo-colic; and ileo-ileal. Most frequent is Ileocolic and occurs in 90% of cases. The most frequent plain-film findings are a mass to the right side of the spine and reduced large bowel gas [6]. Ultrasound has a 100% diagnostic accuracy in expert hands. Ultrasound has a high sensitivity (98% to 100%) and specifity of 90 -100 % for the diagnosis of Intussusception [9]. Sonographic findings on transverse section has a "target" or "doughnut" appearance, a single hypoechoic ring with a hyperechoic center .Visualization of the entire colon to the terminal ileum is mandatory to rule out ileocolic intussusception.

The main focus in the management is the reduction of the obstructed bowel. Contrast enema with water soluble dye is diagnostic and therapeutic. If reduction does not occur surgery has to be done. The recurrence rate of the intussusception is 10-15%, usually within 24 hours but sometimes after days or weeks [8,11].

Small bowel obstruction:

Commonly presents as decreased oral intake and vomiting, which often becomes bilious in nature. Common causes of small bowel obstruction are adhesions from previous abdominal surgery and incarceration of a hernia, intussusception, appendicitis,

Meckel's diverticulum, malrotation with midgut volvulus, and tumours.Plain abdominal films should be obtained when obstruction is suspected. A paucity of air in the

abdomen is the most common finding in young children with bowel obstruction.Distended loops of bowel may be seen; however, smooth bowel walls are more common than distended bowel in small children. Multiple air-fluid levels also are seen commonly with small bowel obstruction.

In later presentations, the bowel may resemble a tangle of hoses or sausages. An upright or lateral decubitus film will help to determine whether free air is present, caused by perforation. Further study with ultrasonography, CT, an upper-GI series,or an enema should be performed when there is suspicion of underlying pathologies such as appendicitis, midgut volvulus, and intussusception. [8,11]

Meckel's diverticulum:

Meckel's diverticulum is the most common congenital abnormality of the small intestine. The classic presentation of Meckel's diverticulum is painless or minimally painful rectal bleeding. Isolated rectal bleeding is common, particularly in boys less than 5 years of age [8]. Meckel's diverticulum is a remnant of the omphalomesenteric (vitelline) duct that disappears normally by the seventh week of gestation. It contains all layers of the bowel wall and 60% of these diverticuli contain heterotopic gastric tissue. Heterotopic pancreatic, endometrial, and duodenal mucosa have also been reported [8].

The features of Meckel's diverticulum are commonly described by ''the rule of 2s'' [8]: it is present in approximately 2% of the population with only 2% of affected patients becoming symptomatic. Forty-five percent of symptomatic patients are less than 2 years of age [8]. The most common location is 2 feet (40-100 cm) from the ileocecal valve, and the diverticulum typically is 2 inches long. Abdominal films may show signs of obstruction such as dilated loops of bowel or a paucity of bowel gas. Scanning Meckel's diverticulum involves an intravenous injection of technetiumpertechnetate.

This test relies on the presence of gastric mucosa in or near the diverticulum that

has an affinity for the radionucleotide. A scan of Meckel's diverticulum can detect the presence of gastric mucosa within the diverticulum with up to 85% accuracy [8,11]. Mesenteric arteriography can detect the site of active bleeding if bleeding is profuse.

Incarcerated hernia:

The early sign of incarceration of an inguinal hernia is an abrupt onset of irritability, refusal to eat, followed by vomiting, which may become bilious and sometimes faeculent. Inguinal hernias occur in 1% to 4% of the population, more common in males (6:1), more often on the right side (2:1). Diagnosis is by physical examination. Sometimes ultrasound is done if the diagnosis is uncertain, a scrotal ultrasonogram can differentiate an inguinal hernia from a hydrocoele.

Hypertrophic pyloric stenosis:

Hypertrophic pyloric stenosis is a narrowing of the pyloric canal caused by hypertrophy of the musculature. Usually presents during the third to fifth week of life, male to female ratio of 4:1. Symptoms begin with occasional vomiting at the end of feeding and as the disease progresses, the incidence of vomiting increases and becomes projectile. Emesis is nonbilious because the stenosis is proximal to the duodenum. Clinical diagnosis can be made by palpation of the hypertrophied muscle mass, size of an "olive" in the right quadrant. Ultrasonography is done to measure the thickness of the pyloric wall (normally 2.0 mm or less but in HPS is 4.0 mm or more) and the length of the pyloric canal (normally 10.0 mm or less but in HPS is 14-16 mm), leading to the diagnosis. Ultrasonography has been shown to have a

sensitivity and specificity as high as 100% [8]. A false-negative result may occur if the

ultrasonographer measures through the distal stomach or antrum and not through the pylorus itself. A false-positive results if pyloric spasm is present and not pyloric stenosis.

If ultrasonography is nondiagnostic, an upper-GI study is done. The upper GI will show the classic''string sign'' as contrast flows through the narrowed pyloric lumen. There will also be delayed gastric emptying. As with ultrasonography, false-positive results may occur because of pyloric spasm, which also gives the appearance of a string sign. Endoscopy also can be used to diagnose HPS but is not used commonly [8].

Malrotation with midgut volvulus:

Congenital malrotation of the midgut portion of the intestine is often the cause of volvulus in the neonatal period. Volvulus is the twisting of a loop of bowel about its mesenteric base stalk attachment; ischemia subsequently develops, and this constitutes a true surgical emergency because bowel necrosis can occur within hours. The incidence peaks during the first month of life but can present anytime in childhood. The classic finding on abdominal plain films is the ''double bubble sign'' which shows a paucity of gas with two air bubbles, one in the stomach, and one in the duodenum .

Other findings may include air-fluid levels, a paucity of gas distally,

or dilated loops over the liver shadow. The plain film also can be entirely normal. An upper-GI contrast study is considered the gold standard for diagnosing volvulus. The classic finding is that of the small intestine rotated to the right side of the abdomen, with contrast narrowing at the site of obstruction, causing a ''cork-screwing'' appearance. Ultrasonography also has been studied for diagnosing volvulus. The ultrasonography may show a distended, fluid-filled duodenum, increased peritoneal fluid, and dilated small bowel loops to the right of the spine. Sometimes, spiraling of the small bowel around the superior mesenteric artery also can be observed [8].

Hepato-biliary pathology:

Acute presentation of hepato-biliary disease in children is rare. The symptoms are either acute abdominal pain due to cholecystis and gallstones. The clinical presentation and imaging investigations are similar to adults, e.g. an abdominal radiograph to identify calcified gall stones and ultrasound of the pancreas, gallbladder and biliary tree. The imaging of cholecystitis show thickening of the gallbladder wall. The presence of stones cause an acoustic shadow. Dilatation of the common bile duct and intrahepatic ductules occur in obstructive jaundice.


The most frequent cause of pancreatitis in children is trauma. Other causes include viral

infection, congenital anomalies and tumours, especially lymphoma, and a hereditary form - familial calcific pancreatitis. Clinical presentation depends on the severity of the disease, but abdominal pain is invariable. An abdominal mass is palpable if a pseudocyst is present.

Radiological imaging findings of pancreatitis on both ultrasound and CT in children show an enlarged, often hypoechoic gland dilatation of the pancreatic duct, and on CT, peripancreatic fluid, mesenteric oedema, and enhancement pattern with I/V contrast [5].

Renal causes of acute abdominal pain

The renal causes of an apparent acute abdomen, are upper urinary tract infection, especially pyelonephritis, acute presentation of a pelvi-ureteric junction obstruction, or more rarely renal colic due to a stone in the urinary tract. Renal calculi are not uncommon in the paediatric population and have an increased incidence in children with impaired drainage of the renal tract, including the bladder. Radiological investigation includes a plain abdominal X-ray and renal tract ultrasound. Radio opaque calculi are frequently identified on a plain film of the abdomen but may be obscured by overlying faecal material. Ultrasound is very effective in demonstrating

calculi within the kidneys or bladder, but a calculus in a non-dilated ureter may be missed. Acutely infected kidneys may appear ultrasonically normal.Foci of infection are often hypoechoic with focal loss of the corticomedullary differentiation.

Unenhanced CT is increasingly used in the United States for the primary diagnosis, specially for small stones.[10,11]

Gynaecological conditions causing acute abdominal pain

Ovarian cysts

Ovarian cysts may cause lower abdominal or pelvic pain if they become significantly enlarged, or if they are complicated by rupture, torsion or haemorrhage. Ultrasound of uncomplicated cysts have a thin wall and anechoic contents. Following haemorrhage the cyst contents have a variable echo pattern. They may appear echogenic or hypoechoic, but never anechoic. Regardless of their echo pattern, they typically show through-transmission due to their underlying cystic nature [10]. Their echo pattern and general appearance typically alter with time. The cyst wall may be thin or

thick, irregular and occasionally show internal septations [10]. A complex cystic adnexal mass in a young patient may often be treated conservatively, particularly if there are no features which suggest the presence of torsion; however, even if symptoms resolve, a follow-up ultrasound scan should be performed in order to exclude an underlying neoplasm.

Ovarian torsion

Torsion may involve either an ovarian cyst or the entire ovary. It usually presents clinically with acute lower abdominal pain, mimicking appendicitis. It is most common in pre-pubertal girls, due to increased adnexal mobility prior to menarche. It may be associated with a large ovarian cyst or neoplasm. Ovarian torsion should be treated as a surgical emergency in order to prevent ischaemic damage. The ultrasound findings in ovarian torsion are variable [10]. Typically, the ovary is markedly enlarged, with multiple enlarged peripheral follicles. The ultrasound appearances may be non-specific, demonstrating a cystic or complex adnexal mass. Doppler ultrasound may demonstrate either absent or reduced flow compared with the other side, but this may not be evident on trans-abdominal scanning. When an abnormal, enlarged ovary is identified in a young girl with abdominal pain the possibility of ovarian torsion should always be



Abdominal pain is a common complaint in young children. Accompanying signs and symptoms to abdominal pain are often a clue as to the presence of an organic or treatable etiology for the pain. Radiography, ultrasound and computed tomography are the main imaging tools used in evaluating the child presenting with acute abdominal pain.

The imaging protocols should be designed to address a specific potential diagnosis. Attention to the individual patient assures the most efficient utilisation of radiologic resources.

Good communication between the radiologist and physician is important in deciding how best to tailor the selected imaging study to address the clinical problem in hand.