The Role Of Radiological Imaging In The Diagnosis Biology Essay

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Abdominal pain is a very common complaint in children presenting to the emergency department. The pain might be acute or chronic. Most of the causes for abdominal pain in children are benign, self-limitting conditions like gastroenteritis or constipation , but some conditions can be life threatening and require rapid diagnosis and treatment.

According to one study, by the age of 15 nearly 25 % of the children will present to the hospital with complaints of abdominal pain and only 5 % percent will require to be admitted and fewer than that will require surgical treatment.

The task of the emergency physician is to differentiate between a benign, self-limiting condition and a life threatening medical emergency.

Most of the diagnosis can be made by a good detailed history and physical examination. Concentration should be given to the age, sign and symptoms of different abdominal conditions, the location and type of pain. This can leed to the diagnosis. If initial evaluation is not clear patient can be kept for observation and reassessed again.

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Laborotary investigations can be done according to the clinical finding and history and can further help in reaching a diagnosis. The knowledge of the anatomy, the pathophysiology and common abdominal conditions according to age can also give a clue to the cause of the abdominal pain and help in the diagnosis.

The pathophysiology of abdominal pain can be divided into three categories :

1. Visceral pain(splanchnic), which occurs due noxious stimuli such as tension, stretching and ischemia stimulate the pain fibres of the viscera. The pain fibres of the viscera are bilateral, unmyelinated and enter at the spinal cord at different levels, makes the visceral pain poorly localized, dull and felt In the midline.

The pain from the foregut structures, like the lower stomach, oesophagus is felt in the epigastric region. Structures from the from the midgut structures like the small intestines cause pain in the paraumbilical area. Structures in the hindgut like the large intestine cause pain in the lower abdomen.

2. The parietal pain arises due to ischemia, inflammation or stretching of the parietal peritoneum and is transmitted by the myelinated afferent fibres to the specific dordal root ganglia on the same side and at the same dermatome level from where the pain originated. The pain is usually localized, sharp , discrete and is aggravated by any movement or coughing.

3. Referred pain has characteristics of parietal pain but is felt in remote areas supplied by the same dermatome as the affected organ. A good example of referred pain is abdominal pain due to pneumonia as the dermatome T9 is shared by the lung and the abdomen.

Causes of abdominal pain according to location of pain.

Right Upper Quadrant pain: Hepatitis, choelcystitis, Cholangitis, Pancreatitis, Pneumonia,

Left Upper Quadrant Pain: Splenic abscess / infarct , gastritis, pancreatitis

Epigastric Pain: Gastritis, Pancreatitis, pericarditis, Peptic Ulcer

Right Lower Quadrant pain: Appendicitis, Inguinal Hernia, Mesenteric adenitis, ectopic pregnancy, ovarian torsion, ovarian cyst

Left Lower Quadrant Pain: diverticulitis, ovarian cyst / torsion, Ectopic pregnancy, Irritable bowel syndrome, Inflammatory bowel syndrome,

Periumbilical pain: Early appendicitis, Gastroenteritis, Bowel obstruction

Diffuse pain: Gastroenteritis, Bowel obstruction, Peritonitis, Irritable bowel syndrome, metabolic conditions as Diabetic Ketoacitosis,Porphyria

Abdominal pain according to Age:

Neonate: Necrotizing enterocolitis , Volvulus , Testicular torsion, Infantile Colic, Cow Milk protein allergy

2 months-2 years: Gastroenteritis, Viral illness, Trauma (including abuse),Incarcerated hernia, Intussusception, Testicular torsion, Urinary tract infection, Sickle cell with vasoocclusive crisis, Dietary cow milk protein allergy, Tumour, Hirschsprung disease, Toxin, Hepatitis

2-5 years: Gastroenteritis, Viral illness, Trauma (including abuse), Pharyngitis, Constipation, Urinary tract infection, Pneumonia, Appendicitis, Intussusception, Meckel's diverticulum, Testicular torsion, Sickle cell vasoocclusive crisis, Henoch Schönlein purpura, Ovarian torsion, Tumor, Haemolytic uremic syndrome, Hepatitis, Toxin,

>5 years : Gastroenteritis, Appendicitis, Trauma (including abuse) 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, Cholecystitis, Pancreatitis, Urolithiasis, Hepatitis, Meckel's diverticulum, Hemolytic uremic syndrome, pericarditis, Familial Mediterranean fever

If the intial evaluation, laborotary investigation do not lead to a diagnosis than further work up like, radiological examination needs to be done. Imaging has an important role in the evaluation of patients with acute abdominal pain. The radiological imaging modalities available to the physician are important tools to assist in the diagnosis of different abdominal emergencies. The physician needs to choose which modality will give the most information for the diagnosis, depending on the clinical history and most likely diagnosis, so as to not expose the patient to unnecessary harmful radiation.

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There are four radiological imaging modalities available in the diagnosis of abdominal pain. They are:

Plain X-ray :

The plain X-ray film although is less specific or sensitive, is still the most widely available modality in the emergency departments. Due to increased availability of advanced imaging modalities like CT scan, Ultrasound and Magnetic Resonance Imaging , the plain X-ray films have become less useful.

In a paper published by Kellow ZS et al , in Radiology 2008, 248: 887-93 , on the role of abdominal radiography in the evaluation of non trauma emergency patients , they mentioned in their study that the abdominal radiographs interpreted as normal or nonspecific, 81 % of them had positive findings on CT, Ultrasound and Upper Gastrointestinal imaging.They also found that plain radiographs led to change in management in only 4% of the patient.

In another study by MacKersie AB et al., Non traumatic acute abdominal pain: unenhanced helical CT compared with three-view acute abdominal series. Radiology 2005;237:114-22 , they compared unenhanced helical CT, and 3 view abdominal radiographs, they found that overall sensitivity of 30 % , specificity of 88% and accuracy of 56%, with negative predictive value of 51.8%.

Due to the poor yield and exposure to radiation dose, plain radiographs are indicated solely to identify bowel obstruction, constipation and Hirschprung's disease, perforation, foreign body ingestion and localization of catheter placement.

Ultrasound:

Ultrasound has become a sophisticated tool for evaluation of patients with abdominal pain. It allows quick evaluation in unstable patients even while the patient is being resuscitated. It is a non invasive, pain free procedure and there is no risk for exposure to radiation.

The drawback of the ultrasound is that it is operator dependant. In obese patients and bowel gas limit the quality of the study.

In United States residents doing emergency medicine are required to do training in point of care goal directed ultrasound. Ultrasound is a radiological procedure of choice in condition like hypertrophic pyloric stenosis, intussusceptions, acute appendicitis.

Computed Tomography (CT)

CT scan is a relatively new modality of imaging, first commercially available in 1972. Since that time the CT scan machines have developed a lot , by improving imaging quality , by reducing the dose of radiation and increase in speed. It has also become widely available and the cost has become less. The use of CT scan in the evaluation of acute abdominal pain has increased. In a paper published by Levin DC et al, Journal of American college of radiology,2008; 5:1206 -1209, Stated that in the United States, the number of CT examinations performed increased 141% between the year 1996 and 2005 . This was due to the high accuracy of CT scan in diagnosing specific diseases like diverticulitis, appendicitis and bowel ischemia.

In another prospective study done by Lame ́ris W et al, on 'Imaging strategies for detection of urgent conditions in patients with acute abdominal pain: diagnostic accuracy study', published in BMJ 2009;338:b2431, showed that the clinical accuracy of diagnosis of abdominal pain improved from 71 percent to 93 percent after the CT scan was performed.

CT scan gives high resolution multiplanar images and provides rapid and accurate diagnosis. It is useful in stable patients whose differential diagnosis includes a significant abdominal pathology e.g. Tumour.

It's drawback is that it exposes the patient to radiation, contrast dye and the patient needs to be shifted from the treatment area of the emergency department. Radiation exposure also poses a higher risk for malignancy in the future for patients in the paediatric age group.

Magnetic Resonance Imaging (MRI):

It is also a new and good modality of imaging. It has been increasingly used in Abdominal imaging. It is especially useful for hepatic tumours, biliary diseases, small bowel diseases and vascular disease.

It is comparatively expensive and widely available as the CT scan and ultrasound. It also needs the patient to be cooperative, as it is slow and patient needs to stay still for a long period of time. Small children need to be given sedation to do the imaging. This makes MRI not a good modality for imaging in an emergency situation where the patient is generally not stable for sedation and fast imaging is required.

Some of the common causes of abdominal pain are described here with their radiological findings:

Constipation and Gastroentiritis:

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One of the most common cause of abdominal pain in children presenting to the emergency department is constipation and gastroenteritis. Constipation is characterized by infrequent bowel motions with painful defecation due to passage of hard stools.

X-rays are not necessary in the diagnosis. If in doubt and or history suggestive of Hirshcprung's diease, then a plain X-ray of the abdomen can confirm that the colon has a significant amount of stool present.

Appendicitis:

2.3% of all the children with abdominal pain seen in the emergency department are diagnosed to have Appendicitis and is the most frequent reason for emergency abdominal surgery in childhood .

The appendicitis is a clinical diagnosis , but if examination is not clear then radiological examination needs to be done.

The common presentation is periumbilical pain migrating to the right iliac fossa. It can be assoicatied with vomiting low grade fever, tenderness and guarding.

Plain XRay film is not useful and rarley shows a faecolith.

Ultrasound remains the imaging modality of choice. The inflamed appendix is usually difficult to compress, and measures >6 mm in diameter. Presence of fluid collection around the appendix indicate early perforation or inflammation.

When performed by an experienced ultrasonographer it can give sensitivities of 85% to 90% and specificities of 95% to 100% in acute appendicitis.

If ulstrasound is not conclusive than CT scan with or without contrast is the imaging modality of choice. The sensitivity and specificity of CT scan is more than 95 percent.

Intussusception:

Intussusception occurs due to invagination of the prolapsed part of the gut (intussusceptum )into another segment(intussuscipiens) .There are four types, ileocolic the most common; ileo-ileo colic; colo-colic; and ileo-ileal . It affects mostly between the ages of 2 months and 2 years. The peak age of incidence is between the age of 6 - 11 months. It affects male more than females. There is seasonal variation and occurs more in the spring and autumn. The patient typically has colicky abdominal pain, vomiting and passage of bloody mucous stool.

Plain Xray film may show a mass to the right side of the spine with reduced reduced large bowel gas. Ultrasound is the modality of choice and has 100% accuracy in experienced hands. Ultrasound has sensitivity of 98% to 100% and specicity of 90 to 100 %. Ultrasounds shows a single hypocechoic ring with a hyperechoic center.

The reduction of obstructed bowel is the mainstay of the treatment. Contrast enema with water soluble dye is diagnostic and therapeutic and If reduction does not occur surgery has to be done.

Intussusception can recur in 10 -15 percent of cases within 24 hours and sometimes in days or weeks. [8,11].

Small bowel obstruction:

It commonly presents with poor oral intake and bilious vomiting. The common causes of small bowel obstruction are adhesions from previous surgery, incarcerated hernia, malrotation with midgut volvulus and Intussusception.

Plain Xray of the abdomen shows paucity of air, with distended bowels and multiple air fluid levels.

If other underlying pathologies like intussusception , midgut volvulus and appendicitis are suspected then Ultrasound, upper Gastrointestinal study or CT scan should be performed.[8,11]

Meckel's diverticulum:

It is a one of the most common congenital abnormality of the small intestine. It is a finger like projection which arises from the antimesenteric border , 40 to 60 centimetres. from the ileocaecal valve, measuring between 1 to 10 centimetres and nearly 2 centimetres long.It contains hetertrophic gastric tissue .The prevalence is 2 to 3 percent and most patients present before the age of 2 years. A meckel scan which is technetiumpertechnate a radionuclide scan, can detect gastric mucosa in upto 85 percent of cases.

Hypertrophic pyloric stenosis:

It commonly affects infants in the third to fifth week of life.The patients commonly presents with history of projectile non bilious vommitting .The incidence is 1 in every 250 births. Male are affected more than the female, the ratio is 4:1. The musculature in the pyloric canal becomes hypertrophied which leeds to narrowing of the canal.

Ultrasound is the imaging modality of choice which shows the thickness of the pyloric wall to be more than 4.0 mm and the length of 14 - 16 mm (normal 10mm). The ultrasound has sensitivity and specificity of 100 percent. If ultrasound is not conclusive than upper Gastro intestinal studies should be which will show that there is delayed gastric emptying and the string sign due to narrowing of the pylorus.

Incarcerated hernia:

Incidence of Inguinal hernia occurs in 1 - 4 percent. It is more common in males with a ratio of 6:1. The right side is affected more than the left in a ratio of 2 : 1. Sometime the hernia gets incarcerated leading to sudden onset of irritability, vomiting and which may become later bilious.The diagnosis is by physical examination. Ultrasound has to be done sometimes to differentiate hydrocoele from hernia.

Malrotation with midgut volvulus:

Intestinal malrotation is a broad term which includes all anatomical arrangements which result from incomplete rotation of the gut during its embryonic development. Mostly it affects children less than 1 year of age and 60 percent of them before the age of 1 month. The most common type is the midgut volvulus. Volvulus occurs due to the twisting of a loop of bowel about its mesenteric base.

Plain X-ray shows the classic double bubble sign. Upper Gastrointestinal study is the investigation of choice for diagnosing a volvulus.

Hepato-biliary disease:

Children rarely present with acute hepatobilliary disease. Children with conditions like haemaglobinopathies , who have chronic haemolysis can present with gall stones and acute cholecystitis. Plain abdominal X-rays are not very helpful. The imaging modality of choice is the ultrasound, which can show the liver , gall bladder, bile duct, gall stones and the pancreas.

Pancreatitis:

Pancreatitis is the inflammation of the pancreas. It is rare in children. There are several causes of pancreatitis. Trauma is the most common cause of pancreatitis in children. The other rare causes are tumours , congenital anomalies, viral infection like mumps, infectious mononucleosis and hereditary causes as hereditary pancreatitis. Beside the laboratory blood investigation, Ultrasound and CT scan are the imaging modalities used in the diagnosis of pancreatitis.

Renal causes of acute abdominal pain

Urinary tract infection, pylonephritis, renal stones are renal conditions which can present with abdominal pain. Plain abdominal Xray will show radio opaque stones.

Ultrasound is the imaging modality commonly used. In cases of small renal stones Unenhanced CT for primary diagnosis is being used in countries like the United States.

Testicular Torsion:

This a urological emergency. It commonly affects children between the ages of 7 to 12 years but can effect younger children. They present with acute abdominal pain and vomiting. It occurs due to the twisting of the testes on the spermatic cord which leads to contriction of the blood vessels leading to ischaemia and necrosis of the testes. Urgent Ultrasound with Doppler is the imaging modality of choice to detect presence or absence of blood flow in the testes.

Gynaecological causes of acute abdominal pain

Ovarian torsion

A patient with Ovarian torsion can present with acute abdominal pain. It is a complete or partial rotation of the ovarian vascular pedicel leading to obstruction of the both arterial and venous blood flow. It commonly effects female of reproductive age but can affect females at any age. It can be associated with an ovarian tumour. If blood supply is not restored quickly it may affect the viablilty of the ovary. Urgent Ultrasound with doppler is the imaging modality of choice for the evaluation of the ovarian torsion . To rule out any underlying malignancy a follow up ultrasound should be performed later on.

Ovarian cyst

It is a sac filled with liquid or semiliquid material that arises in an ovary. Most of the cysts are asymptomatic. Some of them enlarge and rupure. Sometimes they develop a torsion or become malignant. They can therefore cause pain in the lower abdomen and present as acute abdomen to the hospital. Urgent ultrasound will help in the diagnosis and to rule out other causes like appendicitis.

Conclusion

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.