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Imaging Techniques for Intestinal Obstruction

The small intestine is the only real part of the gastrointestinal tract that is vital for life. It assists a neuroendocrine function, a digestion of food (propulsion, mixing up and absorption of food), and a secretory function. The liver, gallbladder and pancreas are accessory organs of the digestive tract that is strongly associated with the small intestine. The villous surface boosts absorption by increasing the entire surface area. In addition to absorption nutrients, it is in charge of most normal water reabsorption in the GI tract (Edward, 1998).

The small intestine is made up of three segments, which form a passage from tummy (the opening between abdomen and small intestine is called the pylorus) to large intestine. It is duodenum, jejunum and ileum. The duodenum is this short section is the area of the small intestine that takes in semi digested from tummy through the pylorus and carries on the digestion process. The duodenum also uses bile from the gallbladder, liver organ and pancreas to help break down food. The jejunum is the center section of the small intestine holds food through rapidly, with wave-like muscle contractions, on the ileum. The very last segment is ileum. The ileum is the longest part of small intestine. It is where the majority of the nutrition from food are absorbed before emptying in to the large intestine (UPMC, 2010).

By enough time food extends to small intestine, it has already been split up and mashed into liquid by tummy. Every day, small intestine receives between one and three gallons (or six to twelve liters) of this liquid. The tiny intestine bears out most of the intestinal process, absorbing the vast majority of the nutrition get from foods into bloodstream. The surfaces of the tiny intestine make intestinal juices or enzymes that interact with enzymes from the liver and pancreas to do this. Although the tiny intestine is narrower than the top intestine, it is actually the longest portion of the digestive pipe, measuring about 22 foot (or several meters) typically, or three-and-a-half times the length of body (UPMC, 2010).

1. 2 Large Intestine

The large intestine is greater in diameter than the tiny intestine. It begins at the ileocecal junction, where in fact the ileum enters the large intestine and ends at the anus. The top intestine consists of the colon, rectum and anal passage. Its main function is to secrete mucin and form feces for excretion. It reabsorbs water and electrolytes but to a much less extent than the small intestine. It generally does not have sodium cotransport system (Edward, 1998). Unlike small intestine, the top intestine produces no digestive enzymes.

The wall membrane of the large intestine gets the same types of cells that are located in other parts of the digestive tract but there are some distinguishing characteristics. The mucosa has a huge quantity of goblet cells but does not have any villi. The longitudinal muscle coating, although present, is imperfect. The longitudinal muscle is bound to three region rings, called teniae coli that run the entire length of the intestines (National Cancer tumor Institute, 2012).

The rectum carries on from the sigmoid intestines to the anal canal and has a solid muscular layer. It uses the curvature of the sacrum and it is firmly mounted on it by connective muscle. The rectum and ends about 5 cm below the tip of the coccyx at the start of the anal passage. The last 2-3 3 cm of the digestive system is the anal canal, which carries on from the rectum and starts to the outside at the anus. The mucosa of the rectum is folded to create longitudinal anal columns. The even muscle level is solid and forms the internal anal sphincter at the superior end of the anal passage (National Tumors Institute, 2012).

1. 3 Intestinal Obstruction

Intestinal obstruction, also called ileus (from the Greek eilo, indicating to roll-up) (Ivan, 1996). Intestinal obstruction is identifies a lack of movements of the intestinal items through the intestine. Because of its smaller lumen, obstructions are more prevalent and occur quicker in small intestine, nonetheless they may appear in large intestine as well. With regards to the cause and location, blockage may express as an serious problem or a little by little developing situation. For instance, twisting of the intestine might lead to sudden total blockage, whereas a tumor leads to progressive blockage (Barbara, 2002).

Obstruction of the intestine causes the bowel to be susceptible to ischemia. The intestinal mucosal hurdle can be broken, allowing intestinal bacterias to invade the intestinal wall and causing liquid exudation, which leads to hypovolemic and dehydration. About 7L of substance each day is secreted into the small intestine and abdomen and usually reabsorbed. During obstruction, fluid accumulates, causing stomach distention and pressure on the mucosal wall structure, which can result in peritonitis and perforation (Unbound Treatments, 2011).

Intestinal obstruction is most common on seniors individuals, because of the higher occurrence of neoplasm and other causative diseases in this people. In neonates, intestinal obstruction may be triggered by imperforate anus or other anatomic abnormalities. Obstruction can also be extra to meconium ileus. In paediatric population, Hirschsprung disease can resemble intestinal obstruction (Christy, 2011).

Intestinal obstruction occurs in two varieties. Mechanised obstructions are those caused by tumor, adhesions, hernias or other tangible obstructions. Functional, or adynamic, obstructions result from neurologic impairment, such as spinal-cord injury or lack of propulsion in the intestine and tend to be referred to as paralytic ileus. Adynamic or paralytic ileus usually related to irritation or the disruption of innervation (Barbara, 2002).

2 FACTORS BEHIND DISEASE

Intestinal obstruction can be brought on by many different things. It occurs in two basic types which is mechanical obstruction and paralytic ileus. Functional blockage or paralytic ileus is one of the significant reasons of the intestinal blockage in newborns and children. It is common in the following situations:

  • after abs surgery, in which the ramifications of the anesthetic combined with inflammation or ischemia in the operative area hinder conduction of nerve impulses
  • in the initial stage of spinal-cord injuries (vertebral shock)
  • with inflammation related to severe ischemia
  • in pancreatitis, peritonitis, or infection in the abs cavity
  • with hypokalemia, mesenteric thrombosis or toxaemia
  • kidney or lung disease

Mechanical blockage may result from the following:

  • Scar muscle in the belly, often called adhesions. This tissues can wrap around a bit of bowel. The items of the colon are averted from moving normally through the intestine
  • Bowel that twits on itself or develops a terrible kink. This is called volvulus
  • Fecal impaction or hard stool that cannot pass through the bowel
  • Cancer such as cancer of the colon or cancer of the pancreas
  • Hernias is protrusion of the stomach contents through the stomach wall

(Barbara, 2002)

3 PATHOPHYSIOLOGY

When mechanical obstruction of the movement of intestinal articles occurs, a collection of events advances the following. First, intestinal blockage occurs when gases and essential fluids accumulate in the region proximal to the blockage, distending the intestine. Gases come up generally from swallowed air but also from bacterial activity in the intestine. Second, progressively more strong contractions of the proximal intestine take place in order to move the articles onward. The increasing pressure in the lumen contributes to more secretions entering the intestine and also compresses the veins in the wall membrane, preventing absorption, as the intestinal wall structure becomes edematous. The intestinal distention contributes to continual vomiting with additional loss of substance and electrolytes. With small intestinal obstruction, there is absolutely no opportunity to reabsorb smooth and electrolytes, and hypovolemia quickly results (Barbara, 2002).

If the blockage is not removed, the intestinal wall structure becomes ischemic and necrotic as the arterial blood circulation to the tissues is reduced by the pressure. If twisting of the intestine (e. g. : volvulus) has took place or if immediate compression of arteries (e. g. : intussusception or strangulated hernia) results from the primary cause of blockage, the intestinal wall structure becomes quickly necrotic and gangrenous. Ischemia and necrosis of the intestinal wall eventually lead to decreased innervation and cessation of peristalsis. A reduction in bowel sounds implies this change.

Usually, the obstruction promotes rapid duplication of intestinal bacterias, a few of which produce endotoxins. As the influenced intestinal wall structure becomes necrotic and much more permeable, intestinal bacterias or poisons can drip into peritoneal cavity (peritonitis) or into the blood circulation (bacteremia and septicemia). With time, perforation of the necrotic section may occur, resulting in generalized peritonitis (Barbara, 2002).

For functional blockage or paralytic ileus usually results from neurologic impairment. Peristalsis ceases and distention of the intestine occurs as fluids and electrolytes gather in the intestine. In this kind of obstruction, reflex spasms of the intestinal muscle do not happen, however the remainder of the process is similar to that of mechanised obstruction (Barbara, 2002).

4 Indication AND SYMPTOMS

With mechanical obstruction of the tiny intestine, severe colicky stomach pain evolves as peristalsis increase in the beginning, nausea and constipation characterizing small bowel obstruction. It may also cause drowsiness powerful thirst, malaise and aching may dry up dental mucous membranes and the tongue. Borborygmi are audible rumbling noises caused by motion of gas in the intestine and intestinal rushes can be noticed as the intestinal muscle forcefully contracts in an attempt to propel the material forward. These are noisy enough to be observed without stethoscope. Palpation elicits stomach tenderness with moderate distention; rebound tenderness occurs when obstruction has induced strangulation with ischemia.

The indications of paralytic ileus differ significantly in that bowel sounds decrease or are absent and pain is dependable. Vomiting and belly distension occur quickly with obstruction of the small intestine. Vomiting is recurrent and comprises first gastric contents and then bile-stained duodenal articles. No stool or gas is handed. Restlessness and diaphoresis with tachycardia is present original. As hypovolemia and electrolyte imbalance progress, signs or symptoms of dehydration, weakness, dilemma and shock are obvious (Barbara, 2002).

Signs and symptoms of large colon obstruction develop more slowly and gradually because the intestines can absorb smooth from its articles and distend well beyond its normal size. Constipation may be only scientific effect for days. Colicky stomach pain will then appear instantly, producing spasms that lastly less than 1 minute each and recur every few minutes. Constant hypogastric pain and nausea may develop, but vomiting is usually absent at first. Large bowel blockage can cause remarkable abs distention; loops of the top bowel may become visible on the abdominal. Eventually, complete large bowel obstruction may cause fecal vomiting, ongoing pain or localized peritonitis. Patients with incomplete obstruction may screen the above signs and symptoms in a milder form. However, leakage of liquid stool around the obstruction is common in partial obstruction (Lippincott Williams & Wilkins, 2007).

5 IMAGING MODALITIES

5. 1 Lab Test

Laboratory analysis of patients with suspected obstruction should include an entire blood matter and metabolic -panel. Hypokalemic, hypochlomeric metabolic alkalosis may be known in patients with severe emesis. Enhanced blood vessels urea nitrogen levels are steady with dehydration, and haemoglobin and hemotocrit levels may be increased. The white blood vessels cell count number may be raised if intestinal bacteria translocate in to the bloodstream. It could cause the systemic inflammatory response symptoms or sepsis. The introduction of metabolic acidosis especially in a patient with a growing serum lactate level, may indicate colon ischemia (Patrick G. Jackson & Manish Raiji, 2011).

5. 2 Ordinary Radiography

The initial imaging study of preference for confirming colon obstruction with clinical signs and symptoms of intestinal blockage should include pain upright abdominal radiography. This radiography can easily determine whether intestinal perforation has happened. The free air is seen above the liver organ in upright movies or kept lateral decubitus motion pictures. Radiography is 60-70% level of sensitivity for diagnosis of small colon blockage and it performs better in high-grade blockage. Radiography can be find the diagnosis of small bowel blockage include distended loops of small colon, collapsed colon, the "string of pearls signal resulting from small amount of residual air weighed against the large amount of retained liquid and pseudotumour related to distended fluid crammed loops.

In large bowel obstruction, it's important to note the degree of caecal distension on the simple abdominal motion pictures, since marked distension will point to the necessity for urgent decompression to prevent caecal perforation. In patients with small colon blockage, supine views show dilation of multiple loops of small bowel with a paucity of air in the large bowel (Figure 4). Those with large bowel obstruction may have dilation of the intestines with decompressed small bowel in the setting up of the skilled ileocecal valve. Up-right or lateral decubitus videos may show laddering air substance level (Physique 5). These studies show together with too little air and feces in the distal colon and rectum are highly suggestive of mechanical intestinal blockage (Patrick G. Jackson & Manish Raiji, 2011).

Limitations:

  • Fails to identify the reason for obstruction generally in most cases
  • In blockage of ileocaecal region, it might be difficult to determine if the level in the proximal large colon or distal ileum
  • Cannot reliably detect the existence of ischaemic complication

5. 3 Computed Tomography

5. 3. 1 Small bowel obstruction

Generally, it is definitely the imaging modality of preference when plain belly radiography and the clinical features suggest an serious small bowel obstruction. CT is delicate for detection of high-grade blockage (90-96%). Although CT is highly very sensitive and specific for high-grade obstruction, its value diminishes in patients with incomplete blockage. In these patients, dental contrast materials may be seen traversing the space of the intestine to the rectum without discrete area of move. It useful in:

  • Confirming or excluding small colon blockage (versus pseudo-obstruction)
  • Defining the amount and site of obstruction
  • Identifying the reason for small bowel blockage (73-95% awareness)
  • Confirming or excluding the examination of ischaemia (>90% awareness and specificity)

The advantages are:

  • Superior to enteroclysis in exhibiting extraluminal masses, uncovering abscesses, malignancy, anterior adhesions as well as features of strangulation.
  • It is ability to depict other causes of an acute abdomen

The limitations:

  • Lower level of sensitivity (about 50%) for the diagnosis and location of low-grade small bowel obstruction

(Diagnostic Imaging Pathways, 2009)

5. 3. 2 Large Colon Obstruction

It indicated instead of contrast enema in evaluation of large colon obstruction, specifically with older and immobile patients. CT conclusions in patients with intestinal obstruction include dilated loops of colon proximal to the website of blockage with distally decompressed bowel. The presence of discrete change point helps guide operative planning (Shape 6). Absence of contrast material in the rectum is also an important signal of complete blockage. Because of this, rectal administration of contrast material should be prevented (Patrick G. Jackson & Manish Raiji, 2011). The advantages are:

Does not require insertion of rectal pipe and contrast which is therefore better tolerated when compared to a contrast enema

In one study, successfully diagnosed colonic blockage in 96% of patients and pseudo-obstruction in 93% of patients

The limitations for this are bogus negative and fake excellent results and limited diagnostic with partly obstructing lesions (Diagnostic Imaging Pathways, 2009).

Figure 6: Axial computed tomography check showing dilated, contrast- stuffed loops of colon on the patients left (yellow arrows), with decompressed distal small bowel on the patients right (red arrows). The reason for obstruction, an increased umbilical hernia, can also be seen (inexperienced arrows), with proximally dilated bowel entering the hernia and decompressed bowel exiting the hernia (Patrick G. Jackson & Manish Raiji, 2011).

5. 4 Comparison Fluoroscopy

Contrast studies, such as small bowel follow-through, can be helpful in the prognosis of a incomplete intestinal blockage in patients with high professional medical suspicion and in clinically secure patients in whom primary conservative management had not been effective. The use of water-soluble contrast material is not only diagnostic, but may be can use for therapeutic in patients with partial small-bowel obstruction. Distinction fluoroscopy may also be useful in determining the region of intestine that require for surgery (Patrick G. Jackson & Manish Raiji, 2011).

There are several versions of distinction fluoroscopy. In the tiny bowel follow-through review, the patient beverages contrast materials, then serial abdominal radiographs are taken to visualize the passage of compare through the digestive tract. The benefit of small bowel follow-through is will not require nasointestinal intubation, and in comparison to enteroclysis, it is better to perform and does not require additional knowledge. The limitations because of this technique are they devote some time for contrast to attain the blockage and barium is diluted because of unnecessary residual intraluminal substance resulting in non-uniform small colon filling (Diagnostic Imaging Pathways, 2009).

Enteroclysis entails naso- or aro-duodenal intubation, followed by the instillation of comparison material straight into the small bowel. Although this study has superior level of sensitivity weighed against small bowel follow through, it is more labor-intensive and is also rarely performed. The advantage enteroclysis are it has ability to gauge the severity of obstruction objectively. The constraints are it dependence on nasoenteric intubation and demonstration of extrinsic causes is sometimes difficult. Rectal fluoroscopy can be helpful in determining the website of a suspected large bowel obstruction (Patrick G. Jackson & Manish Raiji, 2011)

5. 5 Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging (MRI) may be more delicate than CT in the analysis of intestinal blockage. MRI enteroclysis, which involves intubation of the duodenum and infusion of contrast material straight into small bowel. It can more reliably determine the location and cause of blockage. However, MRI is not universally available and incredibly expensive (Patrick G. Jackson & Manish Raiji, 2011).

5. 6 Ultrasonography

In patients with high-grade blockage, ultrasound analysis of the tummy has high level of sensitivity for intestinal obstruction, approaching 85 percent. However, because of the wide availability of CT, it includes largely changed ultrasonography as the first-line inspection in steady patients with suspected intestinal blockage. Ultrasonography remains a valuable investigation for unstable patients with an ambiguous examination and in patients that contraindication with rays visibility, such as women that are pregnant (Patrick G. Jackson & Manish Raiji, 2011).

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