Imaging Techniques for Intestinal Obstruction

imaging Techniques for Intestinal stoppageThe weakened gut is the only deduct of the gastro enteric tract that is essential for life. It serves a neuroendocrine function, a digestive function (propulsion, mixing and absorption of food), and a secretory function. The liver, g onlybladder and pancreas atomic number 18 accessory organs of the digestive system that is virtually associated with the lesser intestine. The villous railway linefoil improves absorption by increasing the overall surface field of force. In addition to absorption nutrients, it is responsible for almost water resorption in the GI tract (Edward, 1998).The teeny intestine is made up of three segments, which form a passage from fuckister (the opening amongst stomach and short intestine is called the pylorus) to outsize intestine. It is duodenum, jejunum and ileum. The duodenum is this short section is the part of the humiliated intestine that takes in semi digested from stomach through the pylorus and continues the digestion process. The duodenum in addition uses bile from the gallbladder, liver and pancreas to help digest food. The jejunum is the middle section of the atrophied intestine carries food through speedyly, with wave-like muscle contractions, towards the ileum. The exit segment is ileum. The ileum is the long part of clear intestine. It is where most of the nutrients from food atomic number 18 absorbed in the lead emptying into the boastful intestine (UPMC, 2010).By the time food reaches piddling intestine, it has already been broken up and mashed into liquid by stomach. Each day, down in the mouth intestine receives between one and three gallons (or six to twelve liters) of this liquid. The downhearted intestine carries out most of the digestive process, absorbing almost all of the nutrients get from foods into subscriber linestream. The walls of the small intestine make digestive juices or enzymes that employ together with enzymes from the liver and pancreas to do this. Although the small intestine is narrower than the large intestine, it is in truth the longest section of the digestive tube, measuring about 22 feet (or seven-spot meters) on average, or three-and-a-half times the continuance of body (UPMC, 2010).1.2 Large intestineThe large intestine is larger in diameter than the small intestine. It begins at the ileocecal junction, where the ileum enters the large intestine and ends at the anus. The large intestine consists of the colon, rectum and anal retentive commodeal. Its first function is to secrete mucin and form stool for excretion. It reabsorbs water and electrolytes but to a much lesser extent than the small intestine. It does non have sodium cotransport system (Edward, 1998). Unlike small intestine, the large intestine produces no digestive enzymes.The wall of the large intestine has the same fictional characters of tissue that be put up in other parts of the digestive tract but on that compass point are some distinguishing characteristics. The mucosa has a large number of chalice cells but does non have any villi. The longitudinal muscle layer, although drive home, is incomplete. The longitudinal muscle is limited to three district bands, called teniae coli that run the entire length of the colon (National genus Cancer Institute, 2012).The rectum continues from the sigmoid colon to the anal pottyal and has a thick muscular layer. It follows the curvature of the sacrum and is firmly attached to it by link tissue. The rectum and ends about 5 cm below the tip of the coccyx at the beginning of the anal canal. The last 2 to 3 cm of the digestive tract is the anal canal, which continues from the rectum and opens to the outside at the anus. The mucosa of the rectum is folded to form longitudinal anal columns. The smooth muscle layer is thick and forms the internal anal sphincter at the spiffing end of the anal canal (National Cancer Institute, 2012).1.3 Intestinal ObstructionInt estinal bar, also called ileus (from the Greek eilo, means to roll up) (Ivan, 1996). Intestinal stop is refers to a lack of discoverment of the enteric table of contents through the intestine. Be possess of its smaller lumen, impediments are more common and lapse more rapidly in small intestine, but they can pass along in large intestine as soundly. Depending on the cause and location, barricade whitethorn manifest as an acute problem or a gradually developing situation. For example, twisting of the intestine could cause sudden arrive restriction, whereas a tumor leads to progressive prohibition (Barbara, 2002).Obstruction of the intestine causes the gut to let vulnerable to ischaemia. The enteric mucosal barrier can be damaged, allowing intestinal bacteria to invade the intestinal wall and causing politic exudation, which leads to hypovolemic and dehydration. About 7L of gas per day is secreted into the small intestine and stomach and commonly reabsorbed. During c losure, fluid accumulates, causing group AB distention and pressure on the mucosal wall, which can lead to peritonitis and perforation (Unbound Medicine, 2011).Intestinal obstruction is most common on elderly individuals, due to the higher incidence of tumour and other causative indispositions in this population. In neonates, intestinal obstruction whitethorn be caused by imperforate anus or other anatomic abnormalities. Obstruction may also be secondary to meconium ileus. In paediatric population, Hirschsprung disease can resemble intestinal obstruction (Christy, 2011).Intestinal obstruction occurs in two forms. Mechanical obstructions are those resulting from tumor, adhesions, herniations or other tangible obstructions. structural, or adynamic, obstructions result from neurologic impairment, such as spinal cord accidental injury or lack of propulsion in the intestine and are frequently referred to as paralytic ileus. Adynamic or paralytic ileus usually related to inflam mation or the disruption of pique (Barbara, 2002).2 CAUSES OF unhealthinessIntestinal obstruction can be caused by many varied things. It occurs in two basic types which is automatic obstruction and paralytic ileus. Functional obstruction or paralytic ileus is one of the major causes of the intestinal obstruction in infants and children. It is common in the following situationsafter ab surgery, in which the tack togethers of the anesthetic combined with inflammation or ischemia in the operative area interfere with conduction of nerve impulsesin the initial stage of spinal cord injuries (spinal shock)with inflammation related to desolate ischemiain pancreatitis, peritonitis, or infection in the abdominal muscle fossawith hypokalemia, mesenteric thrombosis or toxaemiakidney or lung diseaseMechanical obstruction may result from the followingScar tissue in the belly, a great deal called adhesions. This tissue can wrap around a piece of catgut. The contents of the intestine are prevented from moving normally through the intestine gut that twits on itself or develops a bad kink. This is called volvulusFecal impaction or hard stool that cannot pass through the intestineCancer such as colon cancer or cancer of the pancreasHernias is protrusion of the abdominal contents through the abdominal wall(Barbara, 2002)3 PATHOPHYSIOLOGYWhen mechanical obstruction of the flow of intestinal contents occurs, a sequence of events develops as follows. First, intestinal obstruction occurs when gases and fluids accumulate in the area proximal to the blockage, distending the intestine. Gases arise mainly from swallowed air but also from bacterial activity in the intestine. Second, progressively strong contractions of the proximal intestine occur in an effort to move the contents onward. The increasing pressure in the lumen leads to more secretions move into the intestine and also compresses the veins in the wall, preventing absorption, as the intestinal wall becomes edema tous. The intestinal distention leads to persistent vomiting with additional loss of fluid and electrolytes. With small intestinal obstruction, there is no opportunity to reabsorb fluid and electrolytes, and hypovolaemia quickly results (Barbara, 2002).If the obstruction is not removed, the intestinal wall becomes ischemic and necrotic as the arterial blood supply to the tissue is reduced by the pressure. If twisting of the intestine (e.g. volvulus) has occurred or if immediate compression of arteries (e.g. intussusception or strangulated hernia) results from the primary cause of obstruction, the intestinal wall becomes rapidly necrotic and gangrenous. ischaemia and necrosis of the intestinal wall eventually lead to decreased innervation and cessation of peristalsis. A decrease in intestine sounds indicates this change.Usually, the obstruction promotes rapid reproduction of intestinal bacteria, some of which produce endotoxins. As the affected intestinal wall becomes necrotic and m ore permeable, intestinal bacteria or toxins can leak into peritoneal cavity (peritonitis) or into the blood supply (bacteremia and septicemia). In time, perforation of the necrotic segment may occur, leading to generalized peritonitis (Barbara, 2002).For usable obstruction or paralytic ileus usually results from neurologic impairment. peristalsis ceases and distention of the intestine occurs as fluids and electrolytes accumulate in the intestine. In this type of obstruction, reflex spasms of the intestinal muscle do not occur, but the residual of the process is similar to that of mechanical obstruction (Barbara, 2002).4SIGN AND SYMPTOMSWith mechanical obstruction of the small intestine, severe colicky abdominal chafe develops as peristalsis increase initially, nausea and constipation characterizing small bowel obstruction. It may also cause drowsiness intense thirst, malaise and aching may dry up oral mucous membranes and the tongue. Borborygmi are audible sound sounds caused b y movement of gas in the intestine and intestinal rushes can be heard as the intestinal muscle forcefully contracts in an attempt to propel the contents forward. These are loud enough to be heard without stethoscope. Palpation elicits abdominal tenderness with moderate distention bounce tenderness occurs when obstruction has caused strangulation with ischemia.The signs of paralytic ileus differ importantly in that bowel sounds decrease or are absent and pain is steady. Vomiting and abdominal distension occur quickly with obstruction of the small intestine. Vomiting is recurrent and consists first gastric contents and then bile-stained duodenal contents. No stool or gas is passed. Restlessness and diaphoresis with tachycardia is present initial. As hypovolemia and electrolyte imbalance progress, signs of dehydration, weakness, confusion and shock are seeming(a) (Barbara, 2002).Signs and symptoms of large bowel obstruction develop more slowly because the colon can absorb fluid from its contents and distend well beyond its normal size. Constipation may be only clinical effect for days. Colicky abdominal pain may then appear suddenly, producing spasms that last less than 1 minute each and recur every a couple of(prenominal) minutes. Continuous hypogastric pain and nausea may develop, but vomiting is usually absent at first. Large bowel obstruction can cause dramatic abdominal distention loops of the large bowel may become visible on the abdomen. Eventually, complete large bowel obstruction may cause fecal vomiting, continuous pain or localized peritonitis. Patients with uncomplete obstruction may display any of 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).5IMAGING MODALITIES5.1 laboratory TestLaboratory evaluation of patients with surmise obstruction should hold a complete blood numeration and metabolic panel. Hypokalemic, hypoc hlomeric metabolic alkalosis may be noted in patients with severe emesis. Elevated blood urea nitrogen levels are undifferentiated with dehydration, and haemoglobin and hemotocrit levels may be increase. The white blood cell count may be elevated if intestinal bacteria translocate into the bloodstream. It can cause the systemic inflammatory response syndrome or sepsis. The development of metabolic acidosis especially in a patient with an increasing serum harbour level, may signal bowel ischemia (Patrick G. capital of Mississippi Manish Raiji, 2011).5.2 Plain skiagraphyThe initial imaging study of choice for confirming bowel obstruction with clinical signs and symptoms of intestinal obstruction should include pain upright abdominal radiography. This radiography can quickly determine if intestinal perforation has occurred. The free air can be seen above the liver in upright films or left askance decubitus films. Radiography is 60-70% sensitivity for attainion of small bowel obst ruction and it performs infract in top-quality obstruction. Radiography can be find the diagnosis of small bowel obstruction include distended loops of small bowel, collapsed colon, the string of pearls sign resulting from small amount of residual air compared with the large amount of retained fluid and pseudotumour related to distended fluid alter loops.In large bowel obstruction, it is important to note the degree of caecal distension on the plain abdominal films, since marked distension will point to the need for urgent decompression to prevent caecal perforation. In patients with small bowel obstruction, 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 colon with decompressed small bowel in the setting of the competent ileocecal valve. Upright or lateral decubitus films may show laddering air fluid level (Figure 5). These findings show in conjunction wi th a lack of air and stool in the distal colon and rectum are highly suggestive of mechanical intestinal obstruction (Patrick G. Jackson Manish Raiji, 2011).LimitationsFails to diagnose the cause of obstruction in most casesIn obstruction of ileocaecal region, it may be difficult to determine whether the level in the proximal large bowel or distal ileumCannot faithfully detect the presence of ischaemic complication5.3 Computed Tomography5.3.1 Small bowel obstructionGenerally, it is considered the imaging modality of choice when plain abdominal radiography and the clinical features suggest an acute small bowel obstruction. CT is reactive for catching of high-grade obstruction (90-96%). Although CT is highly sensitive and specific for high-grade obstruction, its value diminishes in patients with partial obstruction. In these patients, oral personal line of credit fabric may be seen traversing the length of the intestine to the rectum with no clear-cut area of transition. It se rviceable inConfirming or excluding small bowel obstruction (versus pseudo-obstruction)Defining the degree and site of obstructionIdentifying the cause of small bowel obstruction (73-95% sensitivity)Confirming or excluding the diagnosis of ischaemia (90% sensitivity and specificity)The wagess areSuperior to enteroclysis in showing extraluminal masses, revealing abscesses, malignancy, anterior adhesions as well as features of strangulation.It is ability to depict other causes of an acute abdomenThe limitations humble sensitivity (approximately 50%) for the detection and location of low-grade small bowel obstruction(Diagnostic imagery Pathways, 2009)5.3.2 Large Bowel ObstructionIt indicated as an alternate to air enema in evaluation of large bowel obstruction, especially with elderly and immobile patients. CT findings in patients with intestinal obstruction include dilated loops of bowel proximal to the site of obstruction with distally decompressed bowel. The presence of discrete transition point helps guide operative planning (Figure 6). Absence of contrast material in the rectum is also an important sign of complete obstruction. For this reason, rectal administration of contrast material should be avoided (Patrick G. Jackson Manish Raiji, 2011). The advantages areDoes not require insertion of rectal tube and contrast and is therefore better tolerated than a contrast enemaIn one study, successfully diagnosed colonic obstruction in 96% of patients and pseudo-obstruction in 93% of patientsThe limitations for this are ridiculous negative and false positive results and limited diagnostic with partly obstructing lesions (Diagnostic Imaging Pathways, 2009).Figure 6 Axial computed tomography scan showing dilated, contrast- filled loops of bowel on the patients left (yellow arrows), with decompressed distal small bowel on the patients right (red arrows). The cause of obstruction, an increased umbilical hernia, can also be seen (green arrows), with proximally di lated bowel entering the hernia and decompressed bowel exiting the hernia (Patrick G. Jackson Manish Raiji, 2011).5.4 Contrast FluoroscopyContrast studies, such as small bowel follow-through, can be helpful in the diagnosis of a partial intestinal obstruction in patients with high clinical suspicion and in clinically stable patients in whom initial worldly-minded management was not effective. The use of water-soluble contrast material is not only diagnostic, but may be can use for remedy in patients with partial small-bowel obstruction. Contrast fluoroscopy may also be useful in determining the area of intestine that need for surgery (Patrick G. Jackson Manish Raiji, 2011).There are several variations of contrast fluoroscopy. In the small bowel follow-through study, the patient drinks contrast material, then serial abdominal radiographs are taken to visualize the passage of contrast through the intestinal tract. The advantage of small bowel follow-through is does not require nas ointestinal intubation, and compared to enteroclysis, it is easier to perform and does not require additional expertise. The limitations for this procedure are they take time for contrast to reach the obstruction and barium is diluted because of excess residual intraluminal fluid resulting in non-uniform small bowel filling (Diagnostic Imaging Pathways, 2009).Enteroclysis involves naso- or aro-duodenal intubation, followed by the instillation of contrast material directly into the small bowel. Although this study has superior sensitivity compared with small bowel follow through, it is more labor-intensive and is rarely performed. The advantage enteroclysis are it has ability to gauge the severity of obstruction objectively. The limitations are it need for nasoenteric intubation and demonstration of extrinsic causes is sometimes difficult. Rectal fluoroscopy can be helpful in determining the site of a suspected large bowel obstruction (Patrick G. Jackson Manish Raiji, 2011)5.5 Magn etic Resonance Imaging (MRI)Magnetic resonance imaging (MRI) may be more sensitive than CT in the evaluation of intestinal obstruction. MRI enteroclysis, which involves intubation of the duodenum and excerpt of contrast material directly into small bowel. It can more reliably determine the location and cause of obstruction. However, MRI is not universally on hand(predicate) and very expensive (Patrick G. Jackson Manish Raiji, 2011).5.6 UltrasonographyIn patients with high-grade obstruction, ultrasound evaluation of the abdomen has high sensitivity for intestinal obstruction, approaching 85 percent. However, because of the wide availability of CT, it has largely replaced ultrasonography as the first-line investigation in stable patients with suspected intestinal obstruction. Ultrasonography remains a precious investigation for unstable patients with an ambiguous diagnosis and in patients that contraindication with radiation exposure, such as pregnant women (Patrick G. Jackson M anish Raiji, 2011).