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Types of Enema Therapies

Barium enema has been validated as an effective therapy by extensive experience over a long period. At some institutions, it remains the therapy of choice. However, there is a tendency to replace barium with other contrast agents, primarily because of the sequelae if perforation occurs during barium enema therapy (Bramson and BliCKman 1992; MeYeR 1992). The advantages and disadvantages of barium enema therapy are summarized in Table 1.2.

The use of water-soluble contrast agents in enema therapy has been supported in North America (SwischuK et al. 1994). The principal reason for use of these agents is to avoid the chemical peritonitis caused by barium if perforation occurs. There are few reports on the use of water-soluble contrast media. The reduction rate (80%) and perforation rate (3%) do not surpass those of other contrast agents (SwischuK et al. 1994).

Air enema therapy was not used for a long time in the Western Hemisphere but it has become popular in some countries, chiefly in North America (Gu et al. 1988; Shiels et al. 1991; Daneman and Navarro 2004), after successful experiences in Argentina and China (Guo et al. 1986) were reported. This method is quick and clean with a high reduction rate (73%-95%) and less radiation exposure than barium enema therapy (Fig. 1.54). The decreased radiation exposure is related to the shortened time required to achieve reduction and the milder (in terms of kilovolts and milliamperes) radiographic technique used. The average dose to reduce an intussusception by fluoroscopy is roughly estimated as 2567 mR (Henrikson et al. 2003). Air enema therapy requires precise control of the pressure and a thorough knowledge of the technique and potential complications. Immediate paracentesis using a large-caliber needle may be necessary if tension pneumoperito-neum is produced secondary to perforation during pneumatic reduction (Kirks 1994). The advantages and disadvantages of air enema therapy are summarized in Table 1.3. The most important studies of US guidance of intussusception reduction have been performed in the Eastern Hemisphere, where there is extensive experience with the technique, and in

Europe. The procedure is usually performed with saline solution (Fig. 1.55). Studies have shown a high reduction rate (76%-95%) with few complications, results similar to those of other hydrostatic methods (Wang and Liu 1988; Woo et al. 1992; Riebel et al. 1993; Rohrsohneider and Troger 1995). The principal advantage of this technique is the lack of radiation exposure. As a result, there is no limit to the procedure time, a fact that may improve the success rate. US has a high accuracy and reliability for monitoring the reduction process and for the visualization of all components of the intussusception,

Table 1.2. Advantages and disadvantages of barium enema therapy

Advantages

- Maximum experience with this method

- Good results with optimized method (55%-90% of cases)

- Good evaluation of ileoileal residual intussusceptions

- Low perforation rate (0.39%-0.7%) Disadvantages

- X-ray exposure required, thus limiting procedure time

- Perforation causes chemical peritonitis

- Visualization of only intraluminal content with easy recognition of pathologic lead points and residual intussusception when they exist. The easiest way to initiate an US-guided enema service could be to replace the contents of the barium bag with saline or warm water. To easily visualize the reduction process, the procedure should start at low pressures with the enema bag 60 cm above the table, and slowly raising the height of the bag. If the apex of the intussusception stops its retrograde course, the bag is progressively elevated. The reduction process can be easily monitored. If the apex of the intussusception has not been visualized passing through the

Table 1.3. Advantages and disadvantages of air enema therapy Advantages

- Excellent results (70%-95.6% of cases)

- Less X-ray exposure than with barium enema

- Easy, quick, clean technique Disadvantages

- X-ray exposure required, thus limiting procedure time

- Higher perforation rate (0.14%-2.8%) with risk of tension pneumoperitoneum

- Visualization of only intraluminal content

- Less control of residual ileoileal intussusceptions

Fig. 1.54a,b. Air enema therapy. a Image obtained at the beginning of an air enema study shows the meniscus sign and a mass in the middle of the upper abdomen. b Image obtained after complete reduction shows gas passing freely into the small intestine [From del Pozo (1999)]

Fig. 1.54a,b. Air enema therapy. a Image obtained at the beginning of an air enema study shows the meniscus sign and a mass in the middle of the upper abdomen. b Image obtained after complete reduction shows gas passing freely into the small intestine [From del Pozo (1999)]

Fig. 1.55a-g. Reduction of an intussusception with sonographically-guid-ed saline enema. a The fluid in the colon outlines the intussusceptum in its initial location in the transverse colon. This is the sonographic equivalent of the meniscus sign. The enema pushes the intussusceptum into the ascending colon (b), to the ileo-cecal valve (c), and finally passing through the valve (d). e,f Complete reduction is verified when multiple bowel loops, including the terminal ileum are filled with fluid. The thickened and collapsed terminal ileum must not be confused with a residual intussusception. The ileo-cecal valve (arrows) appears thickened on the longitudinal scan. g On the axial image, the collapsed ileum produces the "mercedes-benz" sign seen: ® [From Del Pozo (1999)]

b a d c f e ileocecal valve and you are not sure that the reduction has been achieved, an ultrasound examination may be repeated some hours later (del Pozo 2005). The advantages and disadvantages of US-guided saline enema therapy are summarized in Table 1.4.

There has been little experience with US-guided air enema therapy. This modality attempts to unite the advantages of air enema therapy (quick and clean method, high reduction rate) with those of US guidance (no radiation exposure). Despite air preventing or hindering passage of the ultrasound beam, adequate visualization of the ileocecal valve and thus detection of perforation with pneumoperitoneum are possible and good results have been reported (Gu et al. 2000; Yoon et al. 2001). However, small residual ileoileal intussusceptions can be obscured by the presence of a large amount of intraluminal air. Intraluminal air could also interfere with a subsequent US study if one is required.

Definite contra-indications to enema therapy are shock that is not readily corrected with intravenous hydration, and an established perforation with clinical signs of peritonitis. Criteria that are linked to a lower reduction rate and a higher perforation rate, especially if more than one is present, are as follows: (a) patient age less than 3 months or greater than 5 years; (b) long duration of symptoms, especially if greater than 48 h; (c) passage of blood via the rectum (hematochezia); (d) significant dehydration; (e) obstruction of the small intestine; and (f) visualization of the dissection sign during enema therapy (Katz et al. 1993). The dissection sign refers to contrast material within the lumen of the intus-suscipiens that "dissects" for a long distance over the surface of the intussusceptum. Two indicators of ischemia and irreducibility at US are fluid trapped within the intussusception (del Pozo et al. 1996b)

Table 1.4. Advantages and disadvantages of US-guided saline enema therapy

Advantages

- No X-ray exposure, thus procedure time not limited

- Excellent results (76%-95.5% of cases)

- Visualization of all components of the intussusception

- Easier recognition of lead points and residual intussusceptions

- Low perforation rate (0.26%) Disadvantages

- Less clean technique and absence of blood flow at Doppler imaging (Kong et al. 1997). In cases with clinical or imaging high-risk factors, a more cautious and gentle approach is advisable during enema therapy.

In conclusion, plain radiography is of limited value in the diagnosis of intussusception. US, an accurate and safe modality, may also allow one to detect lead points and identify alternative diagnoses. Nonsurgical treatment of intussusception is possible in most cases. There is a trend toward performing enema therapy with agents other than barium (e.g. air, saline solution, water-soluble agents) as other agents will not stay in the peritoneal cavity if perforation occurs. In the absence of large, randomized studies, the reported differences in reduction and perforation rates are probably due more to complications that occurred before enema therapy, the pressures exerted, and the patient selection criteria than to the type of enema used. However, liquid agents appear to cause fewer perforations. Use of US guidance eliminates the disadvantage of radiation exposure, thus allowing a greater number of attempts at hydrostatic reduction.

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