**2. Radiological examination of the small bowel**

The small bowel is the longest part of the digestive tract; however, it is the least examined using radiological techniques. Although simple in structure—it is a tube of regular caliber with fairly constant folds—examination is problematic due to its length and motility, the lower incidence of small bowel disease, frequent overlapping between loops, and the difficulty in differentiating between a healthy bowel and a diseased one.

Originally, the small bowel could only be examined using radiological techniques, some of which were barium-based. These techniques have improved over the years. Below we describe the methods used to date.

Efficacy of the Pediatric Colonoscope Used as a Push Enteroscope 229

2. *Computed tomography enterography and computed tomography enteroclysis.* These techniques are dedicated examinations of the small bowel that allow the detection of both vascular lesions and tumors. Computed tomography–based techniques optimize luminal distension by enabling larger volumes of neutral oral contrast to be administered via a peroral or nasojejunal tube, thereby providing optimal visualization of mucosal detail and vasculature. It is also possible to evaluate wall thickness. In addition, uptake of intravenous contrast enables us to characterize tissues and lesions. An additional advantage of computed tomography enterography is that it can identify small bowel strictures/obstruction prior to capsule endoscopy and provide important information on luminal and extraluminal findings that cannot be detected on capsule endoscopy. Moreover, computed tomography enables us to perform invasive diagnostic and therapeutic procedures such as fine-needle aspiration, biopsy, and percutaneous

3. *Magnetic resonance imaging*. Magnetic resonance imaging is based on the magnetic properties of the protons of water molecules and lipids, which act as small magnets that line up in the magnetic field of the device when a radiofrequency pulse is applied, thus generating 2 signals of differing intensity (T1 and T2). As the images take some time to be acquired, movement, including respiration, can produce artifacts. The lumen must be well distended, either by direct enteral infusion of contrast (magnetic resonance– enteroclysis) or ingestion of large volumes of contrast. Interest in magnetic resonance imaging for evaluation of the small bowel is growing, due to the absence of ionizing radiation, the excellent contrast resolution, direct multiplanar acquisition, and the use of non-nephrotoxic intravenous contrast. Nevertheless, magnetic resonance imaging

does not provide clear advantages in most diseases of the digestive tract.

The current indications in the small bowel are as follows:

embolization, balloon-catheter occlusion)

4. *Abdominal angiography.* The use of arteriography for the study of digestive disorders has been partly superseded by advances in other, less invasive imaging techniques, such as computed tomography angiography or magnetic resonance angiography. However, it continues to be indicated and is difficult to replace, especially for therapeutic purposes.



In the digestive tract, ultrasound provides scant and indirect information on extrinsic and wall disorders. However, it does enable us to evaluate wall morphology and thickness, caliber, compressibility, and peristalsis. The most characteristic ultrasound sign in gastrointestinal disease is the so-called pseudokidney sign or target sign, which is composed of an echogenic center (intestinal content) surrounded by a hypoechoic halo corresponding to a thickened intestinal wall. This sign is specific and can result

examinations, as well as allergy to iodine contrast and the risk of severe shock. 5. *Abdominal ultrasound.* Ultrasound represents a huge advance in the diagnosis and treatment of digestive diseases. The technique is harmless, fast, inexpensive, and examiner-dependent. It is indicated mainly for examination of solid organs involved in

digestive disorders, especially the liver, biliary tract, spleen, and pancreas.

drainage.

1. *Intestinal transit.* Today, barium-based examination of the small intestine is limited by the huge advances made in enteroscopy, especially capsule endoscopy, which has made it possible to examine sections of the digestive tract that were previously inaccessible. Nevertheless, intestinal transit can sometimes provide us with important information. It is used exclusively for diagnosis, and findings must be confirmed by histology or other techniques.

Contrast can be administered in 2 ways:


 - Using enteroclysis: Contrast is introduced via a tube in the distal duodenum to obtain faster and more uniform opacification, thus increasing the technique's sensitivity (Figure 1). The contrast may be single or double (barium and methylcellulose or air). The latter has been of little use in the small intestine due to its poor diagnostic yield.

Fig. 1. Jejunal stenosis (arrow) in a patient with Crohn disease

Currently, the indications for a contrast study of the small intestine are as follows:


1. *Intestinal transit.* Today, barium-based examination of the small intestine is limited by the huge advances made in enteroscopy, especially capsule endoscopy, which has made it possible to examine sections of the digestive tract that were previously inaccessible. Nevertheless, intestinal transit can sometimes provide us with important information. It is used exclusively for diagnosis, and findings must be confirmed by histology or other

 - Using enteroclysis: Contrast is introduced via a tube in the distal duodenum to obtain faster and more uniform opacification, thus increasing the technique's sensitivity (Figure 1). The contrast may be single or double (barium and methylcellulose or air). The latter has been of little use in the small intestine due to

techniques.

Contrast can be administered in 2 ways: - Orally, with a single contrast.

Fig. 1. Jejunal stenosis (arrow) in a patient with Crohn disease



Currently, the indications for a contrast study of the small intestine are as follows:





its poor diagnostic yield.

disease)

contrasts.



	- Uncontrollable gastrointestinal bleeding due to therapeutic failure or failure to locate the bleeding source or impossibility of applying endoscopy. Angiography enables hemostatic therapy to be administered (vasoactive substances, particle embolization, balloon-catheter occlusion)
	- Acute mesenteric ischemia. Therapy can also be administered, namely, embolectomy, fibrinolysis, and perfusion of substances to treat vascular spasm.

The contraindications for this technique are those which are typical of radiologic examinations, as well as allergy to iodine contrast and the risk of severe shock.

5. *Abdominal ultrasound.* Ultrasound represents a huge advance in the diagnosis and treatment of digestive diseases. The technique is harmless, fast, inexpensive, and examiner-dependent. It is indicated mainly for examination of solid organs involved in digestive disorders, especially the liver, biliary tract, spleen, and pancreas.

In the digestive tract, ultrasound provides scant and indirect information on extrinsic and wall disorders. However, it does enable us to evaluate wall morphology and thickness, caliber, compressibility, and peristalsis. The most characteristic ultrasound sign in gastrointestinal disease is the so-called pseudokidney sign or target sign, which is composed of an echogenic center (intestinal content) surrounded by a hypoechoic halo corresponding to a thickened intestinal wall. This sign is specific and can result

Efficacy of the Pediatric Colonoscope Used as a Push Enteroscope 231

contact with the esophagus or a bronchus, delay in evacuating the stomach, retention in an afferent loop, retention in lesions of the small intestine (stenosis, diverticula, tumors), or malfunctioning capsule (short recording time, interference by magnetic sources, or error in

Capsule endoscopy makes it possible to examine the whole small bowel, and several studies have shown its superiority over other more conventional modalities, including barium xray. However, this technique is not completely reliable, and a series of limitations have yet to be resolved, including the real significance of specific findings and false negatives attributable to the presence of food and liquid residue, the lack of distension or propulsion, and rapid passage through large segments. The main drawback of capsule endoscopy is that it exclusively diagnostic, with limited capacity for locating the lesion accurately and no

Although numerous advances have recently been made in endoscopy for diagnosis and treatment of gastrointestinal diseases, they have taken little account of the small bowel, as access by endoscopy is often difficult. The most recent discoveries—capsule endoscopy, double-balloon enteroscopy, and spiral enteroscopy—have improved our ability to examine the small bowel. Capsule endoscopy has given rise to a new challenge, namely, how to diagnose and treat the lesions found. In this section, we describe the different methods used

Fig. 3. Jejunal stenosis in a patient with Crohn disease. Geographic ulcers at the level of the

*Push Enteroscopy.* For several years, push enteroscopy has been the most widely used and effective procedure for direct examination of the intestinal mucosa. It comprises a 200-cm– long endoscope and a 2.8-mm working channel. One of its limitations is that is only allows us to visualize the proximal and medial jejunum, leaving much of the small intestine unexplored. In order to progress, smooth and intermittent aspiration maneuvers are necessary to avoid suction artifacts on the mucosa. Minimal insufflation should be applied

**4. Endoscopic methods for examination of the small intestine** 

to perform enteroscopy, from the earliest to the most recent.

the images due to disconnection of a sensor).

options for biopsy or therapeutic procedures.

stenosis

from inflammatory abnormalities (neoplastic or other). In pediatric patients, the technique reveals conditions such as concentric pyloric stenosis and intussusception, in which ultrasound findings alone are characteristic and diagnostic.
