**5.8 CT angiography (CTA)**

*Digestive System - Recent Advances*

**5.3 DAE**

**5.4 CTE**

**5.5 MRE**

**5.6 Bleeding scan**

in 52% of cases [35].

**5.7 Meckel's scan**

and spiral enteroscopy.

intubation of the small bowel. The actual depth of insertion of small bowel by push enteroscopy is difficult to measure but varies (120–180 cm beyond the ligament of Treitz) among endoscopists and patients [25]. Push enteroscopy has both diagnostic and therapeutic potential including biopsy, hemostasis, and tattooing [26].

DAE includes balloon-assisted enteroscopy (single balloon and double balloon)

Single-balloon enteroscopy (SBE) and double-balloon enteroscopy (DBE) were developed in 2006 and 2001, respectively, to examine the entire small bowel mucosa. Both procedures are bidirectional, i.e., the enteroscope is introduced anterogradely through the mouth and retrogradely through the anus, and the midway point is marked by tattooing or endoclipping [27]. Although the rate of complete visualization of the small bowel is three times (66 vs. 22%) higher with DBE than that with SBE [28], the diagnostic and therapeutic yields of these two procedures do not differ significantly [29]. In spiral enteroscopy (SE), the small bowel is pleated on the enteroscope by a screw operated by a machine, and the rotational force is converted into a linear force. In one study, complete enteroscopy was successful in 92% of cases of bidirectional DBE and 8% of cases of SE, although

the diagnostic and therapeutic outcomes were not statistically different [30].

and neoplastic condition of the small bowel [32].

CTE is a useful tool in the evaluation of mid-GI bleed due to vascular lesion. Characteristic enhancement of the vascular lesion can be seen [31]. They are classified as angioectasia, arterial lesions (Dieulafoy's lesion and arteriovenous malformation), and venous lesions (vascular lesion with unusual morphology). Active bleeding is evidenced by progressive accumulation of contrast material over the three phases on the dependent surface of the intestine or distributed over a wide area by peristalsis. CT enterography is also useful in the detection of inflammatory

MRE is a noninvasive radiation-free method of evaluating the entire small bowel. It can detect the mural thickening (>4 mm) and mass lesion of the small bowel. These lesions could be secondary to inflammatory and benign conditions (like Crohn's disease, adenoma, lipoma, fibroepithelial polyps) or malignant conditions (like neuroendocrine tumors, GIST, adenocarcinoma, lymphoma, and Peutz-Jeghers syndrome) [33, 34].

Bleeding scan is a nuclear medicine test performed by injecting 99 m technetium-labeled red blood cells (RBC). It can detect extravasation of tagged RBC if the bleeding rate is 0.1 ml/minute or more. It is a highly sensitive test in detecting active bleeding in the gastrointestinal tract and can localize the site of bleeding accurately

Meckel's scan is also a nuclear medicine test performed by injecting 99 m technetium pertechnetate which has affinity for the gastric mucosa. It is positive in

**26**

CTA is increasingly being done in patients with less brisk mid-GI bleeding. CTA can detect the bleeding site if the bleeding rate is 0.3 ml/minute or more [36]. However, CTA exposes the patient to ionizing radiation, and intravenous contrast is required. So patients with contrast allergy, renal failure, and pregnancy should avoid CTA.
