Intestinal Ultrasound Versus Double Balloon Enteroscopy (DBE) in Diagnosis of Malabsorption Syndrome

Malabsorption is impaired absorption of nutrients caused by any disruption in the process of normal absorption. Normal nutrient absorption requires 3 steps:

1. Luminal and brush border processing (e.g Celiac disease, crohn's disease, short bowel syndrome, radiation enteropathy, HIV enteropathy and drug-induced enteropathy).
2. Absorption into the intestinal mucosa.(e.g Lactose intolerance).
3. Transport into the circulation (e.g Primary intestinal lymphangiectasis, secondary obstructions from lymphoma, and infectious causes such as Whipple disease) (van der Heide, 2016).

Malabsorption may be either global or partial (isolated). Global malabsorption results from diseases with diffuse small bowel mucosal involvement or reduced absorptive surface, leading to impaired absorption of almost all nutrients (Keller and Layer, 2014).

Partial or isolated malabsorption results from diseases that interfere with the absorption of specific nutrients (van der Heide, 2016).

Malabsorption disorders are multifactorial, making diagnosis difficult. Symptoms are nonspecific and are frequently mistaken for other conditions, resulting in missed diagnoses . A comprehensive history can often be diagnostic. Several laboratory studies, imaging,and endoscopic evaluations are available to aid in diagnosing malabsorption disorders (Nikaki and Gupte ,2016).

The diagnosis of diseases involving the small bowel is challenging (black box of the gastrointestinal tract) due to the anatomy of this intestinal portion and the lack of tools for proper diagnosis (Jeon and Kim, 2013).

Despite recent advances in technology, endoscopic investigation of the small bowel remains challenging, with imaging techniques now playing an increasingly crucial role in the diagnosis and monitoring of diseases of the small bowel (Nylund et al.,2009).

Although computed tomography(CT)and fluoroscopic studies remain the gold standard investigations, both carry a significant radiation dose, so magnetic resonance imaging(MRI) and ultrasonography(US)are increasingly used as the first-line investigation, especially when imaging patients with inflammatory bowel disease where subsequent repeat imaging to monitor disease activity is useful, but the cumulative radiation dose from CT and fluoroscopic examinations is a concern (Panes et al., 2013).

Intestinal ultrasound has become an important diagnostic tool in the detection of bowel diseases. An advantage of ultrasound imaging compared with endoscopy and contrast radiography is that it permits evaluation of the transmural aspects of inflammatory or neoplastic pathology within its surrounding structures. Other advantages are that it is widely available, noninvasive, can be performed without preparation, and lacks radiation exposure (which may be particularly desirable in patients such as pregnant women) (Atkinson et al., 2017).

On the other hand, important limitations of ultrasonography are that the alimentary tract cannot be visualized over its entire length, many of the findings are nonspecific, and obtaining and interpreting the images is operator-dependent. Furthermore, ultrasound is far less useful in obese patients in whom high-frequency scanning may not be possible (Bryant et al., 2018).

There are three enteroscopy methods currently available: double balloon enteroscopy (DBE), single balloon enteroscopy and spiral enteroscopy. DBE was developed in 2001 by Hironori Yamamoto, and it began to be used in 2004. It enabled the visualization of almost all the bowel, DBE may be performed by anterograde or retrograde way, and the complete enteroscopy can be fulfilled by performing DBE by one extremity (Ferro et al., 2010).

The initial reason for the development of device assisted enteroscopy was the need for better endoscopic access to the small bowel in order to diagnose and/or treat intestinal pathology ( Ching et al.,2017).

Indications for DBE are multiple and are increasingly expanding because the procedure allows, besides the diagnosis of diseases, interventions like biopsies and other therapeutics ( Miranda 2014).

The most common indications for DBE are obscure gastrointestinal bleeding, Crohn's disease and celiac disease ( Ching et al.,2017).

The value of DBE for the surveillance and treatment of hereditary polyposis syndromes is clear ( Beggs et al.,2010).

Therapeutic options of DBE are diverse and comprehend any procedure performed during enteroscopy with diagnostic and curative purpose, including biopsy, polypectomy, argon plasma coagulation (APC), sclerotherapy with adrenaline injection and dilatation with balloon (Gurkan et al.,2013).

Other indications for DBE have since emerged. These new indications can be divided into the following categories: pediatric enteroscopy, DBE-assisted colonoscopy, (Tan et al.,2017) endoscopic access to gastrointestinal segments out of reach of conventional endoscopes and ERCP in patients with altered anatomy ( Cai et al.,2017).

Despite its long duration, DBE is a relatively safe procedure with a complication rate comparable to that of conventional endoscopic procedures ( L. Xin et al.,2011).

The most prevalent major complications are perforation, bleeding, acute pancreatitis and enteritis. Most commonly, there may be minor complications, which include abdominal discomfort and minimal trauma to the intestinal mucosa. It allows the patient to receive medical discharge in the same day ( Pata et al., 2010).