**3. Role of small bowel endoscopy in suspected CD**

There is no single reference standard for diagnosis of CD. Constellation of clinical history, biochemical and stool biomarkers, endoscopy, cross sectional imaging and histopathology is required for diagnosis of CD [9, 10]. Upto 30% CD patients have isolated small bowel disease. Improvement in endoscopic techniques (VCE, DAE, NMSE) as well as radiographic techniques (CTE/MRE) have revolutionised the diagnosis of small bowel CD [5]. However, options for histopathological confirmation in isolated CD is still limited, which is important in resource limited countries where infections (eg. tuberculosis) still predominate and needs to be excluded prior to initiation of therapy [11].

### **4. VCE in CD**

The original VCE (PillCam, Given imaging Ltd., Yokñeam Illit, Isareal) (**Figure 1A**) was designed for visualisation of small bowel which has undergone many modifications such as higher image resolution and increasing diagnostic yield by faster adjustable frame rate and real time analysis capability [12].

#### **4.1 VCE in suspected small bowel CD**

European society of gastrointestinal endoscopy (ESGE) recommends VCE as the first line investigation in suspected small bowel CD in whom ileo-colonoscopy is negative in the absence of obstructive symptoms/known stenosis (**Figure 2**) [2]. This recommendation is based on the high sensitivity and negative predictive value (NPV)(ranging from 96–100%) of VCE in small bowel CD. However, the accuracy and diagnostic yield of VCE in suspected CD could not be determined precisely due

**Figure 2.**

*Algorithm for small bowel evaluation in a suspected or known case of Crohn's disease (CD). DAE- device assisted enteroscopy, MRE- magnetic resonance enteroclysis, CTE- computed tomography enteroclysis, VCE- video capsule endoscopy.*

to lack of gold standard for CD diagnosis and non-specific nature of findings on VCE. The lesions detected in VCE can be due to other causes such as non-steroidal anti-inflammatory drugs (NSAIDs) use, cryptogenic multifocal ulcerated stenosing enteritis, intestine tuberculosis, lymphoma, small bowel malignancy and intestinal Behcet's disease. VCE findings like small mucosal breaks or erosions are seen in upto 20% of normal individuals. Hence, the positive predictive value (PPV) of VCE is dependent on the patient population and criteria for CD diagnosis in VCE [13]. Lewis score (LS) can be helpful in this regard. LS <135 signifies clinically non-significant lesion. LS > 135 detects significant small bowel lesion with 83.2% overall accuracy. LS between 135–790 is mild and > 790 indicates moderate to severe disease [14].
