This observational study aims to evaluate the relationship between small bowel ultrasound findings and tissue transglutaminase (tTG) antibody blood levels in assessing celiac disease activity. The traditional gold standard for diagnosing and monitoring celiac disease involves an invasive duodenal biopsy. Researchers want to determine if combining a painless, non-invasive small bowel ultrasound with tTG antibody blood tests can accurately predict disease severity and monitor a patient's response to a gluten-free diet.

The study will enroll 140 participants aged 2 years and older, including newly diagnosed patients, patients currently on a gluten-free diet, and a control group. All participants will undergo a clinical assessment, blood tests for tTG antibodies, and a high-resolution small bowel ultrasound. Newly diagnosed patients will also undergo an upper gastrointestinal endoscopy and biopsy to confirm their diagnosis. Researchers will score the ultrasound severity based on factors like bowel wall thickness and compare it to the antibody levels. A cohort of patients will be monitored over time with serial assessments at baseline, 6 months, and 12 months.

Celiac disease is an immune-mediated systemic disorder triggered by gluten ingestion in genetically susceptible individuals. While the gold standard for diagnosis is a duodenal biopsy demonstrating villous atrophy, this procedure is invasive. Tissue transglutaminase (tTG) antibody testing, particularly IgA anti-tTG, has become the preferred serological test. Small bowel ultrasonography (SBUS) has emerged as a non-invasive imaging modality capable of detecting structural changes such as increased bowel wall thickness, dilated fluid-filled bowel loops, and enlarged mesenteric lymph nodes. Studies have shown correlations between ultrasound findings and histological severity. However, limited data exists on the correlation between quantitative tTG levels and specific ultrasound patterns. This study aims to evaluate this relationship to assess celiac disease activity and evaluate the diagnostic accuracy of combined non-invasive parameters.

This is a prospective cross-sectional and longitudinal observational study conducted at AL-Rajhi University Hospital, Assiut University, Egypt. Patients will undergo comprehensive clinical assessments, including medical history, physical examination, and dietary history evaluation. Laboratory investigations will include measuring IgA tissue transglutaminase antibody (tTG-IgA) by ELISA, total serum IgA to exclude deficiency, and routine tests such as complete blood count, iron studies, and liver function tests. All participants will undergo small bowel ultrasonography after fasting for 4-6 hours. The ultrasound will systematically scan all small bowel segments, assessing parameters like bowel wall thickness, layering, lumen diameter, intraluminal fluid content, and peristaltic activity. A severity score ranging from 0 to 11 will be calculated based on these parameters. Newly diagnosed patients will additionally undergo an upper gastrointestinal endoscopy with a minimum of 4-6 duodenal biopsies, graded according to the Marsh-Oberhuber classification. The treatment monitoring cohort will undergo serial assessments at baseline, 6 months, and 12 months.

Inclusion Criteria:

• Patients aged ≥2 years with suspected celiac disease based on clinical symptoms (chronic diarrhea, abdominal distention, weight loss, failure to thrive).
• Newly diagnosed celiac disease patients with positive tTG antibodies and/or duodenal biopsy confirmation.
• Previously diagnosed celiac disease patients on gluten-free diet requiring follow-up assessment.
• Patients with first-degree relatives with celiac disease undergoing screening.
• Patients who provide informed consent (or parental consent for minors).

Exclusion Criteria:

• Previous small bowel surgery or resection.
• Inflammatory bowel disease (Crohn's disease, ulcerative colitis).
• Small bowel obstruction from other causes.
• IgA deficiency (requires alternative antibody testing).
• Patients on immunosuppressive therapy.
• Pregnancy.
• Poor quality ultrasound images due to excessive bowel gas or obesity.
• Refusal to participate in the study.

The study population consists of individuals aged 2 years and older recruited from the Department of Gastroenterology and Hepatology at AL-Rajhi University Hospital, Egypt. This includes patients with suspected or newly diagnosed celiac disease, previously diagnosed patients being monitored on a gluten-free diet, individuals undergoing screening due to a family history of celiac disease, and a control group of individuals with negative serology.