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The development of the intestinal tract begins as a tube that joins the stomach to the cloaca. The proximal portion of this tube becomes the segment that extends from the distal duodenum to the proximal ileum. The more caudal portion develops into the terminal ileum and proximal two thirds of the transverse colon. The epithelium develops from simple endodermal tubules early during embryogenesis. Between 9 and 10 weeks, the stratified epithelium converts to simple columnar epithelium. Formation of villi begins at 9 weeks. The epithelium completes its morphological differentiation in 4-5 days before birth. Primordial lymphoid structures appear in the intestine roughly halfway through gestation. Aggregates of T and B cells form early Peyer's patches by 16 weeks' gestation, with organised Peyer's patches present by 19 weeks. 1
PRACTICAL POINTS
Evaluation of a small-intestine biopsy specimen
In the histological evaluation of the duodenal biopsy specimen, a clinical pathological correlation is essential for diagnosis. Communication between the clinician and the pathologist is essential for evaluation of all duodenal biopsy specimens.
Initial evaluation should begin with a careful examination of the requisition to ascertain the relevant clinical features of the patient and to ascertain the biopsy site.
The following clinical data should be provided to the pathologist:
Age and sex of the patient
Signs and symptoms, site of the biopsy, endoscopic findings, radiological findings
Clinical diagnosis or impression
Medical and surgical history
History of taking drugs or alcohol
History of immunosuppression
Findings of previous biopsies.
Indications for a duodenal biopsy
The main indications for a duodenal biopsy are
Evaluation of patients with malabsorption
Investigation on patients with iron-deficiency anaemia
Diagnosis or monitoring of gluten-sensitive enteropathy (GSE)
Diagnosis of neoplasia
Investigation on patients with diarrhoea, particularly in patients in whom infection is suspected (AIDS)
Confirmation of ulceration induced by non-steroidal anti-inflammatory drugs (NSAIDs) or in cases of bleeding from an unknown site.
The issue of carrying out a duodenal biopsy regardless of the indications for endoscopic and macroscopic findings is somewhat controversial. On the one hand, a routine duodenal biopsy may yield an unsuspected pathology, which may have major clinical implications. In contrast, a duodenal biopsy on an apparently normal mucosa increases the risk of anaesthesia and procedural complications. Overall, the costs to benefits ratio may not...