Serdar Balcı

Malabsorption and Diarrhea

Serdar BALCI, MD


Malabsorptive Diarrhea

Chronic malabsorption

Chronic malabsorptive disorders

Pancreatic insufficiency

Celiac disease

Crohn disease

Intestinal graft-versus-host disease

Environmental enteropathy (tropical sprue)

Localizations of Malabsorption

Robbins Basic Pathology


Cystic Fibrosis


Celiac Disease

Robbins Basic Pathology

Gliadin is deamidated by tissue transglutaminase

Interact with HLA-DQ2 or HLA-DQ8 on antigen-presenting cells

Presented to CD4+ T cells

T cells produce cytokines

Tissue damage and characteristic mucosal histopathology

Robbins Basic Pathology

Robbins Basic Pathology

Robbins Basic Pathology

Intraepithelial lymphocytes activated via IL-15 express NKG2D

NKG2D is a ligand for MIC-A receptor (HLA class I–like protein) found on enterocytes

some factors induce some enterocytes to express MIC-A

Lymphocytes become cytotoxic and kill enterocytes that express surface MIC-A

Robbins Basic Pathology

Robbins Basic Pathology

Normal duodenal bulb

**transition zone that is normally subjected to physiologic peptic injury **

Normal second duodenum and proximal jejunum

The villus-to-crypt ratio 3:1-5:1

Two intraepithelial lymphocytes per 10 enterocytes

crypt hyperplasia

villous atrophy

Robbins Basic Pathology

increased numbers of intraepithelial CD8+ T lymphocytes

intraepithelial lymphocytosis

Robbins Basic Pathology


Environmental (Tropical) Enteropathy


Lactase (Disaccharidase) Deficiency

Defect is biochemical

Biopsies are generally unremarkable

Congenital lactase deficiency

Autosomal recessive disorder

Mutation in the gene encoding lactase


Explosive diarrhea with watery stools and abdominal distention after milk ingestion

Symptoms abate when milk is removed from diet

Acquired lactase deficiency

Downregulation of lactase gene expression

Common among Native Americans, African Americans, and Chinese populations

Occurs in the gut after childhood

Onset is sometimes associated with enteric viral or bacterial infections



acanthocytic red cells (spur cells) in peripheral blood smears


Microscopic Colitis


Graft-Versus-Host Disease

Occurs after allogeneic hematopoietic stem cell transplantation

Lymphocytic infiltrate in the lamina propria is typically sparse

Epithelial apoptosis, particularly of crypt cells, is the most common histologic finding

Intestinal graft-versus-host disease often manifests as a watery diarrhea


Irritable Bowel Syndrome

Chronic and relapsing abdominal pain, bloating, and changes in bowel habits including diarrhea and constipation

Psychologic stressors, diet, and abnormal gastrointestinal motility

No gross or microscopic abnormalities are found

Diagnosis depends on clinical symptoms


Infectious Enterocolitis

Robbins Basic Pathology

Bacterial infections induce acute self-limited colitis

Prominent lamina propria and intraepithelial neutrophil infiltrates

Robbins Basic Pathology


-neutrophil infiltration of the crypts

Crypt abscesses

-crypts with accumulations of luminal neutrophils

Crypt architecture is preserved in most cases

Robbins Basic Pathology

Pseudomembranous colitis

Clostridium difficile

-Pseudomembranes composed of neutrophils, dead epithelial cells, and inflammatory debris

Robbins Basic Pathology


Typical pattern of neutrophils emanating from a crypt is reminiscent of a volcanic eruption

Robbins Basic Pathology


Decreases the expression of brush border enzymes, including lactase

Causes microvillous damage

Apoptosis of small intestinal epithelial cells


Clinically characterized by acute or chronic diarrhea and can result in malabsorption

Whipple disease

Tropheryma whippelii

organism-laden macrophages accumulate within the small intestinal lamina propria and mesenteric lymph nodes

lymphatic obstruction

Malabsorptive diarrhea

Histologic features of viral enteritis include increased numbers of intraepithelial and lamina propria lymphocytes and crypt hypertrophy

**Diffuse eosinophilic infiltrates in parasitic infection. This case was caused by Ascaris (upper inset), but a similar tissue reaction could be caused by Strongyloides **

Schistosomiasis can induce an inflammatory reaction to eggs trapped within the lamina propria

Entamoeba histolytica in a colon biopsy specimen. Note some organisms ingesting red blood cells (arrow)

Cryptosporidia organisms are seen as small blue spheres that appear to lie on top of the brush border but are actually enveloped by a thin layer of host cell cytoplasm

The morphology of mycobacterial infection can be similar to Whipple disease, particularly in the immunocompromised host

Mycobacteria are positive with stains for for acid-fast bacteria