Small bowel pathology

Question 1

Answer 1

Normal SB; long villi, see lots of lymphoid follicles in the terminal ileum

Question 2

Answer 2

Normal small intestines; notes long villi (5x as long as crypts), and absorptive cells with well defined brush border

Question 3

Answer 3

Malrotation of small intestine; an embryological anomaly that can result in catastrophic ischemia in infants

Question 4

Answer 4

small bowel atresia, an uncommon embryological abnormality that presents as a surgical emergency shortly after birth; failure of bowel lumen formation

Question 5

Answer 5

Hernias; incarcerated (left) and strangulated (right)

Question 6

Answer 6

Intussusception, a rare cause of SB obstruction in which a peristaltic segment of bowel telescopes adjacent segment; idiopathic in kids, in adults due to meckel’s diverticulum, polyps, or tumors.

Question 7

Answer 7

Meckel’s diverticulum; remnant of omphalomesenteric duct that occurs terminal ileum, usually 2 cm’s in length, in 2% of population, within 2 feet of ileocecal valve

Question 8

Answer 8

Left: omphalocele–incomplete closure of abdominal musculature

Right: gastroschisis–defect in all layers of the abdominal wall

Question 9

Answer 9

Peptic Ulcer Dz of the duodenum; usually related to H. Pylori infection w/ NSAID use; see loss of duodenal villi and formation of erosins or deep ulcers

Question 10

Answer 10

Celiac sprue (dz); presents in childhood due to a gliadin sensitivity (in wheat, rye, oats and barley), pts develop immune rxn that damages the surface enterocytes of SB; often have circulating auto-ab’s that are useful for screening for celiac dz.

See villous blunting, increased lymphs/plasma cells within LP and epithelium, elongation of rete

Question 11

Answer 11

Cryptosporidium parvum, can cause mild diarrhea in healthy pts or more severe dz in IC pt’s, organism attaches directly to surface of SB enterocytes, becoming enveloped by microvilli of brush border.

Question 12

Answer 12

Micobacterium Avium Intracellulare infection; seen almost exclusively in IC pt’s, bacterium accumulates within macrophages, which expand in the LP causing villous blunting leading to diarrhea and malabsorption. Can detect with AFB stain.

Question 13

Answer 13

CMV infection of small bowel; very common in IC hosts (espec. transplant pts), pt experiences fever, fatigue, dysphagia, gastritis, and/or diarrhea

Question 14

Answer 14

Caused by Tropheryma whippeli, a GP actinomycete that accumulates within macrophages in bowel leading to LP enlargement, villous blunting, and malabsorption. Also also affects lymph node, synovium, and CNS.

Usually presents in middle-aged/older Caucasian males with slow onset of polyarthritis, mental status changes, diarrhea, malabsorption, lympadenopathy, and skin hyperpimentation.

EM: see cytoplasmic inclusion bodies

Photo on Right: PAS staing highlights organisms in macrophages

Question 15

Answer 15

Neuroendocrine tumor of GI tract; the most common type of GI tumor, most often affects jejunum and ileum

Question 16

Answer 16

Well differentiated neuroendocrine tumor of SB; see packets/balls/tribecular growth of cells with abundant cytoplasm and round, uniform nuclei.

Most are benign tumors.

Question 17

Answer 17

Small cell carcinoma, a poorly-differentiated neuroendocrine tumor that can affect the GI tract; see thin rims of cytoplasm (hence small cell), packed nuclei, maybe apoptotic bodies

Question 18

Answer 18

GISTS–GI stromal tumors, most common mesenchymal tumors of GI tract, primarily affects stomach, small intestines, colon/rectum. Due to oncogenic mutation in KIT tyrosine kinase. 1/3 of GISTs are malignant, while remainder have risk of recurrence.

Can tx with chemo, rad, or imatinib (Gleevec) and KIT tyrosine kinase inhibitor.

Question 19

Answer 19

Malignant GIST; >95% GISTs have KIT tyrosine kinase and >86% have oncogenic mt in KIT or PDGFRA