Chapter 13: GI Large Intestine Flashcards
What are the regions of the colon?
Ileocecal valve
Cecum
Ascending Colon
Transverse Colon
Descending Colon
Sigmoid colon
Rectum
Between ascending and transverse colon: Hepatic flexure
Between transverse and descending colon: Splenic flexure.
What are unique features of the colonic wall?
Like small intestine, outer longitudinal and inner circular muscle walls.
Longitudinal muscle in three separate bundles: Taeniae coli. Evaginations of colonic wall between the taeniae: Haustra.
Appendices epiploicae: Small serosal masses of fat, invested by peritoneum.
Crypts of Lieberkuhn
A newborn presents with delayed passage of meconium and vomiting in the first few days of life. Radiography shows the fillowing findings.
Histology shows a lack of ganglion cells in the colon. Additionally, elevated acetylcholinesterase is detected.
Hirschprung disease.
Mutations of RET receptor tyrosine kinase gene. (MEN2 syndrome?) Down syndrome.
Complications: Enterocolitis (necrosis and ulceration).
A 70-year-old patient with diabetes mellitus presents with fecal incontinence.
Acquired megacolon.
Often due to laxatives, can be due to diabetes, parkinsonism, myotonic dystrophy, scleroderma, amyloidosis, hypothyroidism.
What are some common anorectal malformations?
Anorectal agenesis and rectal atresia: Supralevator deformaties (bowel ends above pelvic floor)
Anal agenesis and anorectal stenosis: Intermediate deformities
Imperforate anus: Low or transelevator deformity (Bowel ends below pelvic floor), anal opening is covered by cutaneous membrane.
Fistulas: Between rectum and bladder, urethra, vagina, or skin.
A middle-aged patient is given tetracycline and chloramphenicol for an infection. Foul-smelling diarrhea develops. A biopsy is taken and shows the following:
Pseudomembranous Colitis - Clostridium difficile, toxin-mediated.
Raised yellowish plaques that adhere to underlying mucosa. Congested and edematous. Plaques coalesce into extensive pseudomembranes.
Other organisms that produce pseudomembranes: S. aureus, Candida, invasive bacteria, verotoxin-producing E. coli.
A newborn presents with diarrhea, pseudomembranes in the colon, gangrene, and perforation of the bowel.
Neonatal Necrotizing Enterocolitis.
Complicates prematurity - colonization with C. difficile.
A patient presents with colicky abdominal pain and periods of constipation and diarrhea. CBC shows anemia.
A biopsy is taken.
Diverticulosis - acquired herniation of the mucosa and submucosa through the muscular layers of the colon.
Lack of indigestible fiber? Increased intraluminal pressure? Colonic wall defects (Marfan, Ehler-Danlos)?
A patient presents with changes in bowel habits (from diarrhea to constipation), dysuria, left lower quadrant tenderness and a palpable mass in the area.
CBC shows leukocytosis. The patient responds to antibiotics.
Diverticulitis.
A patient presents with abdominal pain, diarrhea, and recurrent fever. A biopsy is performed and is shown below. Full-thickness inflammation of the bowel is noted.
Histology finds discrete, noncaseating granulomas are found in the submucosa.
Crohn Disease. beware intestinal obstruction and fistula. Small bowel cancer and colorectal cancer predisposed.
NOD2, CARD15. Smoking.Impaired cell-mediated immunity, increased suppressor T-cell activity, depressed phagocytic function.
Fecal stream: Bypass helps, pattern of preanastomotic recurrence with side-to-end anastomotic sites, frequency of early inflammatory lesions (aphthoid eroisons).
A patient presents with chronic diarrhea and rectal bleeding, with a pattern of exacerbations and remissions.
Biopsy shows diffuse superficial inflammation of the colon and rectum.
Ulcerative colitis.
Crypt abscesses: Dilated crypts filled with neutrophils.
Inflammatory polyps in progressive colitis.
Toxic megacolon - extreme dilation that carries risk of rupture.
Arthritis, uveitis, erythema nodosum, pyoderma gangrenosum, ankylosing spondylitis, sclerosing cholangitis.
Check out this sweet chart.
Wow
Ulcerative colitis presents a significant risk of…
Which is reflected in changes shown in this histology.
Colorectal cancer. Depends on extent and duration of the disease.
Shown in picture is colorectal epithelial dysplasia. Altered mucosal architecture, epithelial abnormalities (hypercellularity, stratification of nuclei), and epithelial dysplasia (variation in nuclear size, shape, or stain.)
A patient presents with chronic watery diarrhea. Colonoscopy reveals a normal appearing colon.
A biopsy is taken, shown below. Trichrome stain.
Collagenous colitis. Trichrome stain highlights thickening of the collagen table (blue) with entrapment of capillaries.
Intercryptal surface epitheliumn is flattened and contains increased number of intraepithelial lymphocytes.
HLA-A1 and decreased HLA-A3
Similar disease without collagen table thickening is lymphocytic colitis.
A 60-year-old patient with hypertension and dyslipidemia presents with recurrent bouts of abdominal pain.
In an acute event, pain increases suddenly. A biopsy is taken from the splenic flexure.
Ischemic colitis.
Splenic flexure between superior and inferior mesenteric artery supplies.
Hemorrhage, edema, ulcers, nodular lesions, pseudomembrane. Colonic stricture may occur.
