Colon and Appendix Flashcards
colonoscopy is limited by occassional failure to reach the
right colon
large intestine is composed of
cecum, appendix, colon, rectum and anal canal
total length of LI
1.5 m
LI is characterized by
taenia coli, 3 longitudinal bands of muscle that traverse the colon shortening it to form the haustra, the sacculations created by puckering of bowel wall
major functions of LI
formation, transport, evacuation of feces
part of LI that absorb water
cecum, ascending colon
large blind pouch that extends below the level of the ileocecal valve
cecum
cecum lies in the ____ but may be quite mobile
right iliac fossa
cecum is intraperitoneal or extraperitoneal?
usually covered on all sides by peritoneum (intraperitoneal), but may be fixed extraperitoneall, covered only on its ventral surface by peritoneum
worm-like tube that hangs from near the apex of cecum
appendix
consists of 2 lips that project into the cecum forming a sometimes prominent mass
ileocecal valve
ascending colon is intraperitoneal or extraperitoneal
extraperitoneal, lying in the anterior pararenal space, covered only on its ventral surface by peritoneum
curve of hepatic flexure that is closely related to the descending duodenum and right kidney
proximal more posterior curve
hepatic flexure curve that is closely related to the gallbladder
distal anterior curve
transverse colon is intraperitoneal or extraperitoneal
intraperitoneal and suspended from the transverse mesocolon
limits the superior extent of the small bowel loops
transverse mesocolon
closely related to the tail of the pancreas and caudal aspect of the spleen
splenic flexure
splenic flexure is anchored to the diagphragm by
phrenicocolic ligament
serves as the boundary between processes of the left subphrenic space and left paracolic gutter
splenic flexure
descending colon is intraperitoneal or extraperitoneal
extraperitoneal, within the anterior pararenal space and is covered by peritoneum only on its ventral space
forms a redundant loop of variable length from the distal ascending colon in the left iliac fossa to the rectum
sigmoid colon
sigmoid colon is intraperitoneal or extraperitoneal
completely intraperitoneal and is suspended by sigmoid mesocolon that allows considerable mobility
sigmoid colon penetrates the peritoneum at the level of ____ to continue as the extraperitoneal rectum
S2 to S4
rectum extends for approximately ___ cm in close relationship with the sacrum
12 cm
peritoneum forming the pouch of Douglas covers the ____ and _____ aspects of rectum
ventral and lateral aspects
length of anal canal is ___ cm and is invested by the sphincter ani and levator ani muscles
3 to 4 cm long
a series of vertical folds form the _______, beneath which are the veins that when dilated are hemorrhoids
rectal columns of Morgagni
thickness of the wall of the normal colon does not exceed __ mm
5 mm
generic term for a lesion that protrudes from the mucosal surface of the GI tract
polyps
approximately 50% of colorectal adenocarcinoma occur in the
rectum and rectosigmoid area
approximately 25% of colorectal adenocarcinoma arise from
sigmoid colon
Most colorectal adenocarcinoma are what form and size
constricting annular lesion, 2 to 6 cm in diamter, with raised everted edges and ulcerated mucosa
nearly all cancers of the colon arise from
pre-existing adenomas
infiltrating scirrhous adenocarcinoma tumors are common in
gastric carcinoma
infiltrating scirrhous adenocarcinoma when seen in the LI, is associated with
ulcerative colitis
most frequent complication of colorectal adenocarcinoma
obstruction
conditions with increased risk of colorectal adenocarcinoma
ulcerative colitis, crohn disease, familial adenomatpus polyposis syndrome, Peutz-Jeghers syndrome
Bowler hats sign is seen in
polyps, when viewed obliquely
imaging technique that shows improved detection of lymph node metastases in colorectal adenocarcinoma
Diffusion weighted MR
indicative of tumor extension through the bowel wall
pericolonic fat stranding
size of LN enlargement denoting lymphatic spread of tumor
> 1 cm
major indication of colonoscopy and imaging studies of the colon
detection of colon polyps
rules of thumb in polyps at risk of malignancy
polyps less than 5 mm are almost all hyperplastic, with a risk of malignancy less than 0.5%, polyps 5 to 10 mm size are 90% adenomas, with a risk of malignancy of 1 %. Polyps 10 to 20 mm in size are usually adenomas, with a risk of malignancy of 10%. polyps larger than 20 mm are 50% malignant
polyps that are nonneoplastic mucosal proliferation. they are round and sessile. nearly all are less than 5 mm in size
Hyperplastic polyps
polyps that are distinctly premalignant and a major risk for development of colorectal carcinoma. they are neoplasms with a core of connective tissue
adenomatous polyps
at what age does approximately 5-10% of population have adenomatous polyps
older than 40 years
polyps that represent 1% of colon polyps. they are a common cause of rectal bleeding in children
hamartomatous polyp
Peutz-Jeghers polyp is a type of
hamartomatous polyp
polyps that are usually multiple, and associated with inflammatory bowel disease
inflammatory polyps
inheritance pattern of familial adenomatous polyposis syndrome
autosomal dominant with high penetrance
how many of FAPS are inherited and what portion of the cases are spontaneous
2/3 inherited, 1/3 spontaneous
polyps in FAPS are ____ which are usually evident by age 20
tubulovillous adenomas
recommended therapy for FAPS
total colectomy with rectal mucosectomy and ileoanal pouch construction due to high risk for colorectal cancer
patients with FAPS are at risk of numerous extracolonic manifestations such as
carcinomas of the small bowel, thyroid carcinoma, mesenteric fibromatosis
FAPS patient with associated bone and skin abnormalities including cortical thickening of the ribs and long bones, osteomas of the skull, supernumerary teeth, exostoses of mandible and dermal fibromas, desmoids and epidermal inclusion cysts have been diagnosed as
Gardner syndrome
FAPS patients with associated tumors of the CNS have been grouped as
Turcot syndrome
nonneoplastic growths with a smooth muscle core covered by mature glandular epithelihm . they carry no risk of malignant transformation, however, they may develop adenomatous polyps which do carry a risk of malignancy
hamatomatous polyps
hamartomatous polyps that is an autosomal dominant condition, predominantly involving the small bowel, associated with dark pigmented spots on skin and mucous membranes are characteristic
Peutz-jeghers syndrome
syndrome of multiple hamartomas including hamartomatous polyposis of GI tract, with goiter and thyroid adenomas and increased risk of breast cancer and transitional cell carcinoma of the urinary tract. all patietns have mucocutaneoys lesions with facial papules, oral papillomas and palmoplantar keratoses
Cowden disease
disease of older patients with a mean age of onset of 60 years. polyps are distributed throughout the stomach, small bowel and colon. associated findings include nail atrophy, brownish skin pigmentation, and alopecia. patients present with watery diarrhea and protein-losing enteropathy
Cronkhite-Canada syndrome
lymphoma in the colon is less common. if present, what cell type
non-Hodgkin B-cell lymphoma
most common submucosal tumor of colon
lipomas
colonic lipomas are frequent in the
cecum and ascending colon
endometriosis commonly implants on the
sigmoid colon and rectum, within the cul-de-sac
common idiopathic inflammatory disease involving primarily the mucosa and submucosa of colon. disease consists of ulcerations, edema and hyperemia
ulcerative colitis
peak age of onset of UC
20 to 40 years and age after 50
radiographic hallmarks of UC
granular mucosa, confluent shallow ulcerations, symmetry of disease around the lumen, and continious confluent diffuse involvement
deeper ulcerations of thickened edematous mucosa with crypt abscesses extending in the submucosa
collar button ulcers
mucosal remnants in areas of extensive ulceration
pseudopolyps
small islands of inflamed mucosa
inflammatory polyps
mucosal tags that are seen in quiescent phases of the disease
postinflammatory polyps
postinflammatory polyps with a characteristic worm-like appearance. they are seen in an otherwise normal appearing colon
Filiform polyps
polyps that may occur during healing after mucosal injury
hyperplastic polyps
involvement in UC
extend from rectum proximally in a symmetric and continuous pattern. terminal ileum is nearly always normal
may produce an ulcerated but patulous terminal ileum
rare backwash ileitis
complications of UC
strictures, usually 2 to 3 cm or more in length and commonly involving the transverse colon and rectum, colorectal adenocarcinoma, toxic megacolon, massive hemorrhage
CT findings in UC
wall thickening, with halo sign of low density submucosal edema, narrowing of the lumen of colon, pseudopolyps, pneumatosis coli with megacolon
associated extraintestinal diseases of UC
sacroilitis, mimicking ankylosing spondylitis, uveitis and iritis, cholangitis, thromboembolic disease
features of UC
circumferential disease, regional/continuous disease, symmetric disease, predominantly left-sided, rectum nearly always present, confluent shallow ulcers, no aphthous ulcrs, collar button ulcers, small bowel not involved except for terminal ileum, terminal ileum usually normal, terminal ileum patulous, ileocecal valve open, no pseudodiverticula, no fistulae, hight risk of cancer, risk of toxic megacolon
features of crohn colitis
eccentric disease, skip lesions/discontinuous disease, asymmetric disease, predominantly right-sided, rectum normal in 50%, confluent deep ulcers, aphthous ulcers early, transverse and longitudinal ulcers, involves any small bowel segments, terminal ileum usually diseased, terminal ileum narrowed, ileocecal valve stenosed, pseudodiverticula, fistulae common, low risk of cancer, low risk of toxic megacolon
collar button ulcers is found in
UC
formed by asymmetric fibrosis on one side of the lumen, causing saccular outpouches on the other side
pseudodiverticula
a potentially fatal condition characterized by marked colonic distention and risk of perforation
toxic megacolon
caused by a variety of bacteria (Salmonella, Shigella, E.coli) parasites, viruses (CMV, herpes) and fungi (histoplasmosis, mucormycosis). most cause pancolitis with edema, and inflammatory wall thickening with infiltration of pericolonic fat
infectious colitis
occurs as a complications of UC, crohn disease, pseudomembranous colitis, use of antidiarrheal drugs and hypokalemia
toxic megacolon
radiographic findings of toxic megacolon
marked dilation of the colon (transverse colon > 6 cm) with absence of haustral markings, edema and thickening of the colon wall , pneumatosis coli, evidence of perforation
inflammatory disease of the colon and occassionally involving the small bowel, characterized by the presence of a pseudomembrane of necrotic debris and overgrowth of clostridium difficile
pseudomembranous colitis
what contributes to pseudomembranous colitis
antibiotics (any that change bowel flora), intestinal ischemia (especially following surgery), irradiation, long term steroids, shock, and colonic obstruction
CT findings of pseudomembranous colitis
marked wall thickening up to 30 mm (average 15 mm), with halo or target appearance, characteristic stripes of intrauminal contrast media trapped between nodular areas of wall thickening , mild pericolonic fat inflammation disproportionate with the marked colonic wall inflammation and ascites
characteristic stripes of intraluminal contrast media trapped between nodular areas of wall thickening in pseudomembranous colitis is called
accordion sign
pathophysiology of amebic colitis
encysted amoebae are ingested with contaminated food and water. the cyst capsule is dissolved in the SI, releasing trophozoites that migrate to the colon and burrow into the mucosa, forming small abscesses. can spread throughout the body by hematogeneous embolization or direct invasion
colitis that produces dysentery with frequent bloody mucoid stools. it demonstrates a disease that closely mimics crohn colitis with aphthtous ulcers, deep ulcers, asymmetric disease and skip areas
amebic colitis
primary sites of amebic colitis
cecum and rectum
what part of GI tract is characteristically not involved in amebic colitis
terminal ileum
potentially fatal infection of the cecum and ascending colon usually seen in patients who are neutropenic and immunocompromised by chemotherapy
Typhilitis (neutropenic colitis)
concentric, often marked, thickening of the wall of the cecum and ascending colon with prominent pericolonic inflammatory changes are characteristic. patients are also at risk for colon ischemia
typhilitis
mimics UC and crohn colitis both clinically and radiographically. causes include arterial occlusion caused by atherosclerosis, vasculitis, arterial emboli; venous thrombosis due to neoplasm, oral contraceptives, hypercoagulation conditions and low flow states such as hypotension, CHF and cardiac arrythmias
Ischemic colitis
sma supplies the
right colon from the cecum to splenic flexure
ima supplies the
left colon from the splenic flexure to the rectum
watershed areas in colon that is most susceptible to ischemic colitis
splenic flexure region and descending colon
early changes of ischemic colitis
thickening of the colon wall, spasm, spiculation
in ischemic colitis, as blood and edema accumulate within the bowel wall, multiple nodular defects are produced in a pattern called
thumbprinting
submucosal edema may produce a low-density ring bordering on the lumen which is called what sign
target sign
highly suggestive of ischemia
pneumatosis
AIDS associated colitis happens with CD4 count of
below 200
causative agents in AIDS associated colitis
CMV and cryptosporidosis
what part of colon is commonly affected by AIDS associated colitis
right colon
most commonly involved in radiation colitisdue to radiation of pelvic malignancy
rectosigmoid region
radiation colitis is produced by
slowly progressive endarteritis that causes ischemia and fibrosis
colitis that is due to chronic irritation of the mucosa by laxatives including castor oil, bisacodyl and senna. the involved colon may be dilated and without haustra or narrowed. right colon is most commonly affected. bizzare contractions are often observed
cathartic colon
finding that is characteristic of epiploic appendigitis, which presents as inflammation surrounding central fat
ring sign
cause of abdominal pain that may mimic appendigitis, diverticulitis and colitis
epiploic appendagitis
these are pedunculated fatty structures that occur in rows on the external aspect of the colon, adjacent to the anterior and posterior taenia coli
epiploic appendages
epiploic appendages are in greatest concentration in the
cecum and sigmoid colon sparing the rectum
caused by ischemic infarction of epiploic appendages, often resulting from torsion
epiploic appendagitis
CT findings in epiploic appendagitis
presents as 1 to 4 cm ovoid mass with central fat density and surrounding inflammation abutting the wall of colon, hyperdense enhancing rim surrounds the mass “ring sign”, inflammatory changes may extend into the adjacent peritoneum, a central high attenuation dot is often presenting the central thrombosed vessels, infarcted tissue may calcify
acquired condition in which the mucosa and muscularis mucosae herniate through the muscularis propria of the colon wall, producing a saccular outpouching
colon diverticulosis
classified as false diverticula because the sacs lack all of the elements of the normal colon wall
colon diverticulosis
age predilection of colon diverticulosis
rare under age 25, increases with age thereafter to affect 50% of the population over age 75
major risk factor for diverticulosis
low residue diet
cause of painless colonic bleeding that may be brisk and life threatening
diverticulosis without diverticulitis
complications of diverticulitis include
bowel obstruction, bleeding, peritonitis and sinus tract and fistula formation
obstruction due to diverticulitis is often temporarily relieved
by smooth muscle relaxants such as glucagon
fistulas from acute diverticulitis are common to the
bladder, vagina, skin, but may develop to any lower abdominal organ including fallopian tubes, small bowel and other parts of the colon
CT findings of localized wall thickening, inflammation of pericolonic fat, pericolonic abscess, diverticula at or near the site of inflammation and common involvement of the adnexa with fluid collections and fistulae
acute diverticulitis
screening examination of choice for confirming the presence of and often localizing lower GI bleeding in acute diverticulitis
Radionuclide imaging studies
capable of detecting bleeding at rates below 0.1 ml/min
Technetium-99m sulfur colloid or Tc-99m-red blood cell studies
refers to ectasia and kinking of mucosal and submucosal veins of the colon wall. condition results from a chronic intermittent obstruction of the veins where they penetrate the circular muscle layer
angiodysplasia
appendix arises from the
posteromedial aspect of the cecum at the junction of the taenia coli, approximately 1-2 cm from the ileocecal valve
blind-ended tube that is 4 to 5 mm in diameter and approximately 8 cm in length, altho it may be up to 30 cm long
appendix
formed by calcium deposition around a nidus of inspissated feces
appendicolith
normal diameter of appendix when compressed
less than 6 mm
CT is the usual imaging method of choice for acute appendicitis in
men, older patients and when periappendiceal abscess is suspected
distention of all portion of the appendix with sterile mucus
mucocele
appendiceal dilation greater than ___ mm suggests possible mucocele
13 mm
rupture of the mucocel may result in
pseudomyxoma peritonei
most common tumor of appendix, accounting for 85% of all tumors
carcinoid
most common location for carcinoid tumor
appendix
