Chapter 36 - Colorectal Flashcards
Muscular anatomy of colon?
Muscularis mucosa, muscularis propria, plica semilunaris (haustra), taenia coli
Vascular supply of ascending colon?
SMA - ileocolic, right colic arteries
Vascular supply of transverse colon?
2/3: SMA - right and middle colic, 1/3: IMA - L. colic
Vascular supply of descending colon?
IMA - L. colic
Vascular supply of the rectum?
IMA and internal iliac
Vascular supply of sigmoid colon?
IMA - sigmoid a.
% of blood flow to mucosa/submucosa?
80%
What are the watershed areas?
Splenic flexure (Griffith’s point), rectum (Sudak’s point)
What muscle makes up the external sphincter?
Puborectalis, continuation of the levator ani
Neuro control of external sphincter?
CNS (voluntary); inferior rectal branch of internal pudendal n, perineal branch (S4)
What muscle makes up the internal sphincter?
Continuation of circular bands of the colon muscle
Measurement from anal verge to anal canal?
0-5cm
Measurement from anal verge to rectum?
5-15cm
Measurement from anal verge to rectosigmoid junction?
15-18cm
Transition point between anal canal and rectum?
Levator ani
Main nutrients of colonocytes?
Short chain fatty acids (butyrate)
Treatment for stump pouchitis?
Short chain fatty acid enemas
Treatment for infectious pouchitis?
Flagyl
Treatment for lymphocytic colitis?
Sulfasalazine
What is the name of the anterior, rectovesicular/rectovaginal fascia?
Denonvillier’s
What is the name of the posterior, rectosacral fascia?
Waldeyer’s
What are the characteristics of polyps associated with increased cancer risk?
> 2cm, sessile, villous
What are the screening guidelines for patients with FAP?
Starting at 10-12y, annual sigmoidoscopy
What are the screening guidelines for patients with attenuated adenomatous polyposis coli?
Starting in late teens, annual colonoscopy
What are the screening guidelines for patients with HNPCC?
Starting at 20-25y, biennial colonoscopy
What is the treatment when polypectomy shows T1 lesion?
Polypectomy only if 2mm margins, well-differentiated, no vascular involvement; otherwise segmental resection
What is the treatment for extensive low rectal villous adenomas with atypia?
Transanal excision (with or without mucosectomy); APR only if cancer is present
What is the treatment for T2 lesion after transanal excision of polyp?
APR or LAR
What will cause a false-positive guaiac?
Beef, Vit C, iron, antacids, cimetidine
Colonoscopy contraindications?
Recent MI, splenomegaly, pregnancy if fluoroscopy planned
What is the 2nd leading cause of cancer death?
Colorectal cancer
Main gene mutations in colon ca?
APC, DCC, p53, k-ras
Most common site of primary colorectal cancer?
Sigmoid
Poor prognostic factors for primary colorectal cancer?
Age <40, symptomatic patients, obstruction & perforation, rectosigmoid/rectal location, ulcerative tumors, blood vessel/lymphatic/perineural invasion, aneuploidy, elevated CEA prior to resection
5 year survival rate with liver mets?
25% if resectable and leaves adequate liver function
5 year survival with lung mets?
20%
Route of metastasis of colon cancer?
To liver via portal vein, to lung via iliac vein
Rout of metastasis of rectal cancer?
Can go directly to spine via Batson’s plexus
Positive prognostic factor for primary colorectal cancer?
Lymphocytic penetration
Goals of resection for colon ca?
En bloc resection, adequate (2cm) margins, regional adenectomy
Treatment for rectal cancer with rectal pain?
APR
What is the best method of picking up hepatic mets?
Intraoperative ultrasound
Margin needed for LAR?
2cm from levator ani
Side effects of APR?
Impotence and bladder dysfunction
Local recurrence higher with rectal or colon ca?
Rectal ca
Advantages of preoperative chemo/XRT?
Produces complete response in some patients with rectal ca; preserves sphincter function in some
Treatment for low rectal T1 lesion?
Transanal excision if <4cm, negative margins (1cm), well differentiated, no neurologic or vascular invasion; otherwise LAR or APR
Treatment for low rectal T2 or higher?
APR or LAR
Chemo for stage III and VI colon CA (node positive or distant mets)?
Post op chemo, no XRT (III - 5FU, leucovorin, oxaliplatin; IV - 5FU and leucovorin)
Chemotherapy for stage II and III rectal ca?
Pre op or post op chemo and XRT (5FU, leucovorin, oxaliplatin)
Chemotherapy for stage IV rectal ca?
Chemo and XRT +/- surgery (5FU, leucovorin)
When is postop XRT needed for rectal ca?
T3 tumors or positive nodes
Most common site of XRT damage?
Rectum; vasculitis, thrombosis, ulcers, strictures
% of patients that will have recurrence?
20% (50% within 6mo, 100% within 3 years)
% that will have another primary?
5% (main reason for surveillance colonoscopy)
Gene mutation related to FAP?
APC gene, chromosome 5
% of FAP syndromes are spontaneous?
20%
When do polyps present in FAP?
Puberty
Surveillance for FAP?
Flex sig to check for polyps; EGD every 2 years
Treatment for FAP?
Total colectomy at age 20; proctocolectomy, rectal mucosectomy and ileoanal pouch
Tumors associated with Gardner’s syndrome?
Colon ca, desmoid tumors, osteomas
Gene mutation associated with Gardner’s syndrome?
APC gene
Tumors associated with Turcot’s syndrome?
Colon ca, brain tumors
Gene mutation associated with Turcot’s syndrome?
APC gene
Lynch syndrome inheritance?
Autosomal dominant
Gene mutation assocaited with Lynch syndrome?
DNA mismatch repair gene
Lynch I has increased risk of what?
Colon cancer
Lynch II has increased risk of what?
Colon cancer, ovarian, endometrial, bladder, stomach cancer
What is the Amsterdam criteria?
3-2-1; 3 first degree relatives, over 2 generations, 1 with cancer before age 50
Surveillance for Lynch syndrome?
Colonoscopy at 25 or 10y before primary relative got cancer; women need endometrial biopsy Q3y and annual pelvic exams, earlier mammograms
% of Lynch syndrome with metachronous lesions?
50%
Tumors associated with juvenile polyposis?
Hamartomatous polyps
Surveillance for juvenile polyposis?
Colonic surveillance, total colectomy if cancer develops
Cancer risk with juvenile polyposis?
Polyps do not have malignant potential, put patients have increased cancer risk
Characteristics associated with Peutz-Jeghers syndrome?
GI hamartoma polyposis, dark pigmentation around mucous membranes
Surgical options for Peutz-Jeghers?
Need polypectomy if possible (may be too many to resect) - 2% colon, duodenal cancer risk
Other cancers associated with Peutz-Jeghers?
Gonadal, breast, biliary
Characteristics associated with Cronkite-Canada syndrome?
Hamartomatous polyps, atrophy of nails and hair, hypopigmentation
Malignant potential with Cronkite-Canada syndrome?
NO malignant potential
Diet associated with sigmoid volvulus?
High-fiber (Iran, Iraq)
Radiographic findings with sigmoid volvulus?
Bent inner tube sign, bird’s beak on gastrografin enema
Treatment for sigmoid volvulus?
Decompress with colonoscopy (not if having peritoneal signs), bowel prep, sigmoid colectomy on same admission
% of sigmoid volvulus that will decompress with colonoscopy?
80% reduce, 50% recur
Age range for cecal volvulus?
20-30y
% of cecal volvulus that will decompress with colonoscopy?
20%
Treatment for cecal volvulus?
OR for R. hemi; can try cecopexy if colon is viable and pt is frail
Symptoms of ulcerative colitis?
Bloody diarrhea, abdominal pain, fever, weight loss
Layers of colon involved in ulcerative colitis?
Mucosa, submucosa
Location of UC?
Colon only with rare backwash ilitis
Anatomic distribution of UC?
Continguous involvement begining distally, spares anus (unlike Crohn’s)
Rectal involvement in UC?
90%
Endoscopic features of UC?
Contiguous mucosal involvement, rectal involvement, mucosal friabilitiy, distorted vascular pattern
Findings on barium enema of UC?
Loss of haustra, narrow caliber, short colon, loss of redundancy
Medical treatment of UC?
Sulfasalazine, 5-ASA, steroids, methotrexate, azathioprine, infliximab, loperamide
Clinical diagnosis of toxic megacolon?
Fever, tachycardia, dilated colon on abd xray
Treatment of toxic megacolon?
NGT, fluids, steroids, bowel rest, TPN, abx (treat 50%), then surgery
Pathologic features of Crohn’s disease?
Transmural inflammation, granulomas, fissures, sumbucosal thickening/fibrosis, submucosal inflammation
Distinguishing characteristics of Crohn’s colitis?
Small bowel involvement, asymmetric distribution, rectal sparing common, gross bleeding in 70-75%, fistulization, granulomas
Endoscopic features of Crohn’s disease?
Discontinuous mucosal involvement, aphthous ulcers, relatively normal surrounding mucosa, longitudinal ulcers, cobblestoning, vascular pattern normal
Perforation occurs where in UC?
Transverse colon
Perforation occurs where in Crohn’s?
Distal ileum
Surgical indications for UC/Crohn’s?
Hemorrhage, toxic megacolon, acute fulminant UC, obstruction, dsplasia, cancer, intractability, failure to thrive, long-standing disease, prophylaxis against colon CA
Treatment for infectious pouchitis?
Flagyl
Cancer risk for UC/Crohn’s?
1-2% per year starting 10y after initial diagnosis
Surveilance for UC/Crohn’s?
Annual colonoscopy 8-10y after diagnosis
Most common extraintestinal manifestation requiring total colectomy?
Failure to thrive in children
Extraintestinal manifestations that DO NOT get better with colectomy?
PSC, ankylosing spondylitis
Extraintestinal manifestations that get better with colectomy?
Most ocular problems, arthritis, anemia
HLA associated with sacroiliitis and ankylosing spondylitis?
HLA B27
Treatment for pyoderma gangrenosum?
Steroids
% of carcinoids found in colon and rectum?
15% of all carcinoids
Treatment for low rectal carcinoids <2cm?
WLE with negative margins
Treatment for low rectal carcinoids >2cm or invasion of muscularis propria?
APR
Treatment for colon or high rectal carcinoids?
Formal resection with adenectomy
What is the Law of LaPlace?
Tension = Pressure x Diameter
Where is colon perforation with obstruction most likely to occur?
Cecum
Causes of colonic obstruction?
1 Cancer, #2 diverticulitis
What is pneumatosis intestinalis?
Air on the bowel wall, associated iwth ischemia and dissection of air through areas of bowel wall injury
What does air in the portal system indicate?
Significant infection or necrosis of lthe large or small bowel
Treatment for Ogilvie’s syndrome (pseudoobstruction of colon)?
Check electrolytes, discontinue drugs that slow the gut; colonoscopy with decompression and neostigmine; cecostomy
% that are carriers for Entameoba histolytica?
10%, from contaminated food and water with feces that contain cysts
Where does the primary infection occur in amoebic colitis?
Colon
Where does the secondary infection occur in amoebic colitis?
Liver
Risk factors for amoebic colitis?
Travel to Mexico, EtOH, fecal oral transmission
Symptoms of amoebic colitis?
Similar to UC (dysentery); chronic form more common with 3-4 BM/day, cramping, fever
Diagnosis of amoebic colitis?
Endoscopy: ucleration, trophozoites; antiamebic antibodies
Treatment for amoebic colitis?
Flagyl, diiodohydroxyquin
Presentation of actinomyces?
Mass, abscess, fistula, induration; suppurative and granulomatous
Most common location of actinomyces?
Cecum
Treatment for actinomyces
Tetracycline or penicillin, drainage
Treatment for lymphogranuloma venereum?
Doxycycline, hydrocortisone
Presentation of lymphogranuloma venereum?
Proctitis, tenesmus, bleeding; may produce fistulas
What causes diverticula?
Straining. Herniation of mucosa through the colon wall at sites where areteries enter the muscular wall; thickening of curcular muscle adjacent to diverticulum with luminal narrowing
Where to most diverticula occur?
L. side (80%) in sigmoid
Bleeding is more common with diverticula on which side of the colon?
Right
Diverticula present in what % of the population?
35%
How long can a stool guaiac stay positive after a bleed?
3 weeks
Where is the bleeding from in hematemeis?
Pharynx to ligament of Treitz
How much blood do you need to make melena?
50cc
What causes azotemia after GI bleed?
Production of urea from bacterial action on intraluminal blood (inc. BUN, total bilirubin)
Arteriography will detect bleeding at what rate?
> 0.5ml/min
Tagged RBC scan will detect bleeding at what rate?
> 0.1ml/min
What causes diverticulitis?
Perforations in the mucosa in the diverticulum with adjacent fecal contamination
% of patients that will have a complication of diverticulitis?
25%, most commonly abscess formation
Signs of complications?
Obstruction symptoms, fluctuant mass, peritoneal signs, temp >39, WBCs >20
Treatment of uncomplicated diverticulitis?
Flagys, bactrim, bowel rest for 3-4 days
Indications for surgery for diverticulitis?
Recurrent disease, emergent complications, inability to exclude cancer
Characteristics of colovesicular fistula?
Fecaluria, pneumonuria; more common in men
Treatment for colovesicular fistula?
Close bladder opening, resect involved segment of colon, reanastamosis, diverting ileostomy
Most common cause of lower GI bleeding?
Diverticulosis
% of diverticular bleeding that stops? Recurs?
75%, 25%
Cause of bleeding from diverticulosis?
Disrupted vasa rectum, creates arterial bleeding
Diagnosis of diverticular bleeding?
Colonoscopy or angio 1st (therapeutic and will localize bleeding)
When is surgery necessary for diverticular bleeding?
If hypotensive and not responding to resuscitation; subtotal colectomy if source has not been localized
Characteristics of angiodysplasia bleeding?
Usually less severe than diverticular bleeds but more likely to recur (80%)
Soft signs of angiodysplasia on angiogram?
Tufts, slow emptying
Associated cardiac anomaly with angiodysplasia?
Aortic stenosis in 20-30%
Causes of ischemic colitis?
Low-flow state, ligation of IMA at surgery, embolus or thormbus of IMA, sepsis and MI
How is the diagnosis of ischemic colitis made?
Made by endoscopy: cyanotic edematous mucosa covered with exudates; lower 2/3 rectum spared (supplied by middle and inferior rectal artery from internal iliac and internal pudendal arteries)
Symptoms of pseudomembranous colitis?
Watery, green, mucoid diarrhea; pain and cramping
Key finding of pseudomembranous colitis?
PMN inflammation of mucosa and submucosa; pseudomembranes, plaques, ringlike lesions
Most common location of pseudomembranous colitis?
Distal colon
How is the diagnosis of pseudomembranous colitis made?
Fecal leukocytes, stool cultures of C. dif/toxin
Treatment of pseudomembranous colitis?
IV flagyl, PO vanco or flagyl; lactobacillus
When does neutropenic typhlitis (enterocolitis) occur?
Following chemo when WBCs are low
Radiographic finding of neutropenic typhlitis?
Pneumoatosis on plain film
Treatment of neutropenic typhlitis?
Abx; pts will improve when WBC increase
How does TB enteritis present?
Like Crohn’s disease (stenosise)
Treatment of TB enteritis?
INH, rifampin; surgery with obstruction
How can Yersinia present?
Mimics appendicitis
Treatment of Yersinia?
Bactrim or tetracyclin
Causes of megacolon?
Hirschsprung’s disease, trypanosoma cruzi (most common acquired cause, secondary to destruction of nerves)
