Colon & Rectum 3 Flashcards
The rectum is what type of organ?
retroperitoneal
Due to its retroperitoneal location, pelvic location and distance from the small bowel, the rectum can be treated with this modality:
radiation therapy (high doses of radiation to other parts of the colon can damage the small bowel and cause radiation enteritis)
Radiation has many benefits for rectal cancer, is preop or post-op radiation better?
pre-op better
(short-term pre-op radiation (25 gY over 5 days) has shown to decrease local recurrence and improved disease free survival for all stages of rectal cancer)
What about role of chemo in setting of rectal cancer?
beneficial in adjuvant setting of rectal cancer
studies show neoadjuvant radiation + 5-FU/leucovorin/oxaliplatin show reduction in tumor size and tumor eradication in 25% of cases
Most common surgical approach to rectal cancer in US?
rectal cancers stage II or >, get pre-op radiation + 5-FU bases chemotherapy (radiation done over 5-6 days)
surgery; LAR vs APR done in 6-10 weeks post-radiation
Most common symptom of rectal cancer?
hematochezia
often confused for hemorrhoids and rectal Ca diagnosis is delayed until mass is advanced
Precise location of a rectal tumor best determined by a ?
rigid proctosigmoidoscope
When do we perform a local excision of a rectal cancer?
appropriate for small cancers in distal rectum that has not penetrated into the muscularis
this can be done via a transanal approach
complete removal of LN difficult though, can’t stage tumor well
What types of rectal cancers do we perform local excisions on?
mobile tumors < 4 cm in diameter
involves < 40% of rectal wall circumference
located within 6 cm of anal verge
these tumors should be T1/T2 with no LN or mets
What’s transanal endoscopic microsurgery?
approach for local excision of favorable rectal tumors (T1 dx)
used a 4 cm proctoscopy device which provides access to proximal and mid rectum
long instruments then inserted thru ports in proctoscope to remove local tumor
What is fulguration?
tumor eradicated by use of electrocautery
full thickness eschar created at tumor site
both tumor and rectal wall are destroyed
Fulguration can only be used for rectal tumors below the?
peritoneal reflection
Disadvantages of fulguration?
no specimens can be obtained
post-op bleeding
reserved for pts with high operative risk and limited life expectancy
Miles procedure, AKA?
APR
This is complete excision of the rectum and anus by simultaneous dissection thru the abdomen and perineum with suture closure of the perineum and permanent colostomy:
APR
When do we perform an APR?
tumor involves anal sphincters
tumor too close to sphincters to obtain adequate margins
in pts w/poor pre-op sphincter control
Describe the steps of an APR:
rectum + sigmoid are mobilized via abdominal approach
the pelvic dissection is done via abdominal approach, this mobilizes the mesorectum
pelvic dissection carried down to levator ani muscles
the perineal dissection removes the anus, sphincters, and distal rectum
What is an LAR?
resection of rectosigmoid below the peritoneal reflection via an abdominal approach with a colo-rectal anastomosis
In a LAR why do we always resect the sigmoid colon as well?
risk of diverticulosis
risk of compromised blood supply to a sigmoid-anal anastomosis if IMA is taken
What is LAR with a total mesorectal excision?
for cancers involving lower half of rectum, the mesorectum which contains lymphatics are excised in continuity with the rectum
After an LAR, how is intestinal continuity achieved?
anastomoses between descending colon + rectum
In pts who have had chemo or are on steroids, and have an LAR with a colo-rectal anastomosis, how do we protect the anastomosis?
can do a diverting proximal colostomy/ileostomy
ostomy can be closed in 10 weeks once integrity of anastomosis verified by scope
What is LAR syndrome (AKA clustering)?
in pts with LAR, and a colo-anal anastomosis, lose normal rectal capacity
pts have small frequent BMs
How do we treat LAR syndrome (clustering)?
can form a J pouch from the descending colon and then anastomose to anus
improve bowel habits
if the anastomoses is created 9 cm above the anal verge, J pouch has little benefit
With LAR and colo-anal anastomoses, why do we avoid using the sigmoid as the proximal component of the colo-anal anastomosis?
blood supply of sigmoid from IMA is tenuous
presence of diverticular dx in sigmoid is thought to be a risk factor for anastomotic leak
In obese pts and in pts with narrow pelvis, it’s not feasible to fashion a J pouch for the colo-anal anastomosis after a LAR, what can we do?
can create a colonic reservoir with a coloplasty 4-6 cm above the divided end of the colon
What is primary vs secondary prevention in cancer screening?
primary–>identifying environmental factors responsible for cancer and modifying these factors to reduce risk (diet, environmental hazards)
secondary–> finding a precursor lesion or cancer at a stage where mets and death can be prevented
Cancer screening for colo-rectal cancer is what type of screening prevention?
secondary prevention–> finding a precursor lesion or cancer where its not mets and death can be prevented
Screening options for avg risk pts for colo-rectal cancer?
FOBT + flex sig Q 5 yrs
flex sig not good for pts with high risk of cancer or strong family hx, tends to miss lesions
This is gold standard for screening for colo-rectal dx:
colonoscopy
What’s a stoma?
an artificial opening of the intestinal or urinary tract to the abdominal wall
This is an anastomosis fashioned between the colon and the skin of abdominal wall;
colostomy (temporary vs permanent)
Loop colostomy vs end colostomy:
loop colostomy usually fashioned out of t-colo–> divert fecal stream
end colostomy–>usually end of sigmoid or descending colon fused with skin of abdominal wall
When would we do a loop ileostomy?
usually done to protect a distal anastomosis like a colo-anal anastomosis or an IPAA
When is an end ileostomy required?
when colon and rectum removed and anal sphincter can’t be preserved
Most common indication for an end ileostomy?
Crohn’s dx with severe involvement of anorectum
It’s generally preferred to fashion a distal colostomy from what segment of colon?
descending colon
sigmoid arterial blood supply w/IMA is tenuous and riddled with diverticular dx
Descending colostomies pass what type of material?
pass more formed feces
easier to care for
The more proximal the colostomy fashioned, the higher the chances that the discharge is:
liquid
foul smelling
noxious
These colostomies are difficult to maintain because of copious amounts of liquid foul smelling effluent which are difficult to maintain with an appliance;
colostomies from right side of colon
Motility characteristics of colon make it so that the more proximal the colostomy fashioned, the higher the chance of:
colostomy prolapse
Talk to me about tranverse colostomies;
t-loop colostomy will divert fecal stream for at least 6 weeks completely
over time the posterior wall of colostomy will retract and no longer completely divert the fecal stream
incidence of prolapse increases over time
In a 24 hr period, how much succus entericus does the ileum deliver to the cecum?
2L
What do we have to worry about with ileostomies and the skin?
ileal chyme is liquid and contains digestive enzymes (normally inactivated in the colon)
if the effluent comes in contact with the skin, can be damaging
ileostomy thus fashioned to protrude over the skin as a spigot
What are some technical aspects of ostomy creations?
preferred location–> anterior abd wall with area of no creases
visible–> needs to be visible to the pt, not underneath pannus
bring the stoma thru the rectus, via a 2 cm hole that does not compromise stoma blood supply but also does not cause a para-stomal hernia
Most common indication for a descending end colostomy?
APR for rectal cancer
Most commonly performed loop colostomy?
t-loop colostomy
disadvantage; liquid effluent, evental prolapse, only temporary complete diversion
What is procidenita?
rectal prolapse
full thickness rectal intussusception starting 3 inches above dentate line and extending above anal verge
Which pts present with rectal prolapse?
women > 50 (peak age 70s)
When doing an APR, what anatomical landmark helps guide dissection to separate rectum from the levator ani muscles?
coccyx
In pts with colo-rectal carcinoids, what is the greatest prognostic factor?
size of tumor
carcinoids > 2 cm have more mets potential
What pre-op albumin level is a risk factor for anastomotic leak in a colorectal surgery pt?
pre-op serum albumin less than 3.5 g/dL is a risk factor for leak
Risk factors assc. w/anastomotic leaks?
technical poor nutritional status high tension anastomosis vascular compromise septic environment location (highest leak rates in distal rectum)
Hinchey classification
I–> pericolic/mesenteric abscess
II–> walled off pelvic abscess
III–> purulent peritonitis
IV–> feculent peritonitis
For a suspected colorectal Ca, what is the pre-op we do?
CBC, BMP, CEA
completion colonoscopy
bx of lesion
CT a/p/c with IV + oral contrast
Colon cancer tends to mets to what two places most offten?
1st–> liver
2nd–> lung
When to perform an APR vs LAR?
based on tumor location
tumors in superior or mid rectum–> LAR
tumors in lower 1/3 of rectum, 2 cm from anal verge–> APR w/permanent colostomy
tumors on dentate line–> APR w/colostomy
Transanal excision of a colorectal tumor is only acceptable at what stage?
T1 N0 M0 (stage 1)
FAP is associated with malignancies in other areas of the body, commonly where?
duodenum (as a result upper endoscopy recommended in FAP pts at 20-25 y/o or when colonic polyps first appear)
brain cancer also seen in FAP, but rarer
Pts with FAP who undergo a total abdominal colectomy, with ileo-rectal anastomosis should have what type of screening?
yearly endoscopic surveillance of their rectum
What’s the Nigro protocol for?
tx of choice for squamous cell carcinoma of anal canal
5-FU
mitomycin-C
external radiation tx
What is the most common complication after stricturoplasty?
bleeding
Contraindications for stricturoplasty?
malignancy in the diseased segment
active fisutlizing disease, acute inflammation, phlegmon
What is the most common genetic defect seen in colon cancer?
APC on chrom 5
1st mutation seen in the adenoma to carcinoma sequence?
APC mutation
Usual presenting symptoms of carcinoid syndrome?
flushing wheezing non bloody watery diarrhea abd pain right sided heart failure
Test to diagnose carcinoid tumors in symptomatic pts?
24-hr urine 5-HIAA measurements
First line tx for SBP?
usually caused by a single gram negative bacteria
tx: 3rd gen cephalosporin, FQs
Most common cause of SBP?
gram negative enteric bacteria
This opioid antagonist has been used post-op to help resume bowel function faster in pts with partial large or small bowel resections with anastomosis;
alvimopam
What is alvimopam used for?
FDA approved for helping resume bowel function in pts with partial or small bowel resections
What do we see on endoscopy of someone with severe chronic ulcerative colitis?
sloughing
deep ulcers with exposed muscularis
What is a Krukenberg tumor?
metastatic adenocarcinoma to the ovary
stomach is most common primary site 70%
What % of pts with acute appendicitis will have an associated neoplasm?
1%
Where do we place stomas?
stoma should be visible to the pt
located within rectus muscle in a 4-5 cm healthy area of skin without creases
can be put within ostomy triangle
in obese pts; above umbilicus preferred so they can see it
Pt undergoes a left hemi for stage II descending colon cancer, how do we follow him?
CEA + clinical exam every 3-4 months
CT c/a/p every 6-12 months
colonoscopy at 12 months
What part of large colon has greatest risk of rupture from large bowel obstruction?
cecum, has largest diameter
Tx for a low rectovaginal fistula?
rectal advancement flap
Operative indications for c.diff colitis include what?
toxic megacolon
cecal diameter > 12 cm, colonic diameter > 6 cm
suspected bowel perforation
peritonitis
For pts with UC, who have total proctocolectomy, which extra-colonic symptoms improve and don’t?
PSC + ankylosing spondylitis do not improve
50% of pyoderma gangrenosum improve
ocular sxs, arthritis, and anemia improve
AFter an episode of colonic ischemia, why can we see colonic strictures after?
if ischemia involved more than just mucosal and submucosal layers
