Colorectal Flashcards
Data supports what kind of bowel prep for elective colorectal surgery?
combined mechanical and oral antibiotic regimens
How does a miralax, gatorade, and bisocodyl mechanical bowel prep work?
- bisocodyl stimulates colonic peristalsis and reduces the volume of PEG preparation required
- miralax produces an ostomotically balanced solution that washes out the colonic stool burden
- gatorade improves the flavor and patient tolerance of prep
How does magnesium citrate work? What are the downsides?
- it is a hyperosmotic saline laxative that increases motility by increasing intra-luminal volume
- it’s hyperosmotic tone increases the risks of fluid and electrolyte shifts compared to PEG solutions
How does an oral antibiotic prep alone compare to a mechanical bowel prep alone?
oral antibiotic prep is associated with reduced morbidity, SSI, anastomotic leak, and post-operative ileus
What are diverticuli?
pseudodiverticuli at the site of penetrating branches of the vasa recta through the muscularis propria
What percentage of diverticulosis becomes symptomatic?
only about 4%
What recommendations should be given to those with asymptomatic diverticulosis?
to increase fluid and fiber intake in an effort to reduce strain on the colonic wall
Which side of the colon typically forms bleeding diverticuli?
right-sided diverticuli are more likely to bleed
What did the Swedish Antibiotic Therapy of Acute Uncomplicated Colonic Diverticulitis trial show?
no difference in future diverticulitis complications, hospital LOS, or recurrence rates between those admitted for IVF and IV antibiotics and those who weren’t
Antibiotics for diverticulitis require good coverage of what organisms?
gram negatives and anerobics
What did two Swiss and French trials show with regards to the preferred operation for Hinchey 3 and 4 diverticulitis?
- no difference in morbidity and mortality between Hartmann’s and primary anastomosis with DLI
- higher rates of ostomy reversal for DLI
When should patients with new diverticulitis undergo colonoscopy?
approximately 6 weeks after non-operative management
What is the prevalence of cancer and pre-malignant advanced adenoma in those with acute diverticulitis?
about 5%
Describe the natural history of diverticulitis.
we now know that the first episode is likely to be the worst/most complicated
What is the most reliable way to identify the top of the rectum?
where the taenia splay
Why is intervention for diverticular bleeding generally recommended?
because although it is often self-limiting, it has a high risk of near-term recurrence
What are the detection rates for tagged RBC scans, CTA, and angiography?
- tagged RBC: 0.1mL/min
- CTA: 0.3mL/min
- angio: 0.5mL/min
What are the traditional indications for operative management of diverticular bleeding?
- requirement of more than 4-6 units within 24hrs
- continuous bleeding more than 72hrs
- rebleeding on the same admission
For patients with diverticular bleeding undergoing resection, which patients should be considered for an ostomy?
those requiring high-volume transfusion given that this increases the risk of anastomotic leak
How does smoking impact IBD patients?
- it is protective for UC
- it is harmful for Crohns
What are the predominant symptoms of UC?
- diarrhea, often bloody
- and tenesmus
What are the typical histologic features of UC?
- crypt abscesses
- polymorphonuclear cells in the laminate propria
- mucosal ulceration
How does the treatment for UC usually escalate?
- start with mesalamine
- add steroids
- then add infliximab or other biologic
What is mesalamine and how does it work?
- it is 5-ASA and the active component of sulfasalazine
- it modulates local inflammatory response by mediating the action of leukotrienes
What are the indications for colectomy in UC?
- failure of medical management
- severe extra-intestinal manifestations
- growth failure in children
- presence of dysplasia or neoplasia
What is the pathogenesis of toxic megacolon?
it results from any process that causes the mucosa to slough, losing the barrier function
What is the preferred operation for toxic megacolon?
subtotal colectomy with end ileostomy
Which UC patients are better served by an end ileostomy?
those with jobs that don’t allow for frequent stooling, those with poor mobility, those with poor sphincter function
What is the expected frequency of bowel movements from an IPAA?
5-6 bowel movements per day and 1 at night
What are the CRC screening guidelines for UC?
- begin 8 years after disease onset
- undergo annual colonoscopy with surveillance biopsies
What is chromoendoscopy?
a form of surveillance biopsies that uses a dye to identify suspicious areas of mucosa that can then be targeted
What is the risk of delayed surgery for UC in patients with growth failure?
delayed onset of puberty, short stature, and poor bone density
When doing a subtotal colectomy for UC, what should you think about doing with the Hartmann’s stump?
suturing the staple line above the fascia in case it dehisces
How long should a J pouch be?
15cm
How long should the rectal cuff be for a J pouch?
less than 1cm or patients may develop cuffitis
When would you want to hand sew an IPAA?
if there is dysplasia in the lower rectum or polyposis extending to the dentate line and you want to perform a mucosectomy
What steps can you take if you need more mesenteric length to form an IPAA?
- mesenteric windowing
- Kocherize the duodenum
- divide the SMA or ileocolic vessel depending on which is holding tension
What is the problem with an S-pouch anal anastomosis?
it often has emptying problems
Where along the small bowel should the DLI be for an IPAA? When should it be closed and what should be done first?
- as distal as possible without adding tension to the anastomosis, usually about 40cm
- should get a gastrograffin enema at 4-6 weeks
- then can reverse it around 8 weeks
What is important about the views obtained on a gastrograffin enema when studying an IPAA?
must get a lateral since the most common site for a leak is posterior
What is the most common complication after IPAA?
pouchitis
Which UC candidates are at particular risk for recurrent or chronic pouchitis?
those with PSC, so they should generally be offered an end ileostomy
What should you consider in a patient with chronic or recurrent pouchitis after an IPAA for UC?
that they may have terminal ileitis from Crohns
How does an IPAA after fertility?
it alters fallopian tube anatomy and reduces female fertility
What should you do with a patient with an IPAA who has a large for gestational birth?
c-section since these patients are incredibly reliant on sphincter function and can’t risk obstetric injury
What is the problem with a continent ileostomy?
they often prolapse and require revision and this revision often sacrifices a lot of bowel
What does the medical management of toxic megacolon consist of in general?
- fluids
- electrolyte correction
- serial radiographs
- antibiotics
- cessation of anti-motility agents
What is particular about the medical management of IBD-related toxic megacolon?
the mainstay is steroids
What is the preferred option for surgical intervention in those with toxic megacolon? What is an alternative?
- prefer a TAC or subtotal with end ileostomy
- alternative is Turnbull procedure with transverse loop colostomy and DLI
What portion of CD patients have:
- ileocolitis
- perianal disease
- isolated colonic disease
- 50% have ileocolonic disease
- 30% have perianal disease
- 20% have isolated colonic disease
What is the age distribution for Crohn’s?
20s-30s and 50s-60s
What endoscopic and pathology findings are suggestive of Crohns?
- pseudopolyps (seen on both)
- cobblestoning/bear claws/deep linear ulcers
- granulomas
- creeping fat externally
What are some high-risk features of Crohns?
- diagnosis before 30
- tobacco use
- elevated CRP or fecal calpro
- deep ulcers or long segments of disease on endoscopic evaluation
- extra-intestinal manifestations
- perianal disease
- history of bowel resections
What is meant by a top-down strategy for Crohns and what are the benefits/downsides?
- start aggressive up front and then back off, accepting more side effects for better disease control
- more rapid onset, preserving normal bowel architecture, and better long-term side effect profile compared to steroids
- more expensive and insurance companies may limit access unless other meds have been tried
What is first line therapy for low-risk CD patients?
- begin with budesonide for ileocolonic disease
- can use prednisone for other areas of disease or for patients with extra colonic CD
- can add an anti-metabolite or methotrexate for maintenance once remission is induced
Where is sulfasalazine active?
only in the colon because it relies on colonic bacteria for activation
What is first line therapy for high-risk CD patients? Adjuncts? Second line?
- anti-TNF biologics like infliximab, adalimumab, or certolizumab
- in combination with anti-metabolites to improve pharmacokinetics and reduce immunogenicity against the biologics
- second line is ustekinumab (anti-IL12/23) or vedolizumab
What should you do if you don’t plan to resect a Crohn’s colonic stricture?
biopsy it to rule out malignancy
How should Crohn’s fistula or perforation be managed?
- non-operatively upfront if able
- followed by delayed resection given the 30% risk of recurrence unless there are short gut concerns
Which extra-intestinal manifestations of CD will get better with surgical intervention?
pyoderma gangrenous and perianal disease
What are the benefits of intersphincteric proctectomy for benign disease?
- decreases wound size and wound healing complications
- better preserves sexual function
When should endoscopy be performed following Crohn’s resection?
6 months post-op to restate and surveil for recurrence
What are the two major arcades connecting the IMA and SMA?
- marginal artery
- Arch of Riolan
What is the predominant mechanism for colonic ischemia?
non-occlusive
Although the splenic flexure is at high risk of ischemia as a watershed area, why is the right colon also thought to be high risk?
because the vasa recta on this side are less developed and thus low flow states also have significant impact here
What three medical and two surgical conditions may predispose one to ischemic colitis?
- MI
- hemodialysis
- hypercoagulability
- cardiac bypass
- aortoiliac surgery
What should be an early step for management of ischemic colitis?
endoscopic evaluation to confirm the diagnosis grossly and with biopsies and to evaluate the thickness/extent of disease
What is the treatment for ischemic colitis?
- fluid resuscitation
- bowel rest
- treatment of contributing conditions
- broad spectrum antibiotics
Intra-operatively, what adjuncts can be used to assess colonic viability?
doppler and indocyanine green/SPY
What class of bacteria is C. diff?
a gram-positive, spore-forming anaerobic bacillus
How do C. diff toxins work?
- toxin B are cytotoxic
- both A and B interfere with actin cytoskeletons of epithelial cells, rendering them non-functional and simulating an inflammatory cascade
What are the three primary risk factors for C. diff?
- antibiotic use
- recent hospitalization
- age > 65
What antibiotics are most commonly associated with C. diff?
- clindamycin
- cephalosporins
- penicillins
- fluoroquinolones
What are the criteria for severe or fulminant C. diff?
severe: WBC > 15, Cr > 1.5, tachycardia, fever, moderate tenderness
fulminant: hypotension, pressor requirement, intubation, severe oliguria, perforation, megacolon
How common is fulminant C. diff without diarrhea?
occurs in 37% of patients secondary to ileus
What is the difference between the NAAT and EIA tests for C. diff?
- NAAT: looks for C. diff toxin genes and is more sensitive
- EIA: looks for free toxins and is more specific
What is the first line treatment for non-fulminant C. diff?
PO fidaxomicin 200mg q12 for 10 days
What is the second line treatment for non-fulminant C. diff?
PO vancomycin 125mg q6 for 10 days
What is the first line treatment for fulminant C. diff?
- PO vancomycin 500mg q6 and IV metronidazole 500mg q8
- add PR vancomycin if they have an ileus
What is the treatment for third C. diff episode?
vancomycin in tapered pulsed regimen
What is bezlotoxumab? When is it indicated?
- a monoclonal antibody that neutralizes C. diff toxin B
- indicated as an adjunct for recurrent disease treatment
What is the preferred operation for treatment of C. diff?
TAC with end ileostomy (although DLI with integrate vanc enemas has shown reduced morality in early trials)
What is the leak rate for an unprepped right colectomy with primary anastomosis? Left?
about 5% versus 20%
What are options for the surgical treatment of LBO?
- loop colostomy
- segmental resection with primary anastomosis +/- DLI
- resection with end colostomy +/- mucous fistula
What are the benefits of using stents to temporize LBOs?
- provides decompression
- offers time for medical optimization
- allows for evaluation of synchronous lesions
- increases the odds of a single stage operation
What are contraindications to stunting an LBO?
- within 5cm of the anal verge
- short and tethered colon
- closely associated abscess/infection
What is the difference between a cecal volvulus and bascule?
- volvulus is a twisting on the axial plane
- bascule is a fold in the sagittal plane onto itself
What is the preferred operation for those with cecal volvulus?
ileocecectomy
How is sigmoid volvulus managed?
- upfront endoscopic detorsion, evaluation, and decompression
- followed closely by sigmoidectomy given 50-80% recurrence rate
Describe the management of Ogilvie’s syndrome.
- fluid resuscitation, electrolyte replacement, discontinuation of opioids and anti-cholinergic, bowel rest
- can follow with 1-2 doses of neostigmine if failure to improve after 3-4 days
- can follow with endoscopic decompression if this also fails
- last resort is a percutaneous or surgical cecostomy
What is neostigmine?
an anti-cholinesterase inhibitor that makes acetylcholine more available
What are the possible side effects of neostigmine and how are they treated?
- bradycardia treated with atropine
- bronchospasm treated with glycopyrolate
