Colon & Rectum Flashcards
Foregut structures extend all the way to?
2nd part of duodenum
rely on celiac artery
Midgut structures of abdomen?
extends from duodenal ampulla to distal tranverse colon (rely on SMA)
Hindgut structures?
distal third of t-colon, descending colon, rectum
rely on IMA
Avg. diameter and length of cecum?
diameter is 7.5 cm
length approx. 10 cm
Acute dilatation of cecum greater than what number can result in acute ischemic necrosis and bowel perforation?
> 12 cm
Most common location of appendix in relation to the cecum?
retrocecal 65% of time
pelvic 30% of time
These two parts of the colon are retroperitoneal in nature:
ascending + descending colon
How do we mobilize the colon and its mesentery from the retroperitoneum?
dissect along the white line of Toldt
What is the white line of Toldt?
represents the fusion of the mesentery with the posterior peritoneum
What ligaments tether the colon to the hepatic flexure and the splenic flexures?
hepatic flexure; nephrocolic ligament
splenic flexure; phrenocolic ligament
How do we get to the splenic flexure when mobilizing the colon?
dissecting the descending colon upward via white line of Toldt
then lesser sac is entered by reflecting the omentum away from t-colon
Attached to anterior surface of t-colon is greater omentum, which has how many layers?
fused double layer of parietal and visceral peritoneum (4 layers)
contains stored fat
The descending colon, lies ventral to left kidney and extends downward for how long?
25 cm
Where do we see a transition from the thin walled, fixed, descending colon to the mobile sigmoid colon?
level of pelvic brim
In relation to the sigmoid colon, it has a long floppy mesentery, often attached to left pelvic sidewall, producing a small recess called the intersigmoid fossa, often a landmark for what?
left ureter
Rectum along with sigmoid serve as what?
fecal reservoir
The rectum is usually 12-15 cm in length usually lacks what?
tenia coli and appeploic appendages
Why do we say the rectum posterior surface is almost completely extraperitoneal?
its adherent to presacral soft tissues, thus outside the peritoneal cavity
Anterior surface of proximal third of rectum covered by visceral peritoneum, what is this anterior space called?
Pouch of Douglas
What’s the pouch of douglas?
recto-uterine pouch
can serve as site of drop mets from visceral tumors
What’s Bloomer’s shelf?
drop mets from visceral tumors can fall into the pouch of Douglas and form a mass there
often detected by digital rectal exam
Rectum possesses three curves or involutions, known as?
valves of Houston
have no function, don’t impede flow
usually lost after surgical mobilization of rectum
Mobilization of rectum leads to loss of the 3 rectal curves called the valves of Houston, thus adding how much extra rectal tissue?
approx. 5 cm
great for anastomosing in the pelvis
The rectum is intimately close to the presacral fascia, but it is not directly adhered to it, what separates it?
posterior aspect of rectum covered by mesorectum and the mesorectum covered by a thin layer of investing fascia called fascia propria
fascia propria prevents direct rectal adherence to presacral fascia
serves as a bloodless plane for oncologic rectal surgery
What is Waldayer’s fascia?
recto-sacral fascia
thick fascia connecting the presacral fascia to the fascia propria of rectum at the level of S4
Why is Waldayer’s fascia an important surgical landmark?
its division during dissection from abdominal approach leads to entry into deep retrorectal pelvis
What 3 muscles collectively termed the levator ani form the pelvic floor?
pubococcygeus
iliococcygeus
puborectalis
What muscle permits descent of feces?
relaxation of puborectalis straightens the anorectal angle and allows fecal descent
contraction causes the opposite
Puborectalis is in a constant state of contraction or relaxation?
Contraction–> important for continence
Arterial supply to the foregut, midut and hindgut?
Celiac A–> foregut
SMA–> midgut
IMA–> hindgut
Anastomosis of SMA and IMA?
SMA ends at distal t-colon
IMA begins at splenic flexure
Marginal artery of Drummond forms a communication arcade between these two vessels along the mesentery of colon
SMA supplies what??
entire small bowel via 12-20 jejunal-ileal branches to the left
3 main colonic branches to the right (right colic, middle colic, ileo-colic)
Ileo-colic artery supplies?
terminal ileum
cecum
appendix (via appendicular branch)
The middle colic artery off of the SMA supplies what?
gives of left and right branch
supplies proximal and distal T-colon
Griffith’s point?
watershed area by splenic flexure, where left branch of middle colic off of SMA and left colic artery from IMA don’t have a strong communication
anastomosis usually avoided by splenic flexure due to tenuous blood supply
Where do we find the IMA anatomically?
level of L2-L3
3 cm above aortic bifurcation into iliacs
Branches off of IMA?
left colic artery
sigmoid branches
superior rectal artery
What is the arc of Riolan?
AKA meandering mesenteric artery
connects proximal SMA to proximal IMA
Meandering mesenteric artery, AKA arc of Riolan is what?
connects proximal SMA to proximal IMA
Blood supply of rectum?
superior rectal artery –> IMA
middle rectal artery–> internal iliac A
inferior rectal artery–> pudental artery–> internal iliac A
Venous drainage of right and proximal tranverse colon?
SMV (joins splenic vein to go into portal vein)
Distal t-colon, descending colon, sigmoid colon, and most of rectum drain via what vein?
IMVA (joins splenic vein)
Anal canal venous drainage?
drained by middle + inferior rectal veins
empty into the internal iliac vein–> IVC
50% of fecal mass is comprised of?
bacteria
Most colonic bacteria are?
anaerobic species
Principle source of nutrition for colonocytes?
short chain fatty acids–> created by bacterial breakdown of starches
What species of bacteria predominate throughout the colon?
bacteroides species
e.coli, klebsiella, proteus, lactobacillus make up the rest
Unlike most of the mucosal lining of the proximal GI tract, colonic mucosa do not receive nutrition primarily from blood stream but from?
primary energy source if short chain fatty acid butyrate
Primary energy source for colonic epithelium?
butyrate (SCFA)
Na and H2O absorption in colon, active or passive?
H2O–> passive
Na–> active
Mammal cells do not produce butyrate, how do colonic cells get it?
bacteria ferment ingested dietary fiber
Broad spectrum antibiotics destroy local colonic bacteria, thus fermentation of dietary fiber does not occur, thus we don’t have energy for colonocytes to absord Na and water thus we get?
watery diarrhea
How do we define diarrhea?
> 3 loose stools daily
How do we define constipation?
< 3 stools weekly
Most common bacterial species in the colon?
most common bacteria-> bacteroides (anaerobic)
aerobic–> e.coli
Bowel prep and pre-op antibiotics before colonic surgical manipulation?
commonly done in US
(however, some think broad spectrum antibiotics can destroy the normal colonic bacteria, reduce butyrate, less energy for colonocytes, weaker anastomosis)
Absolute contraindications to bowel prep?
complete bowel obstruction
free perforation
Elective colo-rectal cases are classified as?
clean-contaminated
When an elective clean contaminated colo-rectal case is done we need post-op abx?
routine abx for a clean contaminated segmental resection does not reduce infectious complications
promotes c. diff colitis
Typical abx used pre-operatively for elective colonic cases?
2, 3rd gen cephalosporins or fluroquinolone + flagyl or clinda
What is diverticular disease of colon?
abnormal sac or pouch protruding from colonic wall
colonic diverticula are pseudodiverticula (protrusions of mucosa thru the muscularis layers)
Why are colonic divericula pseudodiverticula and not true?
true diverticulum–> all layers of colon protrude thru
pseudo–> they don’t protrusion of normal muscular layers
Age distribution of diverticula?
rare before age 30
2/3 of Americans will have diverticula by age 80
Dietary factors contributing to diverticulosis?
low fiber diet
diet high in carbs and meats
What causes diverticula to form in the colon?
herniations of mucosa thru the colon at sites of penetration of the muscular wall by arterioles
Why do we commonly see bleeding with diverticulosis?
usually diverticula are protrusion of mucosa thru the colonic wall at sites where the arterioles penetrate the muscular wall
sometimes the arterioles are involved in the protrusion and form the dome of the diverticula
Why are colonic diverticula called false diverticula?
they only contain protrusions of mucosa
Where do diverticula form on the colon?
they form on the mesenteric sides
Do not form on the anti-mesenteric sides
Diverticula affect what part of colon mostly?
sigmoid colon 50%
descending colon 40%
Why is sigmoid common site for diverticula?
has smallest colonic diameter
decrease in fiber, requires increased pressures to propel feces forward
narrow sigmoid can generate pressures as high as 90 mmHg to propel feces forward–> diverticula
What causes diverticulitis?
perforation of a colonic diverticula
This is an extraluminal pericolic infection caused by extravasation of feces thru a perforated diverticulum:
diverticulitis
Symptoms of diverticulitis?
LLQ pain alterations in bowel habits fever/chills urinary urgency no rectal bleeding
Preferred imaging modality to reveal diverticulitis?
CT
What is the Hinchey classification of diverticulitis?
I–> pericolic or mesenteric abscess
II–> walled-off pelvic abscess
III–> generalized purulent peritonitis
IV–> generalized fecal peritonitis
Analgesics to use and to avoid in diverticulitis?
AVOID–> morphine (increases intraluminal pressure)
USE—> meperidine (decreases luminal pressure)
After an uncomplicated bout of diverticulitis has resolved, what do we recommend next?
colonoscopy to check for cancer 6 weeks after
After a first attack of uncomplicated diverticulitis, resolved with antibiotics, what are the chances of a second attack?
25%
Do we offer younger pts surgery after first bout of diverticulitis?
50 pts younger than 40 were followed for 9 yrs post-1st attack, 2/3 did not require surgery
these numbers are similar for diverticulitis in pts >50
Diverticulitis in immunocompromised pts?
selective sigmoidectomy after a single attack should be considered
have diminished ability to combat an infection
How do we manage complicated diverticulitis with an abscess?
if abscess >2 cm, it needs to be drained percutaneously
When complicated diverticulitis with abscess have resolved after IV abx and percutaneous drainage, when do we perform surgery (sigmoidectomy)
electively in 6 weeks
Major cause of recurrent diverticulitis after sigmoidectomy is?
failure to remove entirely abnormal thickened bowel
recurrence rate is 12 % if distal sigmoid not resected
What’s a common complication of diverticulitis?
fistula formation after percutaneous drainage from colon to skin
colon to bladder, vagina, small bowel
How do we treat fistulas as a result of diverticulitis?
need to removed diseases sigmoid segment
diverticulitis forms more fistulas between colon and bladder than Crohn’s dx or cancer
Why are sigmoid-bladder fistulas from diverticulitis more common in men?
uterus prevents close adherence of sigmoid to bladder in females
(usually women with fistulas have had a prior hysterectomy)
Sxs of sigmoid-vesicular fistula?
pneumaturia
fecaluria
recurrent UTIs
Most reliable test to confirm colo-vesicular fistula in diverticulitis?
CT
If someone has a colo-vesicular fistula what do we do?
Abx first
C-scope to exclude sigmoid cancer as cause of fistula (which requires extensive removal of involved organs vs diverticulitis as cause which requires segmental sigmoid resection and repair of bladder)
Surgical treatment of colo-vesicular fistulas?
fistula removal
sigmoid resection
anastomosis of distal descending colon to rectum
usually bladder hole is so small, doesnt require repair
leave Foley for 1 week or suprapubic catheter (larger holes repaired with absorbable chromic)
What causes generalized peritonitis from diverticulitis?
diverticulum perforates in peritoneal cavity, not sealed by body’s defenses
an abscess that was local, suddenly expands, bursts into peritoneal cavity
What is the most common surgical technique for control of infection in someone with generalized peritonitis from diverticulitis?
Hartmann’s; rectosigmoid resection, end descending colostomy, closure of rectal stump
When do we restore intestinal continuity after someone has had a Hartmann’s for perforated diverticulitis?
at least 10 weeks
What are two ways that diverticulitis can cause obstruction symptoms?
rare–> narrowing of sigmoid because of mucosal hypertrophy of bowel wall (poses diagnostic dilemma, difficult to distinguish if sigmoid cancer)
likely–> SBO related to inflammatory and infectious aspects of diverticulitis (SB adheres to phlegmon or abscess) (Tx–> NG tube, antibiotics, drainage to treat infection)
What is DAC?
diverticular-associated-colitis
rare
subset of pts can have symptoms and pathology of diverticulitis that mimics Crohn’s/UC
When colon gets twisted around its mesenteric axis, its termed?
volvulus
leads to partial vs complete obstruction
compromise of arterial supply imminent
Colonic volvlus causes what % of large bowel obstructions?
4%
Common locations of colonic volvulus?
sigmoid colon primarily
cecal volvulus next
Most common location of colonic volvulvus?
sigmoid volvulus accounts for 2/3 of all cases
Common age distribution for sigmoid volvuvlus?
present near 7th-8th decade
Factors contributing to sigmoid volvulus?
older age constipation institutionalized pts (psychotropic meds affecting motility)
What do we see on abdominal xray of suspected sigmoid volvulus?
bent-inner tube sign, apex in RUQ
What do we see on CT scan of someone suspected of having sigmoid volvulus?
whorl sign
Contrast enema typically reveals point of obstruction in sigmoid volvlusus with what sign?
bird beak tapering sign
Non-operative tx of sigmoid volvulus?
rectal tube to decompress pt ( keep tube for 1-2 days)
Tx for sigmoid volvulus if unsuccessful decompression with rectal tube?
Hartmann’s
Why is surgical intervention usually necessary in pts with sigmoid volvulus?
even if they get detorsed with rectal tube, recurrence rate is 70%
What’s recurrence rate of sigmoid volvulus after successful detorsion with rectal tube?
70%
What’s a cecal bascule?
“cecal volvulus” although true cecal volvulus almost never occurs
cecum folds over anteriorly on stable ascending colon
Incidence rate of cecal vovulus?
<2 % of all adult intestinal obstruction
25% of all cases of colonic volvulus in US
Age group affected by cecal vovluvlus?
pts in later 50s
sigmoid volvulvus is pts in 70-80s
Why is cecal volvulus possible?
cecum not tethered to retroperitoneum
What do we see on xray with suspected cecal volvulus?
dilated cecum, usually displaced to LUQ
Tx for cecal volvulus?
surgery
What is the surgical procedure of choice for cecal volvulus?
right hemi-colectomy with primary anastomosis, unless ischemia or gangrene present, then ileostomy needed
What’s mechanical large bowel obstruction?
either luminal, mural, or extra-mural obstruction
we see increase in intestinal contractility to relieve the obstruction
Most common cause of colonic obstruction in US vs Europe?
US–> CA
Europe–> colonic volvulus
Other causes of colonic obstruction?
luminal obstruction–> fecal impaction, inspissated barium, foreign body
mural–> cancer, inflammatory processes
extramural–> adhesions, hernias, tumors in nearby organs, abscess, volvulus
Sxs of large bowel obstruction?
failure to pass stool and flatus
increasing abd distention, crampy pain
What makes up colonic gas?
2/3 swallowed air
1/3 fermentation bacterial products
What’s a closed loop obstruction?
distal and proximal ends occluded
seen in volvulus, strangulated hernias, or when cancer occludes colonic lumen in setting on competent ileo-cecal valve
If colonic obstruction is due to cancer in mid to distal rectum, what do we do?
diverting colostomy to relieve the obstruction
neoadjuvant chemo after
with plan to resect primary tumor at later time
IF colonic obstruction is due to cancer in sigmoid colon, how do we proceed?
Hartmanns vs sigmoidectomy with primary colo-rectal anastomosis vs abdominal colectomy with ileo-rectal anastomosis
This is colonic distention, with signs and symptoms of colonic obstruction, in the abscence of an actual physical obstruction.
colonic pseudo-obstruction (Oglvie’s syndrome)
Primary vs secondary pseudo-obstruction?
1—> motility disorder that is a familial visceral myopathy
2–> more common, assc with neuroleptic meds, opiates, parkinsons, lupus, hyperparathyroidism
Cause of colonic pseudo-obstruction?
hypothesis—> SNS overactivity over PSNS
Tx–» neostigmine (PSN mimetic)
You suspect colonic-pseudo obstruction, what test do we perform to differentiate between mechanical obstruction?
water-soluble contrast enema
Preferred initial test for colonic pseudo-obstruction?
water-soluble contrast enema
Colonoscopic use in Ogilvie’s?
can be diagnostic and therapeutic
run risk of over-distending the colon
Initial treatment of Oglivie’s?
NGT decompression
electrolyte correction
IV fluids
When using neostigmine to treat Ogilivies what do we need to make sure?
make sure pt does not have a mechanical obstruction
neostigmine stimulates colonic motility and increased intraluminal pressures in face of mechanical obstruction can cause perforation of bowel
Dosage of neostigmine for Ogilvies?
2.5 mg IV over 3 minutes (pts have sx resolution within 10 mins)
success rate of decompression 90% after single use
SE of neostigmine?
bradycardia (pt needs to be in monitored setting)
Tx–> atropine (unless significant cardiac dx or asthma)
Surgical tx of Ogilvie’s syndrome?
if neostigmine, colonic decompression, or epidural anesthesia don’t work, pt needs ex-lap
loop colostomy usually vents prox and distal colon (if no signs of ischemia or perforation)
Commonly what age affected by ulcerative colitis?
pts < 30 yrs age
second peak around 60 yrs age
This confers a protective effect on ulcerative colitis;
smoking
nicotine has been shown to induce remission in some cases
Smoking effect of UC vs Crohns dx;
UC–> protective
Crohn’s dx–> aggravating
This is a significant risk factor in UC:
+ family hx
high degree of concordance with monozygotic twins
What genes are associated with UC?
HLA
DR2
The major pathologic process of UC involves what layers of colon?
involves the mucosa + submucosa (usually mucosa is not ulcerated, it’s more hyperemic)
muscularis is spared
Hallmark of UC?
rectal involvement
What;s a diagnostic characteristic of UC? And how is this different from Crohn’s?
continuous uninterrupted inflammation of the colonic mucosa, beginning in distal rectum and extending proximally
Crohns–> normal areas of colon (skipped areas) can be interspersed between distinct segments of colonic inflammation
The entire colon, including cecum and appendix, may be involved in UC, but it does not involve what area that is commonly involved in Crohns;
terminal ileum
IS terminal ileum involved in UC?
no, terminal ileum involvement is seen in Crohns
Colonic strictures commonly seen in UC, usually in chronic UC at what %?
5-12 %
Crypt abscesses usually seen in UC, what are they?
neutrophils fill and expand the lumina of the crypts of Lieberkuhn
(crypt abscesses can also be seen in Crohn’s, infectious colitis)
Luminal involvement in UC vs Crohns?
UC–> mucosa + submucosa, spares muscularis
Crohn’s–> transluminal, involves all layers of intestinal wall
pANCA seen in what % of pts with ulcerative colitis?
86%
Do we see perineal disease with UC?
naa
Rectal vs anal involvement in UC?
rectal involvement 100%
anal involvement is rare
Rectal vs anal involvement in UC vs Crohns?
UC–> rectal involvement 100%, anal is rare
Crohns–> rectum is normal (rectal sparing), anal disease is common
What are the extra-intestinal manifestations of UC?
arthritis ankylosing spondylitis erythema nodosum pyoderma gangrenosum primary sclerosing cholangitis
This presents on tibia region as a reg plaque that progresses into an ulcerated painful wound;
pyoderma gangrenosum
What extra-intestinal manifestations of UC completely improve after colectomy?
arthritis
ankylosing spondylitis
erythema nodosum
pyoderma gangrenosum
In pts with UC and primary sclerosing cholangitis, what are we concerned about?
risk of cancer is 5x greater than pts with UC alone
With colectomy for UC, what extra-intestinal manifestation does not resolve?
PSC
A pt with UC who presents with obstructive jaundice and abdominal pain, what do you suspect?
PSC
How do we diagnose UC?
endoscopically
proctosigmoidoscopy is often sufficient in acute phase
What is the risk of developing cancer with UC?
cumulative risk increases with duration of the disease 25% @ 25 yrs 35% @ 30 yrs 45% @ 35 yrs 65% @ 40 yrs
Why do we assume colonic strictures in UC are cancerous until proven otherwise?
high risk of cancer with duration of UC
How do we screen surveillance pts with UC?
surveillance colonoscopy every 1-2 years, beginning 8 yrs after onset of pancolitis, or 12-15 yrs after onset of left sided colitis
For pts undergoing surveillance colonoscopies, traditionally 10 specimens were obtained, but that has changed to what?
at least 30 specimens need to be obtained
What do we do when we find high grade dysplasia on biopsy of colon of someone with UC?
proctocolectomy recommended
What are the three broad categories of drugs for treatment of UC?
aminosalycilates
steroids
immunomodulators
Most common therapy in tx of mild to moderate UC is?
aminosalycilates (sulfasalazine, mesalamine)
How do aminosalycilates like sulfasalazine work for UC?
block cyclooxygenase and lipoxygenase pathways of arachidonic acid and scavenge free radicals in colon mucosa
How do steroids work in UC?
effective in tx of active UC
block phospholipase A2, decreasing prostaglandins an leukotrienes
For UC disease limited to rectum and left colon, how can we use steroids effectively?
hydrocortisone enemas 2-3 x/daily
are less absorbed thus have less side effects
These meds are often used for long-term management in pts with UC:
immunomodulators
What are the two immunomodulator drugs used in UC?
6-mercaptopurine
azathioprine
MOA of 6-MP and azathioprine in UC management?
induce DNA breaks
inhibit proliferation of rapidly dividing cells like T cells
What are the side effects of immunomodulators like 6-MP and azathioprine in UC management?
reversible bone marrow suppression
pancreatitis
This immunomodulator drug has serious side effects:
cyclosporine; nepthrotoxic, hepatotoxic, seizures
This immunomodulator used in UC inhibits IL-2:
cyclosporine
This is a monoclonal antibody used in UC tx:
infliximab–> acts against TNF-a
it can induce remission in a significant number of pts
side effects–> infection susceptibility, lymphomas
What are the indications for surgery in UC?
fulminant colitis with toxic megacolon
massive bleeding
intractable dx
dysplasia/carcinoma
Whats toxic megacolon?
life threatening condition
seen in ptx with UC, Crohn’s, pseudomembranous colitis
bacteria infiltrate walls of colon, cause dilation–> imminent perforation
Surgical procedure for toxic megacolon?
proctectomy and anastomosis ill advised in acutely ill patient
sx–> total abdominal colectomy, end ileostomy with rectal preservation
(preserving the rectum allows for an ileo-rectal anastomosis down the road)
usually rectum can be brought up as a mucus fistula or closed off
Tx for massive bleeding in UC?
massive bleed is rare
usually subtotal colectomy done
What’s the most common indication for operative intervention in UC pts?
colitis with debilitating symptoms refractory to tx
Is segmental colectomy appropriate for UC?
no
Major disadvantage of proctocolectomy with end ileostomy for UC?
requires permanent ileostomy
done in older pts, those with poor sphincter fx, carcinoma in distal rectum
What is the most common operation for UC?
total proctocolectomy with IPAA
(near total proctocolectomy with preservation of anal sphincter complex)
( a distal pouch of ileum is created from 30 cm of ileum and then stapled to the anus using a double-stapled technique)
In order to have a nice repair, the ileo-anal anastomosis needs to be tension free in total proctocolectomy with IPAA, how do we get more ileal length to bring down to anus?
mobilize posterior attachment of entire small bowel up to 3rd part of duodenum
ileoc-colic artery can be resected close to SMA (gives another 2-5 cm) (SMA will feed the pouch after ileocolic resected)
peritoneum of mesentery can be cut on anterior and posterior surface, relaxing incisions can give 1-2 more cm of length
Common complications of proctocolectomy with IPAA for UC?
SBO (27% of pts)–> tends to be severe, 50% of pts will need surgery
pelvic sepsis from pouch anastomosis leaks–> usually diverting ileostomy & abscess drainage needed
pouch-vaginal fistula in women
pouchitis–> 7-30% of pts experience this
Most common procedure performed in emergent setting for UC ?
total abdominal colectomy with ileostomy
(rectum is left in place for future continuity, and has a higher risk of bleeding and nerve injury during the emergent operation)
What is the ideal length of an ileal J pouch?
15-20 cm
Endoscopy in someone with severe-fulminant chronic UC would show what?
mucosal sloughing
deep ulcers with exposed musuclaris
Most common complication of ileal pouches?
obstruction
second most common is sepsis from leaks
