Large Intestines Flashcards
Derived from endoderm except ectoderm derived distal anal canal
LI
LI develops during
4th gestational week
Right colon
Proximal 2/3 of transverse colon
Midgut
SMA
Distal 1/3 or transverse colon
Left colon descending, sigmoid and proximal rectum
Hindgut derived
IMA
Hindgut development
Joining of endoderm and ectoderm at dentate line and division of urogenital sinus and rectum by urorectal septum
Divides endo and ectoderm
Dentate line
Retroperitoneal
Right and left colon
Intraperitoneal
Transverse
Sigmoid
Layers of colon and rectum
Mucosa
Submucosa (similar to SI)
Inner circular muscle: coalesce in anal canal to form internal sphincter
Outer longituginal: taenia coli (cecum to sigmoid)
In rectum, cirumferential
Serosa: midlower rectum at peritoneal reflection
Contiguous and inferior to pelvic floor muscle (levator ani)
External sphincter (voluntary striated)
Attaches to presacral fascia posteriorly and fasia propria of mesorectum anteriorly
Retrosacral Waldeyer’s fascia
Separates rectum from prostate and seminal vesicle from vagina
Denonvillier’s fascia
Colon differentiated from SI by
appendices epiploicae (intraperitoneal fat pad) haustra (circumferential plicae in SI) bands of outer longitudinal (taenia coli)
Largest diameter
Thinnest wall
Inc risk of perforation
Cecum
Most redundant
Inc risk of volvulus
Sigmoid
Narrowest
Inc risk of obstruction
Sigmoid
Colonic and rectal mucosa epithelium
Simple columnar with intestinal glands (crypts of Lieberkuhn) secreting maltase sucrase deeper than in SI
2cm proximal to anal verge
dentate
2 cm proximal to anal verge, epithelium
changes to anal transition zone with mixture of columnar, cuboidal and squamous epithelium
Connects terminal branches of arteries supplying the colon
Marginal artery of Drummond
Watershed area
Junction of SMA and IMA
Vulnerable to ischemia
Splenic flexure
IMV drains to
All others run parallel to artery
spelnic vein
All others portal vein
Rectal submucosal hemorrhoidal plexus drains into
Superior
Middle
Inferior rectal vein
Sympathetic inn of large intestine
Thoracic splanchnic T10-T12 right
L1-L3 left colon and rectum
Parasympathetic inn of large intestine
Vagus right colon
S2-S4 left colon and rectum
Internal anal sphincter innervation
Sympa and para from pelvic plexus
External anal sphincter
Sensation and motor function
Inferior rectal nerve S2-S4 from pudendal
Lymph drainage of colon
Muscularis mucosa (epicolic bowel wall, paracolic, intermediate and main SMA and IMA) nodes
Rectum proximal to anal canal drains to IMA via mesorectum
Proximal anal canal drains to IMA or inguinal nodes
Distal anus drains to inguinal
Key component of radical resection for rectal cancer
Total mesorectal excision
Colon function
Water absortion 5L
Na, K, Cl absorption
Colonic bacteria: FA and NH4
Provide energy to colonocytectrom complex carbs
Short chain FA
Maintain tonic contraction at rest
Internal and external sphincter
Maintained by adequate sensory innervation
Compliance of rectum
Support from pevic floor muscle
Tone from IS and ES
Anal continence
As feces reach rectum, pelvic dloor and IS relax and ES contracts allowing feces to approach anus and anoderm
Rectoanal reflex
Colon lacks
MMEC but has low and high amplitude contraction from vagal stimulation
Normal epithelium mutating to dysplastic epithelium
APC
Early adenoma to intermediate adenoma
KRAS
Intermediate adenoma to late adenoma
DCC/DPC4/JV18?
Late adenoma to carcinoma
p53
Carcinoma to metastasis
Other changes
19, F
RLQ pain, febrile, hemodynamically stable
RLQ rebound tenderness and guarding
WBC= 13, HCG negative
CT: AA without perforation
OR: inflamed, attached to inflamed edematous ovary with purulence
Next step in management?
PID
Right oophorectomy and Appendectomy
Most common surgical emergency of abdomen
7% of population, W 2nd-4th decade
Occlusion of lumen
Acute appendicits
Pain upon palpation of left lower quadrant
Rovsing’s sign
Pain upon hip flexion
Psoas sign
Pain on Internal rotation of right leg
Obturator sign
Atypical symptoms of AA occur in
children
pregnant
elderly
Mild leukocytosis with or without left shift
AA
High sensitivity 95% preferred for dx of AA
CT Scan in most populations: enlarged enhancing appendix >6mm with or without fecalith, periappendiceal fat stranding and wall thickening
Beneficial dx in pregnant women and children
UTZ
AA tx
Gold standard
Lap or open appendectomy
If phlegmon, delay resection start antibiotic and perform interval appendectomy
15% negative appendectomy rate in spite of advances in imaging and technology
Used as landmark to find cecum and appendiceal base
Taenia coli
Divide appendiceal artery, resect appendix and invert and oversew base
Oblique incision
McBurney
Transverse incision
Rocky-Davis
Most common malignancy of appendix
Carcinoid tumor
Yellow mass <2cm at appendiceal tip in association with pain or obstruction
Arises from neuroendocrine enterochromaffin cells
90% in the appendix or distal ileum
Carcinoid tumor
Flushing Wheezing Edema Diarrhea Tricuspid insufficiency
carcinoid syndrome
Most conmonly found in the SI
Carcinoid
If tumor >2cm involves the appendiceal base or terminal ileum or is metastatic,
perform a right hemicolectomy
May alleviate symptoms of carcinoid syndrome
Ocreotide
15% of intestinal obstruction
May be caused by cancer, diverticulitis, volvulus, fecal impaction, postoperative adhesions, hernias or loss of peristalsis (pseudoobstruction)
Large bowel obstruction
Most common cause of LBO
Cancer
Pseudoobstruction
Ogilvie’s syndrome
Confirms LBO
CT
Abdominal radiograph in LBO
colonic distention
SI airfluid level
dilated colon without air in rectum - mechanical obstruction
air in rectum - pseudoobstruction
Tx LBO
Fluid resuscitation
Correct metabolic abnormality
NGT
Antibiotics if ischemic
First line in tx of LBO
surgery
resect and anastomose
Pseudoobstruction tx
NGT
Neostigmine to inc motility
Closed loop obstruction in at least two locations by twistint of bowel >/= 180 deg
Most common in sigmoid, cecum and transverse colon
Volvulus
Anteromedial folding of cecum on itself
Cecal bascule
Axial rotation of cecum around ileocolic vessel, resulting in twisting of mesentery
Cecal volvulus
Rf for volvulus
Redundant segment Megacolon Bedridden condition Chronic constipation Pregnancy
Involves rotation around mesosigmoid
Sigmoid volvulus
Involves rotation of ileum, cecum and ascending colon around mesentery and ileocolic vessel
Cecal volvulus
Volvulus may present with
sudden onset abdominal distention and pain
Confirms dx of volvulus
Abdominal radiograph: bent inner tube narrowing into a bird’s beak (sigmoid)
coffee bean - dilated cecum
Dilated cecum on radiograph
Coffee bean
does not resolve with NGT
Loops that are interposed between liver and diaphragm at risk for volvulus
Chilaiditi’s syndrome
First line for nonstrangulated sigmoid volvulus
endoscopic decompression (sigmoidoscopy, colonoscopy) placement of rectal tube
Passage of air and feces indicate
reduction of volvulus
Emergent surgery
cecal volvulus
cecopexy, right colectomy
Associated with high recurrence and reserved for selected cases
Cecostomy
First line for sigmoid volvulus but not for cecal
Endoscopic decompression
43, M Severe lower quadrant abdominal pain Denies prior nausea or vomiting Febrile but stable Slightly distended abdomen and tender B lower quadrant with guarding Leukocytosis
CT: diverticulosis of sigmoid with adjacent diverticular abscess on antimesenteric side of sigmoid colon
No pneumoperitoneum
Mx?
Admit
NPO
initiate IV antibiotics
Consider IR drainage if abscess is in amenable location
Most common colonic pathology
Diverticular disease
Diverticulosis most affects
sigmoid 95
Rf for diverticulosis
Low fiber diet
Sedentary lifestyle
Tobacco use
Chronic constipation
False diverticula involving herniation of mucosa and muscularis mucosa through muscularis externa at an area of weakness (ie near vessel)
Diverticulosis
More common in young Asian population
Right sided diverticulum
Multiple non inflamed lesions
Asymptomatic
Diverticulosis
Inflammation and infection of diverticulum (from microperforation)
Complicated by abscess, gross perforation or obstruction
Diverticulitis
Asymptomatic or
sudden painless bright red blood per rectum (BRBPR)
Divericulosis
Painless bright red blood per rectum
LLQ pain, fever, leukocytosis
Diverticulitis
Dx of diverticulitis
Clinical with CT (identify complication)
Complications of diverticulosis
phlegmon
abscess
perforation
obstruction
Indications for elective resection
Recurrent attack of diverticulitis
Episode complicated by abscess or microperforation
Diverticulitis in young or immunosuppressed patient
Uncomplicated diverticulosis tx
high fiber diet
bowel rest
oral antibiotics
ir drainage if abscess is present
Sx for diverticulosis perforation
sigmoidectomy and Hartmann
After episode of complicated disease (abscess)
After episode of diverticulitis in young or immunosuppressed
After recurrent attack
Delayed elective resection
Men
Source of bleeding distal to ligament of Treitz
Lower gastrointestinal bleeding
LGIB is a result of
angiodysplasia diverticulosis Meckel’s ischemia IBD infection neoplasm hemorrhoids
Most common cause of LGIB
angiodysplasia
diverticulosis
Negative NGT aspirate in UGI source for GI bleeding
does not rule out UGIB
LGIB mx
Fluid resuscitation
Serial Hct
Suspected LGIB tx
resuscitation, multiple organ support
correct coagulopatht/thrombocytopenia
ET for shock
Surgical consultation
+ aspirate NGT or risk factors for UGIB
Urgent EGD
- aspirate and low risk for UGIB
Urgent colonoscopy
after oral PEG purge
Visualization of LGI source
thermal/injection therapy
Nonvisualization of LGI source
Severe bleeding preventing endoscopic visualization
Angiography (+/- prior TRBC scan) with possible angiographic therapy
NEC affecting terminal ileum, cecum and right colon
Typhilitis
Typhilitis rf
leukemia
immunosupression (AIDS, chemo, transplant)
Confirms dx of typhilitis
CT: dilation of bowel, wall thickening, mesenteric stranding, pneumatosis intestinalis if ischemic)
Typhilitis mx
Medical Immediately instituted NPO NGT fluid resuscitation broad spec antibiotics
Resection in typhilitis if
hemodynamically unstable perforation hemorrhage complete bowel obstruction sepsis
15% of IBD cases have
indeterminate cause
Active form of sulfasalazine
5-ASA
Extra intesinal manifestation of IBD
Primary sclerosing cholangitis (UC) Erythema nodosum Pyoderma gangrenosum Arthritis Sacroileitis Anemia Pancreatic insufficiency Pericarditis Ankylosing spondyltitis Uveitis Scleritis
Patients with IBD should have
annual colonoscopy after disease has been diagnosed for 8-12 years due to risk of colorectal cancer
Indications for emergent surgery UC
toxic megacolon
fulminant/steroid resistant disease
severe bleeding
perforation
Indications for elective surgery UC
Dysplasia or malignancy Stricture Intractable symptoms Inability to tolerate medical management Extra intestinal disease Growth retardation
Second leading cause of cancer deaths
No gender predominance
Colorectal cancer
Rf for CRC
> 50 yrs
hx of colon adenoma
IBD (UC)
fmx of colorectal cancer HCCS
Premalignant
Adenoma
Most common adenoma
Tubular
Adenoma with inc risk for cancer
villous
May present with asymptom, obstruction, rectal bleeding, changes in stool pattern or caliber, tenesmus or anemia
Exam: guaiac + stool, palpable rectal mass or signs of LBO
CRC
Indications for surgery Crohn’s
Fistula Abscess Strictures/obstruction/failed medical management Perforation Hemorrhage Dysplasia/malignancy Growth retardation
CRC may reveal
Anemia
Inc CEA
Screening for CRC
DRE FOBT Flexible sigmoidoscopy Air contrast barium enema CT colonography (virtual colonoscopy) Colonoscopy (preferred)
Staging for CRC
endoscopic ultrasound pelvic MRI (assess depth of local invasion) CT (distant metastases)
Tx for CRC
CIS (adenoma with high grade dysplasia) endoscopic resection
Invasive cancer in polyp (cancer invading through muscularis mucosa) segmental resection if lymphatic or vascular invasion + margin or poorly diff histology
Endoscopic resection if criteria are absent
All other invasive colon cancers: segmental resection add postoperative chemo (5-FU, oxaliplatin, leucovorin) if + lymph node
CRC screening guidelines for average risk patients starting 50
Annual FOBT and flexible sigmoidoscopy every 5 years
Colonoscopy every 10 years
Air contrast barium enema every 5 years
Opinion favors colonoscopy
Outcomes for stage IV disease with hepatic metastases are
improved if hepatic disease is resected
Resection should include at least
12 lymph nodes for optimal staging
If tumor is perforated or obstructing, surgery is directed at removal of malignancy although bypass or colostomt may be all that is possible
Treatment for rectal cancer
May include radiation with chemotherapy
Carcinoma in situ rectal tx
Endoscopic resection or transanal local excision
T1 rectal disease
Radical resection or for small accessible lesions, transanal, full thickness local excision
T2 or higher stage rectal disease tx
Radical resection including at least 5cm distal margin of rectum and mesorectum (for upper rectum and rectosigmoid) or TME 1-2 cm distal margin of rectal wall (for mid to low rectal cancer)
For very low rectal cancers near canal or sphincter tx
APR
T3 or node + rectal disease
Add chemoradiation to radical surgery preferably preoperatively
Dec morbidity compared to postoperative chemoradiation
Also add postoperative chemotherapy for any node + rectal cancer (as for colon cancer)
Surgery for CRC involves
segmental resection including involved portion of colon and lymphatic drainage to the root of associated mesentery
Amsterdam Criteria for HNPCC (3,2,1 rule)
> /= 3 relatives, 1 of whom is a first degree relative with HNPCC related cancer
/= 2 generations affected
/= 1 person affected <50 years
Confirmation that pathologic tumors are not FAP related
Most common surgery for UC
Total proctocolectomy
Most common complication of total proctocolectomy
Pouchitis
Curative for UC but not for Crohn’s disease
Surgery
3rd and 7th decase
Inc risk Ashkenazi Jew
Dec risk with tobacco
Colon (left and rectum)
Diarrhea, hematochezia, abdominal pain (crampy), fever
Colonoscopy, biopsy
Mucosa and submucosa
Continuous, friable mucosa, crypt abscess, pseudopolyp
Fulminanct UC, hemorrhage, toxic megacolon, CRC, extra-intestinal manifestation
For maintenance: Sulfasalazine or 5-ASA
6-mercaptopurine or azathioprine
For acute attack: steroid, sulfa, 5-ASA
Ulcerative colitis
For severe UC tx
Infliximab
For fulminant steroid-refractory UC tx
Cyclosporine
2nd and 6th decase
Inc risk with Ashkenazi Jew
Inc risk with tobacco
Anywhere in GI: most common terminal ileum
Diarrhea, obstruction, abdominal pain, weight loss, hematochezia, fever
Colonoscopy with biopsy, small bowel follow through CT scan
Transmural
Skip lesion (ulceration with interspersed normal mucosa), noncaseating granuloma, fistula perianal, abscess, cobblestoning, stricture
Fulminant colitis, toxic megacolon, extra-intestinal manifestation, colorectal and small bowel cancer
Metronidazole for maintenance of perianal disease
Crohn’s disease
AD
Hamartomatous polyp throughout GI tract
Inc risk of CRC
Juvenile polyposis
AD
Hamartomatous polyp most often located within jejunum/ileum and possibly rectum
Concurrent hyperpigmentation of buccal mucosa
Slightly inc risk of adenomatous degeneration
Inc risk of extra intestinal cancer (breast, gonad, pancreaticobiliary)
Peutz-Jeghers syndrome
AD
PTEN mutation
GI polyp, mucocutaneous lesion, uterine leiomyoma, thyroid and breast tumor
Cowden syndrome
Sporadic
GI polyposis
Epidermal changes including alopecia, nail plate dystrophy, hyperpigmentation
Cronkite-Canada syndrome
APC mutation ch5q
Colonic adenoma with 100% lifetime CRC risk
Inc risk of periampullary, thyroid, adrenocortical cancer
If + APC = flexible sigmoidoscopy annually at 10-15 yrs
Upper GI endoscopy every 1-3 years from 25 years
FAP
APC mutation ch5q Colonic adenoma with inc risk of CRC Desmoid tumor Osteoid tumor Epidermoid skin cyst
As for FAP
Gardner
APC mutation ch5q
Colonic adenoma with inc risk of CRC, brain tumors
As for FAP
Turcot’s syndrome
hMLH1, hMSH2 mutation (DNA mismatch repair genes)
85% lifetime risk of CRC
Screening colonoscopy annually starting at 20-25 years or 10 years earlier than the youngest CRC diagnosis
Endometrial biopsy or transvaginal ultrasound annually starting at 25-35 years
HNPCC (Lynch)
Early onset CRC
Lynch I
Inc risk of brain, stomach, SI, pancreaticobiliary, genitourinary, endometrial malignancy
Lynch II
Engorged anal submucosal cushion
(CT, arteriole and venule) not varicose
Hemorrhoid
Hemorrhoids rf
inc intraabdominal pressure obesity pregnancy staining with defacation most common location are right anterolateral, right posterolateral and left lateral
Internal hemorrhoid
Insensatr
Transitional/columnar epithelium
superior to dentate line
First degree hemorrhoid
Prolapse
Second degree hemorrhoid
+ spontaneous reducing prolapse
Third degree hemorrhoid
+ prolapse requiring manual reduction
fourth degree hemorrhoid
+ nonreducible prolapse
Inferior to dentate line
Squamous epithelium
Innervated anoderm hence sensitive
External hemorrhoid
Most common cause of acute anal pain
thrombosis of external hemorrhoid
perianal abscess
anal fissure
Cause bothersome swelling and diffuclty with hygiene
External hemorrhoid
Cause bright red bleeding BRBPR and mucous discharge
Internal hemorrhoid
Family hx of CRC
>40 years
Suspicious symptom
With hemorrhoid
Perform flexible sigmoidoscopy or colonoscopy
Complication of stapled and traditional hemorrhoidectomy
Pain
Bleeding
Urinary retention
Tear or ulcer in anoderm distal to the dentate line usually midline
Anal fissure
Anal fissures are caused by
Hypertonic internal anal sphincter muscle from insufficient dietary fiber
Small longitudinal ulcer in anoderm with sentinel pile distally or hypertrophic anal papilla proximally
Anal fissure
Best way to diagnose anal fissure
inspection
DRE of anal fissure
internal sphincter spasm and tenderness
Dx for anal fissure
Anoscopy
Sigmoidoscopy
Anal fissure tx
Stool softener
Sitz bath
Nifedipine ointment
Failure of medical management in anal fissure:
lateral internal sphincterotomy
Relaxes internal sphincter
Nifedipine
Occasional complication of lateral internal sphincterotomy
Minor incontinence
Fistula between anal canal and perineal skin
Fistula-in-ano
Anterior or anterolateral external opening track
directly radially to anal canal
Posterior or posterolateral opening tracks
curvilinearly to posterior midline in anal canal
Fistula in ano tx
fistulotomy
Complication if sphincter is divided
Fecal incontinence
Proper evaluation for any anorectal complaint
Careful anal inspection
Rectal exam
Anoscopy
Sigmoidoscopy and sometimes colonoscopy
Infected hair containing sinus in gluteal cleft
Hirsute men 15-40
Pain superior to gluteal cleft
Dx: clinical, abscess or multiple pits or sinuses with hair
Sx: excision, marsupialization
Pilonidal cysy
Inflammation of anorectum
Syphilis, gonorrhea, herpes, HPV, CMV, Chlamydia, chancroid, UC, Crohn’s
Rectal pain, urgency, BRBPR mucuous discharge
Treatment is etiology spec
Proctitis
Protrusion of entire rectal wall through anus
W >60
Rectal prolapse
True rectal prolapse present
circumferential mucosal fold
Mucosal prolapse present with
radial fold in mucosal prolapse
Rectal prolapse dx
Colonoscopy
Contrast enema
Defecography
Rectal prolapse procedure (less invasive)
Delorme’s
Perineal rectosigmoidoscopy
Good operative candidates for rectal prolapse
Laparotomy
Rectopexy with or without rectosigmoid resection
Anal cancer most commonly is
SCC by HPV
Pain, pruritus, sense of anal fullness, rectal bleeding
Anal mass occasionally with lymphadenopathy
Rectal cancer
Confirms dx of rectal ca
Biopsy
Wide locsl excision
small lesion or on perianal skin ca
Chemoradiation
Large lesions and anal canal (Nigro protocol)
Nigro protocol
5-FU
Mitomycin
Recurrent or persistent disease after chemoradiation is treated with
APR
Appendectomy
3cm yellow mass at tip of nonperforated appendix
Mx?
Because tumor is >2 cm
right colectomy indicated for carcinoid tumor
70
diagnosed with colon cancer
What is the incidencr of a synchronous lesion?
5-10% synchronous cancer
20-50% synchronous adenoma
Next step in eval of LGIB if UGI snd LGI endoscopies are negative
Px is hemodynamically stable
Tagged red cell scan
Angiography
Capsule endoscopy
Traits of T1 colon cancer necessitate segmental resection rather than endoscopic resection
Lymphovascular invasion <1mm margin
Poorly differentiated lesion
25, F
Lynch II
Screening recommendation
Anually starting at 20-25 yrd of age
10 yrs earlier than youngest CRC dx
Endometrial biopsy or transv UTZ anually starting 25-35 yrs
Adjuvant chemo regimen for stage III colon cancer
Indications for adjuvant chemotherapy in stage II disease
STAGE III: FOLFOX
Stage II: perforation, obstruction, high-grade lesion, lymphovascular invasion
<12 lymph node in resected specimen
Highly sensitive and specific marker for detecting INTESTINAL INFLAMMATION
Lactoferrin
Level correlates well with histologic inflammation, predict relapses and detect pouchitis
Fecal calprotectin
Earliest radiologic change of UC in barium enema
Fine mucosal granularity
Earliest lesion of Crohn’s
Apthuous ulcer