First Aid For Surgery - Large Intestine

Front 1

Embryology of colon

Back 1

(1) Origin: embryonic midgut [up to mid-transverse colon] and hindgut [rest of colon and proximal anus]; Distal anus is derived from ectoderm; (2) The dentate line marks the transition between hindgut and ectoderm

Front 2

Etiology of malrotation

Back 2

In development, midgut rotates 270 degres counterclockwise around the axis of the SMA. Developmental anomalies include malrotation and failure of right colon to elongate

Front 3

Blood supply of GI tract

Back 3

Foregut: celiac; Midgut: SMA; Hindgut: IMA; Distal anus: internal pudendal artery branches

Front 4

3 ways colon differs from small bowel

Back 4

(1) Taenia coli - 3 distinct bands of longitudinal muscle that converge at the appendix and spread out to form a longitudinal muscle layer at the proximal rectum; (2) Haustra; (3) Appendices epiploicae - fat appendages that hang off antimesenteric side of colon

Front 5

Function of ileocecal valve

Back 5

Prevents reflux of bowel conents from cecum back into ileum

Front 6

Waldeyer's Fascia of rectum

Back 6

Rectosacral fascia that extends from S4 vertebral body to rectum

Front 7

Denonvilliers' fascia

Back 7

Fascia covering the anterior to lower third of rectum

Front 8

Pelvic floor muscles

Back 8

Levator ani (composed of pubococcygeus, iliococcygeus, and puborectalis muscles); innervated by S4 nerve

Front 9

Left sided colon cancers

Back 9

Typically presents with obstruction or a change in bowel habits - small-caliber stools, hematochezia, etc.

Front 10

Right sided colon cancers

Back 10

Tend to present in a more indolent fashion with microcytic anemia, fatigue, and melena (dark, tarry stools) because the proximal colon has a larger circumference and the stool is less solid

Front 11

Splenic flexure

Back 11

Represents a 'watershed' area between the areas supplied by the SMA and IMA. This area is particularly susceptible to ischemic injury as seen in ischemic colitis. The other two watershed zones are the ileocecal area and descending/sigmoid colon junction

Front 12

Superior Mesenteric Artery

Back 12

Supplies the cecum, ascending colon, and proximal 2/3rds of the transverse colon via the (1) ileocolic; (2) right colic; and (3) middle colic arteries, respectively

Front 13

Inferior Mesenteric Artery

Back 13

Supplies the distal two-thirds of the transverse colon, sigmoid colon, and superior rectum via the (1) left colic; (2) sigmoidal, and (3) superior rectal (hemorrhoidal) arteries, respectively

Front 14

InternalIliac Artery

Back 14

Supplies the middle and distal rectum via the (1) middle rectal and (2) inferior rectal arteries, respetively (the inferior rectal artery is a branch of the internal pudendal artery)

Front 15

Internal Pudendal Artery

Back 15

Supplies the anus; is a branch of the internal iliac artery

Front 16

Dentate line

Back 16

A mucocutaneous line that separates proximal, pleated mucosa from distal, smooth anoderm (1-1.5cm above anal verge); (1) Anal mucosa proximal to dentate line lined by columnar epithelial; (2) mucosa distal to dentate line (anoderm) is lined by squamous epithelium and lacks glands and hair

Front 17

Lymphatic drainage of anal canal

Back 17

Above dentate line: drains to inferior mesenteric nodes or tow internal iliac nodes; Below dentate: drains to inguinal nodes

Front 18

Irritable Bowel Syndrome (IBS)

Back 18

Abnormal state of intestinal motility modified by psychosocial factors for which no anatomic cause can be found; often regarded as a wastebasket diagnosis for a change in bowel habits along with complaints of abdominal pain after other causes have been excluded

Front 19

Normal number of BM

Back 19

Anywhere between 3/day to 3/wk

Front 20

Pseudomembranous colitis

Back 20

Acute colitis characterized by formation of adherent inflammatory exudate overlying the site of mucosal injury (a pseudomembrane). Most often 2/2 overgrowth of C. difficile, a gram-positive, anaerobic, spore-forming bacillus; Typically occurs after broad-spectrum antibiotics (esp. clindamycin, ampicillin, or cephalosporins) eradicate the normal intestinal flora

Front 21

Treatment of C. diff colitis

Back 21

Stop offending antibiotic; give flagyl (PO > IV) or vancomycin PO

Front 22

Radiation-induced colitis

Back 22

Associated with XRT to pelvis for endometrial, cervical, prostate, bladder, or rectal cancer; chance of developing disease is dose dependent and can develop up to 20 years after radiation exposure; often results in increased frequency of bowel movements for life

Front 23

Ischemic colitis

Back 23

Acute or chronic intestinal ischemia 2/2 decreased intestinal perfusion of thromboembolism; often affects the splenic flexure and is more common in the elderly. May be seen after AAA repair, in CAD, Afib, cocaine abuse, sickle cell anemia, and prothrombotic conditions

Front 24

Signs and Symptoms of ischemic colitis

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Mild lower abdominal pain and rectal bleeding; classically after AAA repair. Pain more insidious in onset than small bowel ischemia

Front 25

Typical scenario: 70yo white male with h/o HTN develops cramping lower abdominal pain two days s/p AAA repair. A few hours later he develops blood diarrhea. What is the diagnosis?

Back 25

THINK ischemic colitis! Should be suspected in any elderly patient who develops acute abdominal pain followed by rectal bleeding. Furthermore, the most common setting for ischemic colitis is the early postop period after AAA repair when impaired blood flow through the IMA may put the colon at risk

Front 26

Diagnosis of ischemic colitis

Back 26

(1) Clinical history; (2) Plain abdominal xray-may reveal pneumatosis or "thumbprinting" (submucosal edema); (3) CT scan of abdomen may reveal segmental thickening of the bowel wall; (4) Colonoscopy may show pale mucosa with petechial bleeding

Front 27

Ulcerative colitis

Back 27

Inflammation confined to a mucosal layer of colon that extends from the rectum proximally in a continuous fashion 2/2 autoimmine causes; Bimodal incidence; 15-40 and 50-80; white 4x >nonwhite; industrial nations >> developing nations; Nicotine decreases risk (unlike Crohn's disease)

Front 28

Bloody diarrhea and IBD

Back 28

Both UC and Crohn's disease can present with blood diarrhea, but it is more common in UC

Front 29

Treatment for UC

Back 29

Indications: failure of medical therapy, increasing risk of cancer in long-standing disease, bleeding, perforation; Procedure: proctocolectomy (curative). If patient is acutely ill and unstable due to perforation, a diverting loop colostomy is indicated. Once stabilized, the patient may undergo a more definitive operation. In Crohn's disease, the treatment is stricturoplasty and segmented resections because recurrence is the rule and the goal is to preserve as much healthy intestine as possible

Front 30

Diverticular disease

Back 30

Herniation of the mucosa through the muscular layers of the bowel wall at sties where arterioles penetrate, forming small outpouchings or diverticula; are generally numerous, collectively referred to as diverticulosis; diverticulitis refers to inflammation of the diverticula

Front 31

MC site of diverticular disease

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Sigmoid colon is MC'ly involved with progressively decreasing frequency of involvement as one proceeds proximally

Front 32

S&S of diverticulosis

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80% of patients are ASYMPTOMATIC! But MASSIVE, PAINLESS, lower GI BLEEDING is CLASSIC! [and notably absent in diverticulitis]

Front 33

S&S of diverticulitis

Back 33

Persistent abdominal pain initially diffuse in nature that often becomes localized to the LLQ with development of peritoneal signs. LLQ and/or pelvic tenderness; ileus/abdominal distention; anorexia, N/V/changes in bowel habits (usually constipation), large bowel obstrution, fever, elevated WBC count

Front 34

Diagnosis of diverticulosis

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Characteristic history and PE confirmed by diverticula identified on CT/barium enema and/or c-scope; Rx: HIGH-FIBER DIET!, stool softeners

Front 35

Diagnosis of diverticulitis

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Elevated WBCs, CT scan shows pericolonic inflammation with or without abscess formation; barium enema and c-scope may induce perforation and are contraindicated in the acute setting

Front 36

Pathophysiology of diverticulitis

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A peridiverticular inflammation caused by microperforation of the diverticulum secondary to increased pressure or obstruction by inspissated feces. Feces extravasate onto the serosal surface but infection is usually well contained in a patient with a normal immune function

Front 37

Treatment of uncomplicated diverticulitis

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Outpatient: clear liquid diet, PO antibiotics, and non-opoid analgesics with close f/u with c-scope; If patient fails outpt treatment, then admit for IV Abx and hydration with bowel rest. NGT is plaed if evidence of SBO or ileus

Front 38

When to proceed to surgery for diverticulitis?

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When abscess is inaccessible to drainage or when it is not responding to antibiotics

Front 39

What must all patients with a diverticulitis attack do 4-6 weeks later?

Back 39

Undergo a full colonoscopy 4-6 weeks after the attack to rule out malignancy, as sometimes colonic malignancy presents as diverticulitis

Front 40

Lower GI Bleed

Back 40

GI bleeding distal to ligament of Treitz; considered massive if requires 3 or more units of PRBCs within 24h; MCC's are diverticulosis and angiodysplasia. Other causes include IBD, ischemic colitis, and hemorrhoids; Anticoagulation increases risk of LGIB

Front 41

Large bowel obstruction

Back 41

MC in elderly patients; much less common than SBO; TOP 3 CAUSES: (1) adenocarcinoma (65%), (2) Scarring 2/2 diverticulitis (20%), and (3) volvulus

Front 42

S&S of large bowel obstruction

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(1) Abdominal distention, cramping abdominal pain, nausea, vomiting, obstipation, and high-pitched bowel sounds

Front 43

Diagnosis of large bowel obstruction

Back 43

(1) Supine and upright abdominal films: distended proximal colon, air-fluid levels, and no distal rectal air; (2) Establish 8- to 12-hr history of obstipation; passage of some gas or stool indicates partial SBO, a non-operative condition; (3) Barium enema: may be necessary to distinguish between ileus and pseudo-obstruction (Ogilvie's Syndrome)

Front 44

Treatment of large bowel obstruction

Back 44

(1) Correction of fluid and electrolye abnormalities; (2) NG tube for intestinal decompression (as gastric emptying is reflexly inhibited); (3) Broad-spectrum IV Abx (cefoxitin); (4) Relieve obstruction surgically (colonic obstruction is a surgical emergency since NG tube cannot decompress the colon)

Front 45

Volvulus

Back 45

Rotation of a segment of intestine about its mesenteric axis; characteristically occurs in the sigmoid colon (75% of cases) or cecum (25%); More than 50% of causes occur in patients > age 65; RISK FACTORS: (1) elderly; (2) chronic constipation; (3) psychotropic drugs; (4) hypermobile cecum 2/2 incomplete fixation during intrauterine development [cecal volvulus]

Front 46

Treatment of volvulus

Back 46

(1) Cecal volvulus: right hemicolectomy if vascular compromise; cecopexy otherwise adequate; (2) Sigmoid volvulus: sigmoidoscopy with rectal tube insertion to decompress the volvulus, emergent laparotomy if sigmoidoscopy fails or if strangulation or perferation is suspected; elective resection in same hospital admission to prevent recurrence (nearly 50% of cases recur!)

Front 47

Pseudo-obstruction (Ogilvie Syndrome)

Back 47

Massive colonic dilation without evidence of mechanical obstruction; more common in older, institutionalized patients; RISK FACTORS: severe infection, recent surgery, or trauma; S&S: marked abdominal distention with mild abdominal pain and decreased or absent bowel sounds

Front 48

Treatment of Ogilvie Syndrome

Back 48

(1) NGT and rectal tube for proximal and distal decompression; (2) Correction of electrolytes; (3) Discontinue narcotics, anticholinergics, or other offending medications; (4) Consider pharmacologic decompression with neostigmine (a cholinesterase inhibitor); (5) If peritoneal signs develop, patient should undergo prompt ex-lap to treat possible perforation; (6) Refractory cases may need total colectomy

Front 49

Diagnosis of Ogilvie Syndrome

Back 49

Abdominal radiograph with massive colonic distention; Exclude mechanical cause for obstruction with water-soluble contrast enema and/or colonoscopy

Front 50

Histologic types of benign colorectal polyps

Back 50

(1) Inflammatory (pseudopolyp): seen in UC; (2) Lymphoid: mucosal bumps containing intramucosal lymphoid tissue; no malignant potential; (3) Hyperplastic: overgrowth of normal tissue; no malignant potential; (4) Adenomatous: premalignant - classified into either tubular (75%), tubulovillous (15%) or villous (10%) with increasing malignant potential; (5) Hamartomatous: Normal tissue arranged in abnormal configuration; juvenile polyps, Peutz-Jeghers polyps

Front 51

Colorectal cancer

Back 51

2nd MC case of cancer deaths overall - behind lung cancer; incidence increases with increasing age beginning around age 40 and peaks at 60-79 years of age; RISK FACTORS: age >50; personal history of resected colon adenomas/family history of same; low-fiber, high-fat diet; inherited colorectal cancer syndrome (FAP, HNPCC); long-standing UC or Crohn's disease

Front 52

Familial polyposis coli (FAP)

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AD inheritance; (1) hundreds-thousands of polyps between 2nd and 4th decades; colon cancer is inevitable without prophylactic colectomy; (2) Caused by abnl gene on chromosome 5; APC gene; (3) indication for operation: polyps

Front 53

Gardner's syndrome

Back 53

AD inheritance; (1) Innumerable polyps with associated osteomas, epidermal cysts, and fibromatosis; colon CA inevitable without surgery

Front 54

Turcot's syndrome

Back 54

AD inheritance; (1) Multiple adenomatous colonic polyps with CNS tumors (especially gliomas)

Front 55

Peutz-Jeghers syndrome

Back 55

AD inheritance; (1) Hamartomatous polyps of entire GI tract with melanotic pigmentation of face, lips, oral mucosa, and palms; increased risk for cancer of pancreas, cervix, lung, ovary, and uterus

Front 56

Hereditary nonpolyposis colon cancer syndrome (HNPCC or Lynch syndrome)

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AD inheritance; (1) Lynch Syndrome I: Patients without multiple polyps who develop predominantly right-sided colon cancer at a young age. (2) Lynch Syndrome II: Same as Lynch I, but additional risk for extracolonic adenocarcinomas of uterus, ovary, cervix, and breast

Front 57

S&S of colon cancer

Back 57

Typically asymptomatic for LONG time; symptoms, if present, depend on location and size. (1) Right sided cancers: occult bleeding with melena, anemia, and weakness; (2) Left sided cancers: rectal bleeding, obstructive symptoms, change in bowel habits, and/or stool caliber; BOTH: weight loss, anorexia

Front 58

Hemorrhoids

Back 58

Prolapse of the submucosal veins located in the left lateral, right anterior, and right posterior quadrants of the anal canal; Classified by TYPE of epithelium: (1) Internal if covered by columnar mucosa (above dentate line); (2) External if covered by anoderm (below dentate line); (3) Mixed if both types of mucosa involved; Incidence: Male = Female; RISK FACTORS: Constipation, Pregnancy, Increased pelvic pressure, Portal HTN

Front 59

Anal Fissure

Back 59

Painful linear tears in the anal mucosa below the dentate line; induced by constipation or excessive diarrhea

Front 60

S&S of anal fissure

Back 60

Pain with defecation, BRB on toilet tissue, markedly increased sphincter tone/extreme pain on digital examination; Visible tear upon gentle lateral traction of anal tissue

Front 61

Treatment of anal fissure

Back 61

(1) Sitz baths; (2) Fiber supplements, bulking agents; (3) Increased fluid uptake; (4) If nonsurgical therapy fails, options include lateral internal sphincterotomy or forceful anal dilation

Front 62

Anorectal abscess

Back 62

Obstruction of anal crypts with resultant bacterial overgrowth and abscess formation within the intersphincteric space;RISK FACTORS: constipation/diarrhea/IBD, immunocompromise, hx of recent surgery or trauma, CRC, previous anorectal abscess

Front 63

Signs and symptoms of anorectal abscess

Back 63

Rectal pain, often of sudden onset, with associated fever/chills/malaise/leukocytosis and a tender perianal swelling with erythema and warmth of overlying skin; RX: SURGICAL DRAINAGE!

Front 64

Anorectal fistula

Back 64

Tissue tracts originating in the glands of the anal canal at the dentate line that are usually the chronic sequelae of anorectal infections, particularly abscesses

Front 65

Pilonidal Disease

Back 65

Cystic inflammatory process generally occurring at or near the cranial edge of the gluteal cleft; MC seen in young men in their late teens to their 3rd decade; May present acutely as an abscess (fluctuant mass) or chronically as a drainage sinus with pain at the top of the gluteal cleft. RX: I&D under local anesthesia with removal of involved hairs

Front 66

Anal cancer

Back 66

Neoplasms of anorectal region that are classified into tumors of the perianal skin (anal margin carcinomas) and tumors of the anal canal - RARE (1-2% of all colon cancers)

Front 67

Risk factors for anal cancer

Back 67

HPV, HIV, Cigarette smoking, Multiple partners, anal intercourse, immunosuppressed state

Front 68

Signs and symptoms of anal cancer

Back 68

Often asymptomatic; can present with anal bleeding, a lump, or itching; an irregular nodule that is palpable or visible externally (anal margin tumor) or a hard, ulcerating mass that occupies a portion of the anal canal (anal canal tumor)

Front 69

In situ tumors of perianal skin

Back 69

(1) Paget's disease - disease of anus - adenocarcinoma in situ and (2) Bowen's disease - squamous carcinoma in situ