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69 Cards in this Set

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Embryology of colon
(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
Etiology of malrotation
In development, midgut rotates 270 degres counterclockwise around the axis of the SMA. Developmental anomalies include malrotation and failure of right colon to elongate
Blood supply of GI tract
Foregut: celiac; Midgut: SMA; Hindgut: IMA; Distal anus: internal pudendal artery branches
3 ways colon differs from small bowel
(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
Function of ileocecal valve
Prevents reflux of bowel conents from cecum back into ileum
Waldeyer's Fascia of rectum
Rectosacral fascia that extends from S4 vertebral body to rectum
Denonvilliers' fascia
Fascia covering the anterior to lower third of rectum
Pelvic floor muscles
Levator ani (composed of pubococcygeus, iliococcygeus, and puborectalis muscles); innervated by S4 nerve
Left sided colon cancers
Typically presents with obstruction or a change in bowel habits - small-caliber stools, hematochezia, etc.
Right sided colon cancers
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
Splenic flexure
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
Superior Mesenteric Artery
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
Inferior Mesenteric Artery
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
InternalIliac Artery
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)
Internal Pudendal Artery
Supplies the anus; is a branch of the internal iliac artery
Dentate line
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
Lymphatic drainage of anal canal
Above dentate line: drains to inferior mesenteric nodes or tow internal iliac nodes; Below dentate: drains to inguinal nodes
Irritable Bowel Syndrome (IBS)
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
Normal number of BM
Anywhere between 3/day to 3/wk
Pseudomembranous colitis
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
Treatment of C. diff colitis
Stop offending antibiotic; give flagyl (PO > IV) or vancomycin PO
Radiation-induced colitis
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
Ischemic colitis
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
Signs and Symptoms of ischemic colitis
Mild lower abdominal pain and rectal bleeding; classically after AAA repair. Pain more insidious in onset than small bowel ischemia
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?
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
Diagnosis of ischemic colitis
(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
Ulcerative colitis
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)
Bloody diarrhea and IBD
Both UC and Crohn's disease can present with blood diarrhea, but it is more common in UC
Treatment for UC
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
Diverticular disease
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
MC site of diverticular disease
Sigmoid colon is MC'ly involved with progressively decreasing frequency of involvement as one proceeds proximally
S&S of diverticulosis
80% of patients are ASYMPTOMATIC! But MASSIVE, PAINLESS, lower GI BLEEDING is CLASSIC! [and notably absent in diverticulitis]
S&S of diverticulitis
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
Diagnosis of diverticulosis
Characteristic history and PE confirmed by diverticula identified on CT/barium enema and/or c-scope; Rx: HIGH-FIBER DIET!, stool softeners
Diagnosis of diverticulitis
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
Pathophysiology of diverticulitis
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
Treatment of uncomplicated diverticulitis
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
When to proceed to surgery for diverticulitis?
When abscess is inaccessible to drainage or when it is not responding to antibiotics
What must all patients with a diverticulitis attack do 4-6 weeks later?
Undergo a full colonoscopy 4-6 weeks after the attack to rule out malignancy, as sometimes colonic malignancy presents as diverticulitis
Lower GI Bleed
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
Large bowel obstruction
MC in elderly patients; much less common than SBO; TOP 3 CAUSES: (1) adenocarcinoma (65%), (2) Scarring 2/2 diverticulitis (20%), and (3) volvulus
S&S of large bowel obstruction
(1) Abdominal distention, cramping abdominal pain, nausea, vomiting, obstipation, and high-pitched bowel sounds
Diagnosis of large bowel obstruction
(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)
Treatment of large bowel obstruction
(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)
Volvulus
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]
Treatment of volvulus
(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!)
Pseudo-obstruction (Ogilvie Syndrome)
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
Treatment of Ogilvie Syndrome
(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
Diagnosis of Ogilvie Syndrome
Abdominal radiograph with massive colonic distention; Exclude mechanical cause for obstruction with water-soluble contrast enema and/or colonoscopy
Histologic types of benign colorectal polyps
(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
Colorectal cancer
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
Familial polyposis coli (FAP)
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
Gardner's syndrome
AD inheritance; (1) Innumerable polyps with associated osteomas, epidermal cysts, and fibromatosis; colon CA inevitable without surgery
Turcot's syndrome
AD inheritance; (1) Multiple adenomatous colonic polyps with CNS tumors (especially gliomas)
Peutz-Jeghers syndrome
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
Hereditary nonpolyposis colon cancer syndrome (HNPCC or Lynch syndrome)
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
S&S of colon cancer
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
Hemorrhoids
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
Anal Fissure
Painful linear tears in the anal mucosa below the dentate line; induced by constipation or excessive diarrhea
S&S of anal fissure
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
Treatment of anal fissure
(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
Anorectal abscess
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
Signs and symptoms of anorectal abscess
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!
Anorectal fistula
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
Pilonidal Disease
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
Anal cancer
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)
Risk factors for anal cancer
HPV, HIV, Cigarette smoking, Multiple partners, anal intercourse, immunosuppressed state
Signs and symptoms of anal cancer
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)
In situ tumors of perianal skin
(1) Paget's disease - disease of anus - adenocarcinoma in situ and (2) Bowen's disease - squamous carcinoma in situ