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69 Cards in this Set

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why is the rectum less likely to be involved in Ischemic colitis?
The rectum receives blood supply from the internal iliac artery AND the inferior mesenteric artery, which explains why it is less likely to be involved in Ischemic colitis
Colonic Function.

The functions of the colon include:
- concentration of stool (water absorption)

- Secretion of mucus

- Host immunity

- Peristalsis

The absorptive columnar epithelial cells in the colon absorb sodium, chloride, and water; potassium and bicarbonate are secreted

The colon readily reabsorbs bile salts and short chain fatty acids.

The colon has a limited capacity to absorb bile salts and short chain fatty acids.
Diseases of the Colon

A. Colonic Neoplasia. (Colorectal Cancer)

- Second leading cause of cancer death in US

- Both women and men

- All races

- risk inc. after the age of 40 and rises sharply at the ages of 50-55; the risk doubles with each succeeding decade, reaching a peak by age 75.
Adenocarcinoma of the colon arises through the acquisition of multiple genetic mutations in ___________
epithelial stem cells located within the colonic crypts
Most sporadic colonic adenocarcinomas are thought to arise within __________.

As these polyps increase in size and histological abnormality, the risk of carcinoma within the polyp __________
premalignant adenomatous polyps

Diseases of the Colon

A. Colonic Neoplasia.

may be asymptomatic, or present with iron deficiency anemia, occult GI blood loss, hematochezia (passage of bright red blood in stools), alterations in bowel frequency or stool caliber, or obstructive symptoms from advanced carcinoma.
Diseases of the Colon

A. Colonic Neoplasia.

Conditions that attribute an increased risk for colorectal cancer include:
- a personal history of colorectal cancer or adenomas

- first degree family history of colorectal cancer or adenomas,

- a personal history of ovarian, endometrial, or breast cancer,

- ulcerative colitis.
Hereditary Factors:

Colon cancer syndromes account for less than 10% of all colorectal cancers.

These syndromes include:
- Familial Polyposis (FAP)

- Hereditary Nonpolyposis Colon Cancer Syndromes (HNHPCC, also called Lynch syndromes I and II):
Diseases of the Colon

A. Colonic Neoplasia.

Screening Methods:

Proposed screening strategies have included combinations of the following modalities:
1. Fecal occult blood testing.

2. Sigmoidoscopy.

3. Colonoscopy.

4. Double contrast barium enema.

The sensitivity of various screening strategies for detection of colorectal carcinoma is in part dependent on the distribution of adenomatous polyps and cancers in various regions of the colon.
Diseases of the Colon

A. Colonic Neoplasia.

Screening Methods:

Fecal Occult Blood Test
- polyps greater than 2 cm and early carcinomas are prone to bleed at low levels that cannot be directly appreciated by the patient or physician (occult bleeding)

- this screening method is not specific for colorectal neoplasia and a substantial number of patients who have a positive FOBT will be found to have other reasons for occult blood loss (see upcoming flashcard)
Diseases of the Colon

A. Colonic Neoplasia.

Screening Methods:

- permits examination of the distal colon with more acceptable patient tolerance.

- can discover as many as 65-75% of polyps and cancers.

- removal of premalignant polyps may reduce the subsequent incidence of colon carcinoma
Diseases of the Colon

A. Colonic Neoplasia.

Screening Methods:

- involves inspection of the entire colon with a 160 cm long fiberoptic colonoscope and thus potentially can detect all lesions present in the colon.

- added advantage that any tumor encountered can be biopsied and that polyps can be removed or destroyed by electrocautery

- often advocated as a screening modality because of the potential to detect polyps or cancers missed by sigmoidoscopy and FOBT
Name potential conditions that may lead to occult or minimal GI blood loss
anal fissures,
inflammatory bowel disease,
Diseases of the Colon

A. Colonic Neoplasia.


The primary therapeutic modality for most colorectal cancers is _________
surgical excision of the primary tumor

Surgery is usually performed even in the presence of metastatic disease to prevent subsequent bowel obstruction as the tumor grows.

Adjuvant chemotherapy has been shown to improve long-term survival in patients
Diverticular Disease.

Colonic diverticula are small balloon-like sacs or pouches of mucosa that herniate through the muscle layers of the colon.

Definition: (contrast with diverticulITIS)
- DiverticulOSIS refers only to the presence of diverticula in a patient.

Diverticular disease may present as bleeding or inflammation (diverticuLITIS) originating in a colonic diverticulum
Genetic alterations in progression to colorectal cancer

Name the Proto-oncogene that is generally associated with colorectal cancers (Name 1)

Name the Tumor Suppressor Genes that are generally associated.... (Name 3)

Tumor suppressor
HNPCC vs Sporadic CRC

1) Which one has lower age of onset?

2) Which one is more likely to be found with multiple tumors?

3) Which one is more prone to affect the right side (prox to splenic flexure)

What genes predispose HNPCC to replication errors?
1-3) HNPCC

hMLH1, hMSH2
Familial adenomatous polyposis

- Inheritance pattern
- Which gene affected?
- Risk for developing colon cancer?
Autosomal dominant
Germline mutation in FAP gene
100% risk of developing colorectal cancer, usually by 30
Other cancers
10-20% upper GI adenomas

what is it?

- Celecoxib does not affect colon cancer risk
- selective COX-2 inhibitor
- approved for use in FAP
- reduces number and size of polyps

- DOES NOT affect colon cancer risk!!

Typical History
- Bleeding, fatigue, change in bowel habits, abdominal pain



Typical Exam/Lab/Imaging
- Digital rectal exam and hemoccult test
- Hepatomegaly, ascites, lymphadenopathy, weight loss

- Microcytic anemia, elevated CEA, liver panel

- Imaging
CT abdomen/pelvis


Gold Standard for Diagnosis:
- Colonoscopy—gold standard diagnosis

- Colonoscopy with biopsy, polypectomy
Left sided vs. Right Sided Colon Cancers

Differences in clinical presentation:
Right Sided:
- Pain (65%)
- Changes in bowel movement (25.5%)
- Weakness (25.5%)

Left Sided:
- Bleeding (88%)
- Changes in bowel movement (78%)
- Pain (40%)
Hyperplastic vs. adenomatous polyps in terms of cancer risk
Hyperplastic polyps pose NO greater risk for developing cancer than having no polyps

Adenomatous polyps indicate a greater risk for developing cancer
B. Diverticular Disease.

Pseudodiverticulum- mucosa and serosa, no muscle
B. Diverticular Disease.

- colonic diverticula are pseudodiverticula consisting of herniated sacculations of mucosa and serosa without intervening muscular wall

Diverticula most often occur at the site where the vesa recti penetrate the muscle wall into the submucosa.

Diverticulitis results from macroperforation of the bowel within the diverticulum.

- Occur where artery penetrates through muscularis;
inc. fiber intake, dec. contractile pressure
Diverticular disease

- Diverticulitis
- Diverticular bleed

Diverticula are most prevalent in the ascending colon

Diverticula are most prevalent in the sigmoid colon where intraluminal pressures may be highest due to the small caliber of this region of the colon.
Diverticular disease

(presentation, diagnosis, complications)
- Fever, leukocytosis left-sided pain

- CT scan
- Contained or free perforation

Complication: stricture, abscess, peritonitis or fistula

Most patients (-80%) with diverticulosis never present with a clinical problem related to their diverticula

Of the remaining patients (20%) about one-quarter will present with diverticular bleeding and three quarters will develop diverticulitis.
Diverticular disease


Diverticular bleed
Diverticular bleed
- 5%-diverticular bleed

- Painless, sudden, large bleed (HALLMARK)

- 70% right-sided
- 80% spontaneously stop
- Rapid lavage can find and rx source in 30%

Patients with asymptomatic diverticulosis should be encouraged to increase the _______ content of
their diet.
Patients with diverticulitis are initially managed with __________, ____________ if ileus or obstruction are present, and_______.

If the patient does not respond to conservative medical management or if complications such as intraabdominal or pelvic abscess occur __________ may be necessary and is guided by the nature of the complication.
broad spectrum antibiotics

nasogastric suction

fluid replacement

surgical intervention
Ischemic Colitis.

- Damage resulting from an imbalance of colonic blood flow supply and demand

- Heterogeneous in cause and clinical outcome
Ischemic Colitis.

Which side (if any) does it usually present in?
- Left colon and rectum involved in 75%

- Splenic flexure 25%

- Right colon in 10%

- Entire colon involved in up to 10%

- Skip lesions are rare
Ischemic Colitis.

Ischemia secondary to systemic low-flow states usually involves the left colon secondary to less well-developed collaterals and longer vasa recta

RIGHT colon has less well developed collaterals and longer vasa recta and is usually involved in ischemic collitis
Ischemic Colitis

Localized, non-occlusive ischemia classically involves which region of the colon?
watershed areas of the colon such as the splenic flexure and the junction of the sigmoid and rectum
Ischemic Colitis


Age group? young or old?
Predisposing factors? (Name 2)
- Patients generally older than 60

- Atherosclerosis is predisposing factor and 10-15% have diabetes mellitus

- While risk factors are frequently present, most patients have no clear precipitating event
Ischemic Colitis

Signs and Symptoms
- Acute abdominal illness
- Abdominal pain (87%) – sudden, crampy, frequently LLQ

- Diarrhea (68%)
- Hematochezia (usually with minimal blood loss) (60-90%)

- Anorexia, nausea, and vomiting may occur secondary to ileus (38%)

- Peritoneal signs in 10-20%

- Low grade fever, leukocytosis
Ischemic Colitis

Barium Enema
Barium enema – sensitivity 80%
- Most common finding- thumb printing (75%),
- longitudinal ulcers (60%),
- eccentric mural deformity (50%), sacculation (30%)
- Findings typically segmental and transient

- Non-specific
Ischemic Colitis


Colonoscopic findings favoring ischemia over IBD include:
- segmental distribution,
- abrupt transition between injured and uninjured mucosa,
- rectal sparing,
- rapid resolution on repeat colonoscopy
Ischemic Colitis


Ligation of IMA can cause ischemic colitis by itself

Ligation of IMA does NOT cause ischemic colitis by itself

Other points:
- Regional blood flow is the critical factor

- Previous impairment by atherosclerosis or vasculitis increases the risk of ischemia

- Previous impairment is not a prerequisite as shown by cases in long distance runners, cocaine users.
Ischemic Colitis

Major vascular occlusion

Small vessel disease



Colonic obstruction

Hematologic disorders

Cocaine abuse

Long-distance running

Idiopathic (spontaneous) (LARGEST CONTRIBUTOR)
Ischemic Colitis

Differential Diagnosis
- Mesenteric ischemia


- Diverticulitis

- Infectious colitis (esp. C. diff)

- Volvulus

- Bowel obstruction

Like the small intestine, sudden complete occlusion of arterial flow to the colon is very common;

UNLIKE the small intestine, sudden complete occlusion of arterial flow to the colon is very RARE;

Most cases of colonic ischemia result from decreased perfusion pressure and/or vasoconstriction of the splanchnic vessels

The mucosa of the colon is the most sensitive to ischemic injury.
Ischemic Colitis

- Supportive therapy with optimization of the patient's circulatory hemodynamics is usually the only therapy required.

- Any potential causes of splanchnic vasoconstriction should be identified and corrected or avoided.

- Close observation of the patients for signs of progression of ischemia, perforation, or development of peritonitis are essential and may indicate the need for emergent surgical intervention.
Irritable bowel syndrome (IBS)

3 main subsets of IBS:
- constipation-predominant,
- diarrhea-predominant,
- pain-predominant
Irritable bowel syndrome (IBS)

The pathophysiology of IBS is unknown,

The most well accepted mechanism is that IBS patients display visceral hypersensitivity (heightened sensations of pain or discomfort at levels that would not cause symptoms in non-IBS persons).

Possible increase/alteration in serotonin signaling to CNS

Strong association between IBS and
- Somatization
- Anxiety
- Depression
- Prior sexual abuse
Irritable bowel syndrome (IBS)

Diagnosis and histological hallmarks:
- No hallmark radiographic, endoscopic, histologic or laboratory findings

- Diagnosis often made by history and exclusion of other diseases.
Microscopic colitis

2 main forms
Lymphcytic colitis
Collagenous colitis
Microscopic colitis

Lymphocytic colitis—
increased numbers of subepithelial mononuclear cells
Microscopic colitis

Clinical Presentation:

Clinical presentation
- similar to, but generally much less mild than, IBS

Most patients have chronic diarrhea but few other symptoms

Made by endoscopy (in which the colonic mucosa appears normal) and random biopsies show typical histologic features.
Acute Colonic Pseudoobstruction (Ogilvie's syndrome)


- Distension of colon without evidence of mechanical obstruction

Hallmark physical signs
- Abdominal distension
- Tympany to percussion
- Hypoactive or absent bowel sounds

Radiographic signs
- Gaseous distension of colon
- Cecal diameter can be predictive of spontaneous rupture

Differential diagnosis

Young patients vs. old patients
Young patients
- Infection
- Celiac disease

Less common
- Malignancy
- Intestinal Ischemia

Older patients
- Malignancy
- Intestinal ischemia
- Celiac disease

Less common
- Infection
Microscopic colitis

Collagenous colitis—
increased subepithelial collagen deposition and chronic mucosal inflammation.
Acute colonic pseudo-obstruction (APCO or Olgivie’s syndrome)

- Eliminate narcotics and other meds that slow motility
- Move patient
- Nasogastric tube, rectal tube

- Colonoscopic decompression
- Cecostomy (removal of cecum?)
- neostigmine (anticholinesterase)

Clinical Presentation:
- Represent any of a number of symptoms related to disordered movement of feces through the colon and/or anorectum

- May present if defecation occurs infrequently, if stools are too small or too hard, if defecation is painful, if defecation seems incomplete, or if excessive straining is required to pass stool.
Diseases of the Colon

List 8.
1. Colonic Neoplasia
2. Diverticular Disease
3. Ischemia Collitis
4. Irritable Bowel Syndrome
5. Microscopic Collitis
6. Acute Colonic Pseudoobstruction (Ogilvie's syndrome)
7. Constipation
8. Hirschsprung's Disease / Congenital Megacolon
Secondary Constipation

Can be of 3 forms:
- Diabetes, hypothyroid, inc.Ca++, dec. K+,

- MS, CVA, Parkinson, Hirschprung, neurofibromatosis

- PSS, amyloid


Impairment of colonic transit may occur throughout ALL regions of the colon (colonic inertia) or may be predominantly restricted to the DISTAL colon as is seen in Hirschsprung’s disease.

Impaired colonic transit can occur as a side effect of:
- drugs
- a primary motor disorder,
- in association with a large number of metabolic, endocrine, neurological, or myopathic diseases

Usually, First line of therapy is:
increasing dietary fiber
Hirschsprung's Disease/Congenital Megacolon.

- a result of the failure of neural crest cells (precursors of ganglion cells) to complete their caudal migration during normal colonic development.

- The aganglionic segment does not relax and causes a functional obstruction.

- The normal proximal bowel hypertrophies and eventually dilates.

- The rectosigmoid is involved in approximately 75-80% of the cases.

- The entire colon and various lengths of small bowel are aganglionic in 5-10% of cases.
Hirschsprung's Disease/Congenital Megacolon.

Delayed passage of meconium and abdominal distention are often the presenting symptoms in the newborn.

Chronic constipation, abdominal distention, volvulus, or perforation may be symptoms of the disease in a child.

Hirschsprung's disease in the adult is rare but must be considered in the evaluation of patients with chronic constipation dating back to childhood.