Surgical Conditions of the Large Intestine – USMLE Step 2 CK

by / Friday, 25 June 2010 / Published in Internal Medicine, Surgery

Polyps

  • Are neoplastic, hamartomas, or inflammatory
  • Neoplastic polyps are MC adenomas

Adenomas can be classified as:

  • Tubular (these have the smallest potential for malignancy)
  • Tubulovillous
  • Villous (these have the highest risk of malignancy)

Signs and Symptoms:

  • MC presents with intermittent rectal bleeding

Diagnosis:

  • Colonoscopy or sigmoidoscopy

Treatment:

  • Polypectomy

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Diverticular Disease

General Information:

  • Up to half of the population has diverticula
  • The risk increases after 50yr of age
  • Only 1/10 people are symptomatic when diverticula are present
  • A TRUE diverticula is rare, and includes full bowel wall herniation
  • A FALSE diverticula is most common, and involves only a herniation of the mucosa
  • The MCC is a low-fiber diet which causes an increased intramural pressure (this is hypothesis)

Diverticulosis

  • This is the presence of multiple false diverticula

Signs and Symptoms:

  • Most people are asymptomatic, with diverticula found only on colonoscopy or other visual procedures
  • May have recurrent bouts of LLQ abdominal pain
  • Changes in bowel habits is common
  • Rarely, patient may present with lower GI hemorrhage

Diagnosis:

  • Colonoscopy
  • Barium enema can also be used for diagnosis

Treatment:

  • If patient is asymptomatic, the only therapy should be to increase fiber and decrease fat in the diet
  • If patient has GI hemorrhage, circulatory therapy is warranted (IV fluids, maintenance of hemodynamic stability)

Diverticulitis

  • Inflammation of the diverticula due to infection
  • There are many possible complications, such as abscess, extension into other tissues, or peritonitis

Signs and Symptoms:

  • LLQ pain
  • Constipation OR diarrhea
  • Bleeding
  • Fever
  • Anorexia

Diagnosis:

  • CT demonstrating edema of the large intestine
  • DO NOT perform a colonoscopy or barium enema in an acute case, this might aggravate the problem

Complications:

  • Perforation
  • Abscesses
  • Fistula formation
  • Obstructions

Treatment:

  • If there is an abscess, percutaneous drainage is required
  • Most patients are managed well with fluids and antibiotics
  • For perforation or obstruction, surgery is required

Obstruction of the Large Intestine

  • Most common site of colon obstruction is the sigmoid colon

Common causes include:

  • Adhesions
  • Adenocarcinoma
  • Volvulus
  • Fecal impaction

Signs and Symptoms:

  • Nausea/vomiting
  • Abdominal pain with cramps
  • Abdominal distention

Diagnosis:

  • XRAY – showing a distended proximal colon, air-fluid levels, and an absence of gas in the rectum

Treatment:

  • If there is severe pain, sepsis, free air, or signs of peritonitis there must be an urgent laparotomy
  • Laparotomy if cecal diameter is >12cm

Volvulus

  • Twisting and rotation of the large intestine
  • Can cause ischemia, gangrene, perforation
  • The MC site is the sigmoid colon
  • Occurs most commonly in older patients

Signs and Symptoms:

  • High-pitched bowel sounds
  • Distention
  • Tympany

Diagnosis:

  • XRAY – “kidney bean” appearance (ie. Dilated loops of bowel with loss of haustra)
  • Barium enema showing a “bird’s beak” appearance – points to the site of rotation of the bowel

Treatment:

  • Sigmoidoscopy or colonoscopy acts as diagnosis and treatment
  • If this doesn’t work, laparotomy is warranted

Cancer of the Colon

  • Colon cancer is the 2nd MCC of cancer deaths
  • Believed that a low-fiber, high-fat diet increases the risk
  • There are many genetic factors that contribute to colon cancer, such as Lynch syndrome and HNPCC

Lynch Syndrome:

  • LS 1 is an autosomal dominant predisposition to colon cancer that is usually right-sided
  • LS2 is the same as LS 1 with the addition of cancers outside the colon, such as in the endometrium, stomach, pancreas, small bowel, and ovaries

Screening:

  • Screening should start at 40yr in people with no risk factors
  • If a family member has had cancer of the colon, screening should start 10yr prior to when they were diagnosed (assuming this is less than 40yr)
  • Should have yearly stool occult tests
  • Colonoscopy every 10yr
  • And a sigmoidoscopy every 3-5yrs

Diagnosis:

  • Obtain preoperative CEA (allows you to follow the progression or recession of the disease)
  • Endoscopy + barium enema

Treatment:

  • Surgical resection + LN dissection
  • If disease is metastatic, add 5-FU to the post-operative regimen

Follow-up:

  • CEA levels every 3 months for 3 years
  • Perform a colonoscopy at 6 and 12 months, then yearly for 5 years
  • If a recurrence is suspected, a CT should be performed

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