USMLE USMLE Certifications USMLE-STEP-3 Questions & Answers

• Question 531:

  A 56-year-old man comes to the hospital. For the past 5 days he has had colicky abdominal pain, vomiting, abdominal distention, and constipation. The most appropriate measure, after IV hydration and nasogastric decompression, in the initial management of this patient is which of the following?

  A. upper GI endoscopy

  B. supine and erect x-rays of the abdomen

  C. abdominal sonography

  D. antiemetic agents

  E. promotility drugs

  Correct Answer: B Section: (none)

  Explanation:

  This patient presents with classic symptoms of a bowel obstruction. The diagnosis is often made by a thorough history and physical examination. Following the initial evaluation, an acute abdominal x-ray series should be obtained, which includes supine and erect views of the abdomen. The diagnosis is confirmed with the presence of dilated loops of bowel with the presence of air-fluid levels. These plain films may also suggest the location of the obstruction (small vs. large intestine). Abdominal ultrasonography has limited role in the diagnosis or management of intestinal obstruction. Serum electrolyte determination helps in identifying the electrolyte disturbances that have taken place. Fluid loss needs to be corrected with rehydration, and nasogastric suction helps in decreasing abdominal distention. Upper GI endoscopy would increase distention, and is contraindicated. Antiemetics should not be given until a definitive diagnosis is made, and then only if indicated; promotility agents have little to no role in the management of a patient with bowel obstruction, and may even be contraindicated.

  An annular constricting lesion with overhanging edges is typical of annular carcinoma of the colon. Mechanical small bowel obstruction results in multiple air-fluid levels in distended small bowel loops. Intussusception produces a "corkscrew" appearance on barium enema, and sigmoid volvulus produces a "bird's beak" appearance. In diverticulitis, extravasation of barium outside the lumen of the colon typically is seen.

• Question 532:

  Biopsy of a 4-cm sessile polyp of the cecum during a routine screening colonoscopy reveals it to be a villous adenoma with atypia. Attempt at piecemeal snare polypectomy through the colonoscope is unsuccessful. Which of the following is the most appropriate management?

  A. right hemicolectomy

  B. colonoscopy with electrocoagulation of the tumor

  C. colonoscopy with repeat biopsy in 6 months

  D. open surgery with colotomy and excision of polyp

  E. external beam radiation

  Correct Answer: A Section: (none)

  Explanation: Villous adenoma is a premalignant condition. The incidence of carcinoma in a polyp depends on the histology type and size of the polyp. Tubular adenomas are the most common type of polyps (6080%), but are the least likely to harbor carcinoma (less than 5% if smaller than 1 cm in diameter). Villous adenomas are the least common type, but overall the most likely to contain malignant foci (50% if greater than 2 cm in diameter). In this patient, a formal right hemicolectomy is indicated due to the high probability of finding cancer in the specimen. A lesser operation, such as open or laparoscopic polypectomy, would then require a second operative procedure if cancer is present. Colonoscopic fulguration of such a large lesion carries a high risk for perforation and would not allow histologic examination. Observation with repeat colonoscopy in 1 year is also inappropriate.

• Question 533:

  A27-year-old female whose father had a colon resection for adenocarcinoma undergoes her first colonoscopy. Over 100 small polyps are seen distributed mainly in her sigmoid and rectum. Multiple polyps are removed and histologic review reveals tubular adenomas with no evidence of atypia or dysplasia. The most appropriate next step in her management is which of the following?

  A. total proctocolectomy with ileoanal J pouch reconstruction

  B. surveillance colonoscopy in 5 years

  C. surveillance colonoscopy every 2 years until all polyps are removed

  D. flexible sigmoidoscopy with representative biopsy every 6 months for 2 years, then yearly for 3 years, then every 35 years

  E. abdominal perineal resection with sigmoid resection and end colostomy

  Correct Answer: A Section: (none)

  Explanation:

  The patient described has familial adenomatous polyposis (FAP). FAP is a rare autosomal dominant inherited form of colorectal cancer that results from a germline mutation in the APC gene. The disease is characterized by the presence of >100 polyps in the large intestine, as well as extraintestinal manifestations such as epidermoid cysts, desmoid tumors, and osteomas. All patients with FAP will develop colorectal cancer if left untreated. The average age of diagnosis is 29 and the average age of the development of cancer is 39. Once diagnosed, the most definitive treatment requires complete removal of the entire colon and rectum in a timely fashion. Surveillance colonoscopy is not protective against the development of cancer regardless of the frequency. The surgical procedure of choice is a proctocolectomy with permanent ileostomy or creation of an ileoanal anastomosis with ileal reservoir such as a J-pouch. Abdominal perineal resection with sigmoid colectomy leaves a significant portion of colon in situ with subsequent risk of developing colon cancer.

• Question 534:

  A mobile mass is found on rectal examination in a 77-year-old male with complaints of blood in his stool. On workup, he is found to have a stage I (Dukes' A), well-differentiated adenocarcinoma. The most appropriate intervention is which of the following?

  A. transanal excision

  B. abdominal perineal resection

  C. low anterior resection

  D. placement of endorectal wallstent

  E. neoadjuvant chemotherapy followed by transanal resection

  Correct Answer: A Section: (none)

  Explanation:

  Local treatment of rectal cancer is the treatment of choice in selected individuals with low-lying rectal cancers. The lesion must be mobile, nonulcerated, within 10 cm of the anal verge, less than 3 cm in diameter, less that onefourth the circumference of the rectal wall, and stage T1 or T2 on endorectal ultrasound. Transanal excision is the most straightforward technique of local treatment. It entails full thickness excision of the lesion into the perirectal fat with adequate margins. For early lesions into the submucosa only (T1), no adjuvant therapy is required unless poor prognostic features are present on final pathology (poorly differentiated or lymphatic/vascular invasion). If the lesion penetrates the muscular wall (T2), adjuvant radiation therapy with or without chemotherapy is indicated following surgical removal. Overall, the disease free survival rate is 80%.

• Question 535:

  During initial exploration in a patient scheduled to undergo a right hemicolectomy for colon cancer, a deep 4-cm liver mass is seen in the right lobe of the liver. The left lobe appears to be normal. Intraoperative biopsy of the lesion is positive for metastatic colon cancer. The best management of this patient includes which of the following?

  A. Immediately close the patient and refer for chemotherapy only.

  B. Perform right hemicolectomy only.

  C. Perform right hemicolectomy and right hepatic lobectomy.

  D. Perform right hemicolectomy and wide excision of the liver lesion.

  E. Perform liver resection only.

  Correct Answer: B Section: (none)

  Explanation:

  Colon cancer is the most common metastatic lesion of the GI tract to the liver. Approximately 50% of patients with colorectal cancer will have liver involvement. Generally, synchronous liver metastasis should not be resected during the initial operation for the primary tumor. Only a solitary, small, peripherally located lesion in a hemodynamically stable patient would be an acceptable indication for a wedge resection. Otherwise, the planned colon resection should be completed. A second procedure can be planned after a thorough metastatic evaluation is completed using various diagnostic modalities such as intraoperative ultrasound, CT, MRI, and/or PET scan. A delay of weeks to months between surgeries has not been shown to have a negative impact on long-term survival. The delay may help select patients who may benefit the most and exclude those who develop widespread metastatic disease during the interval. Chemotherapy only is inappropriate because, even in the presence of metastatic disease, the primary colon carcinoma should be resected to prevent later complications such as bleeding, perforation, or obstruction. The 5-year survival rate following resection of isolated hepatic metastasis from colorectal cancer now exceeds 50%.

• Question 536:

  A 46-year-old female presents to your office with rectal bleeding, itching, and irritation. On examination, a 3-cm ulcerating lesion is seen in the anal canal. Biopsy of the lesion reveals squamous cell carcinoma (SCC). Which of the following is the most appropriate treatment?

  A. chemotherapy and pelvic radiation protocol

  B. low anterior resection

  C. abdominal perineal resection

  D. wide local excision of the lesion

  E. wide local excision of the lesion and bilateral inguinal lymph node dissection

  Correct Answer: A Section: (none)

  Explanation:

  Anal carcinoma can arise from several epithelial cell types in the anal canal including squamous, basaloid, cloacogenic, and mucoepidermoid. For early, superficial lesions less than 2 cm, an attempt can be made to excise the lesion completely with negative margins. Otherwise, the standard of care is a multimodality chemoradiation protocol, which classically includes itomycin C and 5-FU in combination with external beam radiation therapy to the tumor and the pelvic and inguinal lymph nodes. The long-term survival rate after chemoradiation alone compares favorably with radical surgery. Abdominal perineal resection is reserved for persistent or recurrent disease. Low anterior resection refers to resection of the upper and middle rectum and plays no role in the treatment of anal cancer. Inguinal lymph node dissection is not indicated. Any clinically suspicious node should be biopsied, and if positive, treated with radiation. Thus, even a small anal cancer with a positive lymph node should be treated with chemotherapy instead of surgery.

• Question 537:

  A 26-year-old male presents with abdominal pain and bloody diarrhea. On examination, he has a low-grade fever and mildly tender abdomen. Lower endoscopy is performed which reveals edematous mucosa with contiguous involvement from the rectum to the left colon. Random biopsies are performed which reveals acute and chronic inflammation of the mucosa and submucosa with multiple crypt abscesses. There are no granulomas seen.

  What can you tell this patient about his condition?

  A. He will likely require an operation.

  B. There is no known cure.

  C. The use of intravenous corticosteroids is contraindicated.

  D. Perianal fistulas are characteristic.

  E. There is a substantially increased longterm risk of developing colon cancer.

  Correct Answer: E Section: (none)

  Explanation:

  Ulcerative colitis is a diffuse inflammatory disease of the colon and rectum with unknown etiology. Unlike Crohn's disease, surgical removal of the entire colon and rectum provides a complete cure. Nonetheless, many patients are treated successfully with medical therapy including corticosteroids and can avoid the potential complications of surgery and lifelong ileostomy. Ulcerative colitis usually presents as bloody diarrhea, fever, and abdominal pain. The disease process begins in the rectum, advances proximally in a contiguous fashion, and affects the superficial layers of the colon wall. Crohn's disease is located anywhere from the mouth to anus, has skip lesions, and is transmural in nature. Histologically, superficial inflammation with crypt abscesses is most indicative of ulcerative colitis, whereas deeper involvement with granulomas and fissures are most characteristic of Crohn's disease. Both diseases may present with extraintestinal manifestations such as arthritis, skin lesions, and hepatic dysfunction, but perianal disease with fistula formation is characteristic of Crohn's disease. Patients with ulcerative colitis have a 1020% risk of developing colon cancer within 20 years after diagnosis. The incidence is also increased in those with Crohn's disease but to a lesser extent. Surveillance colonoscopy is essential in patients with long-standing disease

• Question 538:

  The most common cause of surgery in a patient with Crohn's disease is which of the following?

  A. carcinoma

  B. fistula

  C. bleeding

  D. obstruction

  E. abscess

  Correct Answer: D Section: (none)

  Explanation:

  Crohn's disease is a chronic inflammatory disease of the GI tract of unknown etiology. Both medical and surgical treatments are palliative in nature--there is no known "cure." pproximately 70% of patients with Crohn's disease will require an operation during their lifetime. The most common indication for surgery is recurrent bowel obstruction, followed by perforation with abscess and fistula formation.

• Question 539:

  Which of the following is true regarding anorectal abscess and fistula?

  A. The most common cause is a subepithelial extension of a genital infection.

  B. Conservative management should always be considered for fistula-in-ano as many heal spontaneously.

  C. Most acute anorectal abscesses require a course of antibiotics.

  D. The treatment protocol is not altered for patients with valvular heart disease.

  E. Anal fistula is classified as intersphincteric, transsphincteric, suprasphincteric, or extrasphincteric.

  Correct Answer: E Section: (none)

  Explanation:

  The most common cause of anorectal fistula and abscess is infection of the anal glands, which empty into the anal canal at the level of the dentate line. Classification of anal fistula is based upon the relationship of the epithelialized tract to the anal sphincter muscle and can be intersphincteric (most common), transsphincteric, suprasphincteric, and extrasphincteric (least common). A symptomatic fistula is an indication for surgery because it rarely heals spontaneously. Despite popular teaching, there is little use for antibiotics in the primary treatment of anal abscess. As a rule, surgical drainage is required and antibiotics are only indicated if cellulitis is present. However, those patients who are immunocompromised, have valvular heart disease, or poorly controlled diabetes should always be considered for antibiotics.

• Question 540:

  A 48-year-old male truck driver presents for evaluation of bright red rectal bleeding with bowel movements. He also has the feeling that something protrudes through his anus while he strains to move his bowels but that it withdraws into the bowel when he relaxes. He has no abdominal pain, weight loss, or other symptoms. A colonoscopy reveals no polyps or tumors but does note internal hemorrhoids. Which of the following is the best initial treatment for him?

  A. high fiber diet, frequent sitz baths, and topical steroid ointment

  B. rubber band ligation

  C. sclerotherapy injection

  D. infrared coagulation

  E. surgical hemorrhoidectomy

  Correct Answer: A Section: (none)

  Explanation:

  Internal hemorrhoids are highly vascularized submucosal cushions located in the anal canal. They are classified as first degree if no prolapse is present; second degree if prolapse occurs with spontaneous reduction; third degree if they require manual reduction; and fourth degree if they are irreducible. Treatment is based on the symptoms and degree of prolapse. Nearly all patients with first-and seconddegree hemorrhoids should initially be placed on a trial of conservative measures including a bowel management program with high fiber diet to avoid straining and constipation, frequent warm baths, and an anti-inflammatory topical cream. If symptoms continue, both rubber band ligation (a small rubber band is placed at the neck of the hemorrhoid resulting in eventual death and detachment of tissue) and infrared coagulation (controlled burn of the vessels at the neck of the hemorrhoid) are good alternatives to surgical therapy. For refractory first-and second-degree hemorrhoids, most third-degree and all fourth-degree hemorrhoids, surgical