GI, Liver, Biliary tract - Dr Osby 4/3/25

A 17-year-old boy has a history of 10 lb weight loss, diarrhea, moderate anemia, and a vesicular rash on the extensor surfaces of the elbows and knees. A biopsy specimen from the small intestine shows villous atrophy, intraepithelial lymphocytosis and lamina propria inflammation. Which of the following is the most likely diagnosis?

• Celiac disease

• Ulcerative colitis

• Antibiotic associated diarrhea

• Hemolytic uremic syndrome

Answer explanation

The histologic description meets the criteria for celiac disease.

Ulcerative colitis does not involve the small bowel.

C. difficile causes pseudomembranous colitis.

Hemolytic uremic syndrome does not show blunting of the villi of the small intestine; the toxin causes bloody diarrhea with neutrophils rather than lymphocytes and mimics acute inflammatory bowel disease.

An 16-year-old girl comes to the physician to request screening for colon cancer. Her brother and sister died of colon cancer at the ages of 20 and 18 years, respectively. Physical examination shows no abnormalities. Colonoscopy shows approximately hundreds of raised polypoid lesions throughout the colon. The pathologic process in this patient is most likely initiated by a mutation in which gene?

• BRCA1

• APC

• KRAS

• TP53

Answer explanation

This patient most likely has Familial adenomatous polyposis (FAP) an autosomal dominant disorder which develops numerous colorectal adenomas as teenagers. It is caused by a somatic mutation of the adenomatous polyposis coli, or APC gene which is a key negative regulator of the Wnt signaling pathway. Approximately 75% of cases are inherited, while the remainder appear to be caused by de novo mutations. At least 100 polyps are necessary for the diagnosis of classic FAP but thousands may be present. Except for their numbers, FAP- associated polyps are morphologically indistinguishable from sporadic adenomas. Colorectal adenocarcinoma develops in 100% of untreated FAP patients often before age 30 and nearly always before age 50. As a result, prophylactic colectomy is the standard of care.

A 25-year-old man has a 10-year history of intermittent fevers, severe abdominal pain, and diarrhea. A section of bowel resected after a recent severe episode shows marked inflammation with thickening of the bowel wall and stricture. Which of the following is the most likely diagnosis?

• Ulcerative colitis

• Pseudomembranous colitis

• Whipples diease

• Chrohn's disease

Answer explanation

The gross description fits best with Crohn's disease which would have intramural involvement. Ulcerative colitis should be limited to the mucosa and should not show a stricture. Pseudomembranous colitis would show sloughing of the mucosa. Whipples disease would not show intramural involvement.

A 62-year-old man comes to the physician because of a 12-year history of heartburn, which is worse at night. He has had H. pylori treatments multiple times. Upper endoscopy shows esophageal erosions. Tissue obtained on biopsy of the lower esophagus shows intestinal metaplasia. Which of the following is he at risk for?

• Adenocarcinoma

• Squamous cell carcinoma

• Adenoma

• Carcinoid tumor

Answer explanation

Adenocarcinoma is a complication/risk factor for Barrett's esophagus. Squamous cell carcinoma of the esophagus is possible, but due to the intestinal metaplasia, the patient will most likely have a higher chance to develop adenocarcinoma. Adenomas and carcinoid tumors are not a risk factor of Barrett's esophagus.

An asymptomatic 62-year-old man has a positive Fecal immunochemical test (FIT). The surgical specimen shows a well circumscribed pedunculated mass. Which of the following is the most likely diagnosis?

• Tubular adenoma

• Adenocarcinoma

• Ulcer

• Pseudocyst

Answer explanation

A well circumscribed pedunculated mass is most likely to be an adenoma. Adenocarcinoma would be invasive rather than well circumscribed. An ulcer would not be pedunculated but would look like a crater. Pseudocysts are more likely to occur in the pancreas and would not be pedunculated.

A 56-year-old woman comes to the physician because of severe heartburn for the past 2 weeks. A representative Steiner silver-stained gastric biopsy (400x) shows curved rods. The abnormality shown is most commonly associated with which of the following diseases?

• peptic ulcer disease

• reflux esophagitis

• Barrett's esophagus

• Acute gastritis

Answer explanation

A silver stain showing curved rods fits best with H. pylori and is consistent with peptic ulcer disease. Reflux esophagitis (GERD) is due to transient lower esophageal sphincter relaxation. Barrett's is a complication of GERD characterized by intestinal metaplasia. Acute gastritis is due to alcohol consumption, chemicals, NSAIDS/medications, radiation therapy and chemotherapy.