An Osmosis USMLE® Step 2 CK-style clinically-focused practice question to test your medical knowledge. Identify the feature that would most significantly increase the risk for the underlying condition in a 46-year-old woman presenting with episodic lower abdominal discomfort, bloating, hematochezia, and anemia after a four-month history of symptoms.
A 46-year-old woman presents to the clinic with episodic lower abdominal discomfort, bloating, and hematochezia for four months. She has not had diarrhea, and the amount of stool she passes with each bowel movement has been smaller than usual. She reports weight loss of 4 kg (8.8 lbs) over the past four months. Her appetite has remained unchanged, but she feels “full” earlier than usual after starting meals. Past medical history includes gastroesophageal reflux disease (GERD) managed with omeprazole and irritable bowel syndrome diagnosed in her 30s. Family history is positive for endometrial cancer in her mother at the age of 32. Her diet is significant for high consumption of dairy products. Body mass index (BMI) is 20 kg/m2. Temperature is 36.9°C (98.4°F), blood pressure is 124/80 mm Hg, pulse is 76/min, respiratory rate is 14/min, and oxygen saturation is 99% on room air. Abdominal examination shows mild distention with hyperactive bowel sounds and mild tenderness in the left lower quadrant without palpable masses. Digital rectal examination (DRE) reveals stool with blood in it and no evidence of hemorrhoids or fissures. Laboratory results are significant for a hemoglobin of 10.3 g/dL and an MCV of 72 fl.
Which of the following features would most significantly increase this patient’s risk for the most likely underlying condition?
A. Family history of endometrial cancer at an early age
B. History of irritable bowel syndrome (IBS)
C. Body mass index (BMI) <21 kg/m2
D. Chronic use of proton pump inhibitors (PPI)
E. Diet high in dairy
Scroll down for the correct answer!
The correct answer to today’s USMLE® Step 1 Question is…
A. Family history of endometrial cancer at an early age
Correct: See Main Explanation.
Incorrect Answer Explanations
B. History of irritable bowel syndrome (IBS)
Incorrect: Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder. While its symptoms can mimic those seen in colorectal cancer, IBS itself does not increase the risk of developing colorectal cancer.
C. Body mass index (BMI) <21 kg/m2
Incorrect: A low BMI can be seen in colorectal cancer due to cancer-related weight loss. However, having a low BMI is not a risk factor for developing CRC. Conversely, obesity is a recognized risk factor for colorectal cancer.
D. Chronic use of proton pump inhibitors (PPI)
Incorrect: Chronic use of PPIs like omeprazole has been associated with various gastrointestinal problems, including Clostridium difficile infection, atrophic gastritis, malabsorption of minerals and vitamins, and an increased risk of developing gastric polyps. It has not been directly correlated with an increased risk of colorectal cancer.
E. Diet high in dairy
Incorrect: High dairy consumption has been suggested to have a protective effect against colorectal cancer due to its calcium content. Conversely, a diet high in red and processed meats is recognized as a risk factor for colorectal cancer.
Main Explanation
This patient presents with episodic lower abdominal discomfort, bloating, early satiety, weight loss, change in stool caliber, hematochezia, and microcytic anemia. This clinical presentation is highly suggestive of colorectal cancer (CRC). Multiple risk factors can contribute to the development of CRC. In this patient, a family history of endometrial cancer in a first-degree relative at an early age raises the possibility of Lynch syndrome (hereditary nonpolyposis colorectal cancer or HNPCC).
Lynch syndrome is an autosomal dominant condition characterized by a high risk of developing CRC, endometrial cancer, and ovarian cancer. Defective DNA mismatch repair genes, predominantly MLH1, MSH2, MSH6, and PMS2, lead to a rapid accumulation of errors in the DNA, especially in areas known as microsatellites. These genetic errors accelerate the progression from adenoma to carcinoma in the colon.
Signs and symptoms associated with CRC can vary based on the location of the tumor. Right-sided (proximal) colon tumors, encompassing the cecum to the right half of the transverse colon, lead to occult blood loss and iron-deficiency anemia. In contrast, left-sided (distal) tumors involving the left transverse colon to the sigmoid frequently cause changes in bowel habits, colicky abdominal pain, and sometimes blood-streaked stool. Tumors located in the rectum may produce symptoms of tenesmus, rectal bleeding, and stool caliber changes.
Major Takeaway
In patients presenting with clinical signs and symptoms suggestive of colorectal cancer, the finding of early-onset endometrial cancer in a first-degree relative, adenomatous polyps, or early-onset colon cancer in first-degree relatives suggests hereditary colon cancer syndrome.
Want to learn more about this topic?
Watch the Osmosis video: Colorectal cancer
References
- Benson AB, Venook AP, Al-Hawary MM, et al. Colon Cancer, Version 2.2021, NCCN Clinical Practice Guidelines in Oncology. J Natl Compr Canc Netw. 2021;19(3):329-359. Published 2021 Mar 2. doi:10.6004/jnccn.2021.0012
- Benson AB, Venook AP, Al-Hawary MM, et al. Rectal Cancer, Version 2.2022, NCCN Clinical Practice Guidelines in Oncology. J Natl Compr Canc Netw. 2022;20(10):1139-1167. doi:10.6004/jnccn.2022.0051
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