An 84-year-old woman comes to the office due to 2 months of bright red bleeding from the rectum. The patient also has intermittent crampy abdominal pain and a 6-kg (13.2-lb) unintentional weight loss. She reports no fevers, tenesmus, chest pain, palpitations, or vomiting. Medical history is significant for obesity and chronic kidney disease. Temperature is 37.6 C (99.7 F), blood pressure is 130/80 mm Hg, and pulse is 70/min. The patient appears cachectic. There is no palpable lymphadenopathy. Cardiac auscultation reveals normal rate and rhythm and no heart murmurs. Lung sounds are normal. The abdomen is nontender and nondistended. Which of the following is the most likely diagnosis?
This patient has clinical features suspicious for colon cancer. Adenocarcinoma of the colon often presents with fatigue, abdominal pain, and unexpected weight loss, but more specific symptoms are variable and can correlate to the site of the tumor:
Right-sided colon tumors: In the right colon, the lumen is wide, and stool is mostly liquid; obstructive symptoms are uncommon unless the tumor is very large and far advanced. Visible bleeding (ie, hematochezia) can occur but is atypical because blood is diluted by stool before it passes the anal verge. Therefore, adenocarcinoma in the cecum and ascending colon typically presents with occult bleeding and iron-deficiency anemia (Choice B).
Left-sided colon tumors: In the descending and sigmoid colon, tumors may obstruct the flow of stool, leading to crampy or colicky pain and/or a change in bowel habits (eg, constipation). Due to the proximity of these tumors to the anal verge, visible red/maroon hematochezia is common.
Rectal tumors: Bleeding is typically visible as hematochezia or frank red blood. Other symptoms include narrowed stools, tenesmus, and a sensation of a mass in the rectum.
(Choice A) Angiodysplasia is characterized by abnormal dilated and tortuous blood vessels in the intestines. It is most common at age >60 and can present with painless hematochezia or occult bleeding with iron deficiency anemia. This patient's crampy pain and unexpected weight loss are atypical for angiodysplasia.
(Choice C) Diverticular hemorrhage causes acute, self-limited hematochezia that generally lasts up to several days (not months). It is usually painless and does not cause weight loss.
(Choice D) Internal hemorrhoids present with anal pruritus and bright red rectal bleeding, typically on defecation. Crampy pain and weight loss would not be seen.
Educational objective:
Adenocarcinoma in the left side of the colon may obstruct the flow of stool, leading to altered bowel habits; visible hematochezia is common. In contrast, in the right side of the colon, obstructive symptoms are uncommon, and any associated bleeding can be diluted by stool and is less likely to be visible; therefore, right-sided colon cancer often presents with occult bleeding and iron-deficiency anemia.