MKSAP Quiz: A 2-month history of diarrhea, cramps

This month's quiz asks readers to determine the most likely diagnosis for a 26-year-old woman who presents with a history of diarrhea characterized by two to three semibloody stools per day associated with cramping lower abdominal pain.


A 26-year-old woman is evaluated for a 2-month history of diarrhea characterized by two to three semibloody stools per day associated with cramping lower abdominal pain. She reports no fever, chills, nausea, vomiting, or weight loss. She has not traveled internationally. She takes no medication.

On physical examination, vital signs are normal. Abdominal examination shows left and right lower abdominal tenderness to palpation. Rectal examination is remarkable for bright red blood.

Stool testing for enteric pathogens is negative.

Results of colonoscopy show inflamed mucosa characterized by granularity, erythema, friability, and loss of vascular pattern that starts at the anorectal verge and extends proximally in a continuous and symmetric fashion to the splenic flexure where there is an abrupt transition from affected to normal mucosa. The terminal ileum is normal. Biopsy results for the inflamed mucosa reveal crypt abscesses along with distorted and branching colonic crypts.

Which of the following is the most likely diagnosis?

A. Chronic Entamoeba histolytica infection
B. Crohn colitis
C. Cytomegalovirus infection
D. Ulcerative colitis

Reveal the Answer

MKSAP Answer and Critique

The correct answer is D. Ulcerative colitis. This content is available to MKSAP 18 subscribers as Question 54 in the Gastroenterology and Hepatology section. More information about MKSAP is available online.

Ulcerative colitis is the most likely diagnosis in this patient. The differential diagnosis of chronic bloody diarrhea includes inflammatory bowel disease (ulcerative colitis or Crohn colitis) and chronic ulcerating infections such as cytomegalovirus or Entamoeba histolytica. This patient's stool studies for enteric pathogens are negative, making Crohn colitis or ulcerative colitis the most likely cause of her symptoms. The mucosal biopsy results showing crypt architectural distortion confirm a chronic colitis such as ulcerative colitis or Crohn disease. The endoscopic description of inflammation beginning at the anorectal verge and extending proximally in a continuous fashion with transition to normal mucosa at splenic flexure is consistent with left-sided ulcerative colitis. Crohn disease characteristically has a patchy progression pattern resulting in “skip lesions” and may spare the rectum, making Crohn colitis less likely in this case.

Entamoeba histolytica causes amoebic dysentery. In the United States, amebiasis is usually diagnosed in immigrants or travelers returning from endemic areas, or in institutional settings. Although most infected persons are asymptomatic, others may develop bloody or watery diarrhea, abdominal pain, and fever. Rarely, a chronic syndrome of diarrhea, weight loss, and abdominal pain can mimic inflammatory bowel disease. Stool microscopy for ova and parasites can aid in the diagnosis by detecting the protozoa, but stool antigen testing is more sensitive. This patient's negative travel history and findings on colonoscopy and biopsy are not consistent with amebiasis.

Cytomegalovirus infection is an uncommon infection in immunocompetent patients but can occur and cause significant symptoms. The most common presenting symptoms are diarrhea, fever, and abdominal pain; half of patients have grossly bloody stools. The most common finding on endoscopy is well-demarcated ulcerations. On biopsy, histological findings include multinucleated giants cells with eosinophilic inclusions. The rarity of this condition coupled with the patient's colonoscopy and biopsy findings make cytomegalovirus infection an unlikely diagnosis.

Key Point

  • Chronic bloody diarrhea and abdominal discomfort are typical presenting symptoms of inflammatory bowel disease; endoscopic findings help distinguish ulcerative colitis from Crohn disease.