Final answer:
The absence of blood in stool would suggest Crohn's disease over ulcerative colitis, as ulcerative colitis typically presents with bloody diarrhea and Crohn's may affect any part of the GI tract, including areas less likely to cause bloody stools.
Step-by-step explanation:
A patient's health history suggesting inflammatory bowel disease could be due to either Crohn's disease or ulcerative colitis. Among the listed options to distinguish between the two, the absence of blood in stool is more suggestive of Crohn's disease rather than ulcerative colitis. The reason is that Crohn's disease can affect any part of the GI tract, often the ileum, and may not always cause bloody stools, whereas ulcerative colitis primarily affects the colon and rectum and typically presents with bloody diarrhea. Involvement of the rectal mucosa is more common in ulcerative colitis than in Crohn's disease, which often spares the rectum.
Both conditions can exhibit a pattern of exacerbations and remissions and can cause severe diarrhea. Environmental factors such as tobacco use, and a diet high in animal proteins, are known risk factors. Unlike ulcerative colitis, Crohn's disease's symptoms and complications can extend beyond the GI tract, affecting other body tissues.