Which two patients with elevated alkaline phosphatase indicate pathology?

Elevated alkaline phosphatase levels can be indicative of various underlying conditions, particularly those involving the liver, bones, or bile ducts. In the case of the 68-year-old man with hematochezia, the presence of blood in his stool raises significant concern for potential gastrointestinal pathology, which could involve conditions such as liver disease or biliary obstruction. These conditions may lead to elevated alkaline phosphatase levels. Therefore, the combination of his age, symptomatic presentation, and the elevated enzyme suggests a more serious underlying issue that warrants further investigation.

In contrast, while the other options like the pregnant patient and the 56-year-old man with prostate cancer may also have elevated alkaline phosphatase due to more benign or expected physiological changes (e.g., normal increase during pregnancy or bone metastases in cancer), they do not indicate an immediate pathology in the same urgent way as seen in the case of the man with hematochezia. Similarly, an adolescent might have elevated alkaline phosphatase due to rapid bone growth, a normal physiological process. Thus, the patient with hematochezia stands out as most clearly pointing to potential pathology associated with elevated alkaline phosphatase.