患者,男,62岁。间断便血2个月,暗红色,排便次数增多,每天3〜4次,伴下腹痛,消瘦。查体:腹部平坦,柔软,左下腹轻压痛。为明确出血病因,应首选的检查是
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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