The Duration of Chemically Demonstrable Blood in the Feces Following Ingestion of Whole Blood

Abstract

Summary 1.Studies were conducted on 38 normal male subjects to determine how rapidly the stool guaiac test reverts to negative after simulated upper gastrointestinal tract hemorrhage. Subjects ingested their own blood according to one of the following protocols: 120, 330, or 600 cc. at one time, or in amounts of 50 cc. per day over a 10 day period. 2.Ingestion of 120 cc. was followed by a return of the stool guaiac test to negative in less than 5 days in nine of ten subjects. The mean time interval was 3 days, 7 hours. 3.Of ten subjects ingesting 330 and ten 600 cc., the stool guaiac test returned to negative in less than 7 days in 18 of 20 instances. The respective mean time intervals were 5 days, 10 hours and 4 days, 16 hours. 4.Of eight subjects ingesting 50 cc. of blood per day for 10 days, all exhibited a negative guaiac test within 8 days following the last ration of blood ingested. The mean duration was 5 days, 7 hours. 5.The evidence indicates that a patient may suffer upper gastrointestinal hemorrhage of clinically significant degree and describe recently noted abnormal color of the feces, but the guaiac test may become negative over a 3 to 6 day period. This must be taken into consideration when evaluating a history suggestive of melena.