Often defecate is black, a bit constipation, how to do

The patient often has black stool and constipation, which may be caused by visceral hemorrhage, liver, gallbladder or gastrointestinal diseases. He should go to the hospital for stool occult blood test, blood routine test, urine routine test, abdominal organ color Doppler ultrasound, etc. If abnormal, he should be treated as soon as possible.