The stool color would be in varying shades of brown under normal condition. It is the bilirubin and decomposition process which gives the color to the stool. Several factors can cause change in stool color. Presence of blood in your stool is not a matter of concern if it is occasional and limited. It can be due to certain foods you have taken last night or due to hemorrhoids. However if there is persistent change in stool color you need to seek medical help.
Blood in the small intestine would be bright red in color since the iron molecules of the blood is not yet oxidized. As the blood travels through the intestine it undergoes oxidation process taking light red color or maroon color which is reflected in the stool. In medical terms bloody stool is described as melena or hematochezia. Any blood leakage with stool need not always be due to bleeding of internal organs. It is possible to have black tarry stool due to drinks or food items and even certain drugs.
Melena :
Melena can be described as leakage of blood in the upper portion of the abdomen like that of esophagus or stomach. Several kinds of gastric juices and enzymes act upon the fresh red blood changing its color to dark brown or black. This blood while passing through the rectum produces black tarry stool. Melena can also be caused due to blood leak in the intestine or even inside the colon.
Hematochezia :
Bleeding in the lower portion of the abdomen like large intestine or rectum/anus causes hematochezia. Often rectal bleeding due to hemorrhoids or fistulas can cause hematochezia. Blood can be seen as red streaks staining the normal brownish stool changing it into black stool. Blood mixes with the stool giving it a coating of blood color. If the person has diarrhea with bleeding rectum the stool color may change to pinkish red.
Rectal Bleeding :
Blood leakage from the rectum can originate from the colon or the rectum. Often anal fistulas or hemorrhoids can cause bloody stool. Even small tears in the anus region while pushing the hard stool can cause blood. Clots of blood can be seen coming from the rectum. Blood color is a clear indication of the origin point. Blood will be of bright red color if the leakage is from closer areas of rectum like colon or anus. The color of blood would change to dark red or even maroon if the blood leak is from upper portion of the gut like esophagus or stomach.
Blood leaking from the transverse colon should also travel several feet to reach the rectum and hence would change its color causing black tarry stool. Bacteria present in the gut would act on the blood and break down the hematin molecules producing black color. In rare cases volumes of blood from the small intestine or stomach ulcers can cause bright red colored stool. Red blood colored stool clearly suggest that it has to travel rapidly through the colon leaving no time for the bacteria to act on it.
Melena Causes :
Causes of melena include anal fissure, hemorrhoids and anal fistulas and anal tears. It can occur due to internal complications like ulcerative colitis, anal cancer, colon cancer, stomach cancer and Crohn’s disease.
Diagnosis :
Based on the symptoms and consistency of bleeding in stool your doctor would first collect the medical history. He would complete the physical exam paying closer attention to the abdomen checking for any inflammation or tumor. He can order for lab tests like blood analysis, stool and urine culture. He may perform colonoscopy to get clear picture of the colon. If needed, CT scan of the abdomen would be done.
Melena Treatment :
Treatment for melena would be decided after figuring out the root cause through the diagnostic procedures. Treatment includes anti-inflammatory medications combined with diet modification. Constipation and hemorrhoids can be drastically reduced by taking fiber rich diet and drinking plenty of fluids. Ulcers can be infectious and hence treated with antibiotics. OTC drugs like omeprazole and lansoprazole can block the acid production and facilitate healing. Stick on to health diet and control stress for getting ulcers cured quickly. In case of tumor in the gut surgery can be done to remove the tumor depending on its size and location.