Hematochezia vs. Melena - An Insight

Introduction

Hematochezia and melena are acute gastrointestinal (GI) bleeding symptoms. Gastrointestinal bleeding is a medical emergency that requires immediate evaluation and treatment. The main treatment goal of GI bleeding is to stop the bleeding and restore the blood volume levels to avoid hypovolemia (not enough blood to circulate in the body). If GI bleeding is left untreated, hypovolemia can lead to hypovolemic shock. Hypovolemic shock occurs when insufficient blood volume makes it difficult for the heart to pump enough blood to the body. When enough blood does not reach the organs, the organs start shutting down, leading to organ failure. So, hypovolemic shock can cause multi-organ failure and can lead to death.

What Is Hematochezia?

Hematochezia is fresh red blood in feces that arises from the colon. Blood can come out of the anus either separately or mixed with feces.

What Is Melena?

Melena refers to black-colored feces. They usually arise from the upper part of the gastrointestinal tract.

What Causes Hematochezia and Melena?

Hematochezia - Hematochezia usually starts from the colon in the lower gastrointestinal tract. Several factors can cause lower gastrointestinal tract bleeding. Some of them include:

• An inflammatory bowel disease is a group of conditions that cause pain and swelling to the intestines.

• Internal hemorrhoids are swollen veins that form inside the rectum.

• Ischemic colitis is inflammation of the large intestine.

• Diverticulitis is the formation of an infected pouch in the colon area of the large intestine.

• Colon polyps are clumps of cells that form in the colon lining. A neoplastic colon polyp, when left untreated, has the chance of developing into cancer.

• Anal fissures are tears that happen in the lining of the anus.

• Benign Tumors.

• Colon Cancer.

Hematochezia in children is caused due to Inflammatory bowel disease, the presence of any juvenile polyps, or Meckel's diverticulum (congenital abnormality of the small intestine).

Melena - Melena usually begins from the upper gastrointestinal tract. Some factors that cause upper gastrointestinal bleeding include:

• Gastritis is inflammation of the stomach lining.

• Peptic ulcers are sores or ulcers that form in the stomach lining or the upper portion of small intestines.

• Varices are swollen veins forming in the stomach lining and esophagus.

• Mallory-Weiss Syndrome occurs due to a laceration or tear of the mucous membrane at the gastroesophageal junction (esophagus and stomach meet).

• Stomach Cancer.

• Melena in newborns is due to the swallowing of blood during delivery.

What Are the Symptoms of Hematochezia and Melena?

Hematochezia - Hematochezia occurs due to bleeding from the colon. Since the colon is situated very close to the anus, blood from the colon only travels a small distance to leave the anus. Because of this, it will be in a fresh red color. The blood can either mix with the stool or come out separately. Some other symptoms associated with hematochezia include:

• Diarrhea.

• Changes in bowel habits.

• Fever.

• Abdominal pain.

• Weight loss.

Melena - Melena causes black-colored feces, which are easily distinguished from the bright-colored feces caused by hematochezia. In melena, the blood travels from the upper GI tract, and by the time it reaches the anus, it undergoes deoxygenation, which removes the red color and turns it into a darker color. Patients with melena also tend to experience blood in the vomit (hematemesis). Other symptoms seen in melena include

• Abdominal pain.

• Pain during swallowing.

• Indigestion.

How Are Hematochezia and Melena Diagnosed?

The healthcare provider can differentiate hematochezia from melena by the differences seen in the feces. Then, the doctor will do additional tests to confirm the diagnosis.

Hematochezia - The tests done to identify the causes of hematochezia include:

• Colonoscopy - In the colonoscopy procedure, the doctor inserts a narrow tube containing a camera into the rectum. This device gives images of the lower GI tract, including the colon area. The doctor can recognize the origin of the bleeding with the help of images obtained. The doctor might also retrieve tissue samples during the procedure if additional testing is required.

• Endoscopy - In the endoscopy procedure, the doctor inserts a tiny tube containing a camera through the patient's mouth that produces pictures of the GI tract.

• Angiography - This procedure involves the injection of a die material into the vein to make the blood vessels visible on X-rays or Computed Tomography (CT) scans.

• Radionuclide Scanning - In this procedure, the doctor checks blood flow through the camera while the veins are injected with radioactive material.

• Barium X-Ray - A barium contrast material is inserted into the rectum. This contrast material shows the GI tract in the X-ray.

• Laparotomy - Laparotomy is a surgical intervention technique where the bleeding source is, identified by opening the abdomen.

Melena - Healthcare providers use similar tests of hematochezia to identify melena. A few other tests used to identify the cause of melena include

• Esophagogastroduodenoscopy (EGD) - In this procedure, a small tube containing light and a camera will be inserted through the mouth to visualize the stomach, esophageal and duodenal region. By this method, the health care provider can identify the bleeding source in the upper gastrointestinal tract.

• Breath, Blood, or Stool Test - A blood sample, breath test, or stool sample is taken to check for signs of infection usually caused by Helicobacter pylori (a bacterium).

How Are Hematochezia and Melena Treated?

Even though hematochezia and melena occur due to different reasons, their treatment options are usually the same. The main step includes stopping the bleeding. Depending on the bleeding source, the healthcare provider might use one or more treatment options. Some of the treatment options include:

1. Endoscopic clips are used to close the source of bleeding, which can either be a blood vessel or a tissue in the gastrointestinal tract.

2. Using an endoscopic thermal probe, the tissue or blood vessel causing the bleeding is burned to stop the bleeding.

3. In the endoscopic intravariceal Cyanoacrylate injection procedure, cyanoacrylate glue is injected into the affected area. This glue gets hardened once it comes into contact with blood leading to the stoppage of bleeding.

4. The healthcare provider will inject liquid near the bleeding source to stop the blood flow.

5. In the angiographic embolization technique, tiny gelatin sponges are injected into the affected blood vessel to stop bleeding.

6. The blood supply of swollen veins or hemorrhoids is cut off by placing a small band around them, called band ligation, which leads the swollen veins or hemorrhoids to dry up and eventually fall off.

Conclusion

Blood in the stool can be due to hematochezia and melena. If the stool appears bright red, it is hematochezia associated with lower gastrointestinal tract bleeding. If the stool is dark colored, it is melena which is associated with upper gastrointestinal bleeding. The color difference is due to the difference in the source of bleeding. If left untreated, it can cause further complications. Hence, it is important to consult a doctor when bleeding in the stool is observed, and appropriate treatment must be taken.