Rectal Bleeding (cont.)
In this Article
- Rectal bleeding (blood in stool) facts
- What does rectal bleeding (blood in stool) mean?
- What are the causes of blood in the stool (rectal bleeding)?
- What diseases and conditions can cause blood in the stool (rectal bleeding)?
- Anal fissure
- Colon cancer and polyps
- Colitis and proctitis
- Meckel's diverticulum
- Rare causes of rectal bleeding
- How is the cause and site of rectal bleeding determined?
- History and physical examination
- Flexible sigmoidoscopy
- Radionuclide scans
- Visceral angiogram
- Video capsule and small intestine enteroscopy
- MRI and CT tomographic angiography
- Nasogastric tube aspiration
- Blood tests
- How is rectal bleeding treated?
- Find a local Gastroenterologist in your town
If there is major concern about bleeding coming from the stomach or duodenum, an esophagogastricduodenoscopy (EGD) can be done using an endoscope similar to the endoscope used for colonoscopy.
Blood tests such as a complete blood count (CBC) and iron levels in the blood play no role in locating the site of gastrointestinal bleeding; however, the CBC and blood iron levels may help to determine whether bleeding is acute or chronic, since an anemia (low red blood cell count) associated with iron deficiency suggests chronic bleeding over many weeks or months. Gastrointestinal conditions commonly causing iron deficiency anemia include colon polyps, colon cancers, colon angiodysplasias, and chronic colitis.
When a patient looses a large amount of blood suddenly, as with moderate or severe acute rectal bleeding, the lost blood is replaced by fluid from the body's tissues. This influx of fluid dilutes the blood and leads to anemia (a reduced concentration of red blood cells). It takes time, however, for the tissue fluid to replace the lost blood within the blood vessels. Therefore, soon after a sudden large episode of bleeding, there may be no anemia. It takes many hours and even a day or more for the anemia to develop as tissue fluid slowly dilutes the blood. For this reason, a red blood cell count early after bleeding is not reliable for estimating the severity of the bleeding.
How is rectal bleeding treated?
Treatments for rectal bleeding include 1) correcting the low blood volume and anemia, 2) diagnosing the cause and the location of the bleeding, and 3) stopping active bleeding and preventing rebleeding.
Correcting low blood volume and anemia
Moderate to severe rectal bleeding can cause the loss of enough blood to result in weakness, low blood pressure, dizziness, or fainting, and even shock. Patients with these symptoms usually are hospitalized. They need to be quickly treated with intravenous fluids and/or blood transfusions to replace the blood that has been lost so that diagnostic tests such as colonoscopies and angiograms can be performed safely to determine the cause and location of the bleeding.
Patients with severe iron deficiency anemia may need hospitalization for blood transfusions followed by prolonged treatment with oral iron supplements (tablets). Patients with iron deficiency anemia as a result of chronic gastrointestinal blood loss should undergo tests (such as colonoscopy) to determine the cause of the chronic blood loss.
Unless anemia is severe, patients with mild rectal bleeding from colon polyps, colon cancers, anal fissures, and hemorrhoids usually do not need hospitalization. Mild anemia can be treated with oral iron supplements while tests are performed to diagnose the cause of bleeding.
Determining the cause and location of bleeding
Colonoscopy is the most widely used procedure for the diagnosis and treatment of rectal bleeding. Most colonoscopies are performed after administration of oral laxatives to cleanse the bowel of stool, blood, and blood clots. However, in emergency situations such as when the bleeding is severe and continuous, a doctor may choose to perform an emergency colonoscopy without first cleansing the large bowel. In trained and experienced hands, the risk of either elective (delayed) or urgent colonoscopy is small. (Colon perforation, the most common complication, is rare). The benefits usually far outweigh the potential risks.
Colonoscopy is useful for both diagnosing the cause and determining the location of the bleeding. Locating the site of bleeding is especially important in diverticular bleeding. Even though most diverticular bleeding stops spontaneously without the need for surgery, patients with severe, recurrent, or continuous diverticular bleeding may need surgery to remove the bleeding diverticulum. Since a patient typically has numerous diverticula scattered throughout the colon, and colonoscopy may be able to determine which diverticulum is bleeding prior to surgery. Without an accurate knowledge of the location of the bleeding diverticulum, the surgeon may have to perform an extensive colon resection (which is not as desirable as removing a small section of the colon) in order to make sure that the bleeding diverticulum is removed.
Nevertheless, colonoscopy has limitations. During colonoscopy doctors may not find active bleeding from a specific diverticulum. He/she may only find a colon filled with blood along with scattered diverticula. In such situations, the diagnosis of diverticular bleeding is assumed if no other cause for the bleeding such as colitis or colon cancer is found. In these situations, there is always some uncertainty about the location of the bleeding. Small, bleeding angiodysplasias also may be difficult to see and may be missed in a colon filled with blood. This is when radionuclide scans and visceral angiograms may be helpful. If the patient starts bleeding again, an urgent, tagged RBC scan followed by a visceral angiogram may demonstrate the location of the bleeding.
Colonoscopy also cannot positively diagnose bleeding from a Meckel's diverticulum because the colonoscope usually cannot reach the part of the small intestine in which the Meckel's diverticulum is located. But colonoscopy still can be helpful in establishing the diagnosis of a bleeding Meckel's diverticulum. Thus, in a young patient with rectal bleeding, a colonoscopy showing a blood filled colon without another source of bleeding, particularly if accompanied by an abnormal Meckel's scan, makes the diagnosis of Meckel's diverticulum bleeding highly likely. Surgical resection of the Meckel's diverticulum should result in permanent cure with no recurrence of bleeding.
Stopping bleeding and preventing rebleeding
Colonoscopy is more than just a diagnostic tool; it can also be used to stop bleeding by removing (snaring) bleeding polyps, by cauterizing (sealing with electrical current) bleeding angiodysplasias or postpolypectomy ulcers and, occasionally, by cauterizing actively bleeding blood vessels inside diverticula. Cauterization during colonoscopy is usually accomplished by inserting a long cauterizing probe through the colonoscope. Colonoscopy with cauterization has been used to stop bleeding in many patients with bleeding from diverticula or angiodysplasias, thereby decreasing their need for blood transfusions, shortening their hospital stays, and avoiding surgery.
When colonoscopy cannot identify the site of bleeding or is unable to stop recurrent or continuous bleeding, visceral angiograms may be helpful. When a bleeding site is identified by an angiogram, medications can be infused through the angiographic catheter to constrict the bleeding blood vessel and stop the bleeding, Microscopic coils also can be infused through the catheter to plug (embolize) the bleeding blood vessel, thereby stopping the bleeding.
If colonoscopy and visceral angiogram cannot stop continuous bleeding or prevent rebleeding, then surgery becomes necessary. Ideally, the site of bleeding has been identified by colonoscopy, nuclear scans, or visceral angiogram, so that the surgeon can target the site of bleeding for exploration and excision. For example, a surgeon can usually resect a colon cancer, a bleeding polyp, or a Meckel's diverticulum with precision. Sometimes, the exact site of bleeding cannot be established, and the surgeon will have to perform an extensive colon resection under the presumption that a diverticulum or angiodysplasia is the cause of the bleeding.
Mild rectal bleeding from anal fissures and hemorrhoids usually can be treated with local measures such as sitz baths, hemorrhoidal creams, and stool softeners. If these measures fail, several nonsurgical and surgical treatments are available.
eMedicine.com. Lower Gastrointestinal Bleeding.
Previous contributing author and editor: Dennis Lee, MD and Jay W. Marks, MD respectively.
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