Rectal Bleeding (cont.)
Blood tests
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 to
months. Gastrointestinal conditions commonly causing iron deficiency anemia
include colon polyps, colon cancers, colon angiodysplasias, and chronic colitis.
When a large amount of blood is lost suddenly as with moderate or severe acute
rectal bleeding, the lost blood and red blood cells are 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,
early 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 for 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 in 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
certain emergency situations such as when the bleeding is severe and continuous,
a doctor may choose to perform 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, colonoscopy may be able to determine which diverticulum is
bleeding prior to surgery. Without accurate knowledge of the location of the
bleeding diverticulum, the surgeon might 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 these situations, the diagnosis of
diverticular bleeding is assumed if he/she finds no other cause for the bleeding
such as colitis or colon cancer. 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.
Next: Stopping bleeding and preventing rebleeding »
- Colonoscopy - Learn about the colonscopy procedure, what it is, why it is performed, preparation, complications, alternatives and the after effects of the screening exam on MedicineNet.com
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- Fecal Occult Blood Test - Read about the fecal occult blood test in which there are two types, chemical and immunologic. Fecal occult blood tests are used to screen for colon cancer and colon polyps.
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