Type of test Stool

Normal findings

No occult blood within stool

 Test explanation and related physiology

 This test is used for colorectal cancer screening of asymptomatic individuals. Normally only minimal quantities (2-2.5 mL) of blood are passed into the GI tract. Usually this bleeding is not significant enough to cause a positive result in stool for occult blood (OB) testing. This test can detect OB when as little as 5 mL of blood is lost per day.

Tumors of the intestine grow into the lumen and are subjected to repeated trauma by the fecal stream. Eventually the friable neo vascular tumor ulcerates and bleeding occurs. Most often, bleeding is so slight that gross blood is not seen in the stool. The blood can be detected by chemical assay or by immunohistochemistry. Guaiac is the most commonly performed chemical assay.

OB can also be detected by immunochemical methods that detect the human globin portion of hemoglobin using monoclonal antibodies. These tests are called fecal immunochemical test (FIT) or immunochemical fecal occult blood test (iFOBT). These methods are as sensitive as guaiac testing but are not affected by red meats or plant oxidizers as described in the Interfering factors section. Immunochemical methods may fail to recognize OB from the upper GI tract because the globin is digested by the time it gets in the stool.

The DNA stool sample test is more sensitive than guaiac testing in the detection of significant colorectal precancerous, benign, and malignant tumors. Because most precancerous polyps do not bleed, they can be missed by FOBT. In contrast, all precancerous polyps shed cells that contain abnormal DNA. So, a stool-based DNA test designed to detect this DNA promises to be more accurate in the detection of precancerous polyps, which, when detected, can be removed before they turn into cancer. The test is an easy-to-use home kit to collect a stool sample and mail it to a laboratory for analysis. The test checks for DNA changes that could indicate cancer or precancerous polyps and also checks for the presence of blood in the stool that can indicate cancer.

Benign and malignant GI tumors, ulcers, inflammatory bowel disease, arteriovenous malformations, diverticulosis, and hematobilia (hemobilia) can all cause OB in the stool. Other more common abnormalities (e.g., hemorrhoids, swallowed blood from oral or nasopharyngeal bleeding) may also cause OB in the stool.

When OB testing is properly performed, a positive result obtained on multiple specimens collected on successive days war rants a thorough GI evaluation, usually with esophagogastroduo denoscopy (EGD)  and colonoscopy. Regular screening, beginning at age 50 years, can reduce the number of people who die of colorectal cancer by as much as 60%.

Reducing or oxidizing agents (e.g., iron, radish, cantaloupe, cauliflower, vitamin C) can affect the results of guaiac or FIT. Furthermore, neither FIT nor guaiac testing detects slow upper GI bleeding because globin and heme are degraded during intestinal transit.

Interfering factors

 • Vigorous exercise

• Bleeding gums after a dental procedure

• Ingestion of red meat within 3 days before testing

• Ingestion of peroxidase-rich fruits and vegetables (turnips, artichokes, mushrooms, radishes, horseradishes, broccoli, bean sprouts, cauliflower, oranges, bananas, cantaloupes, and grapes) may affect results.

• Diarrhea or blood in the urine or stool (e.g., bleeding hemorrhoids, bleeding cuts or wounds on their hands, rectal bleeding, or menstruation)

* Drugs that may cause GI bleeding include anticoagulants, aspirin, colchicine, iron preparations (large doses), nonsteroidal antiarthritics, and steroids.

* Drugs that may cause false-positive results include colchicine, iron, oxidizing drugs (e.g., iodine, bromides, boric acid), and rauwolfia derivatives.

* Drugs that may cause false-negative results include vitamin C.

 Procedure and patient care

Before

* Explain the procedure to the patient.

* Instruct the patient to refrain from eating any red meat for at least 3 days before the test.

* Instruct the patient to refrain from drugs known to interfere with OB testing.

* Instruct the patient as to the method of obtaining appropriate stool specimens. Tests may be done at home with specimen cards (Hemoccult) and mailed.

* Instruct the patient not to mix urine with the stool specimen.

* Inform the patient as to the need for multiple specimens obtained on separate days to increase the test’s accuracy.

 • Note that in some centers a high-residue diet is recommended to increase the abrasive effect of the stool.

 • Be gentle in obtaining stool by digital rectal examination. A traumatic digital examination can cause a false-positive stool, especially in patients with prior anorectal disease, such as hemorrhoids.

 During

 Hemoccult slide test

 • Place a stool sample on one side of guaiac paper.

 • Place two drops of developer on the other side.

 • Note that bluish discoloration indicates OB in the stool.

 Tablet test

 • Place a stool sample on the developer paper.

• Place a tablet on top of the stool specimen.

• Put two or three drops of tap water on the tablet and allow it to flow onto the paper.

• Note that bluish discoloration indicates OB in the stool.

 DNA Home Test

• Place the bracket on the toilet.

 • Add container to the bracket.

• Have bowel movement.

• Place a small stool sample in the smaller tube.

• Place preservative on the stool in the larger container of stool.

 • Replace the top on the container and mail both the container and the smaller tube to the address on the enclosed label.

 After

* Inform the patient of the results.

• If the tests are positive, inquire whether the patient violated any of the preparation recommendations.

 Abnormal findings

- GI tumor

- Polyps

- Ulcer

- Varices

- Inflammatory bowel disease

- Diverticulosis

- Ischemic bowel disease

- GI trauma

- Recent GI surgery

- Hemorrhoids

- Esophagitis Gastritis

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم شؤون المعارف ينظم دورة متقدمة في تحقيق المخطوطات لملاكاته

قسم الشؤون الفكرية يصدر العدد العشرين من مجلة دراسات إفريقية

المجمَع العلمي يكرم الأساتذة المشاركين في مشروع الدورات القرآنية الصيفية في كربلاء

العتبة العباسية المقدسة تختتم فعاليات البرنامج المركزي الأسبوعي لمنتسبيها

المزيد

الآخبار الصحية

تحذير من "عدوى بكتيرية" تسبب نوبات قلبية

ماذا يحصل لجسمك عند التوقف عن استخدام الزيت في الطهي؟

الأمل في كبسولة.. "فيتامين شهير" يبطئ التقدم في العمر

اشتهاء أطعمة بشكل مفاجئ.. ناقوس خطر للسرطان ؟!

المزيد

الآخبار التكنلوجية

زلزال أفغانستان يحصد أكثر من ألف قتيل.. ويدمر آلاف المنازل !

ناجٍٍ وحيد من انزلاق أرضي.. دمّر قرية سودانية بأكملها !

نهر الفرات.. مورد مائي بين الندرة والتقاسم

ما السر وراء مشية إيلون ماسك الغريبة والسريعة ؟

المزيد

مواضيع ذات صلة

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Pathophysiological and Clinical Interpretations of Changes in circulating BNP/NTproBNP

sputum cytology

sodium (Na), urine

Sims-Huhner test (Postcoital test, Postcoital cervical mucus test, Cervical mucus sperm penetration test)

Quality Specifications of Troponin Measurement Methods

Clinical Relevance of Troponins Measurement

Hyperkalemia

sickle cell screen (Sickledex, Hemoglobin [Hgb] S test)

sexually transmitted disease testing (STD testing)