Fecal occult blood

Fecal occult blood
Classification and external resources

Cards and bottle used for the Hemoccult test, a type of stool guaiac test.
ICD-10 R19.5
ICD-9 792.1
DiseasesDB 30751
MedlinePlus 007008
MeSH D009780

Fecal occult blood (FOB) refers to blood in the feces that is not visibly apparent. A fecal occult blood test (FOBT) checks for hidden (occult) blood in the stool (feces).[1] Newer tests look for globin, DNA, or other blood factors including transferrin, while conventional stool guaiac tests look for heme.

Contents

Purpose

Fecal occult blood testing (FOBT), as its name implies, aims to detect subtle blood loss in the gastrointestinal tract, anywhere from the mouth to the colon. Positive tests ("positive stool") may result from either upper gastrointestinal bleeding or lower gastrointestinal bleeding and warrant further investigation for peptic ulcers or a malignancy (such as colorectal cancer or gastric cancer). The test does not directly detect colon cancer but is often used in clinical screening for that disease, but it can also be used to look for active occult blood loss in anemia[2] or when there are gastrointestinal symptoms.[3]

Nomenclature

In 2007 the nomenclature of overt, obscure and occult bleeding was clarified.

The different methods of testing for "fecal occult blood" as broadly considered actually test for particular components of blood or for aberrantly expressed cellular markers from the intestinal mucosa.

Methodology

There are four methods in clinical use for testing for occult blood in feces. These look at different properties, such as heme, globin, and porphyrins in blood or at DNA from cellular material such as from lesions of the intestinal mucosa.

Additional methods of looking for occult blood are being explored, including transferrin dipstick[17] and stool cytology.[18]

Test performance

Reference standards

The estimates for test performance characteristics are based on comparison with a variety of reference methods including 51-chromium studies, analytical recovery studies in spiked stool samples, analytical recovery after ingestion of autologous blood, rarer studies of carefully quantified blood instilled at bowel surgery as well as other research approaches. Additionally, clinical studies look at variety of additional factors.

Gastrointestinal blood loss in health

In healthy people about 0.5 to 1.5 ml of blood escapes blood vessels into the stool each day.[19][20][21] Significant amounts of blood can be lost without producing visible blood in the stool, estimated as 200 ml in the stomach,[22] 100 ml in the duodenum, and lesser amounts in the lower intestine. Tests for occult blood identify lesser blood loss.

Clinical sensitivity and specificity

Stool guaiac test for fecal occult blood (gFOBT) sensitivity varies depending on the site of bleeding. Moderately sensitive gFOBT can pick up a daily blood loss of about 10 ml (about two teaspoonfuls), and higher sensitivity gFOBT can pick up lesser amounts, sometimes becoming positive at about 2 ml. The sensitivity of a single stool guaiac test to pick up bleeding has been quoted at 10 to 30%, but if a standard three tests are done as recommended the sensitivity rises to 92%.[23] Further discussion of sensitivity and sensitivity issues that relate particularly to the guaiac method is found in the stool guaiac test article.

Fecal Immunochemical Testing (FIT) picks up as little as 0.3 ml but because it does not detect occult blood from the stomach and upper small intestine the test threshold doesn't cause undue false positives from normal upper intestinal blood leakage and it is much more specific for bleeding from the colon or lower gastrointestinal tract.[24] The detection rate of the test decreases if the time from sample collection to laboratory processing is delayed.[25]

Fecal porphyrin quantification by HemoQuant can be false positive due to exogenous blood and various porphyrins. HemoQuant is the most sensitive test for upper gastrointestinal bleeding and therefore may be most appropriate fecal occult blood test to use in the evaluation of iron deficiency [26] Advised to stop red meat and aspirin for 3 days prior to specimen collection [27] False positives can occur with myoglobin, catalase, or protohemes[13] and in certain types of porphyria

The DNA based PreGen-Plus was four times more sensitive than fecal blood testing, including detection of early stage disease, when treatment is most effective.[28] Sensitivity increased to 51.6% compared to 12.9%.[29] Additional clinical trials of the PreGen-Plus method are underway to more fully characterize its clinical performance.[30] Expanding the range of DNA testing by looking at additional known genetic markers, such as CTNNB1, or by analyzing epigenetically methylated genes[31] such as MLH1 which is very common in hyperplastic polyps (HP) with microsatellite instability (MSI)[32][33] and in proximal colon tumours that have poorer differentiation, does not appear to appreciably increase the sensitivity of the method because CTNNB1 mutations are infrequent in sporadic colorectal cancer, and because BAT26 alterations and lack of MLH1 expression show a high degree of overlap.[34]

Clinical application

The stool guaiac test for hidden (occult) blood in the stool can be done at home or in the doctor's office, or can be performed on samples submitted to a clinical laboratory. Testing kits are available at pharmacies in some countries without a prescription, or a health professional may order a testing kit for use at home. If a home fecal occult blood test detects blood in the stool it is recommended to see a health professional to arrange further testing.[35]

Sources of gastrointestinal bleeding

Gastrointestinal bleeding has many potential sources, and positive results usually result in further testing for the bleeding site, usually looking for lower gastrointestinal bleeding before upper gastrointestinal bleeding causes unless there are other clinical clues.[36] Colonoscopy is usually preferred to computerized tomographic colonography.[37]

An estimated 1–5% of large tested populations have a positive fecal occult blood test. Of those, about 2–10% have cancer, while 20–30% have adenomas.

A positive test can result from upper gastrointestinal bleeding or lower gastrointestinal bleeding. The common causes are:

In the event of a positive fecal occult blood test, the next step in the workup is a form of visualization of the gastrointestinal tract by one of several means:

  1. Sigmoidoscopy, an examination of the rectum and lower colon with a lighted instrument to look for abnormalities, such as polyps.
  2. Colonoscopy, a more thorough examination of the rectum and entire colon.
  3. Virtual colonoscopy
  4. Endoscopy refers to upper gastrointestinal endoscopy. It is sometimes performed with chromoendoscopy, a method that assists the endoscopist by enhancing the visual difference between cancerous and normal tissue, either by marking the abnormally increased DNA content (toluidine blue) or failing to stain the tumor, possibly due to decreased surface glycogen on tumor cells(Lugol).[38][39] Infrared fluorescent endoscopy and ultrasonic endoscopy can interrogate vascular abnormalities such as esophageal varices.
  5. Double contrast barium enema: a series of x-rays of the colon and rectum.

Stool color

Although red or black stools can be an indication of bleeding, a dark or black color can be due to black licorice, blueberries, iron supplements, lead, Pepto-bismol, and a red color can come from natural or artificial coloring such as red gelatin, popsicles, Kool-Aid, and large amounts of beets.

Colorectal cancer screening

Screening methods for colon cancer depend on detecting either precancerous changes such as certain kinds of polyps or on finding early and thus more treatable cancer. The extent to which screening procedures reduce the incidence of gastrointestinal cancer or mortality depends on the rate of precancerous and cancerous disease in that population. gFOBT and flexible sigmoidoscopy screening have each shown benefit in randomized clinical trials. Evidence for other colon cancer screening tools such as iFOBT or colonoscopy is substantial and guidelines have been issued by several advisory groups but does not include randomized studies.

Guaiac FOB testing of average risk populations may reduce the mortality associated with colon cancer by about 25%.[40] It is not always cost effective to screen a large population.[41][42][43][44]

If colon cancer is suspected in an individual (such as in someone with an unexplained anemia) fecal occult blood tests may not be clinically helpful. If a doctor suspects colon cancer, more rigorous investigation is necessary, whether or not the test is positive.

The 2009 recommendations of the American College of Gastroenterology (ACG)[45] suggest that colon cancer screening modalities that are also directly preventive by removing precursor lesions should be given precedence, and prefer a colonoscopy every 10 years in average-risk individuals, beginning at age 50. The ACG suggests that cancer detection tests such as any type of FOB are an alternative that is less preferred and which should be offered to patients who decline colonoscopy or another cancer prevention test. However, two other recent guidelines, from the US Multisociety Task Force (MSTF)[46] and the US Preventive Services Task Force (USPSTF)[47] while permitting immediate colonoscopy as an option, did not categorize it as preferred. The ACG and MSTF also included CT colonography every 5 years, and fecal DNA testing as considerations. All three recommendation panels recommended replacing any older low-sensitivity, guaiac-based fecal occult blood testing (gFOBT) with either newer high-sensitivity guaiac-based fecal occult blood testing (gFOBT) or fecal immunochemical testing (FIT). MSTF looked at 6 studies that compared high sensitivity gFOBT (Hemoccult SENSA) to FIT, and concluded that there were no clear difference in overall performance between these methods.

In colon cancer screening, using only one sample of feces collected by a doctor performing a digital rectal examination is strongly discouraged.[48]

Iron deficiency anemia

An extensive literature has examined the clinical value of FOBT in iron deficiency anemia.

Gastrointestinal disease and medications

Conditions such as ulcerative colitis or certain types of relapsing infectious diarrhea can vary in severity over time, and FOBT may assist in assessing the severity of the disease. Medications associated with gastrointestinal bleeding such as Bortezomib are sometimes monitored by FOBT.

Alcoholism

Several aspects of FOBT in alcoholism warrant further discussion.

Outpatient clinics

Several studies have reported clinical benefit from gFOBT testing including urology and gynecology clinics.

Inpatient guaiac testing

Several studies have questioned the traditional Admission Screening Guaiac (ASG). The utility of following stool guaiac in ICU settings is also questioned.

Testing of upper gastrointestinal or aerodigestive tract secretions for occult blood

The use of tests for occult blood in disorders of the mouth, nasal passages, esophagus, lungs and stomach, while analogous to fecal testing, is often discouraged, due to technical considerations including poorly characterized test performance characteristics such as sensitivity, specificity, and analytical interference. However, chemical confirmation that coloration is due to blood rather than coffee, beets, medications, or food additives can be of significant clinical assistance.

A related concept to colon cancer screening by FOBT, based on most neoplasms affecting the surface epithelium and losing small amounts of blood but no visible blood loss, is screening in populations at high risk for esophageal or gastric cancers by testing for blood by swallowing a small capsule that is recovered after 3 to 5 minutes by gentle retrieval by means of an attached nylon thread.[49]

Regulatory impact

Regulations from the Joint Commission may have unintentionally decreased digital rectal examination and FOBT in hospital settings such as Emergency Departments.[50][51]

Fecal occult blood in marathon runners

Gastrointestinal (GI) complaints and low intensity GI bleeding frequently occur in marathon runners.[52] Strenuous exercise, particularly in elite athlete runners and less frequently in other exercise activities, can cause acute incapacitating gastrointestinal symptoms including heartburn, nausea, vomiting, abdominal pain, diarrhea and gastrointestinal bleeding.[53] Approximately one third of endurance runners experience transient but exercise limiting symptoms, and repetitive gastrointestinal bleeding occasionally causes iron deficiency and anaemia.[54] Runners can sometimes experience significant symptoms including hematemesis.[55] Exercise is associated with extensive changes in gastrointestinal (GI) tract physiology, including diversion of blood flow from the GI tract to muscle and lungs, decreased GI absorption and small intestinal motility, increased colonic transit, neuroimmunoendocrine changes in hormones and peptides such as vasoactive intestinal peptide, secretin and peptide-histidine-methionine.[56] Substantial changes occur in stress hormones including cortisol, in circulating concentrations and metabolic behavior of various leucocytes, and in immunoglobulin levels and major histocompatibility complex expression.[57] Symptoms can be exacerbated by dehydration or by pre-exercise ingestion of certain foods and hypertonic liquids, and lessened by adequate training.[56]

Ingestion of 800 mg of cimetidine 2 hr before running a marathon did not significantly affect the frequency of gastrointestinal symptoms or occult gastrointestinal bleeding.[58] Conversely, 800 mg of cimetidine 1 hr before the start and again at 50 miles of a 100-mile running race substantially decreased GI symptoms and postrace guaiac test positivity but did not affect race performance.[59]

Additional studies have reviewed the effect of cimetidine and of PPI

Role of endoscopy in marathon runners with positive FOBT

This is a different process than march hemoglobinuria.

See also

References

  1. ^ Occult Gastrointestinal Bleeding: Detection, Interpretation, and Evaluation. Beg M et al. JIACM 2002; 3(2):153–158. Full text PDF accessioned 2010/10/26 http://medind.nic.in/jac/t02/i2/jact02i2p153.pdf
  2. ^ Harewood GC, Ahlquist DA (2000). "Fecal occult blood testing for iron deficiency: a reappraisal". Dig Dis 18 (2): 75–82. doi:10.1159/000016968. PMID 11060470. 
  3. ^ Bardhan PK, Beltinger J, Beltinger RW, Hossain A, Mahalanabis D, Gyr K (January 2000). "Screening of patients with acute infectious diarrhoea: evaluation of clinical features, faecal microscopy, and faecal occult blood testing". Scand. J. Gastroenterol. 35 (1): 54–60. doi:10.1080/003655200750024533. PMID 10672835. 
  4. ^ Young GP, Cole SR (March 2009). "Which fecal occult blood test is best to screen for colorectal cancer?". Nat Clin Pract Gastroenterol Hepatol 6 (3): 140–1. doi:10.1038/ncpgasthep1358. PMID 19174764. 
  5. ^ Quintero E (October 2009). "[Chemical or immunological tests for the detection of fecal occult blood in colorectal cancer screening?]" (in Spanish; Castilian). Gastroenterol Hepatol 32 (8): 565–76. doi:10.1016/j.gastrohep.2009.01.179. PMID 19577340. 
  6. ^ Effectiveness of Colorectal Cancer Screening Tests: Colorectal cancer screening clinical practice guideline. National Guideline Clearinghouse (NGC), a U.S. government-provided resource for evidence-based clinical practice guidelines, at http://www.guideline.gov/summary/summary.aspx?doc_id=14345
  7. ^ Grazzini G, Visioli CB, Zorzi M et al. (January 2009). "Immunochemical faecal occult blood test: number of samples and positivity cutoff. What is the best strategy for colorectal cancer screening?". Br. J. Cancer 100 (2): 259–65. doi:10.1038/sj.bjc.6604864. PMC 2634712. PMID 19142185. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2634712. 
  8. ^ Berchi C, Bouvier V, Réaud JM, Launoy G (March 2004). "Cost-effectiveness analysis of two strategies for mass screening for colorectal cancer in France". Health Econ 13 (3): 227–38. doi:10.1002/hec.819. PMID 14981648. 
  9. ^ Kuriyama M, Kato J, Takemoto K, Hiraoka S, Okada H, Yamamoto K (March 2010). "Prediction of flare-ups of ulcerative colitis using quantitative immunochemical fecal occult blood test". World J. Gastroenterol. 16 (9): 1110–4. doi:10.3748/wjg.v16.i9.1110. PMC 2835788. PMID 20205282. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2835788. 
  10. ^ Rockey DC. Occult gastrointestinal bleeding. N Eng J Med 1999; 341 (1): 38–46.
  11. ^ "Diagnostic Tests — Fecal Occult Blood Test". http://www.health.harvard.edu/diagnostic-tests/fecal-occult-blood-test.htm. Retrieved 2007-07-18. 
  12. ^ United States Patent 4,378,971 Method and apparatus for quantitatively determining the level of hemoglobin in a biological sample. 1983 April 5, accessioned 2010 November 3 as full PDF at http://www.freepatentsonline.com/4378971.pdf
  13. ^ a b Schwartz S, Dahl J, Ellefson M, Ahlquist D (December 1983). "The "HemoQuant" test: a specific and quantitative determination of heme (hemoglobin) in feces and other materials". Clin. Chem. 29 (12): 2061–7. PMID 6640900. 
  14. ^ PreGen-Plus™ Fact Sheet. full text accessioned 2010 November 3 at http://www.noaw.com/PDF/fs_pregen.pdf
  15. ^ Jin YM, Li BJ, Qu B, Du YJ (August 2006). [accessioned 2010 November 3 at http://www.wjgnet.com/1007-9327/12/5148.pdf "BRAF, K-ras and BAT26 mutations in colorectal polyps and stool"]. World J. Gastroenterol. 12 (32): 5148–52. PMID 16937524. accessioned 2010 November 3 at http://www.wjgnet.com/1007-9327/12/5148.pdf. 
  16. ^ Cravo M, Lage P, Albuquerque C et al. (July 1999). "BAT-26 identifies sporadic colorectal cancers with mutator phenotype: a correlative study with clinico-pathological features and mutations in mismatch repair genes". J. Pathol. 188 (3): 252–7. doi:10.1002/(SICI)1096-9896(199907)188:3<252::AID-PATH354>3.0.CO;2-3. PMID 10419591. 
  17. ^ Sheng JQ, Li SR, Wu ZT et al. (August 2009). [full text accessioned 2010 November 3 at http://cebp.aacrjournals.org/content/18/8/2182.full.pdf+html "Transferrin dipstick as a potential novel test for colon cancer screening: a comparative study with immuno fecal occult blood test"]. Cancer Epidemiol. Biomarkers Prev. 18 (8): 2182–5. doi:10.1158/1055-9965.EPI-09-0309. PMID 19661074. full text accessioned 2010 November 3 at http://cebp.aacrjournals.org/content/18/8/2182.full.pdf+html. 
  18. ^ Sheng JQ, Li SR, Su H et al. (June 2010). "Fecal cytology in conjunction with immunofecal occult blood test for colorectal cancer screening". Anal. Quant. Cytol. Histol. 32 (3): 131–5. PMID 20701065. 
  19. ^ Ahlquist DA, McGill DB, Schwartz S et al. Fecal blood levels in health and disease: a study using HemoQuant. N Eng J Med 1985; 312: 1422–8.
  20. ^ Dybdahl JH, Daae LN, Larsen S. Occult fecal blood loss determined by chemical tests and a 51 Cr method. Scand J Gastroenterol 1981; 16: 245–52.
  21. ^ St. John DJ, Young GP. Evaluation of radiochromium blood loss studies in unexplained iron deficiency anemia. Aust NZ J Med 1978; 8: 121–6.
  22. ^ Schiff L, Stevens RJ, Shapiro N, et al. Observations on the oral administration of citrate blood in man. Am J Med Sci 1942;203:409.
  23. ^ "Screening average risk patients for colorectal cancer – B01". http://www.uptodate.com/. Retrieved 2007-10-25. 
  24. ^ "What Does a Positive Fecal Occult Blood Test Mean? – B01". http://www.wdxcyber.com/ncanc10.htm. Retrieved 2007-07-18. 
  25. ^ van Rossum LG, van Rijn AF, van Oijen MG et al. (August 2009). "False negative fecal occult blood tests due to delayed sample return in colorectal cancer screening". Int. J. Cancer 125 (4): 746–50. doi:10.1002/ijc.24458. PMID 19408302. 
  26. ^ Harewood GC, McConnell JP, Harrington JJ, Mahoney DW, Ahlquist DA (January 2002). "Detection of occult upper gastrointestinal tract bleeding: performance differences in fecal occult blood tests". Mayo Clin. Proc. 77 (1): 23–8. doi:10.4065/77.1.23. PMID 11794453. 
  27. ^ Title etc http://www.mayomedicallaboratories.com/test-catalog/Overview/9220 acc on etc
  28. ^ http://www.mi3.com/pressreleases/2004.12.22.Exact.pdf
  29. ^ Imperiale T, Ransohoff D, Itzkowitz S, Turnbull B, Ross M (2004). "Fecal DNA versus fecal occult blood for colorectal-cancer screening in an average-risk population". N Engl J Med 351 (26): 2704–14. doi:10.1056/NEJMoa033403. PMID 15616205. 
  30. ^ Whitlock EP, Lin J, Liles E, Beil T, Fu R, O'Connor E, Thompson RN, Cardenas T (2008). "Screening for Colorectal Cancer: An Updated Systematic Review". Agency for Healthcare Research and Quality (US); 2008 Oct. Report No.: 08-05-05124-EF-1.. PMID 20722162. 
  31. ^ Baylin SB,Futscher BW, Gore SD. Understanding DNA Methylation and Epigenetic Gene Silencing in Cancer. full text accessioned 2010 November 3 at http://static.cjp.com/gems/blood/DNA-Meth.pdf
  32. ^ Hawkins NJ, Ward RL (September 2001). "Sporadic colorectal cancers with microsatellite instability and their possible origin in hyperplastic polyps and serrated adenomas". J. Natl. Cancer Inst. 93 (17): 1307–13. doi:10.1093/jnci/93.17.1307. PMID 11535705. 
  33. ^ Hamilton SR (September 2001). "Origin of colorectal cancers in hyperplastic polyps and serrated adenomas: another truism bites the dust". J. Natl. Cancer Inst. 93 (17): 1282–3. doi:10.1093/jnci/93.17.1282. PMID 11535695. 
  34. ^ Lüchtenborg M, Weijenberg MP, Wark PA et al. (2005). "Mutations in APC, CTNNB1 and K-ras genes and expression of hMLH1 in sporadic colorectal carcinomas from the Netherlands Cohort Study". BMC Cancer 5: 160. doi:10.1186/1471-2407-5-160. PMC 1334229. PMID 16356174. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1334229. 
  35. ^ "Fecal Occult Blood Test (FOBT)". http://www.webmd.com/colorectal-cancer/Fecal-Occult-Blood-Test-FOBT. Retrieved 2007-07-18. 
  36. ^ Rockey DC (December 2005). "Occult gastrointestinal bleeding". Gastroenterol. Clin. North Am. 34 (4): 699–718. doi:10.1016/j.gtc.2005.08.010. PMID 16303578. 
  37. ^ Walleser S, Griffiths A, Lord SJ, Howard K, Solomon MJ, Gebski V (December 2007). "What is the value of computerized tomographic colonography in patients screening positive for fecal occult blood? A systematic review and economic evaluation". Clin. Gastroenterol. Hepatol. 5 (12): 1439–46; quiz 1368. doi:10.1016/j.cgh.2007.09.003. PMID 18054752. 
  38. ^ Endo M, Sakakibara N, Suzuki H. Observation of esophageal lesions with the use of endoscopic dyes. Progress of Digestive Endoscopy. 1972; 1:34.
  39. ^ Endo M, Takeshita K, Yoshida M. How Can We Diagnose the early stage of esophageal cancer? Endoscopic diagnosis. Endoscopy. 1986, 18:11–8.
  40. ^ Bretthauer M (August 2010). "Evidence for colorectal cancer screening". Best Pract Res Clin Anaesthesiol 24 (4): 417–25. PMID 21058518. 
  41. ^ Mandel JS, Bond JH, Church TR et al. Reducing mortality from colorectal cancer by screening for fecal occult blood. N Eng J Med 1993; 328: 1365–71.
  42. ^ Hardcastle JD, Chamberlain JO, Robinson MHE et al. Randomised controlled trial of fecal occult blood screening for colorectal cancer. Lancet 1996; 348: 1472–7.
  43. ^ Kronborg O, Fenger C, Olsen J et al. Randomised study of screening for colorectal cancer with fecal occult blood test. Lancet 1996; 348: 1467–71.
  44. ^ Kewenter J, Brevinge H, Engaras B et al. Results of screening,rescreening and follow up in a prospective randomized study for detection of colorectal cancer by fecal occult-blood testing: results of 68,308 subjects. Scand J Gastroenterol 1994; 29: 468–73.
  45. ^ Rex DK et al. Am J Gastroenterol. 2009;104:739–750.
  46. ^ Levin B et al. Screening and Surveillance for the Early Detection of Colorectal Cancer and Adenomatous Polyps, 2008: A Joint Guideline From the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. published in two journals – CA: A Cancer Journal for Clinicians 2008; 58: 130–160 and Gastroenterology 2008; 134: 1570–1595 and available as full text at http://onlinelibrary.wiley.com/doi/10.3322/CA.2007.0018/full accessioned 2010 October 26 and as PDF at http://download.journals.elsevierhealth.com/pdfs/journals/0016-5085/PIIS0016508508002321.pdf accessioned 2010 October 26
  47. ^ USPSTF Agency for Healthcare Research and Quality. Screening for colorectal cancer: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2008;149:627–637. Also available at Screening for colorectal cancer, topic page: http://www.uspreventiveservicestaskforce.org/uspstf/uspscolo.htm accessioned 2010 October 26, which has several hyperlink extensions to several extensive reviews, including accessible articles with recommendation statements, clinical background summary, decision analysis, systematic review, and evidence synthesis.
  48. ^ Collins JF, Lieberman DA, Durbin TE, Weiss DG (January 2005). "Accuracy of screening for fecal occult blood on a single stool sample obtained by digital rectal examination: a comparison with recommended sampling practice". Ann. Intern. Med. 142 (2): 81–5. PMID 15657155. 
  49. ^ Qin DX, Wang GQ, Zuo JH et al. (January 1993). "Screening of esophageal and gastric cancer by occult blood bead detector". Cancer 71 (1): 216–8. doi:10.1002/1097-0142(19930101)71:1<216::AID-CNCR2820710133>3.0.CO;2-#. PMID 8416718. 
  50. ^ Adams BD, McHugh KJ, Bryson SA, Dabulewicz J (February 2008). "The law of unintended consequences: The Joint Commission regulations and the digital rectal examination". Ann Emerg Med 51 (2): 197–201, 201.e1. doi:10.1016/j.annemergmed.2007.07.022. PMID 17961818. 
  51. ^ Cleveland NJ, Yaron M, Ginde AA (August 2010). "The effect of removal of point-of-care fecal occult blood testing on performance of digital rectal examinations in the emergency department". Ann Emerg Med 56 (2): 135–41. doi:10.1016/j.annemergmed.2009.12.021. PMID 20060198. 
  52. ^ Halvorsen FA, Lyng J, Ritland S (May 1986). "Gastrointestinal bleeding in marathon runners". Scand. J. Gastroenterol. 21 (4): 493–7. doi:10.3109/00365528609015168. PMID 3487825. 
  53. ^ de Oliveira EP, Burini RC (September 2009). "The impact of physical exercise on the gastrointestinal tract". Curr Opin Clin Nutr Metab Care 12 (5): 533–8. doi:10.1097/MCO.0b013e32832e6776. PMID 19535976. 
  54. ^ Peters HP, De Vries WR, Vanberge-Henegouwen GP, Akkermans LM (March 2001). "Potential benefits and hazards of physical activity and exercise on the gastrointestinal tract". Gut 48 (3): 435–9. doi:10.1136/gut.48.3.435. PMC 1760153. PMID 11171839. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1760153. 
  55. ^ Weaver LT. Do some marathon runners bleed into the gut? (letter response to a previous article) BMJ 1984; 288:65 full text at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1444190/pdf/bmjcred00482-0081c.pdf
  56. ^ a b Brouns F, Beckers E (April 1993). "Is the gut an athletic organ? Digestion, absorption and exercise". Sports Med 15 (4): 242–57. PMID 8460288. 
  57. ^ Venkatraman JT, Pendergast DR (2002). "Effect of dietary intake on immune function in athletes". Sports Med 32 (5): 323–37. doi:10.2165/00007256-200232050-00004. PMID 11929359. 
  58. ^ Moses FM, Baska RS, Peura DA, Deuster PA (October 1991). "Effect of cimetidine on marathon-associated gastrointestinal symptoms and bleeding". Dig. Dis. Sci. 36 (10): 1390–4. doi:10.1007/BF01296804. PMID 1914760. 
  59. ^ Baska RS, Moses FM, Deuster PA (August 1990). "Cimetidine reduces running-associated gastrointestinal bleeding. A prospective observation". Dig. Dis. Sci. 35 (8): 956–60. doi:10.1007/BF01537243. PMID 2384041. 

External links

GI tract
Accessory
Abdominopelvic
Abdominal – general

M: DIG

anat(t, g, p)/phys/devp/enzy

noco/cong/tumr, sysi/epon

proc, drug(A2A/2B/3/4/5/6/7/14/16), blte