What Are the Causes of Bloody Stool?

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10 Causes of Bloody Stool

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In medicine, at face value, a single symptom like bloody stool can usually be attributable to several conditions.  Blood in the stool typically presents as blood red or maroonish and represents a bleed somewhere in the GI tract from mouth to anus.  (If blood is coming from the upper GI tract and is being digested, it can also take on a black, tar-like appearance called melena.  I won't be covering melena in this slide show.)

Using details from your history, physical exam, diagnostic tests and so forth, physicians are able to deduce the etiology or cause of symptoms and rule out various differential diagnoses.  In the spirit of differential diagnoses, I present you 10 possible causes of bloody stool.  Please note that I've conspicuously left out infectious causes of like e.coli.  (Don't worry, I'll be covering bloody diarrhea in a separate article.)

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Bloody Stool Cause #1: Upper GI Bleed

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As any surgeon can attest to, the most common cause of a lower GI bleed is an upper GI bleed.  When you bleed copiously from an anatomical structure proximal to the ligament of Treitz, a ligament that suspends the distal duodenum, the blood can appear undigested in your stool (rapid transit). 

In order to figure out whether you have an upper GI bleed, a gastroenterologist will perform an endoscopy.  Following resuscitation measures like airway stabilization or blood transfusion, patients with serious upper GI bleeds need surgery.

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Bloody Stool Cause #2: Anal Fissure

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Although anal fissures also happen in adults, these fissures are the most common cause of bloody stool in infants.  Such fissures are caused by constipation or passing of a large, firm stool.  Anal fissures are cracks in the skin which are visualized after stretching the skin of the anus.  (Excuse my French, but anal fissures can be visualized around your butthole.)  Fortunately, anal fissures usually heal on their own but stool softening measures and application of petroleum jelly or some other cream can help with pain and discomfort.

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Bloody Stool Cause #3: Polyps

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The nonspecific term polyp refers to any projection from the intestinal tract.  There are several types of polyps which vary depending on their histology and presentation.  Adenomatous polyps are pretty common--affecting about 25 percent of adults aged 50 and older.

Most cases of colorectal cancer evolve from adenomatous polyps, and colorectal cancer is the second leading cause of cancer-related deaths in the United States.  However, with advances in medicine, nonmetastatic adenomatous polyps can be resected or removed by surgery, and chemotherpy can be given to limit any potential spread.  Colorectal cancer is treatable if caught early which is why all people more than 50 should schedule regular screening with colonoscopy, sigmoidoscopy and so forth. 

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Bloody Stool Cause #4: Hemorrhoids

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Hemorrhoids are swollen blood vessels which can extend from the anus; they look like cushions.  Hemorrhoids are often uncomfortable ... itchy, painful, and bleeding bright red blood from the highly vascular circulation feeding the anus and rectum.  Risk factors are plentiful and include diarrhea, constipation, heavy lifting, prolonged sitting and pregnancy.  For most people with hemorrhoids, treatment is nonsurgical and includes increasing fiber in your diet and using a salve like Preparation H.  Depending on location (internal and external), severity of symptoms and so forth, surgical options are also available for the treatment of hemorrhoids.

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Bloody Stool Cause #5: Angiodysplasia

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When the cause of bloody stool is obscure, it's likely attributable to angiodysplasia or vascular malformation of the gut.  Angiodysplasia is commonly associated with end-stage renal disease, von WIllebrand disease and end-stage renal failure. 

Depending on location, angiodysplasia can be treated with endoscopic obliteration.  Other treatments include hormone therapy, periodic blood transfusion and iron supplements.  Fortunately, in most people, angiodysplasia stops on its own. 

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Bloody Stool Cause #6: Inflammatory Bowel Disease (IBD)

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Inflammatory bowel disease (IBD) is a general term for autoimmune disease that causes inflammation of the bowels.  The two most common types of IBD are Crohn's disease and ulcerative colitis.  Initially, treatment for IBD is medication including steroids and immune-modifying agents.  However, the vast majority of people with IBD eventually need surgery.

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Bloody Stool Cause #7: Cancer

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In 2010, colorectal cancer was diagnosed in 142,570 people, and 51,370 people died of the disease.  Thanks to earlier detection and treatment, the number of deaths attributable to colorectal disease declined by 25 percent.  Nevertheless, colorectal cancer is still very deadly.

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Bloody Stool Cause #8: Diverticular Disease

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There are two types of diverticular disease: diverticulosis and diverticulitis.  Both can present in painful fashion and with blood in the stool.

Diverticulosis occurs when pouches or diverticula (singular diverticulum) form in the colon.  These diverticula grow out of weaknesses in the colonic wall and sometimes grow to several centimeters long.  Although classically attributed to a low-fiber diet, the exact cause of such diverticula is unknown.  Bleeding from diverticula can be stopped during endoscopy or abdominal surgery.

When diverticula become infected, the condition diverticulitis results.  Diverticulitis is treated in an inpatient setting using antibiotics.  If surgery is required, physicians usually wait until after the infection has been treated first.

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Bloody Stool Cause #9: Ischemic Colitis

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Ninety percent of all cases of ischemic colitis affect the elderly and can be acute or chronic.  Ischemic injury results when intestinal blood flow to the colon is inadequate (think blood clot or atherosclerosis).  In addition to blood in the stool, ischemic colitis can also present as diarrhea, an urgent need to defecate, abdominal pain and vomiting.

Most cases of ischemic colitis last a short time and resolve on their own.  With more severe cases, people are hospitalized, put on bowel rest and given intravenous fluids and antibiotics.  About 20 percent of people who develop ischemic colitis, however, go on to need surgery.  Prognosis for those who receive surgery is grim with a 60 percent mortality rate. 

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Bloody Stool Cause #10: False Alarm

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Occasionally, pigments and coloring from the food we eat like Kool-Aid, Hawaiian Punch, red gelatin and even beets, can turn your stool red.  If you've ever had your kid go to town on the red popsicles, you probably have witnessed this benign yet disconcerting phenomena. 

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Bloody Stool: Passing Thoughts

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As you can now appreciate, bloody stool can be caused by many things.  Some of these causes are annoying yet pretty harmless like hemorrhoids or anal fissures; other causes are a lot more concerning like cancer.

If you or a loved one complains of blood in the stool, you must see a physician.   I know it's scary to look down and see blood on the tissue or in the bowl, and it may be tempting to ignore it and hope it goes away.  However, with colorectal cancer a leading cause of death throughout the world, you shouldn't ignore blood in your stool.

 Selected Sources

Stephan M, Carter C, Ashfaq S. Chapter 50. Pediatric Emergencies. In: Stone C, Humphries RL. eds. CURRENT Diagnosis & Treatment Emergency Medicine, 7e. New York, NY: McGraw-Hill; 2011. Accessed April 03, 2015.

Bullard Dunn KM, Rothenberger DA. Colon, Rectum, and Anus. In: Brunicardi F, Andersen DK, Billiar TR, Dunn DL, Hunter JG, Matthews JB, Pollock RE. eds. Schwartz's Principles of Surgery, 10e. New York, NY: McGraw-Hill; 2014. Accessed April 03, 2015.

Gomella LG, Haist SA. Chapter 3. Differential Diagnosis: Symptoms, Signs, and Conditions. In: Gomella LG, Haist SA. eds. Clinician's Pocket Reference: The Scut Monkey, 11e. New York, NY: McGraw-Hill; 2007. Accessed April 03, 2015.

Mayer RJ. Chapter 91. Gastrointestinal Tract Cancer. In: Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson J, Loscalzo J. eds. Harrison's Principles of Internal Medicine, 18e. New York, NY: McGraw-Hill; 2012.  Accessed April 03, 2015.

Usatine RP, Smith MA, Chumley HS, Mayeaux EJ, Jr.. Chapter 66. Hemorrhoids. In: Usatine RP, Smith MA, Chumley HS, Mayeaux EJ, Jr.. eds. The Color Atlas of Family Medicine, 2e. New York, NY: McGraw-Hill; 2013. Accessed April 03, 2015.

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