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Bloody Diarrhea, Possible Causes, Symptoms, and Treatment.

Bloody diarrhea is an emergency in which the stool’s color becomes red. Several types of infections and non-infectious diseases can cause it.

In the first instance, it does not matter what the underlying cause of bloody diarrhea is. This symptom is indicative that definitely, something is not going well within the bowel. Asides from the infectious causes (due to infections), there is also the possibility of gut structural damage (diseases), as the reasons for this symptom to exist in a patient.

Many of the infectious causes come from a lack of public health measures within the patient’s community. Or a patient from a developed country traveling to a developing country without taking the correct prevention measures.

Within this article, you will find answers to some of the most common questions about this symptom. There will be questions like the causes of bloody diarrhea, how do you contract some of the diseases that cause bloody diarrhea, and many more. However, first, there will be a brief explanation of basic concepts to understand the topic better.

By reading this article, you will obtain critical insights about bloody diarrhea, other symptoms that could appear, its causes, meaning, complications, and many more. Therefore, please continue reading this article to get pearls on this specific topic by a doctor’s hand.  

What is diarrhea?

According to the medical definition, diarrhea is when the patient has at least three loose, liquid, or watery stools per day. It is a very common condition that, most of the time, its course is self-limited.

Diarrhea has different categories; among them are the following: Infectious, Non-Infectious, acute, and chronic. Acute diarrhea is an incident of diarrhea that persists for less than two weeks. Most of the cases of acute diarrhea are also infectious diarrhea (due to infections).

Chronic diarrhea is described as diarrhea with a duration lasting longer than four weeks, and its cause tends to be non-infectious (a disease). Among the most common causes of non-infectious diarrhea are food malabsorption, inflammatory bowel disease, and medication side effects.

Overall, diarrhea results from a reduction in water absorption or increased water discharge in the bowel. There are different types of diarrhea that, depending on their characteristics, may lead the doctor to a specific underlying diagnosis for it.

We already know that there are types of diarrhea in which there is a lack of water absorption or increased discharge in the gut. However, there are diarrheas in which the germ that causes the disease may affect the bowel directly. But how can the germ affect the bowel? It may attach directly to the cells within the bowel walls, causing bleeding and/or mucus secretion. This can be seen mainly in infectious causes of diarrhea.

On the other hand, there are cases in which the bowel cannot absorb the nutrients, causing diarrhea. This is a particular case in patients with lactose intolerance or celiac disease. As the nutrients cannot go into the organism and have a dense molecular structure, they will bring water out of the body with them by dragging it; therefore, they cause diarrhea.

What are the types of diarrhea?

To fully comprehend the causes of diarrhea, one must know a little about the digestive system first. There are approximately one to two liters of liquid entering the body through the regular diet every day.

Later, those 1 to 2 liters mix up with another 7 liters of digestive discharges, making up 8-9 liters. These discharges or secretions are absorbed first by the small bowel (first 80%) and then the large bowel (remaining 20%), leaving approximately 150cc for its excretion with feces (more than 98% percent of liquid needs to be absorbed). Therefore, diarrhea occurs when there is an alteration of this normal physiologic process of digestion and water absorption.

The following are the different types of diarrhea.

Diarrhea Secondary to Secretory Dysfunction

Also known as secretory diarrhea, it occurs when toxins from bacteria attack the bowel tissue, or there is an abnormal amount of hormones that stimulate water discharge by the gut, as in some types of tumors.

The bowel has the function of absorbing or discharging water from the digestive tract and the food intake. In secretory diarrhea, there is little or no gut structural damage at all. However, there is damage or an alteration to the regulatory mechanism of water in the bowel.

In this type of diarrhea, the bowel may be secreting more water than normal. At the end of the day, the bowel does not absorb all the necessary liquid due to this abnormal water discharge. Toxins and hormones create a misbalance within the cells that damages the water regulatory mechanism.

In secretory diarrhea, characteristically, diarrhea does not stop, even if the patient stops eating food, which is very helpful in other diarrheas.

Osmotic Diarrhea

Osmotic diarrhea happens when there is an oversupply of solute (a material, habitually a solid, that is dissolved in a liquid) in the bowel when they should not be there. This happens when a person drinks solutions with an excess of sugar or salt, for example. The cells cannot absorb that amount of solutes within the bowel, causing water’s discharge to maintain balance.

This is also the case of osmotic laxatives. They produce a misbalance within the digestive tract in order to extract water from the body and alleviate constipation. This type of diarrhea stops when the patient stops the intake of the causing agent. 

Diarrhea Secondary to Malabsorption

There are several conditions that may cause diarrhea secondary to malabsorption. Depending on the condition that causes it, it can be fatty or just watery diarrhea. Among the conditions that cause this type of diarrhea are some of the following:

  • Crohn’s disease
  • Celiac disease
  • Biliary disease

Diseases have different mechanisms by which they can block absorption of a specific type of food. Some of them affect the absorption of the fatty acids from the food intake like a biliary disease. Others affect the small bowel’s surface, making it difficult to absorb nutrients like Crohn’s disease. The final result is that the body does not absorb the nutrients and causes diarrhea.

Exudative Diarrhea

Exudative diarrhea has a direct correlation to pathologies that cause inflammatory reactions within the bowel. Inflammatory reactions may cause the discharge of fluids like blood or pus that may alter nutrients’ absorption. These fluids may cause a direct hit on the bowel asides from the malabsorption, increasing the stool’s volume and frequency.

Of course, this type of diarrhea is a very important mechanism for developing bloody diarrhea. The following conditions run with mucosal inflammation within the bowel:

  • Diverticulitis
  • Inflammatory Bowel Disease
  • Invasive Enteric Infections: Shigellosis, Salmonellosis, among others.
  • Ulcerative colitis
  • Crohn’s disease

Diarrhea Secondary to Altered Bowel Movement

This type of diarrhea, as its name says, will depend entirely on the bowel movement. If the bowel movement becomes too fast, the patient will suffer from diarrhea. This will happen because the food will not have enough time to be absorbed.

On the other hand, if the bowel movement becomes too slow, bacteria may grow within the bowel, causing infectious diarrhea. This also includes mild or partial intestinal obstructions that may slow down the bowel movement. It can also promote the overgrowth of bacteria in the bowel, causing diarrhea.

What is acute bloody diarrhea?

Acute bloody diarrhea is an emergency due to its relation to disorders that can be life-threatening. Sometimes, it also means that measures must be taken to prevent the spread of the disease within the community. However, not all of the causes may be in direct correlation with an infectious disease. Some of them may be non-infectious, like anatomic bleeding, inflammatory bowel disease, among others.

The latter point may help while making a differential diagnosis in children and adults. Adults are more likely to suffer from non-invasive causes (gut diseases), while children are more likely to suffer from infectious causes (gut infections). The older the patient, the more complicated it can be. It will also depend on the other symptoms of the patient and the characteristics of diarrhea. For example, generally, these patients may suffer from dehydration because of the continuous loss of liquids.

Acute bloody diarrhea can also be confused with rectal bleeding. That is why the physician must perform an excellent history and physical examination of the patient. While rectal bleeding may not be as severe as acute bloody diarrhea, it may indicate another type of disease.

For example, acute bloody diarrhea may talk to the physician about infections like bacterial gastroenteritis or a Clostridium difficile infection. On the other hand, it may also speak of parasitic infections due to entamoeba histolytica.

Rectal bleeding may have causes like anal fissures, hemorrhoids, among others. Bleeding through the stool may not always be visible. For example, physicians may ask tests to detect occult blood within the stool. Nonetheless, it is essential to visit a doctor anytime the blood is visible on the stool.

What does diarrhea with blood or bloody diarrhea mean?

It can mean a lot of things, but the most important one is that you should visit a doctor. Diarrhea with blood is not a normal event. Still, the severity will also depend on the other symptoms the patient presents.

The most common symptom these patients have alongside bloody diarrhea is abdominal pain. Sometimes, this situation can mean that the patient does not take care of essential hygiene measures. For example, the patient’s water may not be clean, which means it can carry parasites or bacteria. This is a serious issue because it may involve a whole community and must be taken care of quickly.

On the other hand, it may represent different types of diseases that go from inflammatory bowel disease to colon cancer. However, there are mild cases in which the cause is more trivial, like hemorrhoids or anal fissures. Nonetheless, that does not mean it can go unseen by a doctor. If these conditions do not receive proper attention, it may complicate over time. 

Gastrointestinal diseases may affect children more seriously. The fact that blood appears on diarrhea may affect the whole growing process. Diarrhea per se produces dehydration to anybody. Children are at higher risk of becoming severely dehydrated with bloody diarrhea.

The most common cause in kids for bloody diarrhea is infectious causes. This means that simple diarrhea may become severe diarrhea and a life-threatening condition. However, most of the cases in children are viral diarrheas that cease by themselves without treatment. The only treatment in those cases is to prevent dehydration through rehydration therapy.

Ultimately, red diarrhea means that there is a process that may be affecting the bowel tissue. Whether it is bacteria, virus, parasites, or any other condition, it can become a severe disease if not treated properly.

What causes blood in diarrhea?

Bloody diarrhea is a very global term, and it can mean many things. Several possible causes may produce blood in diarrhea. They can go from a “simple” infection to Colon Cancer. This will also depend on the age of the patient. Nonetheless, it is a condition that should be seen by a doctor.

The following list will include infectious to non-infectious causes and a brief description of the most important ones.

  1. Infectious
    • Bacteria: Escherichia coli, Shigella (Shigellosis), Salmonella (Salmonellosis), Clostridium difficile, Campylobacter jejuni, Yersinia, Aeromonas.
    • Viruses: Cytomegalovirus (CMV).
    • Parasites: Entamoeba histolytica, Schistosomiasis, Trichuris trichiura (Whipworm), Hookworm, Balantidium coli, Ascaris lumbricoides (Acariasis).
  2. Ischemic Colitis
  3. Inflammatory Bowel Disease
  4. Diverticulitis
  5. Colon Polyps
  6. Anatomical Gastrointestinal Bleeding:
    • Hemorrhoids
    • Angiodysplasia
    • Gastric/Peptic Ulcer
  7. Colon Cancer
  8. Medications

Escherichia Coli Diarrhea (bloody diarrhea)

Usually, E. coli bacterium lives within the intestines of healthy people. Nonetheless, there are different strains of this bacterium, and some may indeed cause disease to the human body.

For example, there is a strain commonly known as Enterohemorrhagic Escherichia coli or EHEC. This bacterium produces a toxin that receives the name of Shiga Toxin. It will cause an inflammatory process within the bowel affecting the tissue and causing diarrhea.

The bacteria will also affect the bowel’s blood vessels and other parts of the body, causing bloody or red diarrhea. People may recover very quickly from this infection without any antibiotics. This is because antibiotics may cause more harm than good with this type of infection. Despite this, the treatment of diarrhea requires, in this case, rehydration and close monitoring by a doctor.

Most people will have general symptoms like diarrhea (It can go from watery to bloody), stomach cramping, and nausea. People often get this infection from exposure to contaminated food or water, especially raw vegetables or undercooked ground beef.

The infection can also travel from person to person if they do not wash their hands properly. Like young infants or older adults, people at extreme ages are more likely to have complications because of the infection. The latter point sources on the fact that they may suffer from a condition that receives the name of Hemolytic Uremic Syndrome. It is a condition that is potentially life-threatening, affecting the kidneys.

Many of these high-risk groups could develop with this infection a very low red blood cell count and a low platelet count. Therefore, these groups are targets for red blood cells and platelet transfusions as part of the therapy. 

Shigellosis bloody diarrhea

A family of bacteria causes the disease, and they are named Shigella. The infection is common in developing countries. It results from poor sanitation conditions, contaminated food, or direct person to person contact.

Sadly, the infection is very common in infants younger than five years old. So, It is no surprise also that it is widespread in places like child care settlements. For example, the situation is evident when the daycare staff does not wash their hands properly, subsequent to changing diapers or assisting toddlers with bathroom training.

The infection occurs when someone accidentally ingests this bacterium. It is a bacterium that releases toxins within the gastrointestinal tract. These toxins will produce an inflammatory response and will damage the bowel tissue.

Usually, the symptoms appear from 12 hours to 3 days after ingesting the bacterium. Among the most common symptoms are the following:

  • High fever
  • Abdominal cramps
  • Vomiting
  • Diarrhea with blood and/or mucus

These symptoms tend to last from five to seven days, and it may require antibiotics if the infection is severe. The infection can be severe in people at extreme ages of life or with a deficient immune system. It includes infants, older adults, or people with HIV infection.

Generally, treatment to prevent dehydration is enough with this condition. People at high risk can get severe complications from the disease. The complications that could take place include seizures (especially in infants), rectal prolapse, dehydration, bacteremia (bacteria in the blood), among others.

Salmonellosis bloody diarrhea

Salmonella infection is a common disease that affects the gastrointestinal tract. The bacterium resides within the bowel in humans and animals, and they are spreaders of the bacteria through feces. People acquire the infection through food or water that does not meet the minimum sanitation requirements.

In most cases, the infection presents itself as gastroenteritis and enterocolitis. It is important to know that there are two types of Salmonella. One of them is the Salmonella typhi, which causes Typhoid fever. The other types are Nontyphoidal Salmonella. For educational purposes, this article will talk about Nontyphoidal Salmonella. 

Salmonella infection can be acquired after eating undercooked meat, poultry, milk, or eggs, including their products. Symptoms may appear from 8 hours to approximately three days after the contact.

The most common symptoms include:

  • Nausea
  • Fever
  • Diarrhea with or without blood
  • Fever
  • Headache
  • Abdominal pain

It is a condition that generally lasts between two to seven days. However, diarrhea may last up to 10 days. For the bowel to return to normal, it may take several months.

The risk of acquiring a salmonella infection is higher if you travel to countries in development or poor sanitation policies. Some medications and conditions can increase the risk of developing Salmonella infection. For example, antiacid medication may help the salmonella to survive as well as recent use of antibiotics.

Also, conditions like inflammatory bowel disease or HIV infection promote the survival of salmonella. Salmonella infection can develop further complications if not treated on time. People can suffer from severe dehydration, reactive arthritis (joint swelling), or bacteremia.

Traveler’s Diarrhea

Although it is not within the list, it is a very common disease while traveling, as its name says. The most common causes of this disease are Enterohemorrhagic Escherichia coli, Salmonella, and Shigella. It affects from 30% to 70% of travelers. Poor hygiene practice in local restaurants is the largest contributor to the risk of developing a Traveler’s diarrhea. The symptoms of this disease usually resolve spontaneously within 12 hours.

Entamoeba histolytica bloody diarrhea

Commonly known as amoebiasis or amoebic dysentery, it is a condition caused by a microscopic parasite. The parasite is Entamoeba histolytica.

Sometimes, the parasite can live within the bowel for years without causing any symptoms. However, it can also cause severe disease. These amoebas can invade the intestine wall, causing intestinal ulcers, bleeding, an increase in mucus production, and diarrhea.

They can also migrate from the bowel through the blood to other organs like the liver or the brain. As with many gastrointestinal infections, this parasite spreads through feces. Afterward, the parasite can contaminate water supplies that have poor sanitation measures.

The symptoms vary depending on the severeness of the disease. If it is mild, people can suffer from mild abdominal pain and two to three loose stools daily. On the other hand, if the symptoms are severe, it may include high fever, severe abdominal pain, and ten or more daily diarrhea episodes with blood and mucus.

The disease may last from a few days to several weeks. Sadly, the patient can suffer from complications or another episode of the disease; that is why identifying, preventing, and treating this infection is so important. Typical antiparasitic drugs are usually very effective in killing the parasite, although some resistance to standard treatment already exists.

Inflammatory Bowel Disease

This is a term that applies to two specific conditions, Crohn’s disease, and Ulcerative Colitis. Both of them are characterized by chronic inflammation or swelling of the gastrointestinal tract.

This inflammatory process results in damage to the gastrointestinal tract. Although these two conditions define IBD, both of them are a little bit different. Crohn’s disease may alter any part of the intestinal tract.


In contrast, ulcerative colitis affects only the large bowel and the rectum. Crohn’s disease also affects all the layers of the tissue within the intestinal tract. Ulcerative colitis only affects the superficial layers of the large bowel and rectum.

The cause for this disease is unknown to this day; some scientists agree that it may result from a defective immune system.

These diseases, although different, may have some symptoms in common. The following list has some of them:

  • Persistent diarrhea
  • Abdominal pain
  • Weight loss
  • Bloody diarrhea
  • Fatigue

Symptoms may range from mild to severe. People are very likely to have periods of active illness with periods of remission as well. This disease is one of the most common causes of chronic diarrhea, affecting the patient’s lifestyle. It is a disease that can also develop serious complications. Among them are the following:

  • Colon cancer
  • Bowel obstruction
  • Fistulas
  • Anal Fissure
  • Perforated colon
  • Severe dehydration

On the other hand, it is essential to know that IBD is not the same as Irritable Bowel Syndrome. These are two very different diseases. Also, IBD is not the same as Celiac disease. Celiac disease is an inflammatory response to gluten.

When should I suspect inflammatory bowel disease?

Inflammatory Bowel Disease affects nearly 3 million people in the US. Most people with IBD are diagnosed in their twenties or thirties. However, this is a condition that is not so common.

To suspect that you suffer from IBD, first of all, you should know if someone in your family suffers from this condition. Then, by knowing this, patients suspecting this disease should assess themselves, looking for symptoms, in order to describe them to the doctor (a gastroenterologist preferably).

The symptoms of IBD can go from mild to severe. It is a condition that has active periods and remission periods. People with IBD suffer from persistent diarrhea with blood on it. They also suffer from abdominal pain and cramping, unintended weight loss, fatigue, and loss of appetite. This is because of the active bleeding through the feces that can cause anemia. People who feel that they may be suffering from a chronic disease can visit their doctor even more if it involves bloody diarrhea. 

Can hemorrhoids cause bleeding in the stool or bloody diarrhea?

The short answer is yes, they can cause bleeding in the stool, but why? What are hemorrhoids?

Hemorrhoids or piles are vessels (veins) in the anus or lower rectum that are swollen. Hemorrhoids can develop inside the anus or outside the anus. The veins around the anus tend to tighten under pressure; this can cause them to swell.

Some of the causes that increase the rectum pressure are the following:

  • Having chronic diarrhea or constipation
  • Obesity
  • Pregnancy
  • Sitting for long periods on the toilet
  • Having anal intercourse
  • Eating a low fiber diet

All of these causes interfere directly with the blood flow to and from the area. This will ultimately cause the blood vessels to pool and enlarge. This phenomenon also explains why pregnant women suffer from hemorrhoids. As the uterus enlarges, it will generate direct pressure on the veins. Due to this vein inflammation, the stool is very likely to have blood on it. 

External hemorrhoids are the most uncomfortable of the two. The skin around the vein becomes irritated and later erodes. Patients may suffer from itching or irritation in the anus, pain or discomfort, swelling, and bleeding. These hemorrhoids can also form blood clots within them. This will cause sudden and severe pain.

People often can feel a lump around the anus. Later the clot will dissolve but will leave this lump in the skin that may itch, even excessively.

Internal hemorrhoids are usually painless. Although they produce bleeding, the patient will not feel any discomfort. These hemorrhoids, on the other hand, may prolapse. This could cause several problems. If hemorrhoid protrudes, it can accumulate mucus and stool, which will irritate.

How common is infection compared with inflammatory bowel disease?

It isn’t easy to tell, as it is very variable. Approximately 1% of the population in the United States have inflammatory Bowel Disease. Still, infectious diseases are widespread and, when summed up, of course, throw a larger number.

It is easy for children to tell that the infection cause is the most common as it is even very rare for them to suffer from structural damages (gut diseases). On the other hand, with adults, it is slightly different. They similarly suffer from infectious causes of gastrointestinal problems, but as people grow older, several non-infectious diseases could appear rare for the youngster, like inflammatory bowel disease.

Moreover, gastrointestinal infections are very common in people with unhealthy habits or communities with poor sanitation measures. Consequently, it is no surprise that it is far more common for people to suffer from gastrointestinal infection than Inflammatory Bowel Disease. Having this in mind, doctors should always check if it is a case of IBD, and patients should be aware of this condition’s existence.

Can constipation cause blood in the stool or bloody diarrhea?

Yes, constipation and straining to pass a large bowel movement can cause blood in the stool. Diets with low fiber content or not drinking enough water may cause constipation. While suffering from constipation, the patient will apply more pressure to defecate. This will ultimately affect the veins around the anus. Also, while suffering from constipation, the feces can become dry. This will similarly cause damage to the bowel and rectum tissue. It can also cause anal fissures. 

Constipation refers basically to a decrease in bowel movements. The definition says that having fewer than three movements per week is constipation. The longer a person takes to go to the bathroom; it becomes more difficult for the poop to come out.

These people often have pain while having bowel movements and feel that the bowel is not fully empty. This is a widespread condition that could affect anyone but especially older people, women after pregnancy, and people on medications or unhealthy diets. This happens when the large bowel absorbs too much water from the waste, drying out the feces and making them hard.

How doctors diagnose Intestinal Infections?

First of all, doctors will need to have a wider view of the panorama. They will make a complete history in which they will ask the patient’s symptoms and the date it began. They will also perform a full body examination to look for signs that may refer to one diagnosis or another. After doing this, the doctor may indicate a series of exams depending on the pathology.

The most common tests are the following:

  • Blood test: A simple blood test may help the doctor to tell what is causing diarrhea. If it is an infectious cause, it may show on the blood test.
  • Stool test: This is one of the most critical tests. Doctors indicate this test to see if there is the presence of bacterium or parasites within the stool that may be causing diarrhea. Doctors can also ask for occult blood within the stool to make a differential diagnosis. Sometimes the blood cannot be visible to the naked eye. It will take a microscopic study to see if there is bleeding.
  • Flexible Sigmoidoscopy or Colonoscopy: The doctor will use a thin tube that will go inside your rectum. This will allow him to see inside your large bowel. This device also helps the doctor to take samples of tissue (biopsy) for further studies. This is a very helpful test for conditions like Inflammatory Bowel Disease. It is important to know that flexible sigmoidoscopy enables the doctor to see the lower colon. On the other hand, the colonoscopy allows him to see the entire colon.

Do you have bloody diarrhea?

These tools gather the most important signs, symptoms, and risk factors for diagnosing the disease underneath your bloody diarrhea. They will tell anybody who uses it about their symptoms because of a disease or infection. Using them is free and would only take a few minutes.

What do you think?

Written by Dr. Esteban Kosak

Doctor of Medicine - MD Recently Graduated from Medical School and inspired to aid the global population during this situation. I think that we shall no longer be waiting to see a doctor when we feel sick. Several times we feel disease searches in Google drive us to a rabbit hole and come out thinking that we may die of cancer or something very serious, given that symptoms may seem to fit a wide variety of illnesses. Since I recently graduated from medical school. I have all the medical information fresh in my mind. My thorough experience as an expert researcher allows me to very-well known the different diseases and conditions that affect human bodies. Empowered by the United Nations 17 Sustainable Development Goals (SGDs). I think that we all can provide a grain of sand to help humanity. That's why we created Symptoms.Care a place where you can come and screen your symptoms and find what different illnesses can be related to them. Armed with the right information you can instantly, discretely, secure and from the comfort of your home talk with a Doctor that can Evaluate your Symptoms and help you seek the right treatment.


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