Causes of Dog's Bloody Stool: What's Happening?
Blood in stool is a result of gastrointestinal bleeding caused by certain factors, which then exits the body through the anus along with feces. The manifestation of blood in stool varies depending on the location of the bleeding in the digestive tract, ranging from simple blood in stool, blood after stool, blood before stool, mixed blood and stool, or blood mixed within the stool. The color of the blood in stool also differs based on the bleeding site, the amount of blood lost, and how long the blood remains in the digestive tract. The farther the bleeding site is from the anus, the less the blood loss, the longer the blood stays in the digestive tract, resulting in darker blood, often blackishred or even black. Conversely, if the bleeding is more severe, the blood in stool will appear lighter.
Blood in stool often comes with symptoms such as abdominal pain, urgency to defecate, fever, a tendency towards bleeding throughout the body, skin changes, and abdominal masses.
Fresh red blood in stool and dark red blood in stool typically indicate lower gastrointestinal bleeding (small intestine, colon, rectum, anus), where the stool is often bright red or dark red, sometimes mixed with mucus and pus. This is commonly seen in anal fissures and colorectal cancer. Blood in stool with dysentery appears as puslike stool, with frequent bowel movements and symptoms like left lower abdominal pain.
Black tarry stool, which is often caused by upper gastrointestinal bleeding (esophagus, stomach, duodenum) or small intestine bleeding, occurs when blood remains in the intestines for a longer period. The red blood cells break down, and the hemoglobin combines with sulfur in the intestines to form ferrous sulfide, turning the stool black. Due to the粘附的mucus, the stool has a glossy appearance, resembling tar, hence the name "tarlike stool." The presence of tarlike stool indicates a significant amount of bleeding, usually over 60 milliliters. However, certain foods and medications can also make stool appear black, and a fecal occult blood test can help distinguish these cases.
Occult blood in stool refers to small amounts of gastrointestinal bleeding (less than 5 milliliters per day) that do not change the color of the stool. It is only detected through a positive fecal occult blood test. All diseases that cause gastrointestinal bleeding can lead to occult blood in stool, and it is commonly associated with conditions like gastric ulcers and gastric cancer. Persistent positivity may indicate gastrointestinal tumors, while intermittent positivity may suggest peptic ulcers.
Diagnosis is based on medical history, clinical symptoms, and physical examination:
Acute onset and a short course of illness suggest acute blood in stool due to various causes, such as food poisoning, Salmonella infection, dysentery, and drug intoxication.
Abdominal symptoms, such as diarrhea and abdominal pain, are often associated with eating habits.
Systemic symptoms, such as fever and systemic reactions, may indicate acute intestinal infections.
Parasitic blood in stool requires further examination of feces or blood to confirm the diagnosis.
Distinguishing blood in stool based on color and symptoms:
Anal and rectal diseases: Blood in stool is usually normal, with fresh blood attached to the outside or dripping out after defecation. In rectal cancer, the blood in stool may contain necrotic and ulcerated tissue.
Colonic diseases: Blood in stool is usually bright red, with minimal blood, and accompanied by large amounts of mucus or pus. Sometimes, pathogenic bacteria can be found in stool examination or culture. Cancerous stools may contain necrotic and ulcerated tissue.
Small intestinal diseases: Blood in stool is usually small in amount, dark red, and has a thin, red bean soup or tomato juicelike appearance, with a foul smell. Conditions like intestinal tuberculosis and regional enteritis have minimal bleeding. Acute hemorrhagic necrotizing enteritis has an acute onset, with symptoms of infection and intoxication, easy to shock, and accompanied by episodic severe cramping pain around the umbilicus and diarrhea.
Acute infectious diseases: Fever and systemic symptoms of infection and intoxication are present, with varying amounts of blood in stool.
Diagnosis based on the color of blood in stool:
1. Fresh red stool: This usually originates from the lower end of the ileum, colon, rectum, and anus, and is often bright red or dark red, sometimes mixed with mucus or pus. Common causes include:
Anal and rectal diseases: Hemorrhoids usually occur during defecation; anal fissures have less blood, bright red, and in a threadlike form covering the stool; rectal polyps or colorectal cancer usually have minimal blood, not mixed with stool, with blood attached to the surface of the stool, bright red, and can be diagnosed by rectal examination or rectoscopy.
Intestinal acute or chronic infections: Bacterial dysentery has minimal blood, often mixed with stool, and appears as puslike or pusmucous stool, bright red or reddishbrown. Amoebic dysentery has dark red stool, less in amount, with a foul smell, and right lower quadrant tenderness. The stool examination can reveal amoebic trophozoites or cysts; intestinal typhoid fever usually occurs in the 2nd to 4th week, with typical symptoms like persistent fever, splenomegaly, and rash.
Colonic tumors or polyps: The bleeding from colonic polyps is bright red; advanced colon cancer can present with bright red blood in stool, sometimes with palpable masses in the abdomen and lymphadenopathy in the inguinal area.
Ulcerative colitis: The bleeding is often intermittent, with minimal blood in stool, and contains pus or mucus.
Blood disorders: Blood in stool is a local symptom of blood disorders, usually with minimal bleeding and a tendency towards bleeding in other areas. Diagnosis can be confirmed through blood tests.
2. Tarlike stool: This is a characteristic symptom of upper gastrointestinal bleeding, commonly seen in peptic ulcer disease and portal hypertension, often accompanied by vomiting of blood.
3. Occult blood in stool: This refers to stool with no color change, but a positive occult blood test. It is usually caused by small amounts of gastrointestinal bleeding, and all diseases that cause gastrointestinal bleeding can lead to occult blood in stool. Additionally, consuming animal blood or liver can cause a positive occult blood test. It is important to differentiate these cases. For example:
Eating animal blood or liver: Black stool
Taking bismuth, iron, charcoal powder, or traditional Chinese medicine: Grayishblack stool without luster, negative occult blood test
Amoebic dysentery: Dark red, jamlike, puscontaining stool
Bacterial dysentery: Blossomlike mucuspus stool
Acute hemorrhagic necrotizing enteritis: Washed meatwaterlike stool, with a foul smell. Pay attention to whether the blood is mixed with or separate from the stool.