Ischemic colitis is inflammation and injury to the large intestine (colon) caused by a temporary reduction in blood flow, known as ischemia. It is the most common form of intestinal ischemia, typically occurring when the body diverts blood away from the colon due to low blood pressure or underlying vascular disease. The seriousness of this condition depends entirely on the degree and duration of the blood flow reduction. Most people affected are older, particularly those over 60, and often have existing cardiovascular problems or other contributing factors like certain medications or recent surgery.
The Spectrum of Ischemic Colitis Severity
The severity of ischemic colitis varies across a wide spectrum, ranging from a mild and self-limiting event to a life-threatening emergency. The majority of cases fall into the milder category, known as transient or non-gangrenous ischemic colitis. In these instances, the restricted blood flow only damages the superficial layers of the colon’s inner lining, the mucosa and submucosa, which are capable of healing quickly.
This milder form is often temporary, with symptoms improving within two to three days and the colon healing completely within one to two weeks with supportive care. The seriousness is moderate and temporary, usually requiring a brief hospital stay for observation and recovery. Recovery is complete, and long-term complications are uncommon.
A much smaller percentage of cases progress to the most severe form, sometimes called fulminant or gangrenous ischemic colitis. In these instances, the lack of blood flow is severe and prolonged enough to cause full-thickness tissue death (necrosis) across the entire wall of the colon. This deep tissue damage carries a high risk of life-threatening complications, including perforation of the bowel and sepsis.
This severe form requires immediate surgical intervention to remove the dead section of the colon and carries a substantially higher risk of poor outcomes. The seriousness is also higher when the ischemia affects the right side of the colon, which is less protected by overlapping blood vessels than the left side. Right-sided ischemia is associated with a worse prognosis, a greater need for surgery, and higher mortality rates.
Immediate Warning Signs and Symptoms
Ischemic colitis usually begins suddenly, with specific symptoms that should prompt urgent medical evaluation. The most common signs include the sudden onset of cramping abdominal pain, often localized to the left lower quadrant of the abdomen. This pain is frequently followed within 24 hours by the passage of blood mixed with stool or bloody diarrhea.
Patients might also experience abdominal tenderness, a feeling of urgency to have a bowel movement, and sometimes nausea or vomiting. While the abdominal pain is usually mild to moderate in the transient form, any occurrence of bloody stool should not be ignored and warrants prompt attention.
Certain symptoms indicate a rapid progression to the more severe, life-threatening form of the condition. These warning signs include a high fever, severe pain that becomes widespread across the abdomen, and signs of peritonitis (severe tenderness and rigidity of the abdominal wall). Signs of shock, such as confusion, fainting, low blood pressure, and a rapid heart rate, suggest that the damage is extensive and may have led to perforation or sepsis. Seeking emergency care immediately is paramount, as the window for intervention in severe cases is quite small.
Diagnosis, Treatment, and Long-Term Outlook
Diagnosis involves a thorough physical examination and laboratory tests to assess the degree of inflammation and check for signs of infection. Imaging is essential, with a CT scan of the abdomen being the first test commonly performed to rule out other conditions and look for characteristic signs of bowel wall swelling. While colonoscopy with a biopsy is often considered the most definitive way to confirm the diagnosis, it may be avoided initially if there is a concern about bowel perforation.
Treatment is highly dependent on the initial assessment of severity. For the majority of people with transient ischemic colitis, the treatment is supportive and conservative, focusing on allowing the colon to heal itself. This typically involves temporary bowel rest (no food or drink by mouth), along with intravenous fluids to maintain hydration and correct electrolyte imbalances. Many healthcare providers also prescribe antibiotics to help prevent infection in the damaged tissue.
If the person’s condition worsens, or if initial imaging strongly suggests full-thickness damage or perforation, immediate surgical intervention is necessary. Surgery involves removing the dead, gangrenous segment of the colon and may require creating a temporary or permanent stoma.
The long-term outlook for the majority of people who have the mild, transient form is excellent, with a full recovery occurring within a few weeks. However, approximately 10% of people may develop long-term issues like a stricture, which is scar tissue that narrows the colon and may require follow-up treatment or surgical removal. Recurrence is uncommon, but the long-term prognosis is linked to managing the underlying vascular diseases that caused the initial event.