Intestinal Angioedema – Causes, Symptoms, Diagnosis, Treatment

Intestinal angioedema is a fairly rare condition where there is swelling of the wall of the bowels (intestines). It can affect the small or large intestine and is often misdiagnosed for other gastrointestinal conditions. The edema will cause a range of symptoms that are vague and unless acquired, hereditary or drug-related angioedema has been diagnosed, intestinal angioedema will often be missed as a possible diagnosis.

Causes of Intestinal Angioedema

Angioedema affects the deeper layers of the skin (lower dermis) or subcutaneous tissues as well as submucosal layers. The intestines are lined with mucosa and beneath this is the submucosal layer. In angioedema, the vessels of the submucosa become ‘leaky’. This allows fluids from the blood to empty into the interstitial fluid of the submucosal lining and this results in swelling (edema) of the intestinal walls.

Most reported cases of intestinal angioedema are attributed to drug-related angioedema, a type of angioedema often seen with the use of ACE (angiotensin converting enzyme) inhibitors. ACE is an enzyme in the body and one of its actions is that it is responsible for the contraction of the muscles of the blood vessels. This results in hypertension and an ACE inhibitor blocks the muscle contractions, leading to relaxation of the vessel muscles.

ACE inhibitors also help to increase the level of bradykinin which further assists with vasodilation. This helps to ease the high pressure within the blood vessels. However, bradykinin is one of the vasoactive substances that can increase vascular permeability causing a ‘leaky’ vessel. Fluid from the blood vessels can enter the interstitial spaces of the submucosa, thereby causing swelling (edema). Severe swelling will narrow the lumen of the small intestine. Discontinuing the drug usually resolves the condition within a short period of time.

Patients with acquired and hereditary angioedema may also be prone to intestinal angioedema. These types of angioedema are due to C1-INH (C1-inhibitor) deficiency. This enzyme is responsible for inhibiting the activity of a type of immune chemical known as a complement. With C1-INH deficiency, the complement C1 can now continue to act without being inhibited. It leads to activation of the kinins which then contributes to increased vascular permeability (‘leaky vessels’). As mentioned above, this causes swelling of the submucosa of the intestines.

It is possible that intestinal angioedema could occur in allergic or idiopathic edema but this is not often reported. Refer to Angioedema Causes.

Intestinal Angioedema Signs and Symptoms

The common symptoms of intestinal angioedema include :

  • Abdominal pain – pain may aggravate shortly after eating.
  • Nausea and vomiting.
  • Intestinal cramps.
  • Abdominal distenstion may be present in severe cases. This may be mistaken for gas bloating.

Abdominal pain may also result in a lack of appetite which can contribute to loss of weight over a period of time. It is possible that digestion and absorption can be severely affected if the angioedema affects large tracts of the intestine. This could lead to a number of possible conditions including malabsorption syndromes leading to nutritional deficiencies. This is not commonly reported though.

Intestinal angioedema will often not occur in isolation. Other areas of the body may be affected simultaneously like the air passages and skin. Urticaria (hives) may be present. There may also be shortness of breath due to the impaired air intake.

Diagnosis of Intestinal Angioedema

A CT scan is effective in identifying the narrowing of the lumen and with the presence of other signs and symptoms of angioedema, a quick diagnosis can be made. A colonoscopy may also assist with identifying the intestinal narrowing.  In some cases of severe abdominal pain, which is unresponsive to most therapeutic measures, a laparoscopy may be conducted but a diagnosis of intestinal angioedema can be missed with this procedure. Other procedures which can assist with the diagnosis include a barium swallow (small intestine angioedema) and an MRI.

A good case taking may be sufficient to make the diagnosis of intestinal angioedema in certain cases. The use of ACE-inhibitors, history and/or signs and symptoms of hereditary or acquired  angioedema or episodes of urticaria should alert the attending physician to the possibility of intestinal angioedema. However, since this condition is rare, other more common causes of abdominal pain with or without nausea and vomiting may first be suspected.

A blood test for C1-INH may assist with a diagnosis of acquired or hereditary angioedema.


Treatment should be directed at the type of angioedema diagnosed. In drug-related angioedema, the drug should be discontinued and symptomatic relief may be seen as soon as 24 hours. With acquired and hereditary angioedema, some of the treatment options include :

  • Serine proteinase inhibitors (serpins)
  • Kallikrein inhibitors
  • Anabolic steroids

Intestinal angioedema should be diagnosed and treated by a medical practitioner. Antihistamines and other ‘allergy’ medication may not be effective for treating this condition.

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