Echocardiography is also used if there is a suspicion of pulmonary hypertension or high-output cardiac failure due to large liver lesions, sometimes followed by cardiac catheterization to measure the pressures inside the various chambers of the heart. Liver AVMs may be suspected because of abnormal liver function tests in the blood, because the symptoms of heart failure develop, or because of jaundice or other symptoms of liver dysfunction. The most reliable initial screening test is Doppler ultrasonography of the liver; this has a very high sensitivity for identifying vascular lesions in the liver. If necessary, contrast-enhanced CT may be used to further characterize AVMs. It is extremely common to find incidental nodules on liver scans, most commonly due to focal nodular hyperplasia (FNH), as these are a hundredfold times more common in HHT compared to the general population. FNH is regarded as harmless. Generally, tumor markers and additional imaging modalities are used to differentiate between FNH and malignant tumors of the liver. Liver biopsy is discouraged in people with HHT as the risk of hemorrhage from liver AVMs may be significant. Liver scans may be useful if someone is suspected of HHT, but does not meet the criteria (see below) unless liver lesions can be demonstrated.Brain AVMs may be detected on computed tomography angiography (CTA or CT angio) or magnetic resonance angiography (MRA); CTA is better in showing the vessels themselves, and MRA provides more detail about the relationship between an AVM and surrounding brain tissue. In general, MRI is recommended.
These lesions may bleed intermittently, which is rarely significant enough to be noticed (in the form of bloody vomiting or black stool), but can eventually lead to depletion of iron in the body, resulting in iron-deficiency anemia. Arteriovenous malformation
Arteriovenous malformations (AVMs, larger vascular malformations) occur in larger organs, predominantly the lungs (pulmonary AVMs) (50%), liver (30–70%) and the brain (cerebral AVMs, 10%), with a very small proportion (<1%) of AVMs in the spinal cord.Vascular malformations in the lungs may cause a number of problems. The lungs normally "filter out" bacteria and blood clots from the bloodstream; AVMs bypass the capillary network of the lungs and allow these to migrate to the brain, where bacteria may cause a brain abscess and blood clots may lead to stroke. HHT is the most common cause of lung AVMs: out of all people found to have lung AVMs, 70–80% are due to HHT. Bleeding from lung AVMs is relatively unusual, but may cause hemoptysis (coughing up blood) or hemothorax (blood accumulating in the chest cavity). Large vascular malformations in the lung allow oxygen-depleted blood from the right ventricle to bypass the alveoli, meaning that this blood does not have an opportunity to absorb fresh oxygen. This may lead to breathlessness. Large AVMs may lead to platypnea, difficulty in breathing that is more marked when sitting up compared to lying down; this probably reflects changes in blood flow associated with positioning.