Cystic bronchiectasis is also associated with an increased bronchoarterial ratio, meaning that the bronchioles are larger than the blood vessels that run alongside them. Infectious causes
Bacterial, mycobacterial, and fungal infections are common causes of lung cavities. Globally, tuberculosis is likely the most common infectious cause of lung cavities. Less commonly, parasitic infections can cause cavities. Viral infections almost never cause lung cavities; in a small study of immunocompromised patients with a lung infection, the presence of a cavity on CT scan essentially ruled out viral infection. In the same study, about one-third of the cavities were caused by a bacterial infection, another third were caused by a mycobacterial infection, and another third were caused by a fungal infection. Bacterial
Bacteria can cause lung cavities in one of two ways; they can either enter the lung through the trachea (windpipe), or they can enter through the bloodstream as septic pulmonary emboli (infected blood clots). Community-acquired pneumonia is an uncommon cause of lung cavities, but cavitary pneumonia is occasionally seen with Streptococcus pneumoniae or Haemophilus influenzae infection. However, since these two species of bacteria are such common causes of pneumonia, they may cause a significant fraction of all cavitary pneumonias. The most common bacterial causes of lung cavities are Streptococcus species and Klebsiella pneumoniae. Less commonly, the bacteria Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter, Escherichia coli, and Legionella can cause cavitation.
Bowel infarction or gangrenous bowel represents an irreversible injury to the intestine resulting from insufficient blood flow. It is considered a medical emergency because it can quickly result in life-threatening infection and death. Any cause of bowel ischemia, the earlier reversible form of injury, may ultimately lead to infarction if uncorrected. The causes of bowel ischemia or infarction include primary vascular causes (for example, mesenteric ischemia) and other causes of bowel obstruction. Causes
Primary vascular causes of bowel infarction, also known as mesenteric ischemia, are due to blockages in the arteries or veins that supply the bowel. Types of mesenteric ischemia are generally separated into acute and chronic processes, because this helps determine treatment and prognosis.Bowel obstruction is most often caused by intestinal adhesions, which frequently form after abdominal surgeries, or by chronic infections such as diverticulitis, hepatitis, and inflammatory bowel disease. The condition may be difficult to diagnose, as the symptoms may resemble those of other bowel disorders. Bowel volvulus describes a specific form of bowel obstruction, where the intestine and/or mesentery are twisted, resulting in ischemia. Management
An infarcted or dead intestinal segment is a serious medical problem because intestines contain non-sterile contents within the lumen. Although the fecal content and high bacterial loads of the intestine are normally safely contained, progressive ischemia causes tissue breakdown and inevitably leads to bacteria spreading to the bloodstream.