**5.5 Liver**

Radiation injury to the liver, also known as radiation-induced liver disease (RILD), is unique in that it is often during the healing process that tissue function undergoes disorganized repair, including injury to the reticulum network, and limits the vascular relationship to the hepatocyte. While acute damage to hepatocytes affects liver function, as the cells divide during repair they tend to become disorganized, particularly if the structural reticulum of the liver is damaged. Increased distance between the hepatocytes and the blood supply leads to decreased liver function. This phenomenon explains why the state of the liver before exposure to radiation also plays an important role in this process. For example, a cirrhotic liver due to heavy alcoholic use or hepatitis will likely have pre-existing disorganized architecture, making this liver more susceptible to radiation damage. This includes veno-occlusive disease which also separates vascular anatomy from the hepatocyte. For these reasons, imaging studies such as magnetic resonance imaging before the delivery of radiation are obtained for evaluation of anatomy and function [25]. Disorganized repair can lead to migration of infusional therapies including radiolabeled therapy as the vascular anatomy can be disrupted and limit efficacy in spite of placement of therapy in close approximation to disease.

#### **Figure 2.**

*(A) and (C) Therapy driven pneumonitis outlining the radiation therapy field while on immune check point inhibition. (B) and (D) Improvement after immunotherapy withdrawal. Courtesy of the Department of Radiation Oncology, University of Massachusetts Medical School.*

Patients with RILD typically experience symptoms that mimic cirrhosis, which include abdominal pain, elevated liver enzymes, jaundice, and ascites within four months of radiation exposure. Livers with pre-existing damage typically have earlier onset, with more severe symptoms. Treatment is symptomatic with keen observation of potential veno-occlusive and metabolic disease secondary to a congested liver with decreased function. Careful consideration must be given for medications that are metabolized in the liver, especially chemotherapeutic agents that are also hepatotoxic [25, 26].

## **5.6 Renal**

All components of the kidney, including structures crucial for filtration, such as cells of the glomerulus, are susceptible to radiation damage. The signs of acute radiation damage are usually seen within 3–18 months, typically mimicking signs of renal failure. These signs include decreased glomerular filtration rate (GFR), increased serum β2-microglobulin, albuminuria, and other markers of poor renal function. Later signs of kidney radiation damage, which include hypertension and eventual renal failure, are often hard to distinguish from other pathological causes. For treatment of these sequelae, the use of hypertension medications such as angiotensin-converting-enzyme inhibitors (ACE) inhibitors are theoretically beneficial. Monitoring of renal function, both short and long term, also remains crucial in the standard of care for these patients [27–29]. In aging patients who are

**11**

**Figure 3.**

*Radiation Injury and Emergency Medicine DOI: http://dx.doi.org/10.5772/intechopen.95262*

**5.7 Cardiovascular system**

techniques and optical tracking.

exposure [34].

effort to spare as much renal function as possible.

not candidates for surgery, radiation therapy with stereotactic techniques is being used more frequently to treat sub-total renal volumes for renal malignancies in an

The mechanism of radiation damage to the heart and blood vessels involves immediate cellular damage followed by fibrotic and disorganized repair, leading to reduced function in all cardiac segments including electrical conduction, myocardium, valves, and vascular anatomy. The time period is variable due to differences in size and functional architecture. However, what is clear is that unintended radiation exposure to the heart and blood vessels has a strong association with cardiovascular disease and complications [30–33]. The lack of mitigation and therapeutic strategies in response to radiation of cardiovascular tissues explains why radiation oncologists spend such a large amount of effort to minimize cardiovascular

Generous radiation exposure to the heart can result in acute pericarditis. This diagnosis should always be in the differential in a patient with history of radiation exposure who presents with sharp, radiating chest pain that is relieved when sitting up. Anti-inflammatory medications like aspirin, colchicine and prednisone can offer symptomatic relief, with pericardiocentesis being an option in severe cases. Long term, patients who receive radiation exposure to the heart have a higher risk of heart disease and use of echocardiograms and nuclear stress tests in these patients is recommended if symptoms warrant use. Large blood vessels like the aortic, carotid, and femoral arteries can experience hyperplasia and atherosclerotic change from radiation doses. These changes can result in rupture and fistula formation, necessitating immediate treatment. This usually requires very high doses and prolonged exposure usually not seen in modern radiation therapy [30–33]. With improvements in survival, patients can receive therapy with intentional overlap to previously treated volumes for second malignancies. These patients are vulnerable to vascular injury, including larger arteries and survivorship plans need to include periodic surveillance of vessels to optimize follow up care. **Figure 3** demonstrates cardiac sparing for left-sided breast cancer treatment with breath-hold treatment

*Cardiac sparing with deep inspiration breath-hold (DIBH), (left-free-breathing (FB); right-DIBH). Image* 

*courtesy of the Department of Radiation Oncology, University of Massachusetts Medical School.*

not candidates for surgery, radiation therapy with stereotactic techniques is being used more frequently to treat sub-total renal volumes for renal malignancies in an effort to spare as much renal function as possible.
