Final answer:
Vasodilation in the lungs and kidneys in a patient with cirrhosis is largely due to portal hypertension and compensatory mechanisms, including the development of systemic shunts and alterations in substances that regulate blood flow, as well as the body's response to fluid and sodium retention.
Step-by-step explanation:
A patient with cirrhosis experiences vasodilation in the lungs and kidneys due to a combination of factors. Cirrhosis, which involves scarring of the liver, leads to portal hypertension since the scarred tissue obstructs the blood from flowing through the liver from the intestines back to the heart. This creates a need for the blood to find alternate routes, avoiding the first-pass detoxification typically performed by the liver.
In the case of the kidneys, changes in substances like endothelin can result in pathological vasodilation or constriction affecting renal function. The interplay between various factors in cirrhosis, such as ascites, sodium and water retention, and potential renal impairment or hepatorenal syndrome, can further contribute to vascular changes in these organs. Lastly, conditions such as hepatic encephalopathy highlight the systemic impact of a malfunctioning liver, which can lead to alterations in blood flow and vessel diameter elsewhere in the body.