Chemotherapy frequently causes peripheral edema, which is swelling due to fluid retention in the body’s tissues. This side effect is especially common in the feet, ankles, and lower legs because gravity pulls the excess fluid downward. Edema occurs when the balance of fluid within the blood vessels shifts, causing it to accumulate in the surrounding interstitial space. While often mild, this fluid buildup can cause discomfort, skin tightness, and difficulty wearing shoes.
How Chemotherapy Affects Fluid Balance
The cytotoxic agents used in chemotherapy can directly compromise the integrity of the vascular system, leading to capillary leak syndrome. Capillaries, the body’s smallest blood vessels, become more permeable, allowing plasma proteins and fluid to escape from the bloodstream into the surrounding tissues. This leakage reduces the volume of fluid circulating in the vessels while causing localized swelling.
Specific chemotherapy agents, such as docetaxel and gemcitabine, are associated with this increased capillary permeability. The loss of proteins from the blood exacerbates the problem, as these proteins normally help draw fluid back into the vessels. When they leak out, the osmotic pressure that maintains fluid balance is disrupted, promoting further fluid retention.
Beyond vascular changes, some chemotherapy drugs can also affect the kidneys, which regulate the body’s fluid and electrolyte balance. Nephrotoxicity, or damage to the kidneys, can impair their ability to properly filter waste and excrete excess sodium and water. This reduced kidney function leads to systemic fluid overload, which manifests as peripheral edema.
Common Co-occurring Causes of Edema
While chemotherapy drugs can trigger fluid retention, swelling is frequently caused or worsened by co-administered medications, most notably corticosteroids. Drugs like dexamethasone are anti-inflammatory agents often given with chemotherapy to manage allergic reactions and prevent nausea. These steroids possess mineralocorticoid activity, causing the kidneys to retain sodium and, consequently, water.
Corticosteroid-induced fluid retention is a common cause of edema and is often more pronounced than swelling caused solely by the chemotherapy agent. Another factor is hypoalbuminemia, a condition where the level of albumin—a protein in the blood—is low due to malnutrition or underlying disease. Since albumin helps keep fluid within the blood vessels, its deficiency makes it easier for fluid to leak out and pool in the lower body.
Reduced mobility during treatment can also play a role in the development of swelling. Patients who feel fatigued or ill may spend more time sitting or lying down, which slows the natural circulation of blood and lymph fluid. When muscles are not contracting to help pump fluid back toward the heart, gravity allows fluid to passively collect in the lowest points of the body.
Practical Steps for Relief and Management
Managing mild to moderate edema can be accomplished through simple techniques aimed at counteracting gravity and improving circulation. Elevating the legs is an effective strategy; the feet should be raised above the level of the heart for periods throughout the day. This action helps the pooled fluid drain back toward the torso for processing.
Gentle, regular activity, such as short walks, helps the calf muscles contract and pump fluid out of the lower extremities. Even small movements, like rotating the ankles while seated, can stimulate circulation. It is important to avoid standing or sitting in one position for long periods to keep the circulation moving.
Dietary modifications can support the reduction of edema by limiting water retention. Reducing the intake of high-sodium foods, such as canned soups, processed meats, and fast food, helps the body excrete excess fluid more efficiently. Adequate hydration is also necessary, as drinking enough water helps the kidneys function properly.
Compression garments, such as support stockings or socks, provide external pressure that prevents fluid from accumulating in the tissues. These should only be used after consulting with an oncology team. The team can ensure the correct pressure level is chosen and confirm there are no underlying blood clot risks.
When Swelling Requires Urgent Medical Attention
While mild swelling is a common side effect, certain signs indicate a need for immediate medical evaluation due to serious underlying complications. Sudden, painful swelling that occurs rapidly and is confined to only one leg or arm may signal a deep vein thrombosis (DVT), a blood clot in a major vein. A DVT requires urgent care, especially if the area is also warm or red to the touch.
Signs of fluid overload affecting the heart or lungs also require emergency attention. Patients experiencing a sudden, rapid weight gain of several pounds, or who develop shortness of breath, particularly when lying flat, should seek help. This could indicate pulmonary edema, where fluid has backed up into the lungs, or a strain on the heart.
Swelling accompanied by a fever, a red streak, or skin that is visibly broken and weeping fluid may suggest a localized infection. Any new or worsening swelling that extends up the body, or is accompanied by a significant decrease in urine output, also warrants immediate contact with the medical team. These symptoms point to potential systemic issues that require prompt diagnosis.