Edema — Fluid Retention and Swelling in Cancer Care

Edema occurs when microvascular filtration exceeds lymphatic drainage, causing excess interstitial fluid to build up in tissues. In healthy physiology, a delicate balance of hydrostatic pressure, oncotic pressure, and lymphatic clearance maintains fluid equilibrium. In oncology, this balance can be disrupted through multiple distinct mechanisms.

Mechanisms include mechanical venous or lymphatic obstruction by tumour masses, disruption of lymphatic vessels secondary to lymph node dissection or radiation therapy (leading to lymphedema), hypoalbuminaemia caused by cancer cachexia or hepatic dysfunction, and increased vascular permeability induced by medications such as corticosteroids, nonsteroidal anti-inflammatory agents, or specific targeted anti-cancer drugs.

Identifying and managing edema is crucial for patient comfort, mobility, and safety. Swollen limbs can become heavy, painful, and prone to skin breakdown or bacterial infections like cellulitis. Moreover, sudden swelling in a single leg may signal a deep vein thrombosis (a dangerous blood clot), which is a heightened risk in oncology patients. By tracking fluid retention, clinical teams can pinpoint whether the swelling is a manageable medication side effect, an indicator of nutritional decline, or a sign that treatment needs adjustment.

Diagnosing edema involves clinical examination, assessing for pitting (indentations after pressure) and skin changes. Further tests investigate underlying causes: venous ultrasound rules out deep vein thrombosis, blood tests evaluate renal, hepatic, and albumin levels, and CT scans check for mechanical tumour compression.

Edema can affect patients across many cancer types. It is especially prevalent in breast cancer and gynaecological cancers (often presenting as lymphedema after lymph node removal), advanced abdominal or ovarian cancers (causing ascites, a form of abdominal edema), liver cancer, and cancers causing superior vena cava obstruction, such as lung cancer.

Management targets the root cause. If drug-induced, adjusting dosages or switching therapies may be considered. Diuretics can help clear general fluid overload. For lymphedema, treatment includes specialized physiotherapy, manual lymphatic drainage, and medical compression garments. When caused by tumour compression, local radiotherapy or vascular stenting may be required to relieve obstruction.