Swelling of the lower extremities

The patient is sent for lymphoscintigraphy, which showed impaired lymphatic drainage of both lower extremities consistent with obesity-induced lymphedema.

Lymphedema is a chronic condition caused by the abnormal development of the lymphatic system (primary lymphedema) or injury to lymphatic vasculature (secondary lymphedema). Chronic interstitial fluid accumulation may lead to fibrosis, persistent inflammation, and adipose deposition, which often results in massive hypertrophy. Obesity, which affects approximately 40% of the US population, is a rising cause of secondary lymphedema. Obesity-induced lymphedema (OIL) is a result of external compression of the lymphatic system by adipose tissue and increased production of lymph, which results in direct injury to the lymphatic endothelium. As BMI increases, lymphedema worsens and ambulation becomes more difficult, placing patients in an unfavorable cycle of weight gain and lymphatic injury.

The diagnosis of OIL is made by history and physical and is confirmed with diagnostic imaging. The classic presentation of lymphedema is edema of the lower extremities and a positive Stemmer sign. The Stemmer sign is positive if the examiner is unable to grab the dorsal skin between the thumb and index finger. The gold standard for lymphatic imaging is radionuclide lymphoscintigraphy. It involves injecting a tracer protein into the distal extremity, which should be taken up by the lymphatic vasculature and visualized in patients with normal lymphatic function. Lymphoscintigraphy has a high sensitivity (96%) and specificity (100%) for the diagnosis of lymphedema.

The risk for lymphatic dysfunction increases with elevated BMI. A BMI threshold appears to exist between 53 and 59, at which point lower-extremity lymphatic dysfunction begins to occur and is almost universal when BMI exceeds 60. Sixty percent of patients with OIL will develop massive localized lymphedema; the higher the BMI, the greater the risk for massive localized lymphedema. Typical areas of localized lymphedema include the lower extremities, genitals, and abdominal wall. In addition, patients with OIL are at increased risk for infections, such as cellulitis. Other complications of OIL include functional disabilities, psychosocial morbidity, and malignant transformation.

Patients at risk for OIL should be counseled and educated about weight management interventions, such as intensive treatment programs, lifestyle changes, and medications before their BMI reaches 50, a threshold where irreversible lower-extremity lymphedema may occur. Although weight loss may reduce symptoms of OIL, irreversible lymphatic dysfunction also may occur. Individuals at risk for OIL are often referred to a bariatric surgical weight management center.

Lymphedema management consists of compression regimens, physiotherapy, and manual lymphatic drainage. Adipose deposition in the late stages of lymphedema may decrease the response to such manual treatments. Operative procedures are typically used when these treatment options have been inadequate. Patients with chronic advanced lymphedema, in whom lymphatic impairment is accompanied by deposition of fibroadipose tissue, may also require debulking surgery.

Courtney Whittle, MD, MSW, Diplomate of ABOM, Pediatric Lead, Obesity Champion, TSPMG, Weight A Minute Clinic, Atlanta, Georgia.

Courtney Whittle, MD, MSW, Diplomate of ABOM, has disclosed no relevant financial relationships.

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