Chapter 23: Lower Extremity Swelling and Differential Diagnosis

INTRODUCTION

This brief section introduces definitions of acute and chronic edema, emphasizing the importance of understanding the modern view of edema pathophysiology and epidemiology for diagnosis. As an organizational principle, the causes of peripheral edema are categorized at their highest level as increased capillary filtration, decreased lymphatic drainage, or a combination of the two.

PATHOPHYSIOLOGY

Starling Principle and its Revision

This section begins with a review of the dynamics of fluid exchange at the capillary level and reviews the foundational Starling principle of fluid exchange, which has shaped the medical understanding of edema for more than a century, and how this principle has been revised by modern research.

Deleterious Effects of Fluid Stasis

The deleterious effects of fluid stasis, drawing upon recent research into the cellular and molecular underpinnings of the vicious circle of inflammation, fibrosis, adipose deposition, and recurrent infections seen in chronic edema are reviewed.

Causes of Increased Capillary Filtration

Causes of increased filtration are subdivided into increased hydrostatic pressure, decreased osmotic pressure, and increased capillary permeability, with individual causative conditions identified.

Causes of Reduced Lymphatic Drainage

Causes of decreased lymphatic drainage (lymphedema) are subdivided into primary and secondary causes. The author explains the varying definitions of lymphedema found in the literature. This section concludes with a brief review of obesity as a growing cause of edema. A figure representing these classifications and divisions is included.

EPIDEMIOLOGY

A brief review of the challenges involved in estimating the incidence and prevalence of chronic edema. Evidenced-based estimates of the prevalence of primary lymphedema, cancer-related lymphedema, phlebolymphedema, and lipedema (a primary cause of chronic swelling) are provided.

CLINICAL DIAGNOSIS

A systematic approach to differential diagnosis is supported by a figure outlining key considerations during the exploration of patient history, physical examination, and diagnostic testing. Differentiating between potential systemic versus localized causes of edema is emphasized as a central goal throughout the diagnostic process.

History

Essentials of patient history include medications, patient or family comorbidities related to potential systemic or localized causes, prior surgeries or cancer treatments, and patient-reported symptoms of pain or positional or temporal changes to edema.

Physical Examination

Essentials of the physical examination include observation of unilateral versus bilateral swelling, size and dimension of lymphedematous limbs, skin changes, signs of systemic (cardiac, hepatic, renal) or venous causes, and duplex ultrasound examination when venous causes are suspected. The section concludes with a brief review of the goals of efficient diagnostic testing to explore systemic causes of edema.

Treatment and Surveillance

This chapter concludes with an ...