Case 1: Unilateral leg swelling in a toddler

A previously healthy three-year-old boy presented to the paediatric emergency department with a two-day history of left lower extremity swelling, tenderness and refusal to walk. There was no history of fever, recent travel, immobilization or trauma to the extremity. In the month leading up to his presentation, the patient was also noted by his mother to have decreased appetite and was requiring increasingly larger diaper sizes. His review of systems was otherwise unremarkable. On examination, he was afebrile, with a normal heart rate and elevated blood pressure (115/68 mmHg). He was alert and in no acute distress. Examination of the left lower extremity revealed warmth, swelling and erythema of the inguinal region, with increased thigh girth compared to the right. There was no pitting edema distally. Bloodwork revealed a decreased hemoglobin level (104 g/L) and normal white blood cell and platelet counts, electrolyte levels, renal function and uric acid. Urinalysis was normal. The lactate dehydrogenase level was elevated (1028 U/L; normal range 150 U/L to 360 U/L). Ultrasound examination led to the diagnosis. Ultrasonography revealed a well-circumscribed mass replacing the right kidney consistent with Wilms tumour, with inferior vena cava, common femoral and left external iliac vein extension. A computed tomography (CT) scan provided further definition (Figure 1). Coronal reformat from contrast-enhanced computed tomography shows enhancing tumour thrombus filling the inferior vena cava (white arrow) and extending into the right common iliac vein (black arrowhead) and more distally into the left common iliac vein (white arrowhead). The large mass in the right kidney (star) has similar attenuation to the tumour thrombus Our patient presented with localized lower extremity swelling, an uncommon presentation of Wilms tumour. The evaluation of localized edema in paediatric patients requires consideration of the pathogenesis. Localized edema can be categorized into three etiologies: venous obstruction causing increased capillary hydro-static pressure; vascular wall dysfunction causing increased capillary permeability; or lymphatic dysfunction causing increased interstitial hydrostatic pressure. Edema always occurs distal to the site of obstruction in the context of venous obstruction by thrombosis or external compression. The severity is determined by the degree of obstruction, and signs of thrombophlebitis (tenderness, erythema) may be present. With localized edema, venous thrombosis is a likely etiology and the clinician must look for underlying causes. Angioedema leading to increased capillary permeability is characterized by swelling in the deep layers of the cutaneous or submucosal tissues and can be allergic or hereditary in nature. The distribution of swelling is generally not in dependent areas but in the face, tongue, lips or larynx. Finally, localized edema can also be a result of lymphatic dys-function leading to accumulation of interstitial fluid, and may accompany reactive lymphadenitis, autoimmune diseases or genetic conditions. Isolated lymphedema of the leg is often idiopathic in nature. The evaluation of a child presenting with localized swelling requires a thorough history and physical examination. On history, important details to obtain include: location and duration of swelling, associated systemic symptoms, allergies, medications, weight gain and family history. Physical examination should include vital signs, growth parameters and localization of the area of swelling for erythema or tenderness. Laboratory studies may include a complete blood count, renal and liver function tests, and urinalysis. In a child with suspected venous thrombosis, in addition to Doppler ultrasonography, coagulation studies should be considered. Therapeutic interventions for the localized edema will be tailored according to the underlying cause. In our patient, unilateral lower extremity edema was secondary to Wilms tumour with intravascular extension. Wilms tumour accounts for approximately 6% of all childhood cancers (1). The most common initial presentation is the discovery of an asymptomatic abdominal mass. Other presenting complaints include abdominal pain, hematuria and hypertension. Intravascular tumour extension occurs in approximately 11% of cases, with involvement of the inferior vena cava, hepatic veins or right atrium (1). Currently, there are no reported cases of Wilms tumour extension downward into the femoral or iliac veins, as observed in our patient. Initial diagnostic studies include ultrasonography and CT scan of the abdomen and pelvis to determine the location/size of the mass. Magnetic resonance imaging can be used to evaluate for intravascular tumour extension. A CT scan of the chest for pulmonary involvement should be performed because this is the most common site of metastasis (1). Either upfront chemotherapy followed by surgery (European approach), or the reverse (North American approach), are used for therapy and have similar outcomes. One potential risk of upfront chemotherapy is adverse effect on staging and histological evaluation, leading to over- or undertreatment (1). For patients with intravascular tumour extension, strong consideration of preoperative chemotherapy is recommended (1), and studies have shown no significant differences in survival compared with patients without intravascular extension (2). The survival rate for Wilms tumour is approximately 90%. Following the diagnosis of Wilms tumour, our patient received neoadjuvant chemotherapy for eight weeks followed by surgical resection of the tumour and intravascular tumour thrombus. He is currently doing well. In children presenting with localized edema, especially of the lower extremities, a complete history and physical examination, including a thorough abdominal examination, should be performed to rule out potential life-threatening causes such as a malignancy resulting in venous obstruction. Children who present with a thrombotic event usually have an underlying cause for thrombosis that must be explored. Wilms tumour is common in children and has a high survival rate with appropriate therapy.

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