Lymphedema is the accumulation of tissue fluid in the interstitial spaces, resulting from anatomical or functional lymphatic obstruction or defective lymphatic drainage.1 Local data about the prevalence of this condition are not available, but it is estimated to affect 2 to 3 million inhabitants in the US.2 Lymphoscintigraphy has emerged and become the standard investigation in the evaluation of lymphedematous extremities. We reviewed our experience in the use of lymphoscintigraphy for this purpose in a single regional hospital.

We retrospectively identified all the cases with suspected lower limb lymphedema referred for lymphoscintigraphy from 1998 to 2011. Case records and imaging studies were reviewed.

Studies conducted from 1998 to 2007 were performed with a single detector system (Picker Prism 1000; Picker International, Cleveland [OH], US). Studies performed after 2007 were performed with a single photon emission computed tomography–computed tomography imaging system (Siemens Symbia T6; TruePoint SPECT CT, Siemens Medical Solutions, Illinois, US). The interdigital web space between the first and second digits on the patient’s lower limbs was anaesthetised with local anaesthetic cream, and subsequently 0.5 mCi of Technetium-99m filtered sulphur colloid (through 0.22 micron filter) was injected into the preanaesthetised interdigital web spaces, creating a wheal. About 1 to 2 minutes after the injection, patients were encouraged to exercise their toes. Two-phase dynamic images were obtained at 5 minutes (from toes to knee) and 10 minutes (from knee to groin). Anterior whole-body scans were obtained at 15, 30, 45, and 60 minutes. Delayed 4-hour and 24-hour whole-body scans were obtained whenever deemed necessary.

There were 24 patients with suspected lymphedema of lower extremities who had undergone lymphoscintigraphy. The patients were aged 14 to 83 (mean, 58) years; 13 were males and 11 were females. Apart from mild pain during injection, all patients tolerated the examination well without any serious complication.

A predictable sequence should be seen in patients with normal lymphatic anatomy and function. In the lower limb, there should be symmetrical migration of radionuclide through discrete lymph vessels (3-5 per calf and 1-2 per thigh). Ilioinguinal nodes should be visualised within 1 hour. Typically, 1 to 3 popliteal nodes and 2 to 10 ilioinguinal nodes are seen. Figure 1 shows a normal lymphoscintigraphic examination of the lower limbs.

Abnormal lymphoscintigraphy scans manifest a wide range of findings, including interruption of lymphatic flow, collateral lymph vessels, dermal backflow, reduced number of lymph nodes, dilated lymphatics, delayed or non-visualisation of lymph nodes and even the lymphatic systems.

There were eight patients confirmed to be positive for lymphedema. These included one with lymphangiectasia (Fig 2), five with lymphatic obstruction (Fig 3), and two with lymphatic leakage (Fig 4). The Table summarises the lymphoscintigraphic findings and follow-up data on these eight cases.

Lymphedema of the extremities is typically a chronic disease, which is often misdiagnosed and results in significant functional impairment, and may give rise to reduced coordination and mobility.3 Therefore, prompt and accurate diagnosis of the condition is important.

Decades ago, lymphangiography had been used to investigate lymphatic disorders, but it was a time-consuming investigation involving direct cannulation of lymph vessels. Moreover, complications such as infections, hypersensitivity, oil embolism, and lymphatic obstruction were reported.4 Lymphoscintigraphy has replaced lymphangiography and become the investigation of choice. Its advantages include being non-invasive, free from adverse effects, and low radiation exposure to patients. Furthermore, it can be repeated and can even be used to follow-up after treatment response.5 The reported sensitivity and specificity of lymphoscintigraphy is approximately 66 to 100% and 83.5 to 99%, respectively.6

Lymphedema can usually be diagnosed clinically. The differential diagnosis of suspected lower-extremity lymphedema includes obesity, chronic venous insufficiency, Milroy’s disease,7 and systemic diseases (eg hypoalbuminaemia). Lymphoscintigraphy enables confirmation of the diagnosis in unclear cases, assessing the risk of developing lymphedema,8 predicting the outcome of therapy,9 and assessing the results of lymphedema treatment.10 11 12 13

Lymphoscintigraphy can usually identify the approximate anatomical site of lymphatic obstruction adequately. However, when greater anatomical details are warranted, cross-sectional imaging techniques like computed tomography and magnetic resonance imaging can be used to supplement the findings.14 This point was well illustrated in this study.

Lymphoscintigraphy aids the diagnosis of underlying lymphatic disorders and hence, guides subsequent treatment, which have proven to be effective in the management of lymphedema.15 16 17 18 19 Conservative treatment includes physical therapy, drug therapy, and psychosocial rehabilitation.14 Operative treatment includes microsurgery, liposuction, and surgical resection.14 The treatment choice depends on the cause of lymphedema, disease severity, functional impairment, and availability of local expertise.

Lymphoscintigraphy is a safe and effective investigation for suspected lymphatic disorders. Our local experience supports its use in the investigation of lower-extremity lymphedema in our locality.

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