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Page 8 of 14 Calderwood et al. Plast Aesthet Res 2021;8:40 https://dx.doi.org/10.20517/2347-9264.2021.14

[15]
nodal lymphatic vessels . Lymph nodes in primary lymphoedematous limbs have also been shown to have
[13]
reduced peak enhancement and slower washout, indicating abnormal function . One paper documented a
variety of lymph node appearances and categorized them according to three major categories;
[27]
aplasia/hypoplasia, hyperplasia, or structural abnormalities .

Normal lymph nodes may appear as a converging plexus of lymphatic vessels or have a large fatty
component in the centre . Another study found that normal inguinal lymph nodes have a consistent
[21]
appearance of being spherical or oval and measure approximately 1 cm in diameter, whilst the lymph nodes
in primary lower limb lymphoedema tend to have greater variation in outline, number, and volume .
[15]
ROLE IN DIAGNOSIS AND STAGING
Lymphoedema diagnosis is based on history and clinical assessment, and the most popular staging system
used is the International Society of Lymphology (ISL) system. Stages range from 0/Ia (subclinical) to III,
based on the degree of oedema and fibrotic soft tissue changes and the change in oedema on limb elevation
[Table 1] [11,12,28] . Early diagnosis and management can prevent chronic lymphoedema, and it is suggested that
those at risk of developing lymphoedema (i.e., post-operative or those receiving cancer treatment) should
[35]
commence physiotherapy in stage 0/Ia to prevent the progression of the disease . It has been found that
MRL can be helpful in both diagnosing and staging lymphoedema and can identify impaired or abnormal
lymphatic drainage patterns before any clinical signs are evident [2,14] . This makes it a valuable tool in early
detection and, therefore, early management of the disease. There is a strong correlation between the severity
of lymphoedema found on MRL with the clinical staging of the disease, both in primary and secondary
lymphoedema [19,23] . Comparison of the affected limb to the contralateral unaffected limb can also assist both
with diagnosis and establishing the extent of disease.

Due to its high spatial resolution, MRL is capable of visualizing lymphatic vessels and lymph nodes with
precise anatomical detail in lymphoedematous limbs. It allows clinicians to view lymph transport and
identify the cause of obstruction to the lymphatic system or any anatomical abnormalities that may be the
cause of primary lymphoedema [8,13,15,36] .

[15]
Enhanced MRL has also proven useful for the diagnosis and staging of malignant lymph nodes . Flow
velocities on dynamic contrast-enhanced studies can provide a means of quantitatively grading impaired
[2]
lymphatic transport . This diagnostic tool involves calculating the speed of the lymphatic fluid in affected
vessels by measuring the distance contrast travels between each time sequence, which correlates with the
transport capabilities of the lymphatic vessels [13,15,25] .

Other MRI sequences (for example, T2 STIR) can detect extra-lymphatic changes, such as the composition
of subcutaneous tissue, differentiating predominantly fluid accumulation in the early stages of the disease
from the later stages that predominantly have adipose and fibrosclerotic tissue deposition . As well as
[2]
indicating the type of subcutaneous fluid present, it also provides information on the location and volume
of this extracellular fluid. Differentiating these stages is important not only in staging the disease, but also in
determining which surgical procedure is suitable to manage it [2,11] .

In a study by Mihara et al. , all 21 patients with known stage 1 lymphoedema were positively identified
[36]
using MRI, However, only 13 showed positive findings with lymphoscintigraphy for qualitative assessment,
giving a higher sensitivity for the diagnosis of lymphoedema in the early stages of the disease using MRL
(sens = 1) than with using lymphoscintigraphy (sens = 0.62). In addition to this study, non-contrast MRL
has successfully been able to classify primary lymphoedema into its main pathological groups; hyperplasic,