Urogenital ImagingLymphocoele, retroperitoneal
A lymphocoele is an abnormal collection of lymphatic fluid, usually caused by iatrogenic disruption of lymphatic vessels. Lymphocoeles are most commonly seen after
renal transplantation and retroperitoneal
lymph node
dissection. Retroperitoneal
lymph node
dissection is usually performed for staging of testicular or gyneacological malignancy, and up to 27% of such patients develop postoperative lymphocoeles. These usually develop within 10 - 21 days of surgery. Lymphocoeles may occur in both peritoneal and retroperitoneal compartments, though a retroperitoneal location is more common. Imaging appearances with
CT and MR are relatively nonspecific; lymphocoeles typically appear as encapsulated fluid collections of varying complexity. Distinction between lymphocoeles,
cystic tumour recurrence and other
abdominal fluid collections can be difficult. Intraperitoneal lymphocoeles may be associated with chylous ascites from
lymph leakage. Chylous ascites may be recognized by negative
CT density measurements (< -20
Hounsfield units HU) or by the presence of a fat-fluid level. Both findings are due to the presence of fat in
lymph. At
ultrasound, most lymphocoeles are anechoic with an appearance similar to simple cysts (
Fig.1). A complex mass may be seen in 25% of cases. Distinction from an abscess,
haematoma, urinoma or fluid-filled bowel is often difficult, especially if internal debris is present. Given the poor
specificity of
CT,
MRI and
ultrasound, percutaneous aspiration is often required for definitive diagnosis. Small, anechoic lymphocoeles often resolve spontaneously, while larger, echogenic lesions may require drainage, sclerosing therapy or surgical resection.
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