Retroperitoneal lymph node mapping with intratesticular injected patent blue dye in rats

Endolymphatic injection of several dyes have been previously studied to identify retroperitoneal lymphatic structure in animals and humans with malignant diseases. However, there have been no studies, to our knowledge, that demonstrate the utility of injecting patent blue dye into the testicular parenchyma to detect retroperitoneal lymphoid structure. The aim of this experimental study was to investigate whether intratesticular patent blue dye injection is feasible and is an accurate method for retroperitoneal lymph node mapping in rats.

Twenty male albino Wistar rats were included in the study and divided over two equal groups. The first group underwent patent blue violet (PBV) injection into the spermatic funiculus, while the second group underwent PBV injection into the testicular parenchyma. After the injection, the color changes in the retroperitoneal lymphatic structures and the urinary bladder were anticipated. The time interval between the injection and the staining of lymphatic structures and urinary bladder was measured for each intervention. Blue stained retroperitoneal nodal tissues were dissected and removed. These nodal tissues were examined histologically.

After PBV injection, intense staining of the ipsilateral spermatic cord lymphatics was seen and anticipated color changes in the retroperitoneal lymphatic structures and urinary bladder were evaluated visually. Both application routes of dye resulted in the same distribution of retroperitoneal lymph nodes in the same time frame. All retroperitoneal nodular tissues removed were noted histologically to be lymph nodes and were found to be consistent with the ipsilateral lumbar lymph and the ipsilateral suprarenal lymph nodes according to the staining order in both groups. No toxic effects were observed histologically. There were no statistically significant differences in the time intervals between the two groups.

We demonstrated that both funicular and intratesticular injections of patent blue dye are feasible and accurate methods for retroperitoneal lymph node mapping in rats. This shows that intralymphatic dye injection is not absolutely necessary to detect retroperitoneal lymphatic structures and may have applications beyond testis cancer.