Teaching Case

A 36-year-old man was admitted to the trauma centre after a traffic accident, underwent CECT immediately after damage control according to trauma protocols. The patient's detailed medical history and family history revealed no colic-like pain or history of deep vein thrombosis. Laboratory tests were within the normal range.

CECT torso in portal venous phase was acquired, that revealed an oval, hyperdense lesion approximately 8 mm in diameter on the hilum of the left kidney (Figures 1 and 2). It also appeared hyperdense on virtual non-contrast images with an attenuation of ~535 (Figure 1B). On careful inspection of the portal venous phase, the lesion appeared to be embedded in the lumen of the left renal vein, causing a luminal narrowing of ~50%. Lesion was lying along the long axis of the left renal vein (Figures 2A and 2B). The rest of the renal vein and the other vessels appeared morphologically normal. No atherosclerotic softening or calcified plaques were present. There was no evidence of hydronephrosis (Figure 2C).

Background

Renal vein stones are called phleboliths, which are focal calcifications within the vein lumen [1]. They occur secondary to small focal blood clots in a vein that may arise due to slow flow or after trauma and harden or degenerate over time due to calcification [1]. The typical location is the iliac veins, but they can occur anywhere in the body [2, 4]. The left renal vein is also an uncommon site; is more commonly affected than the right because of its long course. To our knowledge, this is the first case of renal vein phlebolith described in the literature.

Clinical and imaging perspective

These are clinically insignificant but can sometimes be confused with renal stones due to the close anatomic location of the ureter and renal pelvis; therefore, knowledge of this entity is necessary at this point to avoid confusion with renal stones on imaging [3]. On CT, they appear as an oval, homogeneously hyperdense, calcified lesion with or without a radiolucent canter [5]. Sometimes a calcified renal vein thrombosis may look like this. However, a detailed history and absent mural thickening will be helpful to rule out.

Teaching  point

Phleboliths are also called "stone in the vein”, occur in association with a vascular malformation, but are also described in the literature without it.

The MC location is the iliac veins, but any vein in the body can be affected.

They often seen in the older age group of women.

Etiopathogenesis: slow venous blood flow or as a result of trauma.

Clinical significance: usually harmless, but sometimes present a diagnostic dilemma because of close proximity to the renal pelvis/ureter.

On CT: oval hyperdense lesion with or without radiolucent canter. The Long axis of lesion will be parallel to long axis of the vein.