A rare cause of back pain

A 22-year-old male patient with left back pain radiating to the left iliac fossa and groin for the last ten months. There were no other relevant signs or symptoms or laboratory tests alterations.

An abdominal ultrasonography showed no alterations in the left kidney or hydronephrosis.
However, when placing the probe in the most painful area, the left iliac fossa, echogenic material in the left external iliac vein, compatible with thrombosis, was seen (Fig. 1a). There was also thrombosis of the left common femoral vein (Fig. 1b), right external and common iliac veins, and the infrarenal segment of the inferior vena cava (IVC) (Fig. 1c).

A contrast-enhanced abdominal computed tomography in venous phase was then performed. On it, the suprarenal, renal and upper segment of the infrarenal IVC were not seen (Fig. 2a, b, c); instead, retroperitoneal collaterals were depicted (Fig. 2 a, c). The rest of the visible infrarenal segment of the IVC was thrombosed (Fig. 2a). The hepatic portion of the IVC was normal and drained into the right atrium (Fig. 2d).

With these findings, an IVC agenesis was diagnosed.

Congenital anomalies of the IVC are uncommon, with a reported incidence of approximately 4% of the population [1], and they may be a challenge at surgery. Because of this, they should be carefully described in patients under consideration of abdominal surgical procedures, especially kidney surgery [2].

Congenital absence of the entire or part of the IVC is the rarest of all the IVC congenital anomalies [3], with an estimated prevalence of 0.07% [5]. It is thought to occur due to a failure in the embryonic vein development, or a venous thrombosis and atrophy in the perinatal period [1].

This type of anatomic malformation, which more commonly involves the suprarenal segment, may be asymptomatic or present with recurrent deep venous thrombosis and thromboembolic attacks in relatively young patients [4]. This is because absence of the IVC causes blood stasis in the lower limbs and formation of varices, which are generally bilateral [3]. Back pain has also been described in patients with deep vein thrombosis and agenesis of the renal and infrarenal segment of the IVC [5].

The gold standard for the study of this anomaly is conventional venogaphy [2]. However, nowadays it has been replaced by non-invasive imaging techniques (contrast-enhanced computed tomography), now being reserved only for therapeutic procedures [2]. The CT protocol for the study of anomalies of the IVC should include a venous phase, ideally with a delay of 70-90 seconds, as at that time, the enhancement of the entire IVC is the most homogeneous [1].

In this imaging technique, agenesis of the IVC may be recognised as absence of one ore more segments of the IVC, together with partial thrombosis of this vessel and prominent venous collateralisation. As previously said, lower limb thrombosis and thrombosis of the external and iliac veins may also be depicted [1]. Deep vein thrombosis that is recurrent, bilateral, involves the iliac veins, or is seen in young patients (usually under 30 years), should raise the suspicion of an anomaly of the IVC [4].

Treatment of patients with IVC agenesis and deep vein thrombosis is controversial. However, anticoagulant therapy has been proposed [5]. This is the treatment that our patient has been following until now (one year later), which has improved his back pain.