A 35-year-old male diagnosed with retroperitoneal lymph node metastases four months after orchiectomy due to a mixed non-seminoma (95%) and seminoma (5%) germ cell tumor of the right testis, presented with aggravated morphine-demanding pain in the right flank. Symptoms debuted prior to scheduled chemotherapy with curative intent.
Contrast-enhanced dual-energy computer tomography (DECT) of the abdomen was performed with standard protocol for a venous phase on the same day as the patient’s pain aggravated to identify the cause. The scan revealed an anatomical variation of the right testicular vein entering the right renal vein, and a thrombus (HU 42) extending from the distal part of the testicular vein and bulging into and partially occluding the renal vein (Fig. 1). Mild hydronephrosis and hydroureter were also seen on the right side, but the right kidney appeared without any sign of venous stasis. Retroperitoneal lymph node metastases forming a conglomerate measuring 3.0 x 5.3 cm in the coronal plane was found, located between the aorta and inferior vena cava, and was stationary in size compared to a recent previous scan.
Testicular vein thrombosis (TVT) is a rare condition most often involving the left side . Few reports of a right-sided TVT can be found in the previous literature [1-3]. The aetiology of TVT in previously described cases includes underlying cancer , underlying Factor V Leiden mutation , abusive use of cocaine , complication of cardiac catheterization  and direct trauma to the inguinal region . Spontaneous cases of TVT [1, 6-9] and pulmonary embolism secondary to TVT  have also been reported. It has been documented that patients with germ cell tumours and regional malignancy have an increased risk of venous thromboembolism (VTE) in general and TVT [1, 10, 11]. Furthermore, it has been suggested that the left-sided predominance of TVT is related to the typical anatomical presentation of the left testicular vein entering the left renal vein, subsequently resulting in a lower blood-flow through the left testicular vein compared to the right testicular vein, which typically enters the inferior vena cava .
Most often, TVT presents with acute onset of testicular pain, mimicking an incarcerated inguinal hernia or testicular torsion. TVT presenting as pain in the flank is a rarity. Diagnostic considerations, in this case, included growth of retroperitoneal lymph node metastases, ingrowth of tumour in surrounding organs and mass effect of tumour on surrounding tissues, but other common conditions such as cholelithiasis and nephrolithiasis could also have explained the patient´s symptoms. The advantage of performing a DECT, in this case, was the ability to reconstruct numerous types of images (Fig. 2), and thereby allowing for exclusion of many differential diagnoses from one type of imaging modality. While exposure to ionizing radiation should always be taken into consideration, especially in young patients , the use of other imaging modalities such as ultrasound or non-contrast CT, would potentially have overlooked the diagnosis TVT in this case.
Following diagnosis, the patient was started on therapeutic doses of heparin therapy (Tinzaparin 175 IU/kg) and continued receiving chemotherapy (cisplatin, etoposide and bleomycin) without any complications.
Unilateral pain in the flank can occur as a result of numerous conditions. When present in a patient with a history of cancer, and especially germ cell tumours with regional malignancy, TVT should be remembered as an important and potentially life-threatening differential diagnosis [1, 5]. Choice of image modality is essential to reveal the correct diagnosis, assuring that the patient can receive the correct treatment.
Written informed patient consent for publication has been obtained.
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