Teaching Case

A 69-year-old male with clear cell renal cell carcinoma from the left kidney disseminated to lungs, bones, mediastinal lymph nodes, pancreas, adrenal glands, and right kidney. Currently in second-line therapy with Axitinib. The patient had three weeks of macroscopic haematuria and a cystoscopy that did not find the source of bleeding.

Non-enhanced CT of the abdomen showed no stones in the kidneys nor ureters.

After contrast injection, in late arterial phase, the exophytic and necrotic kidney tumour was stationary in size compared with previous scan and had no signs of active bleeding.

In late arterial phase several small vessels in a network configuration were seen anterior, and in the middle of the left kidney with contrast in the left renal vein. There was no contrast in the left renal vein in the late portal phase, which was suspicious for a new developed connection between the left renal vein and the vessel network.

The delayed phase showed wall thickening of the left renal pelvis and proximal ureter. Contrast was excreted through slim ureters without any anomalies or filling defects.

The bladder was sparsely filled with a well-placed urethral catheter and several elongated hyperdense contrast defects (HU-value > 60), compatible with blood clots.

Background

Renal cell carcinoma (RCC) is the most frequent kidney cancer and emerges in the renal parenchymal epithelium[1]. The most common histological variant is the clear cell RCC, which constitutes roughly 75% of RCCs, with one of its characteristics being a hypervascular tumor[2], [3], and having a greater potential of angiogeneis[2] [4]. It has previously been described that patients can develop arteriovenous fistula (AVF) secondary to RCC[5], [6].

An arteriovenous malformation (AVM) is an abnormal connection between arteries and veins that bypasses capillaries and if it is not traumatic it can be either congenital or acquired[7]. AVM usually represents congenital causes and AVF usually represents acquired causes[7].    

Since the abnormal dilated vessels lie just beneath the urothelium, they can cause haematuria[7], [8].

Clinical Perspective

According to Maruno et al. haemturia occurs in 21-72% of patients with nontraumatic AVF[7], however, AVF secondary to RCC is an atypical imaging presentation[6].

Furthermore, in this case, the cystoscopy had not presented any reason for the macroscopic haematuria, hence this CT imaging was needed.

Imaging Perspective

It has previously been described that the CT-scan typically will show early enhancement of the affected renal vein[6]–[8]. Additionally, CT in delayed phase will show dilated renal vein and AVF with the same density as vena cava inferior.[8]. The key finding in this CT scan was that in the late arterial phase there was contrast in the left renal vein and a suspected connection to the vascular arterial network, which was well-matched with an AVF. There was no contrast in the renal vein in the late portal phase nor in previous scans with late arterial phase.

Since the referring physician suspected that the patient could be actively bleeding, the on-duty radiologist decided to do a multiphase protocol including late arterial phase.

Outcome

Transarterial embolisation has previously shown 100% elimination of macroscopic haematuria in patients with RCC[3]. The patient was stabilised and underwent a renal angiogram. Through the left renal artery, the angiogram depicted the AVF at the lower pole of the left kidney, and abnormally small vessel growth in the rest of the left kidney. Selective transarterial embolisation of the arteries to the lower pole was performed. One year and seven months later the patient remains symptoms free and has continual follow-ups in the oncology outward clinic for his metastatic RCC.

Take Home Message / Teaching Points

AVF is a rarely seen complication to RCC and with unexplained heamaturia, good multiphase protocol CT is needed with late arterial phase for diagnostic purpose.

Written informed patient consent for publication has been obtained.