Teaching Case

Gross haematuria and left flank pain.

The patient presented with gross haematuria and left flank pain. Abdominal ultrasound revealed a left renal mass. Cystoscopy was unremarkable for intravesical pathology, whereas repeated urine specimens from the left ureter showed abnormal cells. Retrograde pyelography demonstrated a filling defect on the left upper pole calyces. Finally an abdominal biphasic multislice CT-scan (Toshiba Aquilion Multislice–CT, 1mm beam collimation, 120kV, 110mAs) showed a horseshoe kidney with a left renal mass, measuring 3.5 cm in diameter. It presented as a pelvic tumour with parenchymal infiltration. Multiple renal arteries were seen along the left renal unit. All imaging studies proved negative for metastatic disease. After left nephroureterectomy, the patient was discharged from hospital on post-operative day four. The final histopathologic examination revealed a transitional cell carcinoma of the left renal pelvis with medullary infiltration. The patient's serum-creatinine level returned to normal one month after surgery.

Renal pelvic carcinoma associated with horseshoe kidney is rare. Only 37 cases have been reported in the world literature. The radiological presentation of a horseshoe kidney can be misleading and surgery involving horseshoe kidneys is often complicated by the large anatomical variability of this fusion anomaly.

In our patient, abdominal ultrasound and retrograde pyelography raised the suspicion of a left renal tumour but failed to detect the horseshoe kidney. To determine the tumour resectability and to visualise the renal vessels and excretory system, a biphasic multislice CT was performed (Fig. 1). On this occasion the diagnosis of a horseshoe kidney with a parenchymal isthmus and multiple arteries was made (Figs 1a,1c). The left renal mass presented as an infiltrating tumour originating from the renal pelvis (Fig. 1b). The excretion phase revealed two single ureters (Fig. 1d). Due to impaired function of the non-tumour-bearing right renal unit, a large part of the parenchymal isthmus had to be preserved during left nephroureterectomy. Detailed illustration of the renal vessels by helical CT imaging proved to be indispensable for the planning of nephron-sparing surgery.

Multislice CT provides superior characterisation of the renal anatomy with little patient discomfort at reasonable cost. This single imaging modality should eventually replace conventional radiological studies for preoperative evaluation of renal masses.