A case of renal adenocarcinoma associated with horse-shoe kidney: CT findings

Clinical History

A patient presenting with recurrent lumbar pain was referred for a spiral CT before and after administration of contrast agent.

Imaging Findings

The patient presenting with recurrent lumbar pain, and was referred for a spiral CT before and after administration of contrast agent. The CT scan revealed a horse-shoe kidney, with physiological concentration of contrast agent, and a huge, expansive mass located in the right kidney. This mass included coarse calcifications, which were more evident on an unenhanced scan, and showed heterogeneous contrast enhancement.

Discussion

A number of variations can occur during the embryological development of the kidney. Recognition of these normal variants is needed to avoid misinterpreting them as pathological. Malpositioned and anomalous kidneys are readily evaluated by CT or MRI. Congenital malposition, including ectopy and malrotation, are readily diagnosed, and fusion anomalies such as horse-shoe kidney and cross-fused ectopy are evident from the position and uniformity of the parenchyma and contour.

The horse-shoe kidney is a congenital anomaly occurring in 0.25% of population, with a slight male predominance. This condition results from the fusion of the lower pole of both kidneys, and it is usually detected incidentally because it is asymptomatic. However, some individuals may present with abdominal or lower-back pain, urinary tract infection, stone formation or blood in the urine, because the ureters may be angulated and compressed due to fusion with subsequent inadequate urinary flow.

This congenital anatomical malformation may be associated with cardiovascular anomaly, skeletal anomaly, cerebral anomalies, genitourinary anomalies such as hypospadia, undescended testis, bicornuate uterus, ureteral duplication, trisomy 18, and Turner syndrome. Vascular anomalies are extremely common: most of these anomalies consist of multiple renal arteries thet occasionally arise from unusual sites supplying varying segments of kidney.Sometime, the ateries will enter the kidney directly through the capsule rather than trough the renal hilus. Horseshoe kidney is often associated with transitional cell tumour and there is a predisposition to hypertension and chronic kidney failure because of abnormal vascularisation. However, renal cell carcinoma is not more frequently associated with horse-shoe kidney, with an incidence no greater than among the normal population.

Spiral CT is highly capable of demonstrating the presence of renal anatomical variations and concomitant tumoral pathology as shown in this case. On unenhanced CT, renal cell carcinoma appears isodense, or hyperdense to the renal parenchyma, whereas a heterogeneous appearance is seen in larger lesions. Coarse calcifications may be detected at the periphery of the lesions, near the centre or diffusely throughout the lesion. In the cortical phase after intravenous iodinate contrast medium administration, the lesions are usually heterogeneously hypervascular, with a somewhat patchy and nodular pattern in the periphery encircling an unenhanced area. In the nephrographic and excretory phase the lesions are hypodense compared to the renal parenchyma, with the thick peripheral rim remaining clearly visible. Intralesional necrosis is virtually always present and characteristically eccentrically located.

Differential Diagnosis List

Final Diagnosis

Renal carcinoma in a horse-shoe kidney

URL:	https://www.eurorad.org/case/2049
DOI:	10.1594/EURORAD/CASE.2049
ISSN:	1563-4086