Teaching Case

A 43-year-old man with VACTERL association, including anal atresia and scoliosis, has not been investigated for other possible associated congenital anomalies. During the evaluation for scoliosis, an MRI of the spine was performed. The MRI findings raised the suspicion of a duplex collecting system; therefore, CT urography was requested.

Coronal T2-weighted image (Figure 1) of the lumbar spine MRI shows suspicion of a duplex collecting system and renal cysts in the right kidney.

CT urography on the excretory phase demonstrated a left-sided kidney fused to the right kidney on the right side (Figure 2a). Both kidneys were presented with an incomplete duplex collecting system, with both ureters draining separately into the urinary bladder (Figure 2b and Figure/video 2c).

On the excretory phase of the CT urography, bilateral cystic dilatation of calyces without hydronephrosis (megacalycosis) (Figure 3).

A lumbosacral transitional vertebra at the bone window with neo-articulation and hemivertebrae between L3 and L4 on the left side (Figure 4).

Crossed fused renal ectopia (CFRE) is a rare congenital malformation where both kidneys are located on the same side of the body, with the ureter of the crossed kidney opening into the bladder on the opposite side. Its frequency is around 1:7000, with a male predominance (3:2) [1,2]. This results from an abnormality in the embryonic development of the ureteral bud and metanephric blastema between the 4th and 8th weeks of gestation [3]. CFRE may go unnoticed until it is accidentally discovered [4].

Ultrasound is the primary diagnostic tool used to diagnose CFRE and to look for possible complications, such as kidney stones and dilation of the excretory tract. The CT or MR urography confirms the diagnosis. It allows for a better anatomical study, especially for delimiting the two ureters’ pathways and blood supply for the CFRE [4,6]. There is no standard treatment for these anomalies; management should be customised based on associated conditions [5].

Congenital anomalies of the urinary collecting system include megacalycosis, ureteropelvic junction obstruction, duplex collecting system, and ureterocoele. These anomalies often occur together, and it is not uncommon for multiple anomalies to coexist. Therefore, radiologists need to look for different types of anomalies and avoid satisfaction of search bias.

About two-thirds of patients with congenital upper urinary tract anomalies also have associated anomalies in other organ systems, such as the skeletal, cardiovascular, gastrointestinal, and central nervous systems. Our patient is already known to have hemivertebrae, and radiologists need to consider urinary tract involvement, since both the genitourinary system and the vertebral column originate from the mesoderm and develop simultaneously during the same stage of embryonic life [6].

VACTERL association is generally identified by the occurrence of at least three of the following congenital malformations: vertebral defects, anal atresia, cardiac defects, tracheoesophageal fistula, renal anomalies, and limb abnormalities [7]. In this case, the patient had associated findings of anal atresia, scoliosis, and crossed fused renal ectopia.

Congenital lumbar anomalies should trigger an upper urinary tract evaluation. In our case, despite the patient having been diagnosed with spinal anomalies since childhood and having experienced frequent urinary tract infection (UTI) symptoms, other potential congenital abnormalities were not initially considered. Radiologists are crucial in promptly identifying these anomalies to facilitate early management and prevent complications.

Written informed patient consent for publication has been obtained.