Prof. Jan Baxa, MD, PhD
Department of imaging methods, University Hospital Pilsen and Medical Faculty of Charles University, Pilsen, Czech Republic
May 28, 2025
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History
A 5-month-old baby, suffering from severe hypertension, was presented to the hospital. Ultrasound examination showed bilateral congenital hydronephrosis. Dynamic renal scintigraphy revealed a significant reduction of the right renal parenchyma along with a symmetric split function of 32%. A vesicoureteral reflux (VUR), grade IV, passive and active, and a moderate hypofunction were shown on the left. A contrast CT scan of the abdomen and pelvis was performed with a dual source photon-counting detector (PCD) CT, NAEOTOM Alpha.Pro, to rule out renovascular etiology of the hypertension prior to pyeloplasty.
Diagnosis
CT images showed three renal arteries – two on the left and one on the right – all free from stenosis. An accessory artery, originating off the right side of the aorta, between the celiac artery (CA) and the superior mesenteric artery (SMA), was seen, departing upwards to the left hepatic lobe. Other arteries, within the scope of the examination, were unremarkable. The aorta appeared slender. Bilateral hydronephrosis was seen, more severe on the right, showing a marked reduction of the renal parenchyma with a loss of corticomedullary differentiation. The renal pelvis was 27 mm wide, with a thickened wall of 4 mm on the right and 20 mm on the left. No dilation was seen in the bilateral ureters. The catheterized bladder was empty. There was no free intraperitoneal fluid. An ureteropelvic junction obstruction was suspected and subsequently confirmed by a successful translumbar pyeloplasty surgery (Anderson-Hynes). The patient recovered well and remained normotensive during regular surveillance.
Fig. 1: A coronal MPR image (Fig. 1a) shows bilateral hydronephrosis, more severe on the right, with a marked thickening of the pelvic wall. A MIP image (Fig. 1b, anterior view) and a cVRT image (Fig. 1c, posterior view) show three renal arteries, two on the left (arrows) and one on the right (dotted arrow), without signs of stenosis. An accessory artery (arrowhead), originating off the aorta on the right, between the CA and the SMA, is seen, departing upwards to the left hepatic lobe.
Fig. 2: MIP images show three renal arteries – one on the right (Fig. 2a, dotted arrow) and two on the left (Fig. 2b & 2c, arrows) – all free from stenosis.
Comments
Hypertension in infants can be caused by renovascular or renal parenchymal disease, such as renal artery stenosis or congenital hydronephrosis. If the renovascular etiology is ruled out, the hypertension can be normalized following a relief of the ureteropelvic junction obstruction, one of the most common causes of congenital hydronephrosis, by pyeloplasty.
CT angiography (CTA) is performed for vascular imaging in infants due to its non-invasive nature. However, there are multifold challenges. Firstly, images need to be acquired at free breathing, if anesthesia is not desired, as infants are incapable of cooperating with breathing command. Secondly, high spatial resolution is needed to visualize the tiny vascular structures, such as renal arteries. Thirdly, as infants are vulnerable to radiation, the dose applied should be as low as reasonably achievable (ALARA). And if renal function is impaired, such as in this case, a reduction of the contrast agent must be considered as well.
This case is performed with a new dual source PCD CT, NAEOTOM Alpha.Pro. It allows for a fast-scanning speed of 491 mm/s, enabling a complete acquisition of 288 mm in 0.56 s with 66 ms temporal resolution per image. There are no motion artifacts observed in the images acquired at free breathing. 70 kV X-ray tube voltage was automatically selected by the system, in combination with virtual monoenergetic image reconstruction at low keV (55 keV). These settings contribute to the improvement of image contrast, which is further enhanced by the intrinsically higher iodine contrast of a PCD-CT, and to the reduction of radiation dose. Three tiny renal arteries as well as a small hepatic accessory artery are depicted, providing important information for surgical planning. Renal artery stenosis is successfully ruled out, using only 12 mL of contrast agent and 1 mGy radiation dose, owing to a combination of high spatial resolution, fast speed acquisition and increased contrast enhancement.
Examination Protocol
Scanner | NAEOTOM Alpha.Pro |
|---|
Scan area | Abdomen/pelvis |
Scan mode | Flash scan (Quantum) |
Scan length | 287.6 mm |
Scan direction | Cranio-caudal |
Scan time | 0.56 s |
Tube voltage | 70 kV |
Effective mAs | 96 mAs |
IQ level | 120 |
Dose modulation | CARE Dose4D |
CTDIvol | 1.1 mGy |
DLP | 36 mGy*cm |
Rotation time | 0.25 s |
Pitch | 3.2 |
Slice collimation | 96 x 0.4 mm |
Slice width | 0.4 mm |
Reconstruction increment | 0.2 mm |
Reconstruction kernel | Bv40, QIR 4 |
KeV level | 55 keV |
Spectral reconstruction | Monoenergetic Plus |
Contrast | 350 mg/mL |
Volume | 12 mL + 20 mL saline |
Flow rate | 2.3 mL/s |
Start delay | Bolus tracking triggered at 350 HU in the descending aorta + 3 s |
Images: Courtesy of Department of imaging methods, University Hospital Pilsen and Medical Faculty of Charles University, Pilsen, Czech Republic
