Acute pyelonephritis resulting in intense vascular blush during dynamic renal scintigraphy.

A thirty-year-old male underwent Tc-99m diethylenetriaminepentaacetic acid renal scintigraphy for evaluation of gross hydronephrosis of left kidney. The perfusion phase revealed an intense vascular blush in left renal fossa. The uptake phase of scintigraphy revealed the absence of tracer uptake in left kidney. Contrast-enhanced computed tomography (CECT) was performed for evaluating the cause of vascular blush. CECT demonstrated features suggestive of acute pyelonephritis (APN) involving lower pole of the hydronephrotic left kidney, corresponding to the site of vascular blush seen on renal scintigraphy. The postnephrectomy specimen confirmed the diagnosis of APN suggested on CECT.

CASE REPORT

A thirty-year-old male was undergoing evaluation of chronic left flank pain and intermittent fever. His ultrasonography (USG) revealed the enlarged left kidney with gross hydronephrosis and staghorn calculus. The serum creatinine value was 1.1 mg% (normal 0.7–1.2 mg%). His blood examination had revealed leukocytosis and urine examination had showed 10–15 pus cells/hpf. He underwent dynamic renal scintigraphy for evaluation of hydronephrosis of left kidney detected on USG. The scintigraphy was performed with intravenous (IV) injection of 375 MBq of Tc-99m diethylenetriaminepentaacetic acid and F-0 injection of furosemide in the dose of 1 mg/kg. The dynamic imaging during perfusion phase revealed transit of bolus through aorta [red arrow, Figure 1], vascular blush to right kidney (blue arrow), and an intense vascular blush in region of left renal fossa at level of lower pole of kidney (black arrow). The uptake phase of renal scintigraphy revealed the absence of cortical uptake in left kidney and normal tracer uptake of right kidney [Figure 2]. To evaluate cause of vascular blush in left renal fossa, further evaluation with contrast-enhanced computed tomography (CECT) was performed.

Figure 1

The scintigraphy was performed with intravenous injection of 375 MBq of Tc-99m diethylenetriaminepentaacetic acid and F-0 injection of furosemide in the dose of 1 mg/kg. The dynamic imaging during perfusion phase revealed transit of bolus through aorta (red arrow, Figure 1), vascular blush to right kidney (blue arrow) and an intense vascular blush in region of left renal fossa at level of lower pole of kidney (black arrow)

Figure 2

The uptake phase of renal scintigraphy revealed the absence of cortical uptake in left kidney and normal tracer uptake of right kidney

CECT was performed on a 64 slice scanner (Philips Brilliance) before and after IV injection of noniodinated contrast medium (iohexol 350). Figure 3a precontrast coronal section shows large left renal staghorn calculus with enlarged, hydronephrotic kidney. Figure 3c reveals arterial phase of CECT, depicting enhancement in the lower pole of the left kidney. Figure 3b shows axial section images of postcontrast delayed phase at the level of lower pole. Persistent parenchymal enhancement, perinephric fat stranding, and thickening of Gerota's fascia was seen (arrows). The CECT scan findings suggested a diagnosis of acute pyelonephritis (APN) involving lower pole of left kidney. Figure 3d sagittal CECT section shows that the perinephric fat stranding is extending inferoposterior to the lower pole of left kidney. The postnephrectomy specimen revealed gross hydronephrotic left kidney with APN involving a lower pole.

Figure 3

(a) Precontrast coronal section shows large left renal staghorn calculus with enlarged, hydronephrotic kidney. (c) Reveals arterial phase of contrast-enhanced computed tomography, depicting arterial enhancement in the lower pole cortex of left kidney. (b) Axial section of postcontrast delayed phase at the level of lower pole cortex. Persistent parenchymal enhancement, perinephric fat stranding, and thickening of Gerota's fascia was seen (arrows). The contrast-enhanced computed tomography scan findings suggested a diagnosis of acute pyelonephritis involving lower pole of left kidney. (d) Sagittal contrast-enhanced computed tomography section shows that the perinephric fat stranding is extending inferoposterior to lower pole of left kidney

DISCUSSION

Dynamic renal scintigraphy is an established procedure for the diagnostic work-up of upper urinary tract dilatation. It contributes to the management of patients with hydronephrosis by assessing both urinary flow and renal function.[1]

While performing dynamic renal scintigraphy, radiotracer temporally traverses and recirculates through abdominal aorta, visceral (spleen and liver), and soft tissues before being extracted by renal parenchyma. Therefore, any abnormality involving aorta, visceral organs, and soft tissues within the field of view is highlighted for a brief period and can be brought to notice of referring clinician for further investigations. A careful review of perfusion phase of dynamic renal scintigraphy can help in diagnosing various renal and extrarenal physiological and pathological processes in the field of view.[2]

The various causes of vascular blush in renal scintigraphy described in the literature are renal malignancies, other hypervascular tumors, metastatic bone lesions, oncocytoma, uterine vascularity, fetal uptake in gravid uterus, aortic aneurysm, liver abscess, infrarenal hematoma, and injection abscess.[2345678] Our case adds APN as cause of vascular blush in dynamic renal scintigraphy.

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Conflicts of interest

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