Correlation of contrast-enhanced ultrasonography and computed tomography in complicated pyelonephritis

Clinical History

A 40-year-old woman was referred to our department, reporting fever with chills and right back pain. Physical examination revealed a positive right Giordano sign and 38.8 degrees Celsius fever. The patient had a history of recurrent complicated renal infections.

Imaging Findings

Ultrasound examination detected an enlargement of the right kidney, measuring 16.2 cm in the long axis, and the presence of a hyperechoic mass with indistinct borders. Colour Doppler revealed peripheral-only blood vessels. CEUS revealed a hypovascular mass which on CT+IVC, considering the clinical features, implied complicated pyelonephritis.

Discussion

Acute pyelonephritis results from bacterial invasion of the renal parenchyma. Bacteria usually reach the kidney by ascending from the lower urinary tract. Bacteria may also reach the kidney via the bloodstream. Timely diagnosis and management of acute pyelonephritis has a significant impact on patient outcomes. Less specific or non-urinary symptoms and signs may also be present which may lead to clinical confusion. [1]
Clinical presentation is specific and classical in most cases, consisting of rapid onset of high fevers and flank pain and tenderness.
Imaging studies that may be used in assessing acute pyelonephritis include the following:
- Ultrasonography: is used as a first-line diagnostic tool to evaluate the urinary tract in patients with symptoms of pyelonephritis. Unfortunately, interstitial nephritis is not well characterized in adults on routine grey-scale images. Therefore, most patients with clinically suspected pyelonephritis have negative results from US. Signs such as parenchymal scarring, stones or hydronephrosis often imply the diagnosis. Moreover, CEUS can reveal a low perfusion lesion. [2, 5]
- CT: provides comprehensive anatomic and physiologic information that accurately characterizes both intra- and extra-renal pathologic conditions. CT is excellent for identifying urinary tract gas, calculi, haemorrhage, renal enlargement, inflammatory masses, and obstruction. Involved regions occasionally appear with lower attenuation related to oedema. Less frequently, they have pockets of higher attenuation that are thought to represent haemorrhage. CE CT is also the best modality for fully evaluating the secondary signs of renal inflammatory disease and its complications such as focal or global enlargement of the kidney, perinephric stranding, thickening of Gerota fascia, and abscess formation. [3, 5]
- MRI: is rarely indicated although it is useful in patients for whom exposure to radiation should be avoided or for whom use of iodinated contrast material is contraindicated. MR imaging findings are similar to those of CT and include demonstration of renal oedema, haemorrhage, renal enlargement, abscesses, and perinephric fluid collections. [4]
The presence of an upper urinary tract infection can threaten the viability of the kidney and a percutaneous nephrostomy is usually required on an emergency basis. Imaging is required if complication is suspected in acute pyelonephritis to assess the nature and extent of the lesions, and to detect underlying causes. The current imaging modality of choice in clinical practice is computed tomography. Because of associated radiation and potential nephrotoxicity, CEUS is an alternative that has been proven to be equally accurate in the detection of acute pyelonephritis renal lesions. [6]

Differential Diagnosis List

Final Diagnosis

Complicated pyelonephritis of the right kidney.

URL:	https://eurorad.org/case/14683
DOI:	10.1594/EURORAD/CASE.14683
ISSN:	1563-4086