Detection of parenchymal abnormalities in acute pyelonephritis by pulse inversion harmonic imaging with or without microbubble ultrasonographic contrast agent: correlation with computed tomography

Ultrasound for acute pyelonephritis: a systematic review and meta-analysis

BACKGROUND

There is little consensus regarding the indications and utility of urinary tract imaging and type of imaging to perform in patients presenting with acute pyelonephritis (APN).

AIMS

The aims of this systematic review were to, among patients with APN, (i) identify the proportion of patients investigated with ultrasound (US), (ii) identify the proportion of abnormal US and (iii) identify the proportion of patients with a change in management resulting from abnormal US.

METHODS

A comprehensive search covered two electronic databases (Medline and EMBASE), with selection of studies performed independently by two investigators. Inclusion criteria were English language APN diagnosis and quantification of patients assessed with US or abnormal US results. Quality appraisal used the Newcastle-Ottawa instrument.

RESULTS

There were 35 studies included. The proportion of patients assessed with US was reported in 16 manuscripts and ranged from 20% to 94%, with significant heterogeneity and publication bias. The proportion of abnormal US was reported in 31 manuscripts and ranged from 7% to 79%. The proportion of abnormal US leading to change in management was reported in five studies and ranged from 7% to 59%. There was marked heterogeneity among studies included in all three subgroups.

CONCLUSIONS

Patients with APN are commonly investigated with US, but only a small proportion have abnormalities and appear to be associated with changes in clinical management. The use of routine US for APN is therefore questioned. The identification of clinical variables for appropriate selection of patients to investigate with US requires further research.

An update on pyelonephritis: role of contrast enhancement ultrasound (CEUS)

Acute pyelonephritis (APN) is a bacterial infection causing inflammation of the kidneys. Diagnosis is usually based on clinical and laboratory findings. Imaging is required if a complication is suspected in acute pyelonephritis to assess the nature and extent of the lesions and to detect underlying causes. CT represents the current imaging modality of choice in clinical practice. CEUS is an alternative that has been proven to be equally accurate in the detection of acute pyelonephritis renal lesions. CEUS allows us to distinguish small simple nephritic involvement from abscess complications and to follow their evolution over time during antibiotic therapy. The absence of ionizing radiation and the lack of nephrotoxicity make CEUS an ideal tool in the study of pyelonephritis.

ACR Appropriateness Criteria® Acute Pyelonephritis: 2022 Update

Acute pyelonephritis (APN) is a severe urinary tract infection (UTI) that has the potential to cause sepsis, shock, and death. In the majority of patients, uncomplicated APN is diagnosed clinically and is responsive to treatment with appropriate antibiotics. In patients who are high risk or when treatment is delayed, microabscesses may coalesce to form an acute renal abscess. High-risk patients include those with a prior history of pyelonephritis, lack of response to therapy for lower UTI or for APN, diabetes, anatomic or congenital abnormalities of the urinary system, infections by treatment-resistant organisms, nosocomial infection, urolithiasis, renal obstruction, prior renal surgery, advanced age, pregnancy, renal transplant recipients, and immunosuppressed or immunocompromised patients. Pregnant patients and patients with renal transplants on immunosuppression are at an elevated risk of severe complications. Imaging studies are often requested to aid with the diagnosis, identify precipitating factors, and differentiate lower UTI from renal parenchymal involvement, particularly in high-risk individuals. Imaging is usually not appropriate for the first-time presentation of suspected APN in an uncomplicated patient. The primary imaging modalities used in high-risk patients with suspected APN are CT, MRI, and ultrasound, although CT was usually not appropriate for initial imaging in a pregnant patient with no other complications. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Contrast-enhanced ultrasound of the kidneys and adrenals in children

Pediatric applications of contrast-enhanced ultrasound (CEUS) are growing. Evaluation of the kidneys and adrenal glands in children using intravenous administration of US contrast agents, however, is still an off-label indication. Pediatric CEUS applications for kidneys are similar to those in adults, including ischemic disorders, pseudo- versus real tumors, indeterminate lesions, complex cystic lesions, complicated pyelonephritis, and abscesses. CEUS applications for evaluation of adrenal glands in children are limited, mainly focusing on the assessment and follow-up of adrenal trauma and the differentiation between an adrenal hemorrhage and a mass. This review addresses the current experience in pediatric CEUS of the kidneys and adrenal glands. By extrapolating the established knowledge for US contrast evaluations in the adult kidney to the pediatric context we can note opportunities for CEUS clinical use in children.

Ultrasonographic Demonstration of the Tissue Microvasculature in Children: Microvascular Ultrasonography Versus Conventional Color Doppler Ultrasonography

Microvascular ultrasonographic imaging is the most recent and unique Doppler ultrasound technique. It uses an advanced clutter filter that can remove clutter artifacts and preserve the low-velocity microvascular flow signal. The potential advantages of microvascular ultrasonography are its superiority in detection and visualization of the small blood vessels in tissues, providing radiologists with more information on the vascular structures. Therefore, it has shown particular value in the clinical fields. The aim of this study was to provide microvascular ultrasonographic images for the tissue microvasculature, including the brain, thyroid gland, kidney, urinary bladder, small bowel, ovary, testis, lymph node, and hemangiomas in children, focusing on the comparison with conventional color Doppler ultrasonographic images.

Diagnostic performance of contrast-enhanced ultrasound for acute pyelonephritis in children

The objective of our study was to evaluate the performance of renal contrast-enhanced ultrasound (CEUS) against the 99m-labeled dimercaptosuccinic acid (DMSA) scan and computed tomography (CT) in children for the diagnosis of acute pyelonephritis. We included children who underwent both renal CEUS and the DMSA scan or CT. A total of 33 children (21 males and 12 females, mean age 26 ± 36 months) were included. Using the DMSA scan as the reference standard, the sensitivity, specificity, positive predictive value, and negative predictive value of CEUS was 86.8%, 71.4%, 80.5%, and 80.0%, respectively. When CT was used as the reference standard, the sensitivity, specificity, positive predictive value, and negative predictive value of CEUS was 87.5%, 80.0%, 87.5%, and 80.0%, respectively. The diagnostic accuracy of CEUS for the diagnosis of acute pyelonephritis was 80.3% and 84.6% compared to the DMSA scan and CT, respectively. Inter-observer (kappa = 0.54) and intra-observer agreement (kappa = 0.59) for renal CEUS was moderate. In conclusion, CEUS had good diagnostic accuracy for diagnosing acute pyelonephritis with moderate inter- and intra-observer agreement. As CEUS does not require radiation or sedation, it could play an important role in the future when diagnosing acute pyelonephritis in children.

Localization of acute pyelonephritis in pyrexia of unknown origin using FDG PET/CT

Objectives

Acute pyelonephritis presents with high-grade fever, dysuria, flank pain, leukocytosis, and microscopic hematuria. Urine culture aids in the diagnosis of this infection. It can be complicated or uncomplicated. Complicated pyelonephritis includes uncontrolled diabetes, transplant, pregnancy, acute or chronic renal failure, structural abnormality of the urinary tract, immunocompromised state, and hospital-acquired infections. Gram-negative bacteria commonly involved are Escherichia, Klebsiella, Proteus, and Enterobacter. The FDG PET/CT helps detect occult causes of fever, such as skeletal tuberculosis, thyroiditis, and lymphoma, when other investigations are inconclusive. We present three cases of pyrexia of unknown origin (PUO) in whom FDG PET/CT helped localize the focus of infection in the kidneys.

Methods

The ¹⁸F-FDG PET/CT was performed on all three cases and images were acquired using the Biograph Horizon PET/CT system.

Results

A cortical-based focus of FDG uptake was localized in the kidneys. The focus of abnormality was persistent following diuretic administration at 1-hour delayed regional image. Two cases had supportive evidence of pyelonephritis on DMSA scan. One case also had frank pus drained after DJ stenting of the affected side. All of them responded to treatment.

Conclusion

Physiologic excretion of FDG in the urinary tract may interfere with the detection of the focus of infection in the kidneys on FDG PET/CT. However, occult infection in the kidneys may be detected with adequate precautions, such as the use of diuretics and delayed imaging, as illustrated in this case report. Routine investigations were noncontributory in all three cases presenting with PUO. However, FDG PET provided a diagnostic clue for pyelonephritis.

Nonfetal Imaging During Pregnancy: Acute Abdomen/Pelvis

Abdominal pain is a common occurrence in pregnant women and may have a variety of causes, including those that are specific to pregnancy (eg, round ligament pain in the first trimester) and the wide range of causes of abdominal pain that affect men and women who are not pregnant (eg, appendicitis, acute cholecystitis). Noncontrast magnetic resonance (MR) imaging is increasingly performed to evaluate pregnant women with abdominal pain, either as the first-line test or as a second test following ultrasonography. The imaging appearance of causes of abdominal pain in pregnant women are reviewed with an emphasis on noncontrast MR imaging.

Contrast enhancement ultrasound of renal perfusion in dogs with acute kidney injury

OBJECTIVE

To evaluate the efficacy of contrast-enhanced ultrasound to assess changes in renal perfusion in dogs with acute kidney injury.

MATERIALS AND METHODS

The left kidney of each dog in two groups was examined using contrast-enhanced ultrasound: Group A consisted of 16 healthy dogs and Group B consisted of 12 dogs with acute kidney injury.

RESULTS

All dogs in Group A showed the same sequence of wash-in and wash-out. In Group B the distribution of contrast media showed a similar cortical phase to healthy dogs, but a faster time to maximal medullary enhancement. Group B showed increased medullary peak intensity and medullary area under the curve compared to Group A. Both qualitative and quantitative analyses showed vascular changes especially in the medulla, with more rapid medullary vascularisation and increased medullary perfusion. These results were interpreted as medullary congestion in dogs with acute kidney injury.

CLINICAL SIGNIFICANCE

Contrast-enhanced ultrasound represents an easy to perform, safe, and non-invasive method to detect changes in renal perfusion in dogs with acute kidney injury.

ACR Appropriateness Criteria® Acute Pyelonephritis

Pyelonephritis refers to infection involving the renal parenchyma and renal pelvis. In most patients, uncomplicated pyelonephritis is diagnosed clinically and responds quickly to appropriate antibiotic treatment. If treatment is delayed, the patient is immunocompromised, or for other reasons, microabscesses that form during the acute phase of pyelonephritis may coalesce, forming a renal abscess. Patients with underlying diabetes are more vulnerable to complications, including emphysematous pyelonephritis in addition to abscess formation. Additionally, diabetics may not have the typical flank tenderness that helps to differentiate pyelonephritis from a lower urinary tract infection. Additional high-risk populations may include those with anatomic abnormalities of the urinary tract, vesicoureteral reflux, obstruction, pregnancy, nosocomial infection, or infection by treatment-resistant pathogens. Treatment goals include symptom relief, elimination of infection to avoid renal damage, and identification of predisposing factors to avoid future recurrences. The primary imaging modalities used in patients with pyelonephritis are CT, MRI, and ultrasound. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Acute pyelonephritis in transplanted kidneys: can diffusion-weighted magnetic resonance imaging be useful for diagnosis and follow-up?

PURPOSE

To assess reliability of diffusion-weighted magnetic resonance imaging (DW-MRI) in the management of acute pyelonephritis (APN) foci in transplanted kidneys.

MATERIALS AND METHODS

In the 2012-2014 period, 24 kidney-transplanted patients underwent MR screening for clinical suspicion of APN. Two readers independently analyzed all images, establishing presence and location of APN foci. The 22 patients who were positive at the MR exam constituted the study population. For each patient the apparent diffusion coefficient (ADC) was measured in the APN foci and in three sites of the healthy parenchyma (case-control comparison). The data were matched to the laboratory measurements for white blood cell, C-reactive protein, and serum creatinine.

RESULTS

Forty-six APN foci were found in 22/24 patients. At the acute stage, the difference in ADC between healthy parenchyma and APN foci was significant (2.06 ± 0.16 vs. 1.43 ± 0.32 × 10(-3) mm(2)/s; p < 0.0001). The performance of ADC as APN indicator was tested by the receiving operating characteristics (ROC) curve: the area under curve AUC = 0.99 witnessed an excellent discriminatory ability, with threshold APN/normal parenchyma 1.9 × 10(-3) mm(2)/s. At the 1-month follow-up 43/46 APN foci were no longer visible, with ADC values significantly higher than at the acute stage; all laboratory data were physiological, with WBC significantly reduced from the acute phase (5.2 ± 1.6 × 10(9)/L vs. 10.6 ± 4.8 × 10(9)/L; p < 0.0001). The other 3 patients underwent further therapy and exams, including a third MR.

CONCLUSIONS

DW-MRI with ADC measurement seems to be a reliable tool in diagnosing and monitoring APN foci in transplanted kidneys, with clinical impact on patient management.

Contrast enhanced ultrasonography of kidney in conscious and anesthetized beagle dogs

Contrast enhanced ultrasound (CEUS) is useful to evaluate tissue perfusion in the kidney. In veterinary medicine, sedation or anesthesia may be required in uncooperative or panting patients. The aim of this study was to evaluate and compare the normal kidney perfusion patterns in conscious and anesthetized dogs using CEUS. Eight healthy beagles were used in this study. Scanning was performed in conscious dogs using manual restraint (conscious group), or under general anesthesia using tiletamine-zolazepam and medetomidine (TZM group) or medetomidine (M group). The contrast agent (Sonovue^®) was administered as an IV bolus. The peak intensity (PI), time to peak enhancement from injection (TTP₀) and the time to peak enhancement from the initial rise (TTP_up), upslope, downslope and area under the curve (AUC) were analyzed. Compared to the cortical values in the conscious group, TTP₀ was significantly delayed in the TZM group, and upslope, TTP₀ and TTP_up were significantly different in the M group. The AUCs in the TZM and M groups were not different from those in the conscious group. The upslope of renal medullary perfusion was significantly decreased in the TZM and M groups. TTP₀ and TTP_up were also significantly delayed in these groups. The AUC of the medulla was significantly decreased in the M group. Therefore, TZM is useful as an anesthetic protocol when performing CEUS, and the obtained data may serve as reference values in the evaluation of renal perfusion using CEUS in dogs under anesthesia.

Emergency radiology

US has a relevant role in the initial assessment of non-traumatic emergencies of the abdomen, sometimes being conclusive and some other times for selecting the patients for further imaging with CT. Injection of a contrast medium may give to the radiologist additional information to that obtained at baseline US and Doppler examination, since real-time, contrast-enhanced US (CEUS) may allow observing findings in the abdomen not recognizable at baseline US or even at color Doppler imaging. Extravascular use of microbubbles may also be useful in clinical practice to rapidly solve a number of unclear aspects. CEUS has a number of distinct advantages in acute patients, including its quickness, low invasiveness, and its possible bedside use. The information based on contrast enhancement is useful for initial diagnosis, therapeutic decision making, and follow-up of the critically ill patients. The purpose of this review is to illustrate the possibilities and limitations of abdominal CEUS in the acute setting, with special emphasis on the detection and characterization of acute inflammatory processes, infarcts, and hemorrhages.

Bedside contrast-enhanced sonography of critically ill patients

The transfer of critically ill patients to the radiology department is, in itself, potentially dangerous, so radiologists are frequently asked to perform bedside sonographic studies in the intensive care unit, surgical or medical department, sterile area, and operating room. In these circumstances, injection of a contrast agent may give the radiologist relevant additional information, which is useful for diagnosis and for better therapeutic management of these critically ill patients. Contrast-enhanced sonography may allow detection of findings not recognizable on baseline sonography or even color Doppler imaging. In this pictorial essay, we highlight the value of real-time contrast-enhanced sonography when performed at the bedside in critically ill patients.

Contrast-enhanced ultrasound analysis of renal perfusion in normal micropigs

Contrast-enhanced ultrasound is one of method for evaluating renal perfusion. The purpose of this project was to assess perfusion patterns and dynamics in normal micropig kidney using ultrasonographic contrast media. Eight young healthy micropigs were included in this study. Micropigs were anesthetized with propofol and received an intravenous bolus of microbubble contrast media through an ear vein. Time/mean pixel value (MPV) curves were generated for selected regions in the right renal cortex and medulla. The parenchyma was enhanced in two phases. The cortex was first enhanced followed by a more gradual enhancement of the medulla. A significant difference in perfusion was detected between the cortex and medulla. Following the bolus injection, the average upslope was 0.68 ± 0.27 MPV/sec, downslope was -0.27 ± 0.13 MPV/sec, baseline was 73.9 ± 16.5 MPV, peak was 84.6 ± 17.2 MPV, and time-to-peak (from injection) was 17.5 ± 6.6 sec for the cortex. For the medulla, the average upslope was 0.50 ± 0.24 MPV/sec, downslope was -0.12 ± 0.06 MPV/sec, baseline was 52.7 ± 7.0 MPV, peak was 65.2 ± 9.3 MPV, and time-to-peak (from injection) was 27.5 ± 5.0 sec. These data can be used as normal reference values for studying young micropigs.

Acute complicated pyelonephritis: contrast-enhanced ultrasound

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. The aims of this study of 48 patients are to describe in detail the CEUS findings in acute pyelonephritis, and to determine if abscess and focal pyelonephritis may be distinguished. Very characteristic morphologic and temporal patterns of enhancement are described. These allow differentiation of focal pyelonephritis from renal abscess, and detection of tiny suppurative foci within focal pyelonephritis. The detection of abscesses is important because follow-up in 25 patients revealed a longer clinical course. Typical pyelonephritis CEUS features permit distinction from other renal lesions. As a whole, CEUS is an excellent tool in the work-up of complicated acute pyelonephritis, so it may be considered as the imaging technique of choice in the evaluation and follow-up of these patients who frequently are very young, so as to minimise radiation exposure.

Contrast-enhanced ultrasound of the feline kidney

Contrast-enhanced ultrasound offers a noninvasive means of subjectively and quantitatively evaluating renal perfusion in cats with renal disease, or in renal transplant patients. In this study, we characterized the pattern of ultrasonographic contrast enhancement in 16 normal feline kidneys in eight cats using contrast-enhanced power Doppler and contrast-enhanced harmonic ultrasound techniques. Mean time to peak contrast enhancement for the whole kidney was longer using contrast-enhanced harmonic ultrasound (16.8s, SD 4.7s) than contrast-enhanced power Doppler ultrasound (12.2s, SD 1.8s). The time to peak enhancement for the cortex alone in contrast-enhanced harmonic ultrasound was 13s (SD 3.2s), and for the renal medulla was 25.5s (SD 8.7s). The half time for washout of contrast agent was 39s (SD 14.5s) for contrast-enhanced harmonic ultrasound. The pattern of contrast enhancement in these normal feline kidneys can be used as normal reference values for the evaluation of clinical patients. Contrast-enhanced harmonic ultrasound may allow the differentiation between cortical and medullary perfusion patterns.

Diagnosis of acute pyelonephritis by contrast-enhanced ultrasonography in kidney transplant patients

BACKGROUND

Diagnostic imaging of acute pyelonephritis (APN) in renal transplanted patients is an important clinical issue. While conventional ultrasonography (US) has a limited diagnostic role, contrast-enhanced computer tomography and magnetic resonance imaging (MRI) represent the gold standard diagnostic tests. However, nephrotoxicity of either iodinated or paramagnetic contrast medium limits their use, especially in patients with kidney disease. Contrast-enhanced US (CEUS) may detect poorly perfused parenchymal renal areas, a useful feature in the diagnosis of APN. The aim of this study was to evaluate the diagnostic value of CEUS in APN compared with MRI as the reference test.

METHODS

From a pool of 389 kidney transplant patients, we prospectively recruited 56 patients with clinical suspicion of APN of the transplanted kidney. They underwent both CEUS and MRI, performed in a blinded manner by two different operators. Sensitivity, specificity, accuracy, positive and negative predictive values, and K statistics were calculated.

RESULTS

Thirty-seven out of 56 patients (66.1%) resulted positive for APN with the reference test, gadolinium-enhanced MRI. Thirty-five out of these 37 patients showed positive results for APN with CEUS, and 19 patients showed negative results for APN with both MRI and CEUS: sensitivity 95% (CI 82-99), specificity 100% (CI 83-100), accuracy 96% (CI 88-99), positive predictive value 100% (CI 90-100), negative predictive value 90% (CI 71-97) and K statistics 0.92 (P<0.01).

CONCLUSIONS

Our results suggest, for the first time, the feasibility of CEUS, a low-cost and low-risk diagnostic procedure, in the diagnosis of APN in kidney transplant patients.

Pyelonephritis: radiologic-pathologic review

Urinary tract infections are the most common urologic disease in the United States and annually account for over 7 million office and 1 million emergency department visits. In adults, diagnosis of urinary tract infection is typically based on characteristic clinical features and abnormal laboratory values. Imaging is usually reserved for patients who do not respond to therapy and for those whose clinical presentation is either atypical or potentially life threatening. Urinary tract infection typically originates in the urinary bladder; when it migrates to the kidney or is seeded there hematogenously, a tubulointerstitial inflammatory reaction ensues, involving the renal pelvis and parenchyma. The condition is characterized as pyelonephritis. Complicated and uncomplicated pyelonephritis, xanthogranulomatous pyelonephritis, and tuberculosis are all urinary tract infections for which imaging evaluation adds diagnostic information important for patient care. Computed tomography (CT), when performed before, immediately after, and at delayed intervals from contrast material injection, is the preferred modality for evaluating acute bacterial pyelonephritis. CT is also preferred over conventional radiography and ultrasonography (US) for assessing emphysematous pyelonephritis. Xanthogranulomatous pyelonephritis is a chronic granulomatous process, induced by recurrent bacterial urinary tract infection. Although US is useful in the diagnosis of this condition, CT is the main imaging tool, as it provides highly specific findings and accurate assessment of the extrarenal extent of disease, which is essential for surgical planning. The increasing prevalence of tuberculosis and continued emergence of antibiotic-resistant strains have significance for genitourinary radiologists, as the urinary tract is the most common extrapulmonary site of tuberculosis. Familiarity with the renal manifestations of the disease--pelvoinfundibular strictures, papillary necrosis, cortical low-attenuation masses, scarring, and calcification--will help in the diagnosis, even in the absence of documented pulmonary disease.

Acute pyelonephritis: comparison of diagnosis with computed tomography and contrast-enhanced ultrasonography

OBJECTIVE

To assess the value of contrast-enhanced ultrasonography (US) with the contrast pulse-sequence (CPS) technique for detecting renal parenchymal changes in acute pyelonephritis (APN), compared with contrast-enhanced computed tomography (CT) as the reference standard.

PATIENTS AND METHODS

We examined 100 patients (82 women, 18 men; mean age 30.2 years, range 18-67); children (those aged <18 years) were excluded from the study. All patients had clinical symptoms suggestive of APN. For the US a Sequoia 512 (Acuson, Mountain View, CA, USA) unit including Cadence CPS technology, with a 6C2 probe, was used. A bolus of a 2.4-mL US contrast agent SonoVue (Bracco, Milan, Italy) was injected. For CT a multislice 16-row unit was used (Sensation 16, Siemens, Erlangen, Germany), at a table speed of 2.5 mm/s and a slice thickness of 3 mm; 100 mL of intravenous iodinated contrast agent (flow 3 mL/s) was injected.

RESULTS

On contrast CT, 84 patients (84%) had renal parenchymal changes suggestive of APN; on contrast US, 82 of the 84 (98%) showed renal parenchymal changes, and APN was correctly diagnosed. Seventy-six patients (90%) had unilateral and eight (10%) had bilateral APN, and in two (2%) with APN the diagnosis could not be confirmed by US/CPS (false-negative). No false-positive findings were detected on US/CPS, which had a sensitivity of 98%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 89%.

CONCLUSION

CPS/US is accurate for detecting parenchymal changes in APN; it is very sensitive and specific, and allows small renal parenchymal changes to be detected with no radiation exposure.

Complications of renal transplantation: ultrasonographic evaluation

OBJECTIVE

The purpose of this presentation is to show the ultrasonographic findings of complications of renal transplantation.

METHODS

We reviewed the ultrasonographic findings of complications of renal transplantation, including urologic complications, fluid collections, graft dysfunction, vascular complications, neoplasms, and recurrent native renal disease.

RESULTS

Specific ultrasonographic features of complications of renal transplantation have been illustrated.

CONCLUSIONS

Familiarity with the clinical setting and the appearance of potential renal transplant complications as depicted with the most commonly used modality, ultrasonography, will facilitate prompt, accurate diagnosis and treatment.

Renal pseudotumors

OBJECTIVE

Renal cell carcinoma is the most common malignant tumor to involve the kidneys; however, a number of other entities--called renal pseudotumors--may mimic renal neoplasms on imaging. This article presents the imaging features and pathologic correlation of some of the common and uncommon renal pseudomasses.

CONCLUSION

Many renal lesions look similar to renal cell carcinoma on radiologic imaging. The imaging features of renal pseudotumors presented in this article will help radiologists to identify them and to triage these patients for appropriate management.

Contrast-enhanced sonography of the kidney

Contrast-enhanced sonography (CEUS) is a recently introduced, promising technique in the evaluation of the kidney. CEUS allows real-time assessment of normal and abnormal renal perfusions. As a consequence of the macrocirculation analysis allowed by Doppler techniques, it is possible to obtain real-time information about microcirculation. US contrast media are not nephrotoxic and can be employed safely, even in subjects with impaired renal function. There are several clinical scenarios where CEUS may play the role of a low-cost, scarcely invasive tool, including renal tumors (with special reference to small, indeterminate masses, i.e., differentiation between carcinoma and angiomyolipoma), renal atypical cystic masses (i.e., differentiation of malignant from benign cysts and follow-up of cystic lesions managed conservatively), renal infarction, renal infections, and renal injuries. In addition, CEUS can be useful in the assessment of renal pseudotumors (including any case with possible renal mass on conventional US imaging) and has been employed in radiofrequency ablation guidance. This pictorial review illustrates the CEUS findings recognizable in a wide spectrum of renal disorders and discusses the strengths and limitations of renal imaging with CEUS.

Imaging of acute pyelonephritis in the adult

The diagnosis of acute pyelonephritis in adults is predominantly made by a combination of typical clinical features of flank pain, high temperature and dysuria combined with urinalysis findings of bacteruria and pyuria. Imaging is generally reserved for patients who have atypical presenting features or in those who fail to respond to conventional therapy. In addition, early imaging may be useful in diabetics or immunocompromised patients. In such patients, imaging may not only aid in making the diagnosis of acute pyelonephritis, but more importantly, it may help identify complications such as abscess formation. In this pictorial review, we discuss the role of modern imaging in acute pyelonephritis and its complications. We discuss the growing role of cross-sectional imaging with computed tomography (CT) and novel magnetic resonance imaging (MRI) techniques that may be used to demonstrate both typical as well as unusual manifestations of acute pyelonephritis and its complications. In addition, conditions such as emphysematous and fungal pyelonephritis are discussed.

[Modern imaging technology for childhood urinary tract infection]

Imaging in childhood urinary tract infection (UTI) is still a matter of debate. There are established guidelines, however new knowledge and the changed medical environment have enhanced this ongoing discussion. These new insights have impacted therapy and consequently the imaging algorithm. Modern imaging methods -- particularly MRI and modern ultrasound (US) -- are less invasive with a lower radiation burden. Additionally, it has been shown that VUR is a poor predictor for renal scarring out, which affects long-term results. Furthermore, the majority of UT malformations is depicted by prenatal US. The most crucial aspect of improving long-term outcome appears to be the early and reliable depiction of UTI and effective treatment to prevent renal scarring. This review tries to present this new knowledge and to discuss the potential of modern imaging. Recent changes in imaging algorithms are highlighted and an outcome-oriented algorithm that addresses these recent developments is proposed, without lightly abandoning established standards. It consists of an orienting US and -- for depiction of renal involvement -- amplitude coded color Doppler sonography or renal static scintigraphy (considered the gold standard, particularly for evaluating scars); in future MRI may play a role. Based on this concept, only patients with renal damage as well as patients with complex urinary tract malformations or intractable recurrent UTI may have to undergo VCUG.

Modern pediatric ultrasound: potential applications and clinical significance. A review

After the introduction of ultrasound (US), the new imaging modality was first warmly welcomed, but then lost reputation and importance particularly in radiology leading to an increasing number of other -- particularly computed tomography (CT) -- investigations, which especially in pediatrics was a potentially dangerous development considering the radiation hazards. However, innovative and creative US approaches as well as new US techniques such as amplitude-coded color Doppler, harmonic and high-resolution imaging, and US contrast media or three-dimensional US have been introduced over the past decade and significantly broadened the potential of US. Thus, now, the role of US has been widened in many conditions and queries, and US today may well play a more pronounced and essential role in modern imaging algorithms at still relatively low cost, with sufficient diagnostic accuracy and conspicuity. Particularly in the pediatric setting, these new capabilities are applicable in many queries and almost all body regions and should be used to reduce the number of more invasive or radiating and relatively costly examinations that often additionally need some sedation or intravenous iodinated contrast material. To readily provide this approach for sick children, we need to promote the knowledge about modern US capabilities, to train US staff to guarantee 24-h availability of adequate pediatric US performance, and to make it known to the referring clinicians.

Detection of focal renal perfusion defects in rabbits after sulphur hexafluoride-filled microbubble injection at low transmission power ultrasound insonation

The aim of this study was to assess the feasibility of contrast-enhanced ultrasound (US) at low transmission power insonation for diagnosis of focal renal perfusion defects (RPDs) in rabbits. In seven adult New Zealand White rabbits focal RPDs were induced by polyvinyl alcohol embolizing particles (150-250 microm in diameter) injected into the abdominal aorta. Three other rabbits that were not subjected to embolization were considered as controls. Both kidneys were insonated at baseline and after injection of sulphur hexafluoride-filled microbubbles at low transmission power (mechanical index 0.09-0.12). One sonologist assessed on-site RPD dimensions and conspicuity (visual score 0-4). Digital cine-clips were also reviewed off-site by two other independent readers, blinded, who assigned a confidence level (grades 1-5) for the RPD diagnosis. At on-site analysis RPDs appeared as focal areas of absent or diminished enhancement with a median visual conspicuity score=4. At off-site analysis RPDs >6 mm in diameter were identified at contrast-enhanced US, and the confidence in RPD diagnosis improved significantly (P<0.05) after microbubble injection (area under receiver operating characteristic curve 0.615 vs 0.972 by reader 1; 0.720 vs 0.953 by reader 2). Contrast-enhanced US at low transmission power insonation effectively identified RPDs with diameters >6 mm in rabbits.

Clinical use of renal perfusion imaging by means of harmonic sonography with a microbubble contrast agent in patients after renal transplantation: preliminary study

OBJECTIVE

The purpose of this research was to determine the feasibility of renal perfusion imaging by means of harmonic sonography with a microbubble contrast agent for the evaluation of renal perfusion after renal transplantation compared with technetium Tc 99m diethylenetriamine pentaacetic acid ((99m)Tc-DTPA) scans.

METHODS

During a 10-month period, 100 patients with renal transplantation that included normal perfusion (n=68) and delayed perfusion including chronic rejection (n=19), acute rejection (n=9), arterial stenosis (n=2), and urinary stricture (n=2) underwent sonographic renal perfusion imaging and (99m)Tc-DTPA scans. Sonographic images were obtained every 3 seconds for a total of 3 minutes after administration of a bolus injection of 4 g of the microbubble contrast agent at a concentration of 300 mg/mL. Sonographic renal perfusion images were converted into a renal perfusion curve, and the calculated time at the peak of the curve (T(peak)) was compared with that of the (99m)Tc-DTPA scan.

RESULTS

The T(peak) with the (99m)Tc-DTPA scan was 14.9 seconds in the normal group and 33 seconds in the delayed perfusion group. The T(peak) on sonographic renal perfusion images was 25 seconds in the normal group and 44.8 seconds in the delayed perfusion group. Sonographic renal perfusion images showed good correlation with the (99m)Tc-DTPA scan (r=0.74; P=.0001). The cutoff value of the T(peak) on sonographic renal perfusion images was 35 seconds (sensitivity=85%; specificity=90%).

CONCLUSIONS

The renal perfusion images obtained by means of harmonic sonography with a microbubble contrast agent constitute an effective sonographic technique for the evaluation of renal perfusion abnormalities after renal transplantation compared with a (99m)Tc-DTPA scan.

Ultrasound evaluation of normal and abnormal fetuses: comparison of conventional, tissue harmonic, and pulse-inversion harmonic imaging techniques

OBJECTIVE

To determine the usefulness of tissue harmonic imaging (THI) and pulse-inversion harmonic imaging (PIHI) in the evaluation of normal and abnormal fetuses.

MATERIALS AND METHODS

Forty-one pregnant women who bore a total of 31 normal and ten abnormal fetuses underwent conventional ultrasonography (CUS), and then THI and PIHI. US images of six organ systems, namely the brain, spine, heart, abdomen, extremities and face were compared between the three techniques in terms of overall conspicuity and the definition of borders and internal structures.

RESULTS

For the brain, heart, abdomen and face, overall conspicuity at THI and PIHI was significantly better than at CUS (p < 0.05). There was, though, no significant difference between THI and PIHI. Affected organs in abnormal fetuses were more clearly depicted at THI and PIHI than at CUS.

CONCLUSION

Both THI and PIHI appear to be superior to CUS for the evaluation of normal or abnormal structures, particularly the brain, heart, abdomen and face.

Renal imaging with ultrasound contrast: current status

The application of UCAs to the kidney is still in its infancy; however, there are several areas of great promise. UCAs may replace CT in complex renal cyst evaluation and follow-up, eliminating the need for costly CT scans with their attendant potential contrast nephrotoxicity. This approach may decrease patient and physician uncertainty and improve diagnostic confidence. The use of UCAs is likely to be clinically useful in the evaluation of the indeterminate small renal mass on CT or MR imaging. Another probable useful application will be in renal artery stenosis. Routine application of UCAs may increase the percentage of diagnostic examinations, increase diagnostic confidence, and decrease examination times. It also will likely become the first line of evaluation in pyelonephritis, and be useful in immediate assessment of residual tumor after radiofrequency ablation. Of course, substantial additional work needs to be performed in large groups of patients to prove this currently optimistic outlook.

Potential of modern sonographic techniques in paediatric uroradiology

OBJECTIVE

To describe the potential of modern sonographic techniques in paediatric uroradiology.

METHOD

Ultrasound (US)-now being the primary imaging tool-has revolutionised imaging diagnostic in the urinary tract. Constant developments and technical refinements have secured the role of US in uroradiology. Colour Doppler Sonography (CDS) and innovative applications such as the transperineal approach or application of m-mode US to the urinary tract have helped to develop US from just a basic tool to a sophisticated and respected method. The ongoing introduction of new and even more sophisticated methods further enhance the sonographic potential, which shall be demonstrated by a more detailed discussion of these methods.

RESULTS

Harmonic imaging, extended field of view US, amplitude coded CDS, echo-enhanced US, and three-dimensional US as the most recent new sonographic techniques are successfully applicable to paediatric urinary tract disease. They improve sonographic diagnosis in many conditions, such as detection of vesico-ureteral reflux, renal parenchymal volume assessment, comprehensive visualisation of hydronephrosis and complex pathology, evaluation of renal perfusional disturbances or defects, superior documentation with improved comparability for follow-up, or simply by offering clearer tissue delineation and differentiation.

CONCLUSION

Modern US techniques are successfully applicable to neonates, infants, and children, further boosting the value of US in the paediatric urinary tract. However, as handling became more sophisticated, and artefacts have to be considered, modern urosonography became not only a more powerful, but also a more demanding method, with the need for expert knowledge and dedicated training.

Conventional imaging in paediatric uroradiology

OBJECTIVE

To briefly describe basic conventional imaging in paediatric uroradiology.

METHOD

The state of the art performance of standard imaging techniques (intravenous urography (IVU), voiding cystourethrography (VCU), and ultrasound (US)) is described, with emphasis on technical aspects, indications, and patient preparation such as adequate hydration. Only basic applications as used in routine clinical work are included.

RESULT AND CONCLUSION

Conventional imaging methods are irreplaceable. They cover the majority of daily clinical routine queries, with consecutive indication of more sophisticated modalities in those patients who need additional imaging for establishing the final diagnosis or outlining therapeutic options.

Contrast Agents and Contrast Imaging in Ultrasound

This article reviews studies using ultrasound contrast agents and discusses several of the contrast agents currently available. The anatomical areas that are enhanced by contrast, examination, and techniques, are used in imaging with contrast agents.

Sonographic evaluation of breast nodules: comparison of conventional, real-time compound, and pulse-inversion harmonic images

OBJECTIVE

To compare the use of conventional, real-time compound, and pulse-inversion harmonic imaging in the evaluation of breast nodules.

MATERIALS AND METHODS

Fifty-two breast nodules were included in this study, conducted between May and December 2000, in which conventional, real-time compound, and pulse-inversion harmonic images were obtained in the same plane. Three radiologists, each blinded to the interpretations of the other two, evaluated the findings, characterizing the lesions and ranking the three techniques from grade 1, the worst, to grade 3, the best. Lesion conspicuity was assessed, and lesions were also characterized in terms of their margin, clarity of internal echotexture, and clarity of posterior echo pattern. The three techniques were compared using Friedman's test, and interobserver agreement in image interpretation was assessed by means of the intraclass correlation coefficient.

RESULTS

With regard to lesion conspicuity, margin, and internal echotexture of the nodules, real-time compound imaging was the best technique (p < 0.05); in terms of posterior echo pattern, the best was pulse-inversion harmonic imaging (p < 0.05). Real-time compound and pulse inversion harmonic imaging were better than conventional sonography in all evaluative aspects. Interobserver agreement was greater than moderate.

CONCLUSION

Real-time compound and pulse-inversion harmonic imaging procedures are superior to conventional sonography in terms of both lesion conspicuity and the further characterization of breast nodules. Real-time compound imaging is the best technique for evaluation of the margin and internal echotexture of nodules, while pulse-inversion harmonic imaging is very effective for the evaluation of the posterior echo patterns.

Diagnostic Investigation of Pyelonephritis

Urinary tract infections are common, especially among women, and cause significant morbidity. While prognosis is probably more dependent on whether or not an episode of urinary tract infection is complicated (ie, associated with functional, metabolic, or anatomic abnormalities of the urinary tract) or uncomplicated, anatomic localization of infection has important implications for therapy. Pyelonephritis is difficult to diagnose with a high degree of accuracy based on clinical findings alone. Radiologic imaging plays an important role in the diagnosis and management of selected patients. Noninvasive and inexpensive methods to allow accurate localization of infection are needed.