Acute focal bacterial nephritis: emphasis on gray scale sonography and computed tomography

Clinical features of acute focal bacterial nephritis in adults

Acute focal bacterial nephritis (AFBN) is a localized bacterial infection of the kidneys presenting as an inflammatory mass that can develop into renal abscess. The current reports on AFBN mostly are among children and rarely described in adults. This study was aimed to analyze the clinical features of AFBN in adults and make a review for the disease to give the clinicians some clues to suspect and recognize it in adults. From January 2014 to December 2019, AFBN was diagnosed by contrast-enhanced computed tomography (CT) in 238 adults at the Department of Nephrology, the Second Hospital of Hebei Medical University, Shijiazhuang, China. We reviewed the clinical records of these patients and asked them about their post-discharge status via telephone follow-up. Of all the patients, 195 were female and 43 were male, the median age were 46.87 years. 86.13% presented with fever, 55.89% presented with lower urinary tract symptoms and 97.9% presented with pyuria. In renal ultrasonography, abdominal findings were seen only 22.69% patients. E.coli accounted for 74.73% of the isolated pathogen. After 4 weeks of treatment, the patients had no recurrence of symptoms. We recommend that when a patient presents clinically with acute pyelonephritis, but the fever persist longer after antimicrobial treatment (≥ 4 days in our study), AFBN should be suspected. For the diagnosis, contrast-enhanced CT is the “gold standard”, magnetic resonance imaging (MRI) may be a good option, but the ultrasonography is probably not satisfied. 3–4 weeks of antibiotic therapy may be appropriate for AFBN in adults.

Acute Renal Infection in Adult, Part 1: An Overview of What the Radiologist Needs to Know

Acute renal infection or acute pyelonephritis (AP) denotes the process of inflammation of the renal parenchyma and its collecting system and the urothelium following infection. Uncomplicated AP commonly affects otherwise healthy, young women without structural or functional urinary tract abnormalities and without relevant comorbidities. More severe and complicated AP occurs in patients with a structurally or functionally abnormal genitourinary tract, or in persons with a predisposing medical condition like immune compromised state and diabetes. Complicated AP is characterized by a broader spectrum of clinical presentations, a wider variety of infecting organisms, and a greater risk of progression to a complication, such as intrarenal or perinephric abscess or emphysematous pyelonephritis and has the capacity to damage the organ and at times maybe life threatening. Role of imaging in renal infection is secondary, and in most situations, imaging is done to confirm the clinical diagnosis, map progression of disease in immune-compromised group of patients, or to evaluate for potential complications and therapeutic interventions. This article attempts to discuss the pathophysiology of AP from the standpoint of medical imaging and also brings out illustrative examples of various manifestations of AP and its complications. It provides imaging insight into various stages of inflammation, development of complication, and a roadmap for understanding AP through cross-sectional imaging.

Serial sonographic findings during progression from acute pyelonephritis to renal abscess: a rare case report

Renal abscess, accumulation of infective fluid in the kidney, is a rare pathology. Currently, no reports of the serial imaging changes of acute pyelonephritis (APN) progressing to renal abscess exist. We report clinical and serial sonographic findings of a patient with hyper-immunoglobulin E syndrome, a primary immunodeficiency, who developed APN that progressed to renal abscess. Renal ultrasonography revealed that echogenicity of infectious lesions dramatically changed from isoechoic to hyperechoic and to hypoechoic during progression. These findings are useful for differential diagnosis of APN, acute focal bacterial nephritis, and renal abscess.

Acute focal bacterial nephritis is associated with invasive diagnostic procedures - a cohort of 138 cases extracted through a systematic review

BACKGROUND

Acute focal bacterial nephritis (AFBN) is a rare disease currently described only in case reports and small case series. In this study we summarize the clinical features of AFBN as has been documented in the literature and draw recommendations on the proper diagnosis and therapy.

METHODS

A systematic literature review was undertaken in PUBMED, Web of Science and The Cochrane Library online databases for relevant literature on AFBN in adults.

RESULTS

Literature review revealed a total of 38 articles according to our inclusion criteria, of which we could extract data from 138 cases of AFBN. Fever (98%) and flank pain (80%) were most commonly reported symptoms. E. coli was the most frequent pathogen. Diagnosis was set by CT and/or MRI (52%) with or without sonography or by sonography alone (20%) as well as by sonography combined with IVU. In total, sonography was applied in 83% of cases. All but one patient received antibiotic treatment. Kidney lesions were occasionally mistaken for neoplasms or renal abscesses and as a result, cases were subjected to percutaneous puncture (12.3%), surgical exploration (5.1%) and partial or radical nephrectomy (4.4%). Four cases (2.9%) developed a renal abscess.

CONCLUSIONS

The diagnosis of AFBN is set by characteristic clinico-radiological findings. Differential diagnoses of this interstitial bacterial infection include renal abscess and tumor. Correct diagnosis is occasionally impeded by atypical symptoms. Invasive diagnostic and therapeutic procedures should be limited as the majority of cases respond well to conservative treatment.

Acute focal bacterial nephritis in a cohort of hospitalized adult patients with acute pyelonephritis. Assessment of risk factors and a predictive model

BACKGROUND

Acute focal bacterial nephritis (AFBN) is a complicated form of acute pyelonephritis (APN) characterized by single or multiple areas of localised infection in the kidney without liquefaction or abscess. Studies investigating AFBN in adults are scarce.

AIM

The present study was aimed at evaluating the prevalence, associated factors, and presence of atypical clinical and radiological manifestations in adult AFBN patients. Also, we developed a clinical prediction model to evaluate the probability of AFBN in patients with APN.

METHODS

The clinical records of 377 patients (mean age 54years, 74.0% females) admitted to a hospital over a 5-year period with APN were reviewed.

RESULTS

A total of 57 cases of AFBN were radiologically identified (prevalence, 15.1%). Patients with AFBN were younger and displayed atypical manifestations more frequently than patients without AFBN; these included both clinical and radiological (pleural effusion, gallbladder wall thickening, fluid around the gallbladder, perirenal fluid, and ascites) manifestations. Patients with AFBN showed lower systolic blood pressure and needed more days of therapy to become afebrile, longer total duration of antibiotic therapy, and longer hospital stay than patients without AFBN. Contraceptive use was more frequent in patients with AFBN. A model based on five clinical variables showed good discrimination performance for the diagnosis of AFBN (Area under the curve, 0.77 (95% CI, 0.69-0.89)).

CONCLUSIONS

Patients with AFBN frequently present with atypical clinical and radiological manifestations. Clinical presentation by means of a predictive model may predict the presence of AFBN. Patients with AFBN need more intensive therapy, which is followed by a favourable outcome.

Comparison of acute lobar nephronia and acute pyelonephritis in children: a single-center clinical analysis in southern taiwan

BACKGROUND

Patients with acute lobar nephronia (ALN) require a longer duration of antimicrobial treatment than those with acute pyelonephritis (APN), and ALN is associated with renal scarring. The aim of this study was to provide an understanding of ALN by comparing the clinical features of pediatric patients with ALN and APN.

METHODS

We enrolled all of the patients with ALN (confirmed by computed tomography) admitted to our hospital from 1999 to 2012 in the ALN group. In addition, each patient diagnosed with APN who was matched for sex, age, and admission date to each ALN patient was enrolled in the APN group. The medical charts of patients in these two groups were retrospectively reviewed and analyzed for comparison.

RESULTS

The fever duration after hospitalization in the ALN group and the APN group were 4.85 ± 2.33 days and 2.30 ± 1.47 days respectively. The microbiological distributions and the majority of susceptibilities were similar in the ALN and APN groups. The majority of clinical manifestations are nonspecific and unreliable for the differentiation of ALN and APN. The patients with ALN were febrile for longer after antimicrobial treatment, had more nausea/vomiting symptoms, higher neutrophil count, bandemia, and C-reactive protein (CRP) levels, and lower platelet count (all p < 0.05). In multivariate analysis, initial CRP levels, nausea/vomiting symptoms, and fever duration after admission were independent variables with statistical significance to predict ALN. Severe nephromegaly occurred significantly more in the ALN group than in the APN group (p = 0.022).

CONCLUSION

The majority of clinical manifestations, laboratory findings, and microbiological features are similar between patients with ALN and APN. Clinicians should keep a high index of suspicion regarding ALN, particularly for those with ultrasonographic nephromegaly, initial higher CRP, nausea/vomiting, and fever for > 5 days after antimicrobial treatment.

Tuberculosis of the genitourinary system-Urinary tract tuberculosis: Renal tuberculosis-Part I

Tuberculosis (TB) remains a worldwide scourge and its incidence appears to be increasing due to various factors, such as the spread of human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS). The insidious onset and non-specific constitutional symptoms of genitourinary tuberculosis (GUTB) often lead to delayed diagnosis and rapid progression to a non-functioning kidney. Due to hematogenous dissemination of TB, there is a potential risk of involvement of the contralateral kidney too. Imaging plays an important role in the making of a timely diagnosis and in the planning of treatment, and thus helps to avoid complications such as renal failure. Imaging of GUTB still remains a challenge, mainly on account of the dearth of literature, especially related to the use of the newer modalities such as magnetic resonance imaging (MRI). This two-part article is a comprehensive review of the epidemiology, pathophysiology, and imaging findings in renal TB. Various imaging features of GUTB are outlined, from the pathognomonic lobar calcification on plain film, to finer early changes such as loss of calyceal sharpness and papillary necrosis on intravenous urography (IVU); to uneven caliectasis and urothelial thickening, in the absence of renal pelvic dilatation, as well as the hitherto unreported 'lobar caseation' on ultrasonography (USG). Well-known complications of GUTB such as sinus tracts, fistulae and amyloidosis are described, along with the relatively less well-known complications such as tuberculous interstitial nephritis (TIN), which may remain hidden because of its 'culture negative' nature and thus lead to renal failure. The second part of the article reviews the computed tomography (CT) and MRI features of GUTB and touches upon future imaging techniques along with imaging of TB in transplant recipients and in immunocompromised patients.

The clinical and imaging presentation of acute "non complicated" pyelonephritis: a new profile for an ancient disease

BACKGROUND

Acute pyelonephritis (APN) is differently defined according to imaging or clinical criteria. In adults information on the relationship between imaging and clinical data is lacking.Our study was aimed at analysing the relationship between the clinical and imaging presentation of APN, defined according to imaging criteria (parenchymal involvement at MR or CT scan).

METHODS

All consecutive patients hospitalized for "non-complicated" APN were considered (June 2005-December 2009). Clinical, biochemical and imaging data at hospitalization were analyzed by univariate and logistic regression analysis.

RESULTS

There were 119 patients, all females, median age 32 years (15-72). At hospitalization, inflammatory markers were elevated (CRP median: 12.1 mg/dL, normal < 0.8). Incomplete presentations were frequent: fever was absent in 6.7%, pain in 17.8%, lower urinary tract symptoms in 52.9%. At CT or MR scan the lesions were bilateral in 12.6%, multiple in 79.8%; abscesses were present in 39.5%. Renal scars were found in 15.1%. Positive cultures were correlated with multiple foci (multivariate OR 4.2; CI 1.139-15.515). No other sign/symptom discriminated between small lesions, abscesses or multifocal involvement.

CONCLUSIONS

APN is a protean disease. In the absence of strict correlation with clinical or biochemical markers, imaging studies are required to assess the severity of kidney involvement.

The Use of Ultrasonography in Evaluating Adults with Febrile Urinary Tract Infection

BACKGROUND

Urinary tract infection (UTI) is a common disease. Controversy exists about the role of radiological evaluation in the patient with urinary tract infection.

MATERIALS AND METHODS

From April 2001 to December 2001, patients with febrile UTI admitted to Chang Gung Memorial Hospital, Chiayi were prospectively evaluated by ultrasonography. The inclusion criteria of febrile UTI was a body temperature of more than 38 degrees C with a bacterial count of 10(3) or more per mL in a freshly voided midstream or catheterized urine.

RESULTS

A total of 94 patients were evaluated and all patients recovered. Major abnormal sonograms were present in 17 (18%) of the patients. A history of urolithiasis and a duration of fever > or = 3 days after admission were statistically significant clinical parameters in predicting major abnormal sonogram. Although diabetes mellitus was not statistically significant in predicting major abnormal sonogram, diabetic patients had 2.5 times the likelihood of major structural abnormalities than nondiabetic patients.

CONCLUSION

Ultrasonographic study of patients with febrile UTI should be limited only to those with a duration of fever > or = 3 days and a history of urolithiasis. Ultrasonographic study should also be considered in febrile UTI patients with diabetes mellitus.

Biopsy of renal masses: when and why

Percutaneous image-guided biopsy of renal masses is a safe and accurate procedure. Although once reserved for the diagnosis of unresectable renal cell carcinoma, metastases, lymphoma, and infection, today percutaneous image-guided biopsy has an expanded role. There is increasing awareness that a substantial proportion of small, solid renal masses are benign neoplasms. Although imaging can be used to diagnose most of them, some are incorrectly believed to represent renal cell carcinoma and unnecessary surgery may be performed. Based largely on advances in cytological techniques, percutaneous biopsy can be now be used to diagnose benign neoplasms and thus prevent them from being treated unnecessarily. Concurrent advances in percutaneous ablation have also promoted its use. As a result, there are 8 established indications for percutaneous biopsy, and reason to believe that the number of indications will expand further in the future.

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.

The clinical spectrum of acute 'uncomplicated' pyelonephritis from an emergency medicine perspective

Acute uncomplicated pyelonephritis (APN) is a complex clinical entity, which is defined differently based on clinical or imaging criteria. The aim of this study was to describe the clinical and radiological presentation of APN-upper urinary tract infection (UTI) cases observed between May 2005 and June 2006 and hospitalised in the Emergency Medicine ward of San Luigi Hospital, Orbassano, Turin, Italy. All patients underwent imaging scans and were differentiated on the basis of parenchymal involvement. Of around 45000 patient visits to the emergency room between May 2005 and June 2006, 23 patients were diagnosed as having uncomplicated upper UTI (all female, age 15-57 years). Renal parenchymal involvement was confirmed by imaging in 16 cases (69.6%). The imaging spectrum ranged from a small single lesion to large multiple defects; on admission, 2 cases had no pain and 2 had no fever; lower urinary tract symptoms were present in only 13 patients (7 with parenchymal involvement). All patients with parenchymal involvement had at least one sign of systemic inflammation-infection. Most patients (15) had taken antibiotics before hospitalisation; consequently, urine cultures were negative in 21 cases (14 cases with positive imaging (87.5%)). The data from patients with and without parenchymal involvement overlapped, the only difference being a higher prevalence of high CRP levels in cases with parenchymal involvement.

Case report: renal infarct mimicking renal mass: further rationale for minimally invasive management

A 55-year-old man presented with an exophytic asymptomatic right renal lower-pole mass simulating a renal-cell carcinoma. He underwent retroperitoneoscopic partial nephrectomy, and histopathologic examination revealed a chronic renal infarct with calcifications. We report this case to stimulate the inclusion of focal chronic renal infarct in the differential diagnosis of asymptomatic renal masses, as well as to advocate a minimally invasive approach to appropriate renal lesions.

Sonography in Benign and Malignant Renal Masses

Ultrasonography and CT have allowed improved detection of renal mass lesions. Though ultrasonography is less sensitive in the characterization of the renal mass lesions, it is often the first imaging modality for evacuation of the kidneys. This article gives an overview of the benign and malignant renal mass lesions and the role of ultrasonography in their characterization.

Antibiotic treatment for acute 'uncomplicated' or 'primary' pyelonephritis: a systematic, 'semantic revision'

The definition of acute pyelonephritis is controversial. There are two contrasting approaches: (1) acute pyelonephritis is a severe infectious disease involving the kidney parenchyma, and specific imaging techniques are required for diagnosis; (2) acute pyelonephritis is a urinary tract infection, and diagnosis and therapy follow simplified clinical and laboratory pathways. In this study, recent randomized controlled trials (RCTs) were systematically reviewed and the diagnostic and therapeutic approaches to acute 'uncomplicated' pyelonephritis were analysed. Medline, Embase, Cochrane Central Register of Controlled Trials (CCTR) and Chinal were searched employing Mesh, Emtree and free terms on 'pyelonephritis'. Limits included human, period (1995-2004), and trials-reviews (where available). In total, 904 references and 175 full-text were retrieved; 29 were pertinent RCTs. Seven RCTs were added from reference lists (indexed on urinary tract infections). Imaging examinations were performed in 11 of 14 studies on children (diagnostic requisite in two) and in two studies on adults; scarring was not analysed in adults. Clinical definitions varied widely (fever >37.8 to >39 degrees C, culture titres 10(4) >10(5)). Studies on adults were limited to short-term end-points (microbiological sterilization, clinical improvement). Duration of therapy was 4-20 days. The trend was towards shorter periods of therapy, mainly on an outpatient basis; intravenous therapy, if performed, was usually limited to the first 1-3 days. For acute uncomplicated pyelonephritis, the tendency is towards 2 weeks of mainly oral antibiotic therapy. However, the recent literature on adults does not discriminate among different upper urinary tract infections nor does it provide data on renal scarring. While cost constraints point towards short-term therapies, further studies are needed to assess the prevalence and long-term effect of kidney scars.

Renal Masses in the Adult Patient: The Role of Percutaneous Biopsy

Although percutaneous renal mass biopsy with cross-sectional imaging guidance has long been considered to be safe and accurate, there have been recent advances in imaging, interventional, and cytologic techniques that have increased the role of percutaneous biopsy in the diagnosis of renal masses. Today, biopsy plays a fundamental role in the care of patients with a renal mass. Biopsy results are used to confirm the diagnosis of renal cancers, metastases, and infections, and there is increasing evidence to suggest that biopsy can help subtype and grade many primary renal cancers. Because a considerable fraction of small solid renal masses are benign and do not need treatment, there is an increasing need to diagnose them. Biopsy after a full imaging work-up can help prevent unnecessary and potentially morbid surgical and ablation procedures in a substantial number of patients. Although more data are needed to understand the overall accuracy of biopsy for the diagnosis of benign lesions, many can be diagnosed with the aid of biopsy findings. This article reviews reported experience with percutaneous renal mass biopsy, discusses the technical factors that contribute to results, and details seven specific clinical settings that should prompt the clinician to consider percutaneous biopsy when encountering a renal mass.

Effective duration of antimicrobial therapy for the treatment of acute lobar nephronia

OBJECTIVE

Effective treatment of acute lobar nephronia (ALN) can prevent its progression to renal abscess. The goal of this prospective study was to compare the treatment efficacy for pediatric patients who had ALN with a 3- vs 2-week intravenous plus oral antimicrobial-therapy regimen.

METHODS

Patients who were suspected of having an upper urinary tract infection underwent a systematic scheme of ultrasonographic and computed tomographic (CT) evaluation for ALN diagnosis. Patients with positive CT findings were enrolled and randomly allocated with serial entry for either a total 2-week or a 3-week antibiotic treatment regimen. Antibiotics were changed from an intravenous form to an oral form 2 to 3 days after defervescence of fever. Follow-up clinical evaluations and urine-culture analyses were performed 3 to 7 days after cessation of antibiotic treatment. Patients with persistent infection or relapse were considered as treatment failures.

RESULTS

A total of 80 patients with ALN were enrolled. Forty-one patients were treated with a 2-week antimicrobial protocol, and the other 39 patients were treated with a 3-week course. Seven treatment failures, 1 persistent infection, and 6 infection relapses were identified, all of which were in the 2-week treatment group. Prolonged fever before admission and positive Escherichia coli growth (>10(5) colony-forming units per mL) in urine culture were noted as risk factors for treatment failure. All treatment failures were managed successfully with an additional 10-day antibiotic course.

CONCLUSION

A total of 3 weeks of intravenous and oral antibiotic therapy tailored to the pathogen noted in cultures should be the treatment of choice for pediatric patients with ALN.

Evolution of acute focal bacterial nephritis into a renal abscess

Acute focal bacterial nephritis (AFBN) is a localized bacterial infection of the kidney presenting as an inflammatory mass without frank abscess formation, which may represent a relatively early stage of renal abscess. The pathogenesis of AFBN is thought to be hematogenous infection or ascending infection from the lower urinary tract. For the majority of children, the pathogenesis may be related to ascending infection, because pre-existing malformative uropathy, especially vesicoureteral reflux (VUR), is common in pediatric patients. Few clinical reports have demonstrated the evolution of this condition into renal abscess in children. We report a girl with AFBN associated with VUR that evolved into a renal abscess despite appropriate intravenous antibiotic therapy. We undertook serial radiological observation of its evolution. It is important to differentiate AFBN from renal abscess because the management of the two entities may be different, and follow-up studies are indispensable to determine appropriate therapy.

The sonographic appearance of acute focal pyelonephritis 8 years experience

AIM

Acute focal pyelonephritis (AFP) is a variant of pyelonephritis in which single or multiple discrete areas show changes of inflammation. The reported sonographic appearances of AFP are varied but are typically described as being echopoor. The purpose of this study was to review the sonographic appearances of AFP and attempt to explain the range of findings by correlation with clinical details.

MATERIALS AND METHODS

We reviewed retrospectively the sonographic findings and medical records of 17 cases of AFP. The study group consisted of 13 women and four men (mean age 20 years). Lesions were designated as echogenic, echopoor or of mixed echogenicity as compared to the adjacent renal cortex, and to the liver or spleen.

RESULTS

The abnormal areas were echogenic in 12 patients, echopoor in three and of mixed echogenicity in two. An attempt was made to explain the variation in appearances by correlation with clinical details including the patient's age, the duration of symptoms, the length of antibiotic treatment and the presence of haematuria.

CONCLUSION

Areas of acute focal pyelonephritis may be echogenic, echopoor or of mixed echogenicity. Our data would suggest that areas of increased echogenicity are more common. There is no discernible correlation with clinical findings.

Genitourinary imaging: the past 40 years

During the past 40 years, there has been a dramatic evolution in genitourinary imaging. This evolution has resulted in fundamental changes in the subspecialty. Uroradiology initially focused on radiographic imaging of the urinary tract and was practiced primarily by urologists. After the development of safe intravenous contrast materials, radiologists who focused on the urinary tract and worked closely with urologists forged major advances in urinary tract imaging and intervention. More recently, imaging of the extraurinary genital organs has been added to the subspecialty. Cross-sectional imaging techniques have supplanted radiographic imaging for both urinary and genital imaging. The emergence of the cross-sectional techniques, however, has blurred the traditional organ system-based distinction between gastrointestinal radiology and genitourinary radiology, as both organ systems are imaged simultaneously, and has resulted in a new amalgamation, abdominal radiology, with roots in both specialties. The challenge for the new generation of abdominal radiologists, trained predominantly in cross-sectional techniques, will be to maintain the close interaction with our clinical colleagues that the traditional organ system orientation fostered.

The role of power Doppler ultrasonography in the diagnosis of acute pyelonephritis

OBJECTIVE

To assess the ability of power Doppler ultrasonography (PDU) to detect acute pyelonephritis and to compare the findings from PDU with those from enhanced computed tomography (CT).

PATIENTS AND METHODS

Eleven patients (mean age 18.5 years, range 5-37) admitted to hospital with a clinical diagnosis of pyelonephritis were assessed with PDU and enhanced CT. the latter providing the reference method.

RESULTS

The imaging studies showed normal findings in three patients; a single focus of pyelonephritis was detected by CT in six, whereas a matching defect was detected on PDU in five, with PDU failing to detect an infective focus in one. Multifocal diffuse pyelonephritis was diagnosed correctly by enhanced CT and PDU in two patients.

CONCLUSION

Power Doppler ultrasonography had an overall sensitivity of 88% and complete specificity in the evaluation of patients with acute pyelonephritis.

Focal bacterial nephritis (lobar nephronia) in children

We report 13 patients with 16 episodes of acute lobar nephronia diagnosed in a prospective study that was conducted among 210 hospitalized children with urinary tract infection. In 30 episodes of urinary tract infection, a hypoechogenic or hyperechogenic lesion was found. Twenty patients underwent computed tomography, and in 16 of them acute lobar nephronia was diagnosed. Evolution to renal abscess occurred in 25%. Prolonged intravenous antibiotic treatment was sufficient in all cases.

Mass effect in the renal sinus: an anatomic classification

Before the advent of modern imaging techniques, pathologic processes in the renal sinus were diagnostic enigmas. Many of the conditions create nonspecific deformities of the contrast-filled collecting system. In the past, the discovery of these abnormalities often led to unnecessary exploration. Modern imaging techniques usually allow a specific diagnosis to be made, but because a number of the pathologic conditions affecting the renal sinus have similar appearances on a single type of imaging study, complete delineation may require correlation of a number of diagnostic techniques. An understanding of the normal sinus anatomy allows classification of pathologic processes that occur in this region and ensures an orderly imaging investigation. The anatomic classification is based on the structure from which the mass arises. The source of the mass may be any structure within the renal sinus (intrinsic), the enveloping renal parenchymal (adjacent), or a source outside the kidney itself with subsequent sinus involvement (extrinsic). This classification will be used to review a number of pathologic processes that occur in the renal sinus and pertinent imaging features.

Acute bacterial nephritis: a clinicoradiologic correlation based on computed tomography

PURPOSE

Acute bacterial nephritis (ABN) represents localized, nonliquefied renal infection, and the subsequent alteration of tissue densities can be readily detected by computed tomography (CT). In recent literature, a variety of renal parenchymal alterations observed on CT were reported. However, previous reports on the clinical course of ABN were inconsistent and lacked correlation with radiologic findings. In this investigation, we attempt to correlate the severity of clinical manifestations with CT findings in ABN and draw some conclusions regarding the natural history, pathophysiology, and clinical management of this disease.

PATIENTS AND METHODS

From July 1988 to June 1991, 30 cases of ABN were evaluated at our institute. On the basis of postcontrast-enhanced CT findings, 28 cases were grouped into (1) Group I (7 cases), wedge-shaped lesions (focal or diffuse); (2) Group II (12 cases), focal mass-like lesions; and (3) Group III (9 cases), diffuse (multifocal) mass-like lesions. The clinical features and outcomes of the three groups were compared. The positive detecting rates and clinical usefulness of ultrasonographic (US) and urographic examinations were also studied in each group.

RESULTS

An excellent correlation can be demonstrated between the clinical parameters (including underlying diseases, maximum temperature and leukocyte count, duration of fever, flank pain, leukocytosis, and pyuria; the incidence of septic shock, diabetic ketoacidosis, and acute renal failure; and outcome) and the pattern of renal parenchymal abnormalities detected on CT. The clinical features in Group I patients displayed many similarities with those in uncomplicated acute pyelonephritis (APN) reported previously, and responded to antibiotic therapy promptly. Most patients in Group II were successfully treated with antibiotics but had a protracted clinical course with a slower clinical improvement than Group I. Only one case with a Group II lesion was noted to progress to renal abscess formation and extrarenal involvement. In comparison, 33% of the patients in Group III died despite antibiotic therapy. Our data also show that US examination is sensitive in detecting Group II ABN lesions (62% positive rate), and revealed marked renal enlargement in most Group III lesions (89%). It is therefore a useful initial imaging modality in providing information vital to clinical decision making.

CONCLUSION

Our experiences suggest that renal bacterial infection may show the continuum of severity from uncomplicated APN to ABN, demonstrated on postcontrast CT scan as wedge-shaped lesions to mass-like lesions, and possibly, finally to frank abscess formation. We classify ABN into three subgroups according to CT findings, and good correlation with clinical severity is demonstrated. These findings deliver valuable concepts regarding the pathophysiology and clinical management of this disease.

Acute renal infections

The current status of the pathogenesis of the disease and imaging methods in acute renal infections is reviewed. The spectrum of type of infection includes 1) acute pyelonephritis, 2) acute bacterial nephritis, 3) acute renal abscess, 4) acute pyonephrosis, and 5) infected renal simple cyst. The two most common imaging methods used are ultrasound and computed tomography (CT). Recent experience from the literature suggests that CT offers some advantages over ultrasound particularly in distinguishing degree and type of involvement of the renal parenchyma and in more accurate diagnosis of acute abscess.

Ultrasonography in the differentiation of complicated and uncomplicated acute pyelonephritis

Differentiation of uncomplicated pyelonephritis versus complicated pyelonephritis has always been problematic. No clear physical signs or symptoms are diagnostic. To study differences between the two, we retrospectively reviewed charts of patients admitted to Charity Hospital, New Orleans, with febrile urinary tract infections. Criteria for inclusion were pyuria, positive urinary culture, and signs or symptoms of pyelonephritis. All patients underwent renal ultrasonography (US) before other diagnostic tests. US identified a potential emergency (hydronephrosis or abscess) in 11 of 98 patients (11.2%). The only significant contributing factor was the presence of diabetes mellitus, which was present in five of 11 emergent conditions and eight of 73 of the remainder (P = 0.003). US is inexpensive, easily obtainable in the emergency room, and sensitive enough to screen patients with pyelonephritis for complications. However, we believe it is mandatory in diabetics, because of the high incidence of abnormalities in this population.

Computerized tomography in acute pyelonephritis: the clinical correlations

Computerized tomography was performed on 19 patients diagnosed as having uncomplicated acute pyelonephritis. The relationship was investigated among the laboratory findings, presence of flank pain, clinical course and severity of the lesions detected by computerized tomography. In patients febrile for less than 2 weeks healing as assessed by computerized tomography took an average of 76 days. However, in patients with repeated febrile episodes occurring for longer than 2 weeks healing was delayed until an average 232 days after onset. Computerized tomography findings generally correlated well with the erythrocyte sedimentation rate, C-reactive protein level, and presence of pyuria and flank pain. However, in patients with a prolonged course computerized tomography proved to be a more reliable indicator of progress than either the results of laboratory tests or the symptoms. In conclusion, computerized tomography was useful in the diagnosis, assessment of severity and evaluation of healing of acute pyelonephritis.

Migratory lobar nephronia

Lobar nephronia or focal bacterial nephritis is a pre-abscess stage of localized cellulitis and has been shown to represent a focal imaging manifestation of what is frequently a diffuse renal process. To the best of our knowledge, although multi-focal bacterial nephritis has been described, a migratory pattern has not been observed. This report describes a previously healthy 32-year-old woman with pathologically proven lobar nephronia that exhibited a migratory pattern on serial computed tomography (CT) and a prolonged course on antibiotic therapy. Possible etiologies for this unusual course, along with the CT, sonographic and needle biopsy features of this disease are discussed.

Sonography of renal inflammatory disease

The sonographic findings and differential diagnoses of a wide spectrum of acute and chronic renal inflammatory processes are reviewed. These include focal and diffuse forms of bacterial nephritis, pyonephrosis, intra- and extrarenal abscess, renal tuberculosis and fungal infection, xanthogranulomatous pyelonephritis, and renal parenchymal malakoplakia. The role of ultrasound in the diagnostic and therapeutic management of patients with these diseases is discussed.

Acute and chronic urinary infection: present concepts and controversies

The current approaches to diagnosing the various renal inflammatory diseases are briefly reviewed. Terminology is varyingly used by different individuals. Our current understanding of these disease processes is discussed in an effort to review the current status of both the mundane and the esoteric infections of the kidney.

Renal parenchymal volume during and after acute pyelonephritis measured by ultrasonography

A total of 47 children with acute pyelonephritis were investigated using water delay ultrasonographic equipment (Octoson) for determination of renal parenchymal volume by the stepped section technique. Thirty two patients were repeatedly investigated every to every other week up to seven weeks. Median renal parenchymal volume during acute pyelonephritis of the right kidney was 2.70 cm3/kg body weight and of the left kidney 3.10 cm3/kg; this was significantly larger than the volume of control kidneys, which was 1.82 and 2.07 cm3/kg, respectively. The most enlarged kidneys were found among the youngest children. A significant successive decrease in renal size was found during the first four to five weeks after the acute pyelonephritis. Because of enlargement of the kidneys during acute pyelonephritis we suggest that the first renal size determination to be used for following renal growth should be performed after at least four to six weeks.

Acute focal bacterial nephritis

Clinical and radiographic characteristics of 12 patients with acute focal bacterial nephritis (AFBN) are presented along with review of the literature. Most patients presented with symptoms of an inflammatory or infectious process. Fever and pyuria were the most frequently encountered clinical characteristics. Imaging modalities that were used to establish a definitive diagnosis of focal bacterial nephritis included ultrasound, computed tomography, and intravenous urography with nephrotomography. Ultrasound was found to be the most effective and least costly method of diagnosis. Misdiagnosis of AFBN as abscess or tumor, which it may stimulate, could lead to inappropriate surgical therapy.

Computerized tomography and acute pyelonephritis in children. A clinical correlation

The clinical records and computerized tomography (CT) scans of 14 patients who presented with pyelonephritis to the Children's Hospital of Buffalo between 1976-1985 have been reviewed. The CT findings were as follows: multifocal pyelonephritis (6), lobar nephronia (6), focal pyelonephritis (2). All patients were treated with intravenous antibiotics, and none was surgically drained. Significant underlying diseases were present in 8 patients: diabetes (6), von Gierke disease (1), hepatorenal syndrome (1). The diabetic children tended to have focal disease. Ten voiding cystourethrograms were performed and only four demonstrated reflux. All children became afebrile within a few days. Lobar nephronia was as clinically responsive as pyelonephritis to antibiotic therapy. Urine cultures were most often positive, although there was 1 patient in each category with negative cultures. Blood cultures were rarely positive in any group. Gram negative organisms predominated. CT scanning in children with clinical acute pyelonephritis reveals three major imaging patterns. While distinct radiographically, they behave in a similar clinical manner. Lobar nephronia does not imply a worse clinical prognosis. Intravenous antibiotic therapy alone was adequate for all patients.

Computed tomography in acute pyelonephritis

The computed tomographic findings in nine female patients with acute pyelonephritis were reviewed. The major impact of CT was the demonstration of renal enlargement, abnormal contour, perirenal inflammatory extension and, on contrast-enhanced scans, abnormal nephrograms and impaired renal function. It was concluded that CT can provide specific information about the nature and extent of the inflammatory process, thus complementing intravenous urography so that appropriate therapy may be selected. Follow-up studies can be helpful in monitoring the progress of a patient.

Demonstration of residual contrast medium in renal parenchyma using computerized tomography

Residual contrast medium in the renal parenchyma was demonstrated by computerized tomography in 11 patients with renal trauma, inflammatory renal disease, infarction and a large renal cyst. The contrast medium (10 to 100 ml.) was administered intravascularly 30 minutes to 48 hours before the computerized tomography scan. In each patient the scan demonstrated residual contrast medium (either initially or after a second scan with additional contrast enhancement) in a variety of parenchymal zones that frequently appear to be normal with other imaging techniques. After a suitable interval for accumulation of residual contrast medium, computerized tomography appears to provide better visualization of the renal parenchyma than conventional modes of examination. Persistent retention of contrast medium in the renal parenchyma is believed to represent cortical damage.

CT evaluation of severe renal inflammatory disease in children

We have performed CT scans on 15 children and 2 young adults with severe renal inflammatory disease. Most children with urinary tract infections do not require such evaluation. We have, however, found CT helpful in defining the nature of renal abnormality and in defining the extent of disease in selected patients who either presented as diagnostic dilemmas or who did not respond initially to proper medical treatment. We therefore use CT scanning as our initial examination in such problem patients.