Renal and perirenal infection: the role of computerized tomography

A prospective study on the use of ultralow-dose computed tomography with iterative reconstruction for the follow-up of patients liver and renal abscess

Background

Radiation dose reduction is a major concern in patients who undergo computed tomography (CT) to follow liver and renal abscess.

Objectives

The purpose of this study is to investigate the feasibility of ultralow-dose CT with iterative reconstruction (IR) to follow patients with liver and renal abscess.

Methods

This prospective study included 18 patients who underwent ultralow-dose CT with IR to follow abscesses (liver abscesses in 10 patients and renal abscesses in 8 patients; ULD group). The control group consisted of 14 patients who underwent follow-up standard-dose CT for liver abscesses during the same period. The objective image noise was evaluated by measuring standard deviation (SD) in the liver and subcutaneous fat to select a specific IR for qualitative analysis. Two radiologists independently evaluated subjective image quality, noise, and diagnostic confidence to evaluate abscess using a five-point Likert scale. Qualitative parameters were compared between the ULD and control groups with the Mann-Whitney U test.

Results

The mean CT dose index volume and dose length product of standard-dose CT were 8.7 ± 1.8 mGy and 555.8 ± 142.8 mGy·cm, respectively. Mean dose reduction of ultralow-dose CT was 71.8% compared to standard-dose CT. After measuring SDs, iDose level 5, which showed similar SD to standard-dose CT in both the subcutaneous fat and liver (P = 0.076, and P = 0.124), was selected for qualitative analysis. Ultralow-dose CT showed slightly worse subjective image quality (P < 0.001 for reader 1, and P = 0.005 for reader 2) and noise (P = 0.004 for reader 1, and P = 0.001 for reader 2) than standard-dose CT. However, the diagnostic confidence of ultralow-dose CT for evaluating abscess was comparably excellent to standard-dose CT (P = 0.808 for reader 1, and P = 0.301 for reader 2).

Conclusions

Ultralow-dose CT with IR can be used in the follow-up of liver and renal abscess with comparable diagnostic confidence.

Ultrasound in Renal Pyogenic Infection

A series of 34 patients with renal or perirenal pyogenic infection (18 with pyonephrosis, 10 with renal abscess and 6 with perirenal abscess) is presented to evaluate diagnosis with ultrasound and treatment with percutaneous ultrasound guided aspiration/drainage. Specific findings, defined as sediment echoes or dispersed internal echoes in a hydronephrotic renal collecting system, were noted in 39 per cent of pyonephrosis cases. Abscesses were mainly round or oval hypoechoic lesions measuring from 2 to 15 cm in diameter. Two abscesses were multilocular and one showed a septum. The appearance suggested tumor in 25 per cent. Because of this non-specificity of ultrasound we recommend diagnostic aspirations and further radiologic and other examinations in difficult cases. Four patients were treated by conservative means only, 13 with percutaneous aspiration or drainage, 9 with a combined drainage procedure and surgery, and 8 surgically. The length of the mean hospital stay was shortest in the group with the percutaneous drainage procedure (PDP) although the difference was not statistically significant. PDP was not effective in 12 per cent and surgery was used in these two cases to ensure cure. Complications occurred more often in the PDP group than in the surgery group but the most serious complication was a post-operative one. The different modes of treatment are discussed. The overall mortality was 5.9 per cent.

Urographic Renal Size in Acute Pyelonephritis in Childhood

Eighteen children with acute pyelonephritis were investigated by urography at the time of and about two months after the acute infection. Renal size was evaluated as renal length and parenchymal area. During the acute infection renal size was larger than at the follow-up examination two months later. In conclusion, urography performed in close connection with the acute pyelonephritic infection gives an overestimation of renal size.

Emphysematous Pyelonephritis

Six patients (all women, mean age 59.8 years) with emphysematous pyelonephritis, a rare, severe inflammation causing renal parenchymal destruction and affecting diabetics more commonly than non-diabetics, are described. Four of the patients were diabetics. All underwent ultrasound examination (US), and five computed tomography (CT) of the kidneys. CT was the most reliable diagnostic method. Differentiation between gas and calcification was difficult at US in three patients. Conventional tomography was performed in two patients and showed intra-renal gas. All six patients recovered; three patients had nephrectomy, one as an emergency procedure and two as an elective procedure after two weeks of antibiotic treatment. Infection was eradicated in the other three patients by percutaneous drainage, electrolyte correction and antibiotics. It was concluded that while conventional abdominal radiography may permit the diagnosis of emphysematous pyelonephritis by demonstrating intra-renal gas, CT is the most reliable diagnostic examination. Emergency nephrectomy may not be necessary in all cases.

Prevalence of lower urinary tract infection in South Indian type 2 diabetic subjects

This study was done to determine the prevalence of lower urinary tract infection (UTI), the causative pathogens, their antimicrobial pattern, and the recurrence of infection in type 2 diabetic subjects. A total of 1157 (M: F 428: 729) type 2 diabetic subjects were selected for this study. Midstream urine specimens were collected and the culture tests were done by a quantitative method whereas antimicrobial sensitivity was determined by using the Kirby-Bauer method. A significant colony count was seen in 495 (42.8%) subjects and an insignificant count in 350 (30.3%) subjects; there were a few cases of recurrent UTI. Women (47.9%) had a significantly higher prevalence of UTI than men (34.1%) (χ² = 20.3, P < 0.0001). Except for BMI, UTI was significantly associated with age, duration of diabetes, and poor glycemic control in both sexes. About 533 pathogens of gram positive and gram negative bacilli were isolated from 495 subjects in this study. Escherichea coli (E. coli) was the most commonly found organism. Gram negative pathogens were found to be highly sensitive to sulbactum / cefoperazone and piperacillin / tazobactum. The prevalence of UTI was significantly higher in women than men with E. coli being the major isolated pathogen. Gram negative pathogens were highly sensitive to sulbactum / cefoperazone and piperacillin / tazobactum.

Recent clinical overview of renal and perirenal abscesses in 56 consecutive cases

BACKGROUND/AIMS

The aim of this study was to examine the recent clinical trends and antibiotic susceptibilities of the causative microorganisms in renal and perirenal abscesses, and to elucidate the factors associated with treatment strategies.

METHODS

We retrospectively analyzed 56 patients who were diagnosed with renal and perirenal abscesses at our hospital from January 2000 to September 2007.

RESULTS

The mean age of the patients was 53.5 years, and a female predominance of patients (75%) was observed. Diabetes mellitus (44.6%) was the most common predisposing condition. The mean duration of symptoms before diagnosis was 11.6 days, and fever (75%) was the most common symptom. Escherichia coli (44%) and Klebsiella pneumoniae (28%) were common pathogens, and the rates of susceptibility of E. coli isolates to ampicillin, cephalothin, cefotaxime, trimethoprim-sulfamethoxazole, ciprofloxacin, gentamicin, and imipenem were 18.2%, 27.3%, 72.7%, 72.7%, 63.6%, 63.6%, and 100%, respectively. Abscesses were classified according to the location as follows: renal abscess (n=31, 55.4%) and perirenal abscess +/- renal abscess (n=25, 44.6%). In the renal abscess group, the infection rate of gram-negative organisms was higher than in the perirenal abscess group. Patients were also divided according to the treatment modality: antibiotics only (n=20, 35.7%) and percutaneous intervention or surgery (n=36, 64.3%). Patients who had a perirenal abscess or a large renal abscess required more invasive treatment.

CONCLUSIONS

This study revealed somewhat different results from those of previous studies. Clinical and microbial differences were observed between the renal and perirenal abscess groups. Abscess location and the size of the renal abscess were the factors associated with treatment strategies.

Renal and perirenal abscesses in patients with otherwise anatomically normal urinary tracts

PURPOSE

We characterized evaluation, management and outcomes in a group of patients diagnosed with renal and perirenal abscesses who had otherwise anatomically normal urinary tracts.

MATERIALS AND METHODS

We reviewed our experience with renal/perirenal abscesses at University of Texas Medical Branch from 1991 to 2002. Treatment was determined by physician preference in each individual.

RESULTS

Of 70 patients with renal/perirenal abscesses 26 had otherwise anatomically normal urinary tracts, 24 (92%) had at least 1 possible contributory factor, such as diabetes mellitus, and only 38% had the correct diagnosis at initial presentation. The abscess was intranephric in 39% of cases, intranephric and perinephric in 19%, and perinephric only in 42%. Of the 26 patients 18 were treated with percutaneous drainage or aspiration of the abscess and 12 (66.7%) had positive cultures. Eight of the 12 patients (67%) with positive abscess cultures had the same organism in urine and/or blood. All 26 patients were treated with broad-spectrum intravenous antibiotics. In most patients abscess size influenced additional treatments, such as percutaneous needle aspiration or catheter drainage. None of the patients required open surgical drainage, nephrectomy or nephrostomy tube placement. At a mean followup of 10 months all patients had complete radiographic resolution of the abscess without further complications except 1 who had pyelonephritis and another who was found to have a poorly perfused kidney.

CONCLUSIONS

With accurate diagnosis and minimally invasive therapy patients with renal and/or perirenal abscesses and otherwise anatomically normal urinary tracts have excellent functional and anatomical outcomes.

[Perinephretic phlegmon: about 36 cases]

The authors report a series of 36 cases of perinephric phlegmon during 15 years. The patients are 27 men and 9 women. Mean age was 37 years (ranging between 25 and 70). The promoting factors of PPN are diabetes (27.8%), and kidney calculi (22.3%). Delay diagnosis is more than 3 weeks in 80% of the patients. The clinical symptomatology was dominated by pain, fever and flank mass. Diagnosis is carried out by ultrasonography in 84% and by CT scan whenever it is done. The common germs are negative Gram bacilli and staphylococcus. The treatment consists in antibiotherapy associated to a percutaneous drainage of the collection in 6 patients (16.7%) and a surgical drainage in 30 patients (83.7%). The follow-up are favorable in all cases.

Current treatment and outcomes of perinephric abscesses

PURPOSE

We characterize the treatment and outcomes of perinephric abscesses in a contemporary cohort of patients.

MATERIALS AND METHODS

We reviewed the experience with perinephric abscesses at a single community based hospital. Abdominal computerized tomography (CT) was widely available during the study period and experience with radiographic guided percutaneous drainage was extensive. Therapy and intervention for individual patients were dictated by the treating physician.

RESULTS

Of the 25 patients identified with perinephric abscesses 3 (12%) ultimately died. Although 40% had multiple risk factors for perinephric abscesses only 35% were identified at presentation. Urine cultures were positive in 72% of patients and CT had a diagnostic sensitivity of 92%. Ten patients with a mean abscess size of 1.8 cm. were treated with antibiotics alone (mean hospitalization 10 days) while 11 with a mean abscess size of 11 cm. received antibiotics and initial percutaneous drainage (mean hospitalization 30 days). Of the 11 patients treated with percutaneous drainage 4 ultimately required surgical exploration and nephrectomy.

CONCLUSIONS

The clinical characteristics of perinephric abscesses have not changed significantly but improved imaging with CT allows earlier diagnosis and treatment, which likely contributed to the reduced mortality in our cohort compared to historical series. With accurate staging and careful followup, a variety of treatments can be successful, including antibiotics alone or in conjunction with percutaneous drainage and urinary drainage. Open surgical drainage and nephrectomy may eventually be required in some patients and should be considered if adequate drainage is not achieved.

Radiology of perinephric fluid collections

The perinephric spaces consist of the subcapsular, perirenal, anterior and posterior pararenal spaces. Fluid may collect in one or more of these compartments; this can be readily demonstrated by cross-sectional imaging, particularly computed tomography (CT). This pictorial review illustrates the radiological manifestations of perinephric fluid collections with their differential diagnosis including perinephric abscess, perirenal urine collection, subcapsular and perirenal hematoma, renal lymphangiomatosis, pancreatic pararenal fluid collections and transudate fluid associated with nephropathies.

Renal abscess: early diagnosis and treatment

The purpose of this study was to identify initial clinical characteristics that can lead to early diagnosis of renal abscess in the emergency department and predict poor prognosis. A retrospective review of 88 renal abscess patients, from April 1979 through January 1996, was conducted. Patients were categorized into two groups. In group 1, renal abscess was diagnosed by an emergency physician, whereas in group 2 renal abscess was not diagnosed by an emergency physician. Clinical characteristics included demographic data, predisposing medical problems, duration of illness before diagnosis, time spent in hospital diagnosis, initial signs and symptoms, laboratory tests, and radiology studies that may have been useful in the early diagnostic regimes. Clinical factors were also analyzed for their value in predicting poor prognosis. The mean age of 88 patients with renal abscess was 59.8 years. The most common predisposing disorder was diabetes mellitus, followed by renal calculi and ureteral obstruction. The duration of diagnosis by emergency physicians was shorter for group 1 patients (1.2 +/- .4 v group 2, 2.8 +/- 2.9 days; P < .01) and the blood urea nitrogen level was higher in group 1 (55.7 +/- 42.2 mg/dL, v group 2, 33.5 +/- 33.5 mg/dL; P = .02). In the early diagnosis of renal abscess, emergency physicians should focus on patients who have predisposing disorders, ie, diabetes mellitus, renal stones, immunosuppression, longer duration of symptoms of urinary tract infection, and renal failure, who should promptly be investigated with ultrasound in the emergency department. The cure rate after treatment with routine antibiotics plus percutaneous drainage was 64%. This therapy is recommended for initial treatment. Poor prognosis is associated with elderly patients with lethargy and with elevation of the serum blood urea nitrogen level.

Magnetic resonance imaging of experimental pyelonephritis in rabbits

RATIONALE AND OBJECTIVES

An experimental model of acute focal pyelonephritis was developed in the New Zealand White rabbit, with initial imaging evaluation performed using high-field contrast-enhanced magnetic resonance (MR) in six animals.

METHODS

The left kidney was visualized fluoroscopically after intravenous injection of iodinated contrast. A 0.1 mL mixture of agarose/Streptococcus faecalis was then injected percutaneously into the kidney at the corticomedullary junction with a 25-gauge needle. The animals were imaged at 1.5 tesla on day 5 after injection of bacteria. Breathhold T2-weighted and T1-weighted scans were acquired prior to contrast injection. Using an MR-compatible power injector, 0.3 mmol/kg gadoteridol was then administered, with both dynamic and delayed postcontrast scans obtained. The lesion was confirmed in each animal by gross and microscopic exam.

RESULTS

The area of acute focal pyelonephritis was somewhat difficult to identify on precontrast scans. The lesion was mildly hyperintense on T2-weighted scans and slightly hypointense to isointense on T1-weighted scans relative to normal surrounding renal parenchyma. On early dynamic turbo-fast low-angle shot scans, the lesion could be identified due to differential tissue enhancement. Direct visualization of the lesion, with increased conspicuity relative to precontrast scans, was possible because of delayed positive enhancement at 60 seconds postcontrast. Lesion conspicuity, assessed by signal difference/noise ratio, increased from 0 +/- 5 precontrast to a peak of 12 +/- 6 at 60 seconds postcontrast (P = 0.003; n = 6).

CONCLUSIONS

On dynamic contrast-enhanced MR, acute focal pyelonephritis can demonstrate transient positive contrast enhancement (using a contrast dose of 0.3 mmol/kg) relative to surrounding normal renal parenchyma. This appearance is due to hyperconcentration of the contrast agent in normal parenchyma and T2 effects. The pattern is opposite that seen in spiral computed tomography.

Emphysematous pyelonephritis: drainage or nephrectomy?

Four cases of emphysematous pyelonephritis are reported and the pathogenesis, surgical implications and preferred mode of management are discussed. We have not found percutaneous drainage to be useful, but feel there is an important place for surgical drainage alone because of the potential for renal recovery and the risks of emergency nephrectomy.

Bilateral renal cortical abscesses in a young woman with type 1 diabetes

Serious complications of urinary tract infection, such as papillary necrosis or perinephric abscess, occur more frequently in diabetic patients. However, severe bilateral renal parenchymal infection with multiple intrarenal abscesses is not well recognized. We described an 18-year-old insulin-dependent diabetic woman with such infection, in whom renal imaging showed progression to a major perinephric abscess, but only after 5 weeks of intensive antibiotic therapy. Complete recovery followed surgical drainage and no renal cortical scarring was present on computerized tomographic scan 18 months later.

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.

Perinephric abscess: the missed diagnosis

Perinephric abscess is a life-threatening but treatable process. Most infections of the perinephric space occur as a result of extension of an ascending urinary tract infection, commonly in association with nephrolithiasis or urinary tract obstruction. A large portion of the mortality is the result of failure to diagnose this entity in a timely fashion. This failure may be because of the frequently obscure or nonspecific nature of the clinical presentation. Blood cultures as well as urine cultures may fail to identify correctly the bacterial pathogens responsible for the abscess. Perinephric abscess should be considered in the differential diagnosis of any patient presenting with a urinary tract infection that fails to respond promptly to antibiotic therapy, particularly in those known to have anatomical abnormalities of the urinary tract or diabetes mellitus. Consideration of this diagnosis should enter into the differential diagnosis of fever with abdominal pain or flank pain. Early recognition of perinephric abscess and prompt drainage, either percutaneously or surgically, in combination with appropriate antibiotic coverage, should reduce dramatically the morbidity and mortality from this infection.

Splenic abscess as complication of perinephric abscess

Retroperitoneal extension of perinephric abscess with fistulization to intra-abdominal and intrathoracic structures has been well documented in the literature. Intraperitoneal rupture is much less common, and exceptionally may not present as an acute abdominal condition. We describe herein 1 such case involving the spleen. Since the extent of the disease may not be apparent radiologically, and often is only ascertained at the time of surgery, we recommend an aggressive approach to renal calculi as the most effective means of preventing complicated perinephritis.

Intrarenal gas abscess

Intrarenal abscess owing to gas-forming gram-negative bacteria is rare. Female patients and diabetics, or those with urinary calculi or obstructive uropathic conditions commonly are affected. We report on a nondiabetic man who was infected with Pseudomonas aeruginosa. Initial medical management and subsequent partial nephrectomy offered cure.