Diagnostic performance of 18F-FDG-labeled white blood cell PET/CT for cyst infection in patients with autosomal dominant polycystic kidney disease: a prospective study

Feasibility of 18F-FDG Labelling of Leucocytes in a Centre Without an On-Site Cyclotron and Monitoring of Radiation Dose to Occupational Worker in the Labelling Procedure

Objectives: Differentiation of infection from sterile inflammation is still a major concern for clinicians. The ¹⁸F-WBC positron emission tomography/computed tomography scan has been considered a promising tool for accurate diagnosis of infection owing to its high specificity, but it renders the availability of a medical cyclotron a necessity. The aim of the present study was to determine the feasibility of labeling leukocytes and establish the protocol in a center without the availability of an on-site medical cyclotron. The secondary aim was to monitor radiation doses to occupational workers involved in labeling of leukocytes with ¹⁸F-FDG. Materials and Methods: Leukocyte separation was performed and leukocytes were radiolabeled with ¹⁸F-FDG in a sterile environment according to the procedure described by Bhattacharya et al. In vitro leukocyte viability was assessed using the trypan dye exclusion technique. Labeling efficiency and yield were also estimated for all radiolabeling procedures. Whole-body and extremity doses received by the personnel involved in the radiolabeling procedure were also estimated using pocket dosimeters. Results: Leukocyte labeling was carried out in 35 runs, during which there were two failed labeling attempts due to clotting of the blood sample. The total time involved in the whole procedure was around 2.5 h. The average labeling efficiency was 78.01% ± 6.99% (range 63.46%-86.54%), cell viability was 98%, and the cell suspension was stable up to 4 h. The mean dose was measured as 17 μSv at the chest level and 32 μSv at the extremity level, per procedure. Conclusions: Labeling of leukocytes with ¹⁸F-FDG is possible at a tertiary nuclear medicine setup without the availability of an on-site medical cyclotron, with reasonable labeling efficiency of 78.01% ± 6.99%. In addition, in-house labeling of leukocytes with ¹⁸F-FDG is safe and the radiation doses incurred by the personnel during the labeling procedure are well within the occupational dose limits established by the national regulatory authority.

Fever of Unknown Origin: 18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography Showing Renal Cyst Infection in Autosomal Dominant Polycystic Kidney Disease

Fever of unknown origin (FUO) is a convoluted clinical dilemma. It can be caused by infective, inflammatory, malignant, and other pathologies. The identification of etiopathogenesis is essential for instituting definitive management. ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography-computed tomography (PET-CT) is now an integral part of FUO management. We present the case of a 60-year-old female with autosomal dominant polycystic kidney disease (ADPKD), where the infected renal cyst was detected as the cause of FUO on¹⁸F-FDG PET-CT.

Two cases of fungal cyst infection in ADPKD: is this really a rare complication?

Background

Cyst infection is a prevalent complication in autosomal dominant polycystic kidney disease (ADPKD) patients, however therapeutic and diagnostic approaches towards this condition remain unclear. The confirmation of a likely episode of cyst infection by isolating the pathogenic microorganism in a clinical scenario is possible only in the minority of cases. The available antimicrobial treatment guidelines, therefore, might not be appropriate to some patients.

Case presentation

We describe two unique cases of kidney cyst infection by Candida albicans, a condition that has not been previously described in literature. Both cases presented clear risk factors for Candida spp. infection. However, since there was no initial indication of cyst aspiration and culture, antifungal therapy was not immediately started and empirical treatment was initiated as recommended by the current guidelines. Antifungal treatment was instituted in both cases along the clinical course, according to their specificities.

Conclusion

Our report highlights the possibility of Candida spp. cyst infection. Failure of clinical improvement with antibiotics should raise the suspicion of a fungal infection. Identification of infected cysts should be pursued in such cases, particularly with PET-CT, and when technically possible followed by cyst aspiration and culture to guide treatment. Risk factors for this condition, such as Candida spp. colonization, previous antimicrobial therapy, hemodialysis, necrotizing pancreatitis, gastrointestinal/hepatobiliary surgical procedure, central venous catheter, total parenteral nutrition, diabetes mellitus and immunodeficiency (neutropenia < 500 neutrophils/mL, hematologic malignancy, chemotherapy, immunosuppressant drugs), should be also considered accepted criteria for empirical antifungal therapy.

Diagnostic Performance of PET or PET/CT Using 18F-FDG Labeled White Blood Cells in Infectious Diseases: A Systematic Review and a Bivariate Meta-Analysis

BACKGROUND

Diagnostic performance of positron emission tomography using white blood cells labeled with fluorine-18-fluorodeoxyglucose (¹⁸F-FDG-WBC PET or PET/CT) in patients with suspicious infectious diseases has been evaluated in several studies; however, there is no consensus about the diagnostic accuracy of this method. Therefore, a systematic review and meta-analysis was carried out on this topic.

METHODS

A comprehensive computer literature search screening PubMed/MEDLINE, Embase and Cochrane library databases through March 2019 was performed. Pooled sensitivity, specificity, positive and negative likelihood ratios (LR+ and LR-), and diagnostic odds ratio (DOR) of ¹⁸F-FDG-WBC PET or PET/CT in patients with infectious diseases were calculated.

RESULTS

Eight studies on the use of ¹⁸F-FDG-WBC PET or PET/CT in suspicious infectious diseases were discussed in the systematic review. The meta-analysis of seven studies (236 patients) provided these pooled results on a per patient-based analysis: sensitivity was 86.3% [95% confidence interval (95%CI) 75-92.9%], specificity 92% (95%CI 79.8-97.1%), LR+ 6.6 (95%CI: 3.1-14.1), LR- 0.2 (95%CI: 0.12-0.33), DOR 43.5 (95%CI: 12.2-155). A statistically significant heterogeneity was not detected.

CONCLUSIONS

Despite limited literature data, ¹⁸F-FDG-WBC PET or PET/CT demonstrated a good diagnostic accuracy for the diagnosis of infectious diseases; nevertheless, larger studies are needed.

[18F-FDG positron emission tomography in non-oncological renal pathology: Current indications and perspectives]

Positron emission tomography combined with computed tomography (PET/CT) is a nuclear imaging technique which provides anatomical and functional information. PET/CT is increasingly used in non-oncological nephrology since conventional radiological approaches after injection of contrast agents are relatively contra-indicated in patients with chronic kidney disease (CKD). PET/CT after i.v. injection of ¹⁸F-fluoro-deoxy-glucose (FDG) is not toxic and is characterized by a high sensitivity. The level of irradiation (∼5mSv) is acceptable. CKD does not significantly influence tissue uptake of ¹⁸F-FDG. The purpose of the present review aims at detailing the non-oncological indications of ¹⁸F-FDG PET/CT in general nephrology and after kidney transplantation. Particularly, ¹⁸F-FDG PET/CT appears useful in the diagnosis of cyst infection in patients with autosomal dominant polycystic kidney disease, as well as in the characterization of retroperitoneal fibrosis. In kidney transplant recipients, ¹⁸F-FDG PET/CT may help in the diagnostic work-up of suspected acute rejection, thereby eventually avoiding unnecessary kidney transplant biopsy. Perspectives in ¹⁸F-FDG PET/CT imaging are discussed, including innovative approaches of image analysis.

Infected cyst in patients with autosomal dominant polycystic kidney disease: Analysis of computed tomographic and ultrasonographic imaging features

Purpose

To investigate the imaging features of cyst infection in autosomal dominant polycystic kidney disease (ADPKD) patients using computed tomography (CT) and ultrasonography (US).

Materials & methods

The institutional review board approved this retrospective study. Fifty-one episodes with proven cyst infection in forty-three ADPKD patients were included. Two experienced abdominal radiologists reviewed CT and US images and evaluated the following imaging features in consensus: cyst size, location, cyst shape, intracystic attenuation, intracystic echogenicity, intracystic heterogeneity, wall thickness, the presence of fluid-fluid level, septation, intracystic gas, pericystic fat infiltration, and pericystic hyperemia. Intracystic attenuation was measured for all infected cysts and two presumed normal cysts and compared using the Wilcoxon rank-sum test.

Results

On CT scans, the median size of infected cysts was 5.5 cm (range: 2.3–18.8 cm) and 46 of 51 (90.2%) infected cysts were located in the subcapsular region. Most (48 of 51, 94.1%) infected cysts showed lobulated, focal bulging or irregular shape. Discernible wall thickening (84.1%) was the most frequently found imaging feature of infected cysts followed by relatively higher intracystic attenuation compared to normal cysts (79.1%) and pericystic fat infiltration (52.9%). Fluid/fluid level was found in 3 of 51 (5.9%) infected cysts and intracystic gas was found in 3 of 51 (5.9%) infected cysts, respectively. For hepatic cysts, 11 of 14 (78.6%) infected cysts showed pericystic hyperemia. Intracystic attenuation was significantly higher in infected cysts (median; 19.0 HU) than in presumed normal cysts (median; 8.5 HU) (P<0.001), and exceeded 25 HU in 18 (35.3%) of 51 infected cysts. Among the 41 infected cysts for which US images were available, 35 (85.1%) showed heterogeneous echogenicity.

Conclusion

Minute imaging features such as minimal wall thickening or relatively high attenuation compared to normal cysts would be helpful to detect infected cysts in ADPKD patients.

Clinical experience with white blood cell-PET/CT in autosomal dominant polycystic kidney disease patients with suspected cyst infection: A prospective case series

AIMS

Cyst infection (CI) is a common problem in patients with autosomal dominant polycystic kidney disease (ADPKD). Localization is of great importance in CI. We describe the clinical experience with [18F] FDG-labelled white-blood cell (WBC) PET/CT in detecting CI in ADPKD.

METHODS

Nineteen ADPKD patients (M:F = 7:12) suspected of having CI were enrolled in this prospective study. All underwent WBC-PET/CT and MRI or CT. The degree of their WBC accumulation was evaluated from the maximal standardized uptake value of cystic wall.

RESULTS

Cyst infection was diagnosed in 14 cases [definite (n = 6), probable (n = 1), or possible (n = 7); kidney (n = 11), or liver (n = 3)]. There was no difference in fever or laboratory findings (White blood cell count, C-reactive protein, culture results, and eGFR). The blood culture was positive only in a subset of CI patients (n = 4). Cyst fluid culture yielded bacterial growth in 80% of aspirates. WBC-PET/CT detected 64% of CI cases, whereas conventional imaging, 50%. WBC-PET/CT showed false-positive results in two of five cases with no CI. The reasons for false negatives with WBC-PET/CT were poor host immune reaction, low virulence, or prior antibiotic therapy. Haemorrhagic cysts were the most common cause of false positivity in WBC-PET/CT. However, WBC-PET/CT detected CI in three cases, in which the conventional imaging failed to find CI.

CONCLUSIONS

Clinical information may play little role in the diagnosis of CI. WBC-PET/CT can be used to detect CI with better sensitivity in ADPKD patients, circumventing the exposure to contrast media.

Urinary Tract Infections in Immunocompromised Patients with Diabetes, Chronic Kidney Disease, and Kidney Transplant

CONTEXT

This paper provides a brief overview of urinary tract infections (UTIs) in immunocompromised patients from the perspective of a practicing urologist.

OBJECTIVE

The primary objective was to provide an update on UTIs in immunocompromised patients. Diabetes mellitus (DM), chronic kidney disease, and kidney transplant (KT) are the most common clinical cases encountered by urologists. Diagnosis, management, and future research needs are summarised.

EVIDENCE ACQUISITION

We conducted a nonsystematic review of the literature. A comprehensive search of the PubMed database between 1996 and 2016 was performed.

EVIDENCE SYNTHESIS

Clinical diagnosis of UTIs in immunocompromised patients is challenging. Causative pathogens in DM are slightly different to those in the general population, but without any difference in resistance profiles. Keeping serum glucose under control is the most important preventive measure. The prevalence of UTIs in patients with autosomal dominant polycystic kidney disease (ADPKD) is 21-75%. Lipophilic antibiotics are effective in the treatment of infected cysts, albeit with a trend for lower effectiveness due to increasing resistance rates. UTIs are the most common infections in KT recipients, with a reported rate of 45-72%. Diagnostic challenges exist for both ADPKD and KT patients who develop UTIs. Treatment of UTIs should be tailored according to individual patient characteristics and the severity classification framework suggested by the European Society of Infections in Urology.

CONCLUSIONS

The underlying pathophysiology of UTIs in immunocompromised patients is not well known, which limits UTI management, including early diagnosis, treatment, and prevention. Future research to identify patients at higher risk of UTIs is necessary.

PATIENT SUMMARY

In this report we looked at patients with a weakened immune system who are more likely to develop a urine infection. We focused on the patient groups most commonly encountered in a urology setting. We found that these patients have a higher risk of urinary infection, but the signs of infection may be different to those in the general population. Early diagnosis is imperative in this group. Further research on early diagnosis and better individualised management strategies are necessary.