A new diagnostic scale for renal cyst infection in patients with ADPKD
Autosomal dominant polycystic kidney disease (ADPKD) is a disease caused by mutations in the PKD1 genes in 85% of cases and PKD2 in 15% of cases. It is characterized by the appearance of renal cysts with an increase in the size of the kidneys bilaterally and progression to end stage renal disease between the ages of 50 and 70 years. It is the leading genetic cause of end stage renal disease worldwide (6-8% of incident cases of ESRD in developed countries).
Diagnosis of renal or hepatic cyst infection in patients with this disease is difficult in routine clinical practice. Thanks to a collaboration between the GIGA Nephrology research laboratory and the Nuclear Medicine service of the CHU de Liège, the team of Dr François Jouret proposes a new diagnostic scale for cyst infection based on the intensity of the 18F-FDG signal in positron emission tomography (PET).
This new semi-quantitative threshold should make it possible to standardize (and therefore improve) the management of patients with PRAD suspected of having a cyst infection. Remember that PRAD is the most common genetic kidney disease: it affects 1 / 1,000 people worldwide.
Purpose: [18F]FDG PET/CT (PET/CT) proved useful in the diagnosis of renal and hepatic cyst infection (CyI) in patients with autosomal dominant polycystic kidney disease (ADPKD). However, the definition of CyI by PET/CT is unclear. Here, we characterize the [18F]FDG uptake in CyI in order to infer a visual 4-point diagnostic scale.
Methods: All ADPKD patients hospitalized between 2007 and 2019 for suspected CyI and who underwent an [18F]FDG PET/CT scan were listed. CyI was defined by 5 concomitant criteria: fever ≥ 38 °C; abdominal pain; peak plasma CRP ≥ 70 mg/L; no other cause of inflammation; and favorable outcomes after antibiotics for ≥ 21 days. First, all PET/CT images were visually interpreted. Next, the [18F]FDG uptake around the suspected CyI was scored using a semiquantitative 4-point scale in comparison to blood and liver activities.
Results: Sixty [18F]FDG PET/CT scans were performed for suspected CyI in 38 ADPKD patients. Twenty-nine episodes met the gold-standard criteria for CyI. The visual assessment of PET/CT images reached a sensitivity of 73.1% and a specificity of 70.6%. Using the 4-point scale, an [18F]FDG score ≥ 3 (i.e., cyst uptake > liver) improved the specificity to 85.3%.
Conclusion: [18F]FDG PET-CT is helpful in CyI diagnosis in ADPKD, and the use of a 4-point scoring of [18F]FDG uptake improves its diagnostic yield, with positive and negative predictive values of 78.3 and 78.4%, respectively. External validation is required.
The use of a visual 4-point scoring scale improves the yield of 18 F-FDG PET-CT imaging in the diagnosis of renal and hepatic cyst infection in patients with autosomal dominant polycystic kidney disease