Diabetic Foot Infections: The Diagnostic Challenges

SLR - November 2021 - Andrew E. Fischer

Residency Program: Hennepin Healthcare – Minneapolis, MN

Podiatric Relevance: Diabetic foot infections are severe complications of long-standing diabetes and they represent significant diagnostic challenges. The differentiation between osteomyelitis, soft tissue infection, and Charcot’s osteoarthropathy is very difficult. This review of the literature provides a detailed overview of multiple radiologic and nuclear medicine modalities for the diagnosis of diabetic foot infections and to address evidence-based answers for clinicians.

Methods: The researchers performed a comprehensive review of the literature in an attempt to provide an overview of multiple modalities other than the bone biopsy to diagnose the diabetic foot infection.

Results: The authors provided a detailed review of the current literature and evidence of imaging modalities such as radiographs, MRI, gamma-camera imaging, [¹⁸F]FDG PET/CT imaging, and PET/CT imaging. They also answered questions based on their literature review of the Round Table of 3rd European Congress of Infection and Inflammation.

Conclusions: The authors had many useful conclusions from their review of the literature on imaging. They were able to conclude that while accurate identification and differentiation among different types of diabetic foot pathology and infection remains difficult, there are many useful imaging modalities including MRI, WBC scintigraphy (bone scan), and [¹⁸F]FDG PET/CT.  [¹⁸F]FDG PET/CT  is the most useful currently, although there are no accepted standardized diagnostic flow charts yet available for this modality. In their opinion this is the next step to improving all the imaging modalities. While answering the nine questions from the Round Table they were able to support the majority of the current standard of practice on imaging of the diabetic foot. With regard to [¹⁸F]FDG PET/CT, they concluded that it was not able to differentiate between Charcot and infection. The authors previously suggested a standardized uptake value to aid in the interpretation of [¹⁸F]FDG PET/CT, but there is currently insufficient evidence in the literature to recommend this. They also concluded that MRI may be a useful tool to evaluate therapy following osteomyelitis as normal marrow signal reliably excludes osteomyelitis although they cautioned the patient cannot be considered cured at this point based solely on MRI. Plain radiographs are still the first line imaging modality, although a negative radiograph cannot definitively exclude osteomyelitis as radiographic changes of osteomyelitis may take three to four weeks to become present on film. I agree with the author’s overall conclusion and although we are a long way from being able to replace bone biopsy as the gold standard to diagnose osteomyelitis there are many advanced imaging modalities that are becoming more precise in their criteria to identify and diagnose foot and ankle pathologies in the diabetic foot.