Present a case of acute interstitial nephritis secondary to immune checkpoint inhibitor therapy. Overview of the imaging characteristics found on FDG PET/CT. Discuss the potential role FDG PET/CT can play as an adjunctive test to aid in the diagnosis where renal biopsy is not possible.

Immune checkpoint inhibitors (ICI) are increasingly used in the treatment of multiple malignancies including melanoma, non-small-cell lung carcinoma and renal cell carcinoma. However, ICI treatments can be associated with immunotherapy related adverse events (irAEs) that can involve a range of organ systems. 1,2 Delayed irAEs have been observed and can occur months to years after therapy.1 The most common irAEs involve the gastrointestinal, musculocutaneous and endocrine systems. Less commonly, nephrotoxicity resulting from damage to the tubule-interstitial compartment has also been observed. 2 Imaging findings may...

Case Report: 60-year-old female with a diagnosis of melanoma who is 10 months post adjuvant immunotherapy with the ICI nivolumab. A post treatment surveillance FDG PET/CT demonstrated diffusely increased FDG uptake in the cortex of both kidneys (SUVmax 6.8, baseline study SUVmax 2.9) characteristic of inflammatory nephritis. FDG uptake in the renal cortices in non-inflammatory causes of kidney injury is generally similar to physiological uptake in normal kidneys. 2 This finding on FDG/PET CT can aid in distinguishing ICI related interstitial nephritis from other causes...

Acute interstitial nephritis is one of the less common irAEs associated with ICI therapy. The pattern of diffusely increased FDG uptake localising to the renal cortex associated with acute interstitial nephritis caused by ICI therapy is important for the reporting physician to be aware of. FDG PET/CT may be of use to aid in the diagnosis with appropriate concordant clinical and laboratory features when renal biopsy is not feasible.

References: Ardolino L, Joshua A. Immune checkpoint inhibitors in malignancy. Aust Presc. 2019; 2(2): p62–67. Qualls D, Seethapathy H, Bates H,et al.Positron emission tomography as an adjuvant diagnostic test in the evaluation of checkpoint inhibitor-associated acute interstitial nephritis. Immunother. Cancer.2019; 7 (356). Khaulli, Mark A, Thomas J, et al. Imaging findings in immunotherapy-related renal toxicity. Immunother. Cancer. 2022; 45(3): p62-166. Tucci M, Passarelli A, Todisco A, et al. The mechanisms of acute interstitial nephritis in the era of immune checkpoint inhibitors in melanoma. Ther Adv...