AKI is increasingly common in patients with cancer. Between sepsis, volume depletion, contrast exposure, and nephrotoxic therapies, it is often tempting—and convenient—to attribute kidney injury to acute tubular necrosis.
But what if we are wrong more often than we think?
The Problem: Diagnostic Anchoring in Onconephrology
Cancer patients represent one of the most complex populations we manage. They are exposed to multiple therapies, experience rapid physiologic changes, and frequently have overlapping clinical syndromes. Despite this, many cases of AKI are still labeled as “ATN” early in the course, often without further evaluation. This diagnostic anchoring creates a critical blind spot—one that risks missing treatable and potentially reversible causes of kidney injury.
What Are We Missing?
Several important entities can mimic ATN in patients with cancer:
Immune checkpoint inhibitor–associated acute interstitial nephritis (AIN):
With the widespread use of PD-1, PD-L1, and CTLA-4 inhibitors, AIN is increasingly recognized. It is often delayed in onset, subtle in presentation, and highly responsive to corticosteroids. Without biopsy, it is frequently missed.
Thrombotic microangiopathy (TMA):
TMA can occur in association with VEGF inhibitors, hematologic malignancies, transplantation, and even cancer itself. Importantly, it may present without classic hematologic features. Complement-mediated mechanisms are increasingly implicated. Renal limited TMA is so common and often gets missed due to lack of heme parameters.
Light chain–mediated kidney disease:
Cast nephropathy, light chain deposition disease, and other monoclonal protein–related injuries are not always immediately recognized, particularly outside specialized hematologic settings. Often this is missed in the setting of lymphoma and NON plasma cell based heme cancers.
Drug-induced tubulointerstitial injury:
Proton pump inhibitors, antibiotics, and targeted cancer therapies can all contribute to kidney injury. These often coexist with immunotherapy, further complicating the clinical picture.
Non Dilated Obstruction:
This is definitely missed. We see this in Onconephrology all the time and especially in retroperitoneal mets cancers and or RP masses. Renal sonogram will show NO hydronephrosis but it is still hydronephrosis and b/l PCNs improve the renal function.
Why This Matters
Multiple studies comparing clinical diagnoses with kidney biopsy findings have demonstrated significant discordance. A substantial proportion of cases initially presumed to be ATN are reclassified after biopsy—many into diagnoses that would change management.
Despite this, kidney biopsy is often deferred due to concerns about procedural risk, patient acuity, or the perception that it will not alter treatment decisions. Increasingly, however, that assumption does not hold true.
A Practical Framework: When to Pause and Reconsider
Before assigning a diagnosis of ATN in a patient with cancer, it is worth pausing and asking whether the full differential has been considered.
Red flags that should prompt further evaluation include:
Recent or ongoing immunotherapy
Exposure to VEGF inhibitors or novel targeted agents ( often most folks don't do a good detailed oncology history of meds)
Underlying or suspected hematologic malignancy
Lack of kidney recovery despite supportive care
Presence of proteinuria or active urine sediment
Key questions to consider:
Would identifying AIN change management (e.g., initiation of steroids)?
Could this represent TMA requiring targeted or complement-directed therapy?
Would a kidney biopsy meaningfully guide treatment decisions?
Would this patient benefit from PCN as clinically seems to have hydronephrosis but no signs on imaging?
In this setting, labeling AKI as “ATN” without careful consideration is no longer sufficient.
AKI in patients with cancer is often more than just ATN. It may reflect immune-mediated injury, complement dysregulation, or monoclonal protein–related disease.
Recognizing these possibilities is essential to delivering the right treatment at the right time.
How often are you performing kidney biopsies in patients with cancer and AKI?
Have biopsy findings changed your management in unexpected ways?
Are we underutilizing kidney biopsy in this population?
