Consult Rounds: Histotripsy associated AKI

 

Histotripsy is an emerging non-invasive, non-thermal ablative technology that uses focused ultrasound pulses to mechanically destroy tumors through acoustic cavitation. Approved by the FDA in late 2023 for treatment of liver tumors, histotripsy has generated excitement because it can fragment tissue without surgical incisions, ionizing radiation, or traditional thermal injury. Early studies have also suggested potential downstream immunomodulatory effects beyond localized tumor destruction.

During the procedure, patients typically undergo general anesthesia in an interventional radiology suite or hybrid operating room. Real-time ultrasound guidance is used to localize the lesion and define the treatment field. High-amplitude ultrasound pulses generate dense cavitation bubble clouds that rapidly expand and collapse, mechanically fractionating tissue into acellular debris while largely sparing surrounding structures. Treatment is delivered sequentially in a raster-like pattern across the lesion with continuous imaging feedback.( see above figure created via AI)

While the oncology potential of histotripsy is substantial, nephrologists should be aware of a possible emerging complication: histotripsy-associated acute kidney injury (H-AKI). In a recent brief report published in KI Reports, a patient developed AKI with hematuria shortly after hepatic histotripsy in the absence of alternative clear insults, with improvement following hydration and supportive care.

To further explore whether this represented an isolated event or a broader signal, post-marketing review of the FDA MAUDE database identified additional cases of renal impairment following hepatic histotripsy. Reported patients were often older females with larger treatment volumes (>90 cc). Some required dialysis, while others recovered with conservative management and intravenous fluids. However, MAUDE data remain hypothesis-generating and limited by underreporting, lack of adjudication, and incomplete clinical detail.

Additional support for this phenomenon comes from an abstract presented at the Society of Interventional Radiology describing multiple cases of histotripsy-induced AKI. Interestingly, several reports described dark or discolored urine, raising the possibility of pigment-mediated tubular injury.

At present, no biopsy-proven mechanism has been reported. Proposed pathophysiologic mechanisms include hemolysis with pigment nephropathy, release of cellular debris after extensive tissue fractionation, hemodynamic injury, inflammatory cytokine release, or immune-mediated interstitial injury. Larger treatment fields may increase systemic exposure to hemoglobin, heme pigments, and intracellular contents.

Why does this matter? Histotripsy is rapidly expanding beyond hepatic tumors into renal and other solid organ malignancies. As use increases, nephrologists, oncologists, and interventional radiologists should recognize AKI as a potential procedural complication requiring early identification and supportive management. Future studies are needed to better define incidence, mechanisms, biomarkers, and preventive strategies for H-AKI.