Researchers have proposed a new mechanism of acute kidney injury to account for patients with renal cell carcinoma (RCC) who have an inferior vena cava (IVC) tumor thrombus, according to findings presented at the 26th Annual Meeting of the Society of Urologic Oncology (SUO).1 By analyzing perioperative renal function in these patients, the researchers identified a distinct, reversible pattern of kidney injury linked to venous congestion—suggesting that timely thrombectomy may be critical to preserve renal function.
“The mechanism reframes how we think about renal failure in IVC thrombus. The injury is hemodynamic, not structural. Congestive nephropathy offers a unifying explanation, and it supports timely thrombectomy to relieve venous pressure,” said presenting author Lorraine Scanlon, MD, of London Health Sciences Centre Research Institute in Canada. “Ultimately, it introduces a fourth mechanism of renal dysfunction, and it may change how we counsel patients and design perioperative studies.”
The Clinical Issue
Patients with RCC and IVC thrombus often present with a poor baseline renal function in terms of estimated glomerular filtration rate. This has traditionally been attributed to tumor burden, chronic kidney disease, or comorbidities. But many patients recover their renal function after thrombectomy, which does not fit with structural or irreversible chronic kidney disease.
“This suggests a gap in how we conceptualize renal dysfunction in these patients,” Dr. Scanlon explained.
Acute kidney injury is classified as prerenal with lower perfusion rates, intrinsic with nephron injury, or as postrenal with obstruction leading to hydronephrosis. “This framework is incredibly useful, but none of these mechanisms explain what we see in IVC tumor thrombus,” she commented.
Instead, patients with IVC tumor thrombus have normal arterial inflow, no parenchymal injury, and no ureteric obstruction, so they cannot fall into any one of the three existing acute kidney injury classifications.
Hypothesis and Study Design
Dr. Scanlon suggested that there was a fourth possible mechanism of renal dysfunction: renal venous outflow obstruction, whereby IVC thrombus elevates the venous pressure, increases the interstitial pressure, and lowers the filtration gradient. This leads to a reversible injury that she called a congestive nephropathy.
“It reframes renal dysfunction as venous, not as arterial or as intrinsic,” she commented. “Our hypothesis was simple: if venous congestion is the driver, then relieving it via thrombectomy should preserve renal function, even in patients with worse baseline function.”
Researchers conducted a retrospective cohort study using data collected from 2002 to 2023 with three groups of patients: patients who underwent radical nephrectomy and IVC thrombectomy (n = 23), open radical nephrectomy alone (n = 35), and those who had a laparoscopic radical nephrectomy (n = 23). The primary outcome measurement was the change in the estimated glomerular filtration rate after more than 90 days.
Findings and Clinical Conclusion
The patients with IVC tumor thrombus had larger tumors, higher American Society of Anesthesiologists grades, and worse baseline estimated glomerular filtration rates. However, these patients also showed the best renal preservation.
Across all three groups, all patients experienced a decrease in their estimated glomerular filtration rate for the first day or two after surgery, but the rates recovered and converged at more than 90 days only for the patients with IVC tumor thrombus. “This cannot be explained by nephron loss. It's most consistent with the reversible and venous congestion,” Dr. Scanlon stated.
At 90 days, the absolute change in estimated glomerular filtration rates were –10 for the patients with IVC tumor thrombus who underwent radical nephrectomy and IVC thrombectomy, –25 for patients who underwent radical nephrectomy alone, and –25 for those who underwent laparoscopic radical nephrectomy. The percentage decline in estimated glomerular filtration rate in the IVC tumor thrombus group was –21%, compared with –38% in the other two groups, even though these patients had worse function at baseline.
Additionally, the researchers found that prior to surgery, venous obstruction led to increasing pressure in the patients with tumor thrombus, which caused filtration rates to fall. But after thrombectomy, the outflow rate was restored and the filtration gradient normalized, leading to a recovery in the patients’ renal function, confirming the expected signature of reversibility.
Disclosure: Dr. Scanlon reported no conflicts of interest.
REFERENCE
1. Scanlon L, Cendejas J, Kailavasan M, et al. Relief of venous congestion as a modifiable cause of renal dysfunction in RCC with IVC tumor thrombus. 2025 SUO Annual Meeting. Presented December 4, 2025.
