Morphologic and functional effects of renal cryoinjury

Wilms' tumor presents with bilateral renal involvement in 10% of patients. With the current treatment protocols for Wilms' tumor emphasizing maximal preservation of renal parenchyma, cryosurgery may offer an alternative to bilateral tumor resections in these patients. This study was designed to examine the effects of profound cryotherapy on a significant portion of the renal parenchyma, simulating the clinical application of this technique. Eighteen New Zealand white rabbits underwent unilateral nephrectomy, with four serving as controls. The contralateral kidney in the experimental animals was subjected to cryoinjury with a liquid nitrogen probe. Needle thermocouples monitored surface temperature 1/2 cm from the margin of the probe tip and renal "core" temperature 1 cm within the renal parenchyma directly beneath the tip. The kidney was cooled until the "core" temperature reached -40 degrees C, and this was achieved with a probe temperature of -180 degrees C for an average of 11.8 min. All animals tolerated the cryoinjury well and were sacrificed in pairs at 24 and 72 hr, and 1, 2, 3, 4, and 8 weeks. Transient gross hematuria was noted in 25% of the animals and microscopic hematuria in 50%. Serum blood urea nitrogen and creatinine levels reached maximum levels at 72 hr (BUN, 92 +/- 28 mg%; Creatinine, 7.2 +/- 1 mg%) and gradually returned toward normal thereafter. The cryolesion at 24 hr resembled a hemorrhagic infarct involving 40% of the kidney. By 8 weeks this lesion had contracted to a fibrotic lesion involving 20% of the kidney by weight. The surrounding uninjured renal parenchyma underwent compensatory hypertrophy.(ABSTRACT TRUNCATED AT 250 WORDS)