Endoscopic Renal Papillary Biopsies: A Tissue Retrieval Technique for Histological Studies in Patients With Nephrolithiasis

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Abstract
Purpose: The mechanisms behind calcium nephrolithiasis remain unclear. Previous research has relied on animal models or cell lines, yielding limited insight into the pathophysiology of human calcium stone disease. To determine changes occurring in the human kidney during active stone disease we used an endoscopic renal papillary biopsy protocol in calcium stone formers undergoing percutaneous nephrolithotomy. Materials and Methods: Following stone burden clearance via percutaneous nephrolithotomy 15 idiopathic calcium oxalate and 4 ileal bypass stone formers underwent flexible and rigid nephroscopy. Biopsies from select papillae in the peripheral and interpolar regions were obtained with 5Fr flexible cup biopsy forceps. A papilla adjacent to the accessed calix was biopsied with 10Fr cup biopsy forceps. Cortical biopsies along the access tract were also obtained with the 10Fr forceps. Results: All patients had successful biopsy completion. No complications were attributable to the biopsy process and no blood transfusions were required. Of the 19 patients 12 were contacted for followup at a mean of 21.7 ± 9.0 months with none experiencing adverse sequelae such as bleeding or significant pain. A total of 14 patients had followup serum creatinine available showing that the difference in mean preoperative and postoperative values was not clinically significant (1.00 ± 0.27 and 1.11 ± 0.27 mg/dl, respectively). The quality of biopsied tissue permitted accurate immunohistochemical staining of crystal deposits and mineral analysis. Conclusions: Endoscopic papillary biopsies were performed safely in a small patient population. Tissue obtained using this protocol can be used for detailed histological and analytical studies, which may lead to significant advances in our understanding of stone formation mechanisms.