Renal pathology has always been considered an “exotic” area of pathology. Perhaps more than one reason accounts for this perception. Limited exposure to renal pathology, reflecting the fact that kidney biopsies for medical renal diseases are not a common specimen and are mostly sent to specialized centers rather than being handled at local hospitals, is probably one of the most important reasons for this perception. The complexity of integrating different diagnostic modalities, including light microscopy, immunofluorescence, and electron microscopy, is perhaps another reason. Furthermore, proper renal biopsy interpretation usually requires significant clinical knowledge. The observation that very similar morphologic findings in renal biopsies may signify diseases of quite different nature and pathogenesis, impacting treatment and prognosis, is certainly somewhat unusual and daunting in diagnostic pathology.

Yet, knowledge in renal pathology is important in the daily practice. Correct handling of the renal biopsies to be sent for outside consultation, understanding the diagnostic and biologic significance of the renal biopsy reports, and effective communication with the referring nephrologists all depend on a significant understanding of various aspects of renal diseases from a morphologic perspective. Furthermore, the entire spectrum of renal medical diseases can be seen in the context of nephrectomy for neoplastic or nonneoplastic conditions. It is the responsibility of the general pathologist to make a correct diagnosis in the uninvolved renal parenchyma of these nephrectomy specimens.

Recent years have witnessed significant developments in the pathology of renal medical diseases. New disease entities have been recognized, diagnostic criteria have been revised and updated, and classic disease paradigms have changed. Furthermore, probably in no other field of pathology would the recent understanding of molecular mechanisms of disease have more potential impact on the classification, diagnosis, and treatment of these kidney diseases. We have not quite yet seen the full ramifications of the “revolution” that is about to take place in the treatment of medical renal diseases resulting from our enhanced understanding of molecular pathogenesis of these disorders.

This special section on renal pathology was developed in response to these considerations. The subjects were chosen to cover areas that have changed substantially during the last 5 years and to address subjects of interest to the general pathologist.

Patrick Walker, MD, provides a detailed account of what the proper examination of renal tissue obtained by various means for the evaluation of medical renal diseases entails. He discusses the basic requirements for a successful renal biopsy. There is no doubt that it is necessary to take into account a number of important factors so that the renal biopsy can provide the material that is required to establish a definitive diagnosis. He reviews the value of each of the ancillary diagnostic techniques used in the evaluation of renal biopsies. He also discusses historic aspects associated with the renal biopsy as a procedure to obtain tissue for diagnosis, current practices pertaining to the medical utilization of this procedure, and how the donor and allograft biopsies should be handled. He expands on practical aspects pertaining to the essential elements of the renal biopsy reports. This is a comprehensive article that should be of great value for the general pathologist who must handle but not necessarily “sign out” the renal biopsies.

Luan Truong, MD, and colleagues took on the challenge of addressing renal lesions associated with renal neoplasms, a subject of much interest to the general pathologist who signs out nephrectomy specimens and must look at the uninvolved renal parenchyma. There are alterations of clinical significance in the uninvolved renal parenchyma that can be missed if not carefully evaluated. Because the nephrectomy itself diminishes the overall number of nephrons available, the parenchyma that remains in the opposite kidney, if it is involved by a disease process, compromises remaining renal function. The nephrectomy specimen serves the purpose of being the diagnostic specimen for whatever is the underlying medical disease involving the kidney. This article carefully dissects the challenges that may be encountered when handling these specimens and how to adequately examine the specimens to document the presence of an underlying nephropathy.

Laura Barisoni, MD, and associates discuss the latest findings and diagnostic criteria in podocytopathies. Basic science has clearly advanced this field, and pathologists are taking advantage of this new information by applying it to diagnostic settings. These authors summarize available information and highlight the state of the art regarding this most interesting subject. This article links the morphologic classification of podocytopathies with molecular events that have been elucidated, proposing a classification of these diseases that is amenable to being used for the design of new therapies.

David Thomas, MD, summarizes the current view on focal segmental glomerulosclerosis, the most common cause of nephrotic syndrome, and provides a succinct historic account on the classification of this lesion. The recent Columbia classification of focal segmental sclerosis is described in detail and supplemented with clinical correlations. The strength and the limitation of this classification are discussed with practical diagnostic caveats.

Mark Haas, MD, PhD, was given the task of addressing the diagnosis of glomerular basement membrane disorders, a subject that has been completely revolutionized by information that has been obtained from basic research and applied to diagnostic pathology. Dr Haas summarizes in a succinct yet clear and complete manner the current diagnostic approach to this group of diseases.

Surya Seshan, MD, and J. Charles Jennette, MD, cover another very important subject; that is, renal pathology in systemic lupus erythematosus. Recently, a new classification of lupus nephritis has been approved by the Renal Pathology Society and the International Society of Nephrology based on clinical and pathologic information that has become available during the last 3 decades. They discuss the new classification in light of the older classifications and provide very useful points regarding the diagnosis of lupus nephritis. The considerations covered in this article are very important, not only to pathologists but also to clinicians.

Guillermo Herrera, MD, addresses in a practical fashion the diagnosis of some of the renal disorders associated with underlying plasma cell dyscrasias, emphasizing how research has improved our ability to better understand and diagnose these diseases. In some instances, the diagnosis of some of these conditions requires careful evaluation of the data emanating from all 3 diagnostic techniques used in the daily practice of renal pathology: immunofluorescence, light microscopy, and electron microscopy. This article clearly shows how these techniques work in concert in the diagnosis and characterization of these sometimes diagnostically challenging conditions.

Tibor Nadasdy, MD, and Lois Arend, MD, PhD, discuss a very important and timely subject; that is, renal lesions associated with new therapies. There is a plethora of new therapies with many new drugs entering the therapeutic arena, some with unclear side effects; their renal toxicity may result in a variety of alterations affecting all renal compartments. Because many of these drugs are cleared by the kidney, alterations in the renal parenchyma can be seen. There are also hypersensitivity reactions to these drugs that can become manifest in the renal parenchyma. This article summarizes the information available at the present time. Since one of the most effective ways to address these renal complications is to discontinue the therapy, linking the renal changes to a specific drug is essential, and it is the responsibility of those who examine renal specimens to do so.

This special section on renal pathology represents a compilation of routine but important issues in renal pathology and recent developments in this area. The editors have enjoyed preparing this special section and hope that it is useful to the readers of the Archives of Pathology & Laboratory Medicine. Hopefully, the “exotic” perception and mystery that surround the handling and interpretation of renal biopsies for medical renal diseases have been somewhat mitigated, and readers can start looking at this subject with more transparency and an increased depth of understanding.

Luan D. Truong, MD, attended the University of Saigon, Faculty of Medicine, and Pennsylvania State University, College of Medicine/ Hershey Medical Center. He completed a residency in pathology at Baylor College of Medicine and a renal pathology fellowship at Columbia University, College of Physicians and Surgeons. He currently serves as director of Renal Pathology at The Methodist Hospital, Houston, Texas. He is professor of Pathology and Laboratory Medicine at the Weill Medical College of Cornell University and is adjunct professor of Pathology and Medicine at Baylor College of Medicine. He is a member of the Renal Pathology Society and has served on the Board of Directors of this society. His research activities, partially funded by the National Institutes of Health, focus on the mechanisms of tubulointerstitial injury, with emphasis on tubular cell apoptosis, clinicopathologic correlation of renal disease entities, and renal neoplasms. He has authored or coauthored more than 215 scientific publications, contributed 5 book chapters, and served as the editor or a coeditor for 2 books, all in the area of renal or diagnostic pathology. He has been an invited speaker for several national and international meetings, and he has served as manuscript reviewer for more than 12 journals. He is currently on the editorial board of 2 scientific journals, including his appointment as a section editor of the nephropathology section for the Archives of Pathology & Laboratory Medicine
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Luan D. Truong, MD, attended the University of Saigon, Faculty of Medicine, and Pennsylvania State University, College of Medicine/ Hershey Medical Center. He completed a residency in pathology at Baylor College of Medicine and a renal pathology fellowship at Columbia University, College of Physicians and Surgeons. He currently serves as director of Renal Pathology at The Methodist Hospital, Houston, Texas. He is professor of Pathology and Laboratory Medicine at the Weill Medical College of Cornell University and is adjunct professor of Pathology and Medicine at Baylor College of Medicine. He is a member of the Renal Pathology Society and has served on the Board of Directors of this society. His research activities, partially funded by the National Institutes of Health, focus on the mechanisms of tubulointerstitial injury, with emphasis on tubular cell apoptosis, clinicopathologic correlation of renal disease entities, and renal neoplasms. He has authored or coauthored more than 215 scientific publications, contributed 5 book chapters, and served as the editor or a coeditor for 2 books, all in the area of renal or diagnostic pathology. He has been an invited speaker for several national and international meetings, and he has served as manuscript reviewer for more than 12 journals. He is currently on the editorial board of 2 scientific journals, including his appointment as a section editor of the nephropathology section for the Archives of Pathology & Laboratory Medicine

Luan D. Truong, MD, attended the University of Saigon, Faculty of Medicine, and Pennsylvania State University, College of Medicine/ Hershey Medical Center. He completed a residency in pathology at Baylor College of Medicine and a renal pathology fellowship at Columbia University, College of Physicians and Surgeons. He currently serves as director of Renal Pathology at The Methodist Hospital, Houston, Texas. He is professor of Pathology and Laboratory Medicine at the Weill Medical College of Cornell University and is adjunct professor of Pathology and Medicine at Baylor College of Medicine. He is a member of the Renal Pathology Society and has served on the Board of Directors of this society. His research activities, partially funded by the National Institutes of Health, focus on the mechanisms of tubulointerstitial injury, with emphasis on tubular cell apoptosis, clinicopathologic correlation of renal disease entities, and renal neoplasms. He has authored or coauthored more than 215 scientific publications, contributed 5 book chapters, and served as the editor or a coeditor for 2 books, all in the area of renal or diagnostic pathology. He has been an invited speaker for several national and international meetings, and he has served as manuscript reviewer for more than 12 journals. He is currently on the editorial board of 2 scientific journals, including his appointment as a section editor of the nephropathology section for the Archives of Pathology & Laboratory Medicine
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Luan D. Truong, MD, attended the University of Saigon, Faculty of Medicine, and Pennsylvania State University, College of Medicine/ Hershey Medical Center. He completed a residency in pathology at Baylor College of Medicine and a renal pathology fellowship at Columbia University, College of Physicians and Surgeons. He currently serves as director of Renal Pathology at The Methodist Hospital, Houston, Texas. He is professor of Pathology and Laboratory Medicine at the Weill Medical College of Cornell University and is adjunct professor of Pathology and Medicine at Baylor College of Medicine. He is a member of the Renal Pathology Society and has served on the Board of Directors of this society. His research activities, partially funded by the National Institutes of Health, focus on the mechanisms of tubulointerstitial injury, with emphasis on tubular cell apoptosis, clinicopathologic correlation of renal disease entities, and renal neoplasms. He has authored or coauthored more than 215 scientific publications, contributed 5 book chapters, and served as the editor or a coeditor for 2 books, all in the area of renal or diagnostic pathology. He has been an invited speaker for several national and international meetings, and he has served as manuscript reviewer for more than 12 journals. He is currently on the editorial board of 2 scientific journals, including his appointment as a section editor of the nephropathology section for the Archives of Pathology & Laboratory Medicine

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Guillermo A. Herrera, MD, received his medical degree from the University of Puerto Rico in San Juan. His residency training was at Brooke Army Medical Center, Fort Sam Houston in San Antonio, Texas. He then remained on active duty and served at Walter Reed and William Beaumont Army Medical Centers. Dr Herrera was director of Surgical Pathology at the University of Mississippi in Jackson and at the University of Alabama in Birmingham. Dr Herrera then became chair of the Department of Pathology at Louisiana State University in Shreveport from 1996 to 2006, and later was chair of Pathology at Saint Louis University in St Louis, Missouri, from 2006 to 2008. Dr Herrera recently became the associate director of Nephrocor, a branch of Bostwick Laboratories, in Tempe, Arizona. Dr Herrera has boards in anatomic and clinical pathology and cytopathology. He is the president of the Society for Ultrastructural Pathology, an international organization dedicated to the promotion of electron microscopy and molecular pathology as ancillary diagnostic techniques. He is also a councilor of the Renal Pathology Society. He has occupied several positions in the Board of Directors of both above-mentioned societies.Dr Herrera has published more than 250 manuscripts and book chapters and has edited several books and monographs dealing with several areas of renal pathology. He has given more than 250 lectures at numerous national and international venues.His main contribution to renal pathology has been in enhancing the understanding of mechanisms involved in the renal damage produced by monoclonal light and heavy chains in patients with plasma cell dyscrasias. He has used an innovative translational approach and has successfully incorporated information that has emanated from his basic research laboratory into clinical practice. His basic research work on glomerular light-chain amyloidogenesis, funded by various agencies throughout his 30 years in basic research, has provided new insights into key steps in the process that will potentially lead to new treatments aimed at ameliorating or inhibiting renal damage in this condition. Dr Herrera is a manuscript reviewer for more than 20 journals and is currently on the editorial board of 5 pathology journals, including his appointment as a section editor of the nephropathology section for the Archives of Pathology & Laboratory Medicine
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Guillermo A. Herrera, MD, received his medical degree from the University of Puerto Rico in San Juan. His residency training was at Brooke Army Medical Center, Fort Sam Houston in San Antonio, Texas. He then remained on active duty and served at Walter Reed and William Beaumont Army Medical Centers. Dr Herrera was director of Surgical Pathology at the University of Mississippi in Jackson and at the University of Alabama in Birmingham. Dr Herrera then became chair of the Department of Pathology at Louisiana State University in Shreveport from 1996 to 2006, and later was chair of Pathology at Saint Louis University in St Louis, Missouri, from 2006 to 2008. Dr Herrera recently became the associate director of Nephrocor, a branch of Bostwick Laboratories, in Tempe, Arizona. Dr Herrera has boards in anatomic and clinical pathology and cytopathology. He is the president of the Society for Ultrastructural Pathology, an international organization dedicated to the promotion of electron microscopy and molecular pathology as ancillary diagnostic techniques. He is also a councilor of the Renal Pathology Society. He has occupied several positions in the Board of Directors of both above-mentioned societies.Dr Herrera has published more than 250 manuscripts and book chapters and has edited several books and monographs dealing with several areas of renal pathology. He has given more than 250 lectures at numerous national and international venues.His main contribution to renal pathology has been in enhancing the understanding of mechanisms involved in the renal damage produced by monoclonal light and heavy chains in patients with plasma cell dyscrasias. He has used an innovative translational approach and has successfully incorporated information that has emanated from his basic research laboratory into clinical practice. His basic research work on glomerular light-chain amyloidogenesis, funded by various agencies throughout his 30 years in basic research, has provided new insights into key steps in the process that will potentially lead to new treatments aimed at ameliorating or inhibiting renal damage in this condition. Dr Herrera is a manuscript reviewer for more than 20 journals and is currently on the editorial board of 5 pathology journals, including his appointment as a section editor of the nephropathology section for the Archives of Pathology & Laboratory Medicine

Guillermo A. Herrera, MD, received his medical degree from the University of Puerto Rico in San Juan. His residency training was at Brooke Army Medical Center, Fort Sam Houston in San Antonio, Texas. He then remained on active duty and served at Walter Reed and William Beaumont Army Medical Centers. Dr Herrera was director of Surgical Pathology at the University of Mississippi in Jackson and at the University of Alabama in Birmingham. Dr Herrera then became chair of the Department of Pathology at Louisiana State University in Shreveport from 1996 to 2006, and later was chair of Pathology at Saint Louis University in St Louis, Missouri, from 2006 to 2008. Dr Herrera recently became the associate director of Nephrocor, a branch of Bostwick Laboratories, in Tempe, Arizona. Dr Herrera has boards in anatomic and clinical pathology and cytopathology. He is the president of the Society for Ultrastructural Pathology, an international organization dedicated to the promotion of electron microscopy and molecular pathology as ancillary diagnostic techniques. He is also a councilor of the Renal Pathology Society. He has occupied several positions in the Board of Directors of both above-mentioned societies.Dr Herrera has published more than 250 manuscripts and book chapters and has edited several books and monographs dealing with several areas of renal pathology. He has given more than 250 lectures at numerous national and international venues.His main contribution to renal pathology has been in enhancing the understanding of mechanisms involved in the renal damage produced by monoclonal light and heavy chains in patients with plasma cell dyscrasias. He has used an innovative translational approach and has successfully incorporated information that has emanated from his basic research laboratory into clinical practice. His basic research work on glomerular light-chain amyloidogenesis, funded by various agencies throughout his 30 years in basic research, has provided new insights into key steps in the process that will potentially lead to new treatments aimed at ameliorating or inhibiting renal damage in this condition. Dr Herrera is a manuscript reviewer for more than 20 journals and is currently on the editorial board of 5 pathology journals, including his appointment as a section editor of the nephropathology section for the Archives of Pathology & Laboratory Medicine
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Guillermo A. Herrera, MD, received his medical degree from the University of Puerto Rico in San Juan. His residency training was at Brooke Army Medical Center, Fort Sam Houston in San Antonio, Texas. He then remained on active duty and served at Walter Reed and William Beaumont Army Medical Centers. Dr Herrera was director of Surgical Pathology at the University of Mississippi in Jackson and at the University of Alabama in Birmingham. Dr Herrera then became chair of the Department of Pathology at Louisiana State University in Shreveport from 1996 to 2006, and later was chair of Pathology at Saint Louis University in St Louis, Missouri, from 2006 to 2008. Dr Herrera recently became the associate director of Nephrocor, a branch of Bostwick Laboratories, in Tempe, Arizona. Dr Herrera has boards in anatomic and clinical pathology and cytopathology. He is the president of the Society for Ultrastructural Pathology, an international organization dedicated to the promotion of electron microscopy and molecular pathology as ancillary diagnostic techniques. He is also a councilor of the Renal Pathology Society. He has occupied several positions in the Board of Directors of both above-mentioned societies.Dr Herrera has published more than 250 manuscripts and book chapters and has edited several books and monographs dealing with several areas of renal pathology. He has given more than 250 lectures at numerous national and international venues.His main contribution to renal pathology has been in enhancing the understanding of mechanisms involved in the renal damage produced by monoclonal light and heavy chains in patients with plasma cell dyscrasias. He has used an innovative translational approach and has successfully incorporated information that has emanated from his basic research laboratory into clinical practice. His basic research work on glomerular light-chain amyloidogenesis, funded by various agencies throughout his 30 years in basic research, has provided new insights into key steps in the process that will potentially lead to new treatments aimed at ameliorating or inhibiting renal damage in this condition. Dr Herrera is a manuscript reviewer for more than 20 journals and is currently on the editorial board of 5 pathology journals, including his appointment as a section editor of the nephropathology section for the Archives of Pathology & Laboratory Medicine

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The authors have no relevant financial interest in the products or companies described in this article.

Author notes

Reprints: Luan Truong, MD, Department of Pathology, The Methodist Hospital and Research Institute, 6565 Fannin St, M227 (Main Bldg), Houston, TX 77030 ([email protected])

College of American Pathologists
2009