- Email: [email protected]
Rare Renal Pseudotumor Associated with Chronic Glomerulonephritis Mimicking Renal Cell Carcinoma
Case Report Rare Renal Pseudotumor Associated with Chronic Glomerulonephritis Mimicking Renal Cell Carcinoma Minoru Kobayashi, Kazuhiko Nakano, Akinori Nukui, Masayuki Yuzawa, and Tatsuo Morita We describe a unique case of chronic glomerulonephritis that simulated a renal neoplasm observed on abnormal imaging. Histologic examination of the resected specimen supported the assumption that the observed mass lesion resulted from regional sparing in the development of chronic glomerulonephritis. We believe this case is the first to show the etiology of pseudotumor as an extremely uncommon manifestation of chronic glomerulonephritis by histologic examination. UROLOGY 72: 461.e15– 461.e17, 2008. © 2008 Elsevier Inc.
M
any renal lesions that mimic renal neoplasms on imaging are observed at subsequent surgery and histopathologic evaluation to have been incorrectly diagnosed. These masses may be composed of normal or benign renal tissue and are referred to as renal pseudotumors. These lesions arise from many conditions that are developmental, infectious, granulomatous, and vascular in nature.1 Especially noteworthy, some renal lesions that are composed of normal parenchyma, the cause of which is assumed to be compensatory hypertrophy, mimic renal tumors on imaging.2 We describe a rare case of renal pseudotumor, which was assumed to have resulted from regional sparing in the development of chronic glomerulonephritis.
CASE REPORT A 17-year-old, previously healthy male student presented to a local hospital with the reports of abdominal pain and diarrhea. Two days later, he developed anuria with systemic edema. Initial laboratory investigations showed the following: serum creatinine 29.8 mg/dL, blood urea nitrogen 239 mg/dL, aspartase aminotransferase 1193 IU/L, alanine aminotransferase 1114 IU/L, white blood count 21,900/L, red blood count 238/L, and platelet 17.3/ L. With signs of multi-organ failure, he was transferred to our hospital the same day. Coagulo-fibrinolytic testing showed moderately prolonged prothrombin time (25.1 seconds) and activated partial thromboplastin time (43.7 seconds) and increased levels of fibrinogen degradation product (88.4 g/mL) and fibrinogen (359 mg/dL). Urinalysis showed 3⫹ proteinuria, with a normal range of From the Department of Urology, Jichi Medical University, Tochigi, Japan Reprint requests: Minoru Kobayashi, M.D., Department of Urology, Jichi Medical University, 3311-1, Yakushiji, Shimotsuke-shi, Tochigi, 329-0498, Japan. E-mail: [email protected] Submitted: September 22, 2007, accepted (with revisions): December 3, 2007
© 2008 Elsevier Inc. All Rights Reserved
microscopic hematuria. Chest radiography showed an enlarged cardiac shadow with an enlarged vascular shadow in the lung field, suggesting cardiopulmonary congestion, which resulted in congestive liver damage. Thus, the clinical manifestations and laboratory data were compatible with coincident acute renal failure with disseminated intravascular coagulation (DIC). The patient was treated with continuous intravenous infusion of nafamostat mesylate (80 mg/day) for DIC. Because both kidneys were atrophic on ultrasonography, no medical treatment for acute renal failure was administered and only hemodialysis was performed. Abdominal computed tomography further revealed the presence of a round isodense mass in the middle of the right kidney. Magnetic resonance image confirmed a well-defined mass 3.5 ⫻ 5 cm in size, which had slightly higher signal intensity on T1 and T2-weighted images and identical enhancement to that of the renal parenchyma (Fig. 1A). Based on the clinical background of anuria of unknown etiology and radiologic findings suggestive of renal cell carcinoma, we performed a right nephrectomy 11 weeks after the onset of acute renal failure. The postoperative course was uneventful, although the patient required permanent hemodialysis.
HISTOPATHOLOGIC EXAMINATION Gross examination disclosed the absence of a tumor, although we observed an area with a thickened cortex in the middle kidney in accordance with the imaging findings. Microscopic examination of what appeared to be a tumorous lesion on imaging revealed that the nephrons were relatively preserved in contrast with intensive sclerotic changes in the surrounding parenchyma (Fig. 1B and C). This lesion involved glomeruli by cellular or fibrous crescent changes. Tubular epithelium showed hyaline droplet degeneration. In the surrounding atrophic 0090-4295/08/$34.00 461.e15 doi:10.1016/j.urology.2007.12.006
Figure 1. (A) Gadolinium-enhanced magnetic resonance image shows a well-defined mass with identical enhancement in the tumorous area to that of the renal parenchyma. (B) Histopathology of the resected specimen. Nephrons in the lesion with a tumorous appearance on imaging are relatively preserved compared with the surrounding area (original magnification ⫻100). (C) Sclerotic changes with inflammatory cells are outstanding in the surrounding area (original magnification ⫻200).
renal parenchyma, we observed chronic inflammatory cell infiltration. Furthermore, periodic acid-methenamine-silver staining combined with Masson trichrome staining showed that immune depots were scattered in the mesangium and partly present along the capillary walls. Collectively, we suspected membranoproliferative glomerulonephritis that developed into nephrosclerosis. Accordingly, we considered that the tumorous lesion shared a fundamental pathogenesis with the surrounding area, despite the different degrees of histologic change.
DISCUSSION A number of masses composed of normal or benign renal tissue can mimic renal neoplasm. For example, renal cysts and some renal abscesses may be confidently diagnosed radiologically and managed conservatively. Unfortunately, not a few uncommon lesions mimic neoplasia so closely that they are inevitably resected because of diagnostic uncertainty and concern about potential malignancy. We report a case of chronic glomerulonephritis with demarcated enlargement mimicking a renal tumor. From the histologic findings in the entire resected specimen, we assumed that a regional parenchyma with nephrons that were comparatively spared relative to the observed sclerotic changes had exaggerated perfusion and simulated a tumor. This is an extremely uncommon manifestation of chronic glomerulonephritis. To our knowledge, only Depner et al. have reported a similar case,2 which 461.e16
represented a variant of unilateral glomerulonephritis with sparing of a segment of one kidney and subsequent compensatory hypertrophy in the remaining parenchymal atrophy, which showed tumor-like expansion on renal arteriography. However, because a biopsy sample was obtained only from the contralateral kidney showing glomerulonephritis, the contention that the observed mass lesion resulted from segmental compensatory hypertrophy was not supported histologically. Therefore, we believe that the current case is the first to show the etiology of a unique case of chronic glomerulonephritis as a pseudotumor by meticulous histologic examination of the entire resected specimen. Taken together, segmental or regional sparing and subsequent hypertrophy in non-uniform parenchymal atrophy could be another manifestation of renal pseudotumors. This type of morbidity can result from several underlying pathologies. First, chronic pyelonephritis involves the kidney in a patchy distribution often resulting in irregular cortical outlines with skip areas and focal scarring and simulating renal tumor.3 Second, severe hypertension can lead to uneven attenuation in size resulting from arteriolar nephrosclerosis.4 Third, cortical necrosis resulting from severe ischemia or intravascular coagulation is also a patchy process. Finally, diffuse cortical atrophy is caused most commonly by uniform chronic glomerulonephritis involving both kidneys, which thereby leads to smooth cortical outlines. However, unilateral glomerulonephritis, which might be induced by some protective mechanism sparing a segment UROLOGY 72 (2), 2008
of the kidney, would result in a non-uniform image as in the current case.5,6 In conclusion, the current case is a striking example of the development of regional sparing that simulated a tumor on imaging in the rapid process of chronic glomerulonephritis. Surgeons should be aware of this rare entity of renal pseudotumor to avoid unnecessary surgery. References 1. Bhatt S, MacLennan G, and Dogra V: Renal pseudotumors. AJR 188: 1380-1387, 2007.
UROLOGY 72 (2), 2008
2. Depner TA, Ryan KG, and Yamauchi H: Pseudotumor of the kidney: a sequel to regional glomerulonephritis. AJR 126: 1197-1202, 1976. 3. Kitamura M, Miyanaga T, Sato Y, et al: A case of renal pseudotumor caused by pyelonephritis. Hinyokika Kiyo 40: 241-243, 1994. (Japanese). 4. Mena E, Bookstein JJ, and Gikas PW: Angiographic diagnosis of renal parenchymal disease: chronic glomerulonephritis, chronic pyelonephritis, and arteriolonephrosclerosis. Radiology 108: 523-532, 1973. 5. Dikman SH, Strauss L, Berman LJ, et al: Unilateral glomerulonephritis. Arch Pathol Lab Med 100: 480-483, 1976. 6. Salyer WR, and Salyer DC: Unilateral glomerulonephritis. J Pathol 113: 247-251, 1974.
461.e17
M
any renal lesions that mimic renal neoplasms on imaging are observed at subsequent surgery and histopathologic evaluation to have been incorrectly diagnosed. These masses may be composed of normal or benign renal tissue and are referred to as renal pseudotumors. These lesions arise from many conditions that are developmental, infectious, granulomatous, and vascular in nature.1 Especially noteworthy, some renal lesions that are composed of normal parenchyma, the cause of which is assumed to be compensatory hypertrophy, mimic renal tumors on imaging.2 We describe a rare case of renal pseudotumor, which was assumed to have resulted from regional sparing in the development of chronic glomerulonephritis.
CASE REPORT A 17-year-old, previously healthy male student presented to a local hospital with the reports of abdominal pain and diarrhea. Two days later, he developed anuria with systemic edema. Initial laboratory investigations showed the following: serum creatinine 29.8 mg/dL, blood urea nitrogen 239 mg/dL, aspartase aminotransferase 1193 IU/L, alanine aminotransferase 1114 IU/L, white blood count 21,900/L, red blood count 238/L, and platelet 17.3/ L. With signs of multi-organ failure, he was transferred to our hospital the same day. Coagulo-fibrinolytic testing showed moderately prolonged prothrombin time (25.1 seconds) and activated partial thromboplastin time (43.7 seconds) and increased levels of fibrinogen degradation product (88.4 g/mL) and fibrinogen (359 mg/dL). Urinalysis showed 3⫹ proteinuria, with a normal range of From the Department of Urology, Jichi Medical University, Tochigi, Japan Reprint requests: Minoru Kobayashi, M.D., Department of Urology, Jichi Medical University, 3311-1, Yakushiji, Shimotsuke-shi, Tochigi, 329-0498, Japan. E-mail: [email protected] Submitted: September 22, 2007, accepted (with revisions): December 3, 2007
© 2008 Elsevier Inc. All Rights Reserved
microscopic hematuria. Chest radiography showed an enlarged cardiac shadow with an enlarged vascular shadow in the lung field, suggesting cardiopulmonary congestion, which resulted in congestive liver damage. Thus, the clinical manifestations and laboratory data were compatible with coincident acute renal failure with disseminated intravascular coagulation (DIC). The patient was treated with continuous intravenous infusion of nafamostat mesylate (80 mg/day) for DIC. Because both kidneys were atrophic on ultrasonography, no medical treatment for acute renal failure was administered and only hemodialysis was performed. Abdominal computed tomography further revealed the presence of a round isodense mass in the middle of the right kidney. Magnetic resonance image confirmed a well-defined mass 3.5 ⫻ 5 cm in size, which had slightly higher signal intensity on T1 and T2-weighted images and identical enhancement to that of the renal parenchyma (Fig. 1A). Based on the clinical background of anuria of unknown etiology and radiologic findings suggestive of renal cell carcinoma, we performed a right nephrectomy 11 weeks after the onset of acute renal failure. The postoperative course was uneventful, although the patient required permanent hemodialysis.
HISTOPATHOLOGIC EXAMINATION Gross examination disclosed the absence of a tumor, although we observed an area with a thickened cortex in the middle kidney in accordance with the imaging findings. Microscopic examination of what appeared to be a tumorous lesion on imaging revealed that the nephrons were relatively preserved in contrast with intensive sclerotic changes in the surrounding parenchyma (Fig. 1B and C). This lesion involved glomeruli by cellular or fibrous crescent changes. Tubular epithelium showed hyaline droplet degeneration. In the surrounding atrophic 0090-4295/08/$34.00 461.e15 doi:10.1016/j.urology.2007.12.006
Figure 1. (A) Gadolinium-enhanced magnetic resonance image shows a well-defined mass with identical enhancement in the tumorous area to that of the renal parenchyma. (B) Histopathology of the resected specimen. Nephrons in the lesion with a tumorous appearance on imaging are relatively preserved compared with the surrounding area (original magnification ⫻100). (C) Sclerotic changes with inflammatory cells are outstanding in the surrounding area (original magnification ⫻200).
renal parenchyma, we observed chronic inflammatory cell infiltration. Furthermore, periodic acid-methenamine-silver staining combined with Masson trichrome staining showed that immune depots were scattered in the mesangium and partly present along the capillary walls. Collectively, we suspected membranoproliferative glomerulonephritis that developed into nephrosclerosis. Accordingly, we considered that the tumorous lesion shared a fundamental pathogenesis with the surrounding area, despite the different degrees of histologic change.
DISCUSSION A number of masses composed of normal or benign renal tissue can mimic renal neoplasm. For example, renal cysts and some renal abscesses may be confidently diagnosed radiologically and managed conservatively. Unfortunately, not a few uncommon lesions mimic neoplasia so closely that they are inevitably resected because of diagnostic uncertainty and concern about potential malignancy. We report a case of chronic glomerulonephritis with demarcated enlargement mimicking a renal tumor. From the histologic findings in the entire resected specimen, we assumed that a regional parenchyma with nephrons that were comparatively spared relative to the observed sclerotic changes had exaggerated perfusion and simulated a tumor. This is an extremely uncommon manifestation of chronic glomerulonephritis. To our knowledge, only Depner et al. have reported a similar case,2 which 461.e16
represented a variant of unilateral glomerulonephritis with sparing of a segment of one kidney and subsequent compensatory hypertrophy in the remaining parenchymal atrophy, which showed tumor-like expansion on renal arteriography. However, because a biopsy sample was obtained only from the contralateral kidney showing glomerulonephritis, the contention that the observed mass lesion resulted from segmental compensatory hypertrophy was not supported histologically. Therefore, we believe that the current case is the first to show the etiology of a unique case of chronic glomerulonephritis as a pseudotumor by meticulous histologic examination of the entire resected specimen. Taken together, segmental or regional sparing and subsequent hypertrophy in non-uniform parenchymal atrophy could be another manifestation of renal pseudotumors. This type of morbidity can result from several underlying pathologies. First, chronic pyelonephritis involves the kidney in a patchy distribution often resulting in irregular cortical outlines with skip areas and focal scarring and simulating renal tumor.3 Second, severe hypertension can lead to uneven attenuation in size resulting from arteriolar nephrosclerosis.4 Third, cortical necrosis resulting from severe ischemia or intravascular coagulation is also a patchy process. Finally, diffuse cortical atrophy is caused most commonly by uniform chronic glomerulonephritis involving both kidneys, which thereby leads to smooth cortical outlines. However, unilateral glomerulonephritis, which might be induced by some protective mechanism sparing a segment UROLOGY 72 (2), 2008
of the kidney, would result in a non-uniform image as in the current case.5,6 In conclusion, the current case is a striking example of the development of regional sparing that simulated a tumor on imaging in the rapid process of chronic glomerulonephritis. Surgeons should be aware of this rare entity of renal pseudotumor to avoid unnecessary surgery. References 1. Bhatt S, MacLennan G, and Dogra V: Renal pseudotumors. AJR 188: 1380-1387, 2007.
UROLOGY 72 (2), 2008
2. Depner TA, Ryan KG, and Yamauchi H: Pseudotumor of the kidney: a sequel to regional glomerulonephritis. AJR 126: 1197-1202, 1976. 3. Kitamura M, Miyanaga T, Sato Y, et al: A case of renal pseudotumor caused by pyelonephritis. Hinyokika Kiyo 40: 241-243, 1994. (Japanese). 4. Mena E, Bookstein JJ, and Gikas PW: Angiographic diagnosis of renal parenchymal disease: chronic glomerulonephritis, chronic pyelonephritis, and arteriolonephrosclerosis. Radiology 108: 523-532, 1973. 5. Dikman SH, Strauss L, Berman LJ, et al: Unilateral glomerulonephritis. Arch Pathol Lab Med 100: 480-483, 1976. 6. Salyer WR, and Salyer DC: Unilateral glomerulonephritis. J Pathol 113: 247-251, 1974.
461.e17