黄色肉芽肿性肾盂肾炎的超声特征

Ultrasonographic Features of Focal Xanthogranulomatous PyelonephritisJongchul Kim, MDObjective.T o analyze the ultrasonographic features of focal xanthogranulomatous pyelonephritis.Methods.Ultrasonographic features of 15 patients with pathologically proved focal xanthogranulo-matous pyelonephritis were retrospectively analyzed by 2 radiologists who reached a consensus, in terms of the location, margin, size, and echo texture of the mass, associated calculi, lymphadenopa-thy, or local extension, in comparison with computed tomographic and clinical findings. Results.At ultrasonography, 12 (80%) of 15 masses were well circumscribed. The maximal sizes of the masses ranged from 2.5 to 5.8 (mean, 3.8) cm. Thirteen solid masses (87%) were hyperechoic (n = 7), hypoe-choic (n = 4), or isoechoic (n = 4) to the renal cortex, and the preoperative diagnosis was either renal cell carcinoma (n = 11) or Wilms tumor (n = 2). The preoperative diagnosis of the other 2 cystic lesions (13%) was renal abscess. Renal calculi were found in 1 case, but lymphadenopathy or local extension was not depicted. Clinical inflammatory signs were found in 11 of 15 patients. Conclusions.There were no specific ultrasonographic features that allow for the distinction between focal xanthogranu-lomatous pyelonephritis and renal tumors or abscesses. Focal xanthogranulomatous pyelonephritis should be considered when there are clinical signs of infection or inflammation and a focal solid mass is seen on ultrasonography. Key words:inflammation; kidney; ultrasonography.Received September 2, 2003, from the Department of Diagnostic Radiology, College of Medicine,Chungnam National University, Daejeon, South Korea. Revision requested September 15, 2003.Revised manuscript accepted for publication September 24, 2003.Address correspondence and reprint requests to Jongchul Kim, MD, Department of Diagnostic Radiology, Chungnam National University Hospital,640 Daesa-dong, Jung-ku, Daejeon 301-721, South Korea.E-mail: jckim@cnuh.co.kr.AbbreviationsCT , computed tomography; ESR, erythrocyte sedimenta-tion rate; MR, magnetic resonance; RCC, renal cell car-cinoma; XGP , xanthogranulomatous pyelonephritisanthogranulomatous pyelonephritis (XGP) is a relatively uncommon form of renal granuloma-tous inflammatory disease characterizedhistopathologically by the presence of lipid-laden macrophages (xanthoma cells), as well as other inflammatory cells, including plasma cells, leukocytes,and histiocytes.1T wo forms of XGP , a diffuse form (85%)and a focal (localized, segmental) form (15%), are well known, and the latter is sometimes referred to as the “tumefactive” form of XGP because the findings are more easily confused with a renal tumor.1–8The definitive diag-nosis of focal XGP is most often recognized after histolog-ic examination of the surgical specimen.9Although surgery is considered the only effective treatment of focal XGP , a high index of suspicion of XGP may prevent radical nephrectomy.10Therefore, it may be helpful and useful in© 2004 by the American Institute of Ultrasound in Medicine • J Ultrasound Med 23:409–416, 2004 • 0278-4297/04/$3.50Xclinical fields to know whether there are any characteristic imaging findings more favorable to focal XGP rather than, for example, renal tumors. Ultrasonography is commonly used in the diag-nosis of renal lesions as a primary imaging tool. The purpose of this study was to analyze the ultrasonographic features of focal XGP. Materials and MethodsBetween January 4, 1986, and June 28, 2003, 15 cases of pathologically proved focal XGP were collected at our hospital and at other associated institutions. After clinical examination with imaging studies by ultrasonography, the patients underwent total (n = 13) or partial (n = 2) nephrectomy. In the latter 2 patients, an area of focal disease was identified as an abnormality on ultrasonography, which was confirmed as XGP by biopsy, and a limited resection was performed to remove the focal area of inflammation. Renal ultrasonography was performed with 3.5- and 5-MHz transabdominal probes of an SL-2 system (Siemens Medical Solutions, Erlangen, Germany), a D RF 400 system (D iasonics, Milpitas, CA), and SSD-630, SSD-650, and SSD-280 systems (Aloka Co, Ltd, T okyo, Japan); 3.5-and 4-MHz transducers of Acuson 128XP and Sequoia systems (Siemens Medical Solutions); a 4- to 7-MHz convex probe of an Ultramark 9 HDI system (Philips Medical Systems, Bothell, WA); and a 2- to 4-MHz curved probe of an HDI 3000 system (Philips Medical Systems). Computed tomography (CT) was also performed in all patients with a HiSpeed Advantage CTi Standard system (GE Medical Systems, Milwaukee, Wisconsin) or a Somatom Plus VD30 system (Siemens Medical Solutions). After precontrast abdominal CT, postcontrast CT scanning with an 8- to 10-mm slice interval was done by bolus injection of iopromide (Ultravist 300; Schering AG, Berlin, Germany; 0.6234 g/mL, 140–150 mL). The ultrasonographic features of the 15 patients were retrospectively analyzed by 2 radi-ologists who reached a consensus. Renal lesions were retrospectively evaluated in terms of their location, margin based on the degree of demar-cation from surrounding renal parenchyma, maximal size, echogenicity based on comparison with the renal cortex, signs of perinephric involvement, signs of metastatic disease such as lymphadenopathy or venous invasion, and asso-ciated calculi or hydronephrosis.The hospital records of all patients were retro-spectively examined in detail, and the patients were checked for clinical symptoms and signs. ResultsThere were 13 adults and 2 children younger than 15 years and 10 male and 5 female patients (age range, 6–57 years; mean age, 39 years). The right kidney was affected in 8 (53%) of the 15 patients.On review of hospital records, the positive find-ings on initial clinical and laboratory examina-tions were found to be flank pain in 10 patients, fever in 11, leukocytosis in 9, pyuria in 8, anemia in 9, a raised erythrocyte sedimentation rate (ESR) in 10, and positive urine culture results in 5. Of the 5 patients with positive urine culture results, Proteus mirabilis grew in 2, Escherichia coli grew in 2, and a mixture of these 2 bacteria grew in the remaining patient. Ultrasonography depicted that 12 (80%) of 15 masses were well circumscribed (Figures 1–3) and were confined within the renal outline. Eight masses were based in the cortex (Figures 1 and 3), and the other 7 were based more centrally near the renal sinus (Figure 2). The maximal sizes of the masses ranged from 2.5 to 5.8 (mean, 3.8) cm. Of 15 masses, 13 (87%) were solid, and 2 were cystic. The predominant echogenicity of the solid lesions was hypere-choic to the renal cortex in 7, hypoechoic in 4, and isoechoic in 4. There were no masses that were as echogenic as renal sinus fat. The 13 solid masses included 10 (77%) with inner hypoe-choic or anechoic foci and 3 without inner hypoechoic or anechoic foci, and the preopera-tive clinical diagnoses were renal cell carcinoma (RCC) in 11 cases (Figure 1) and Wilms tumor (Figure 2) in 2 cases. Ultrasonography depicted no evidence of perirenal or vascular (eg, renal vein and inferior vena cava) involvement or local or distant lymphadenopathy in any case. In the other 2 cystic masses, ultrasonography depicted mainly anechoic renal lesions with thick and irregular walls, suggesting the preop-erative diagnosis of renal abscess (Figure 3). A focal bulge of renal contour adjacent to the mass was not noted in any case except 1 large mass of 5.8 cm in maximal diameter. Renal cal-culi were found as highly echogenic foci with clean posterior acoustic shadowing in the periphery of the solid mass in 1 case.410J Ultrasound Med 23:409–416, 2004 Focal Xanthogranulomatous PyelonephritisOn noncontrast abdominal CT , the density of the 13 solid masses compared with surrounding normal renal parenchyma was slightly lower in 2J Ultrasound Med 23:409–416, 2004411KimCA412J Ultrasound Med 23:409–416, 2004Focal Xanthogranulomatous PyelonephritisBA DCJ Ultrasound Med 23:409–416, 2004413KimBAquent peritumoral halo, intratumoral cyst, and calcification in small RCC,1the infrequency of these findings in our focal XGP cases may play a certain role in the differentiation of these 2 renal parenchymal lesions. Most Wilms tumors are expansile masses with well-circumscribed peripheral margins due to the formation of a sur-rounding pseudocapsule composed of fibrous tissue and compressed adjacent normal parenchyma. Occasionally, an infiltrative pattern of growth is seen. A Wilms tumor is typically a predominantly solid but heterogeneous tumor on ultrasonography. The echogenicity is variable; in tumors with areas of necrosis, hypoechoic and anechoic areas may be seen. Calcification or invasion of the renal vein and inferior vena cava may also occur.13Absence of perirenal involve-ment, local or distant lymphadenopathy, distant metastases, a focal renal contour bulge, and vas-cular invasion in our focal XGP cases may also suggest some hints to differentiate a large focal XGP from a large RCC or Wilms tumor. In our study, the predominant echogenicity of the solid lesions was hyperechoic (n = 7), hypoechoic (n = 4), or isoechoic (n = 4) to the renal cortex, and there were no masses that were as echogenic as renal sinus fat. The classification of the predomi-nant echogenicity of the solid lesions of XGP was not found in other reports describing ultrasono-graphic features of focal XGP.6,10,12In our study, however, focal XGP appeared as very nonspecific masses, and there was extensive overlap between the ultrasonographic features of focal XGP and those of renal tumors or abscesses.Co mputed tomography, which is considered the imaging modality of choice, reveals the XGP lesion, but differential diagnosis from hydronephrosis or pyonephrosis, malako-plakia, lymphoma, and especially renal neo-plasms is sometimes difficult.11Computed tomographic features that have been consid-ered characteristic of (but not pathognomonic for) XGP (especially in th e diffuse form) are renal enlargement, strands in perinephric fat, thicken-ing of the Gerota fascia, and thick enhancing septa in the hypodense areas in renal parenchy-ma.12Round or egg-shaped areas of water densi-ty representing dilated calyces and abscess cavities with pus and debris in diffuse XGP may be described as the “bear paw sign.”12Computed tomography usually depicts focal XGP as a clear-ly or poorly defined localized intrarenal mass with fluidlike attenuation,1,3,13as in our cases.There are not many data about magnetic reso-nance (MR) imaging findings in the focal form of XGP,3,4,13,15and we have no experience with MR imaging in XGP. According to a report by Cakmakci et al,3the focal mass had slightly low signal intensity on transverse relaxation time–weighted imaging (probably because of fluid with very high protein content) and was isointense with the renal parenchyma on longi-tudinal relaxation time–weighted imaging. They found that the findings of absent high signal intensity on transverse relaxation time–weight-ed imaging and long-standing low signal inten-sity compared with the renal cortex during the whole course of the dynamic MR imaging study were useful in the differentiation of XGP from RCC. The different signal intensity of the solid component of XGP on longitudinal relaxation time–weighted imaging, compared with the renal parenchyma, seems to depend on the amount of xanthoma cells involved in the granu-lomatous process.4None of our patients, howev-er, underwent MR imaging.The treatment of focal XGP is still controversial. Partial nephrectomy, however, has been tried in the treatment of focal XGP.12–14Quinn et al12said that, “In the relatively rare cases where the focal form of XGP is found, which involves only a sin-gle pole of the kidney, it might be possible to carry out a partial nephrectomy. It is generally accepted that once the diseased kidney has been removed the future prognosis for the affected child is excellent.” Anezinis et al13insisted that focal XGP could appear as a pseudotumoral cys-tic lesion, suggesting that XGP in such cases might be useful to the surgeon to plan an organ-sparing procedure. Osca et al14insisted that,“When focal XGP is diagnosed, local excision such as partial nephrectomy is recommended, since relapse in the affected kidney is unusual.”There also are reports of a few patients who recovered from the disease after administration of antibiotic therapy.10,16Thus, although surgery is considered as the only effective treatment of this disease, a high index of suspicion on the basis of clinical and imaging findings may pre-vent radical nephrectomy.Our retrospective study has some limitations. The number of cases, 15, is not sufficient to be statistically significant. There were no patients who underwent MR imaging. Because our 15 cases were collected not only from our hospital but also from many other associated institutions,414J Ultrasound Med 23:409–416, 2004 Focal Xanthogranulomatous Pyelonephritisultrasonographic imaging standards and tech-niques were not constant among the many oper-ators performing ultrasonography.The characteristics of the condition that might help in a preoperative diagnosis of dif-fuse or focal XGP include the following: the disease is usually unilateral (although very rare bilateral cases have been reported); renal func-tion is absent or grossly impaired on the involved side, especially in diffuse XGP; large, often numerous, renal calculi, including staghorn calculi, with or without hydronephro-sis are present, especially in diffuse XGP; and anemia, a raised ESR, and leukocytosis are often present.12Usually, typical solid tumors of the kidney such as RCC or Wilms tumor would not present with infection. However, if inflam-matory signs are few or absent and a history of urinary tract infection or a stone is absent, the preoperative diagnosis of XGP as differentiated from typical solid renal tumors may be very dif-ficult. Accurate diagnosis of the XGP is usually not achieved preoperatively because symp-toms are not specific and pathognomonic lab-oratory tests are not available. Although the diagnosis of XGP is mainly achieved histologi-cally, a suggestive preoperative diagnosis and determination of the extent of the lesion by ultrasonography, CT, MR imaging, or any com-bination could allow less radical surgery in selected focal XGP cases. D espite the protean clinical and imaging manifestations of focal XGP, awareness of the possibility of this condi-tion occurring in adults and children may allow early recognition and possible treatment.In conclusion, there are no specific ultra-sonographic features that allow for the distinc-tion between the solid form of focal XGP and renal tumors, and there is no way to distin-guish the cystic form of focal XGP from a renal abscess. Focal XGP should be considered when there are clinical signs of infection or inflammation and a focal solid mass is seen on ultrasonography.References1.Dunnick NR, Sandler CM, Amis ES Jr, Newhouse JH.Renal inflammatory disease. In: Dunnick NR, Sandler CM, A mis ES Jr, Newhouse JH (eds). T extbook of Uroradiology. 2nd ed. Baltimore, MD: Williams & Wilkins; 1997:163–189.2.Zorzos I, Moutzouris V, Petraki C, Katsou G.Xanthogranulomatous pyelonephritis: the “great imitator” justifies its name. 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