黃色肉芽腫性腎盂腎炎，乃一罕見慢性腎臟感染病症。因其臨床表現之多樣性，常被誤診為腎臟癌，腎結核或腎膿瘍，所以又被稱為偉大模仿者。茲報告本院兩個案例，其臨床上迥然不同之病癥，適足以展現此罕見疾病多變之特性。第一例為23歲之女性，三個月來有間歇性高燒，併左腰疼痛，因近來持續高燒轉診至本院，理學檢查發現其左腰有明顯敲叩痛，實驗室檢查有白血球過高，貧血，肝功能異常，膿尿，血尿及蛋白尿。尿液和血液培養顯示為鏈球菌感染之敗血症。經腹部電腦斷層及核子醫學腎臟造影，發現該病患有左側腎盂輸尿管結石併阻塞性尿路病變，腎膿瘍，脾臟膿瘍，腰大肌膿瘍及左側無功能腎。經過經皮穿刺引流及抗生素治療後，病患接受手術切除左腎，脾臟，並引流腰大肌膿瘍，術中並因沾粘而同時切除遠端胰臟。術後病理報告為第三期黃色肉芽腫性腎盂腎炎，合併脾臟及胰臟之感染。該病患術後除暫時性腸閉塞，並無其他主要併發症。第二例為49歲之女性，因健檢發現有微視性血尿及膿尿而求診，並無任何症狀。該病患否認有其他過往病史。病患自述近幾個月來，體重明顯減輕，且有貧血現象。觸診其左腰似有一無觸痛感之腫瘤，病患除有輕微白血球過高，嚴重貧血及高血糖外，並無其他異常。尿液及血液培養皆未發現細菌生長。影像學檢查發現該病患亦有左側腎盂輸尿管結石併嚴重腎積水，及產氣性感染，並疑有腎局部腫瘤。經過經皮穿刺引流後，引流液培養出Proteus mirabilis。因無法排除腎臟癌之可能性，該病患接受左腎全切除術。術後病理報告亦為第三期黃色肉芽腫性腎盂腎炎，病患一週後順利出院。腎結石，阻塞性尿路病變，及泌尿道感染，是臨床常見之病症。上述兩案例顯示雖然黃色肉芽腫性腎盂腎炎常合併上述病症，其臨床表現卻可能極不相同，且不易與腫瘤，或其他慢性腎感染區分，故術前診斷相當困難。而可能因此嚴重延誤病患之治療，臨床醫師，在面對這些常見之臨床病症時，必須慎重考慮此一罕見疾病之可能性，以免延誤治療之時機。

Xanthogranulomatous pyelonephritis (XGPN) is a rare disease entity of chronic renal infection that, as a great imitator, is often misdiagnosed as renal cancer, renal tuberculosis, or renal abscess. We report two cases of XGPN with different manifestation: the first one presented with sepsis, renal abscess, splenic abscess, and psoas abscess; while the other one manisfested with a painless renal tumor. Both of the patients had urolithiasis, obstructive uropathy and urinary tract infection. The first case was subjected to nephrectomy, splenectomy, distal pancreaectomy, and psoas abscess drainage with an extended postoperative ileus. The second one received nephrectomy with an uneventful recovery after surgery. XGPN is often associated with urolithiasis, obstructive uropathy, and urinary tract infection, which are all common in urological practice. Clinicians facing these problems must keep this diagnosis of XGPN in mind to avoid delay in treatment that may lead to unfavorable outcomes.