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Case ReportpISSN 1738-2637 / eISSN 2288-2928J Korean Soc Radiol 2015;73(1):62-65http://dx.doi.org/10.3348/jksr.2015.73.1.62

INTRODUCTION

Malakoplakia is a rare chronic inflammatory condition that was first described by Michaelis and Gutmann in 1902. It is characterized histologically by the presence of basophilic inclu-sions within large eosinophilic macrophages (1). The urinary bladder is the most frequently involved site, but the kidney, ret-roperitoneum, testis, prostate and any other organs can also be affected (1-3). It is usually associated with Escherichia coli infec-tion and immunosuppression is a predisposing factor in most patients (1, 3). Renal malakoplakia presents with a palpable mass or flank pain, which may be usually confused with renal malig-nancy or other infectious disease (3-5). The imaging diagnosis of renal malakoplakia is difficult, and it is only proved by patho-logic findings of Michaelis-Gutmann bodies after biopsy or sur-gery. In appropriate clinical settings of a renal mass, febrile uri-nary tract infection and a history of immunosuppression, the

differential diagnosis should include renal abscess, xanthogran-ulomatous pyelonephritis, renal malakoplakia and renal cell car-cinoma (6). Ninety-six cases of renal malakoplakia were found by searching the MEDLINE data base in a report published in 2004 (4). In Korea, there have been 10 case reports of renal mal-akoplakia, including 3 cases with extension to adjacent organ (5). Here, we reported a case of renal malakoplakia with wide retroperitoneal extension with emphasis on imaging findings.

CASE REPORT

A 78-year-old woman was hospitalized in our institution be-cause of right flank pain aggravated by moving for 5 days before admission. She had a history of long-standing rheumatoid ar-thritis and had been taking prednisolone, 5 mg daily for 12 years. On physical examination, right side abdominal tender-ness was elicited. Laboratory tests revealed blood urea nitrogen

Renal Malakoplakia with Wide Extension into the Retroperitoneum: A Case Report광범위한 후복막강 침범을 동반한 신 실질 연반증: 1예 보고

Soo Yeon Choi, MD1, Deuk Jae Sung, MD1, Na Yeon Han, MD1, Beom Jin Park, MD1, Min Ju Kim, MD1, Ki Choon Sim, MD1, Sung Bum Cho, MD1, Yoo Jin Lee, MD2

Departments of 1Radiology, 2Pathology, Anam Hospital, College of Medicine, Korea University, Seoul, Korea

Malakoplakia is a rare chronic inflammatory condition that results from defective phagolysosomal activity. Malakoplakia usually affects the urinary tract, and immuno-suppression is a predisposing factor in most patients. A 78-year-old woman under-going long-term steroid treatment presented with right flank pain. CT demonstrated a large, multilocular cystic mass with focal enhancing solid portion in the right kid-ney and retroperitoneum. The patient underwent ultrasonography-guided biopsy for enhancing the solid portion, and pathologic examination revealed malakoplakia.

Index termsMalakoplakiaKidneyRetroperitoneal SpaceComputed TomographyAnti-Bacterial Agents

Received February 16, 2015Accepted April 21, 2015Corresponding author: Deuk Jae Sung, MDDepartment of Radiology, Anam Hospital, College of Medicine, Korea University, 73 Inchon-ro, Seongbuk-gu, Seoul 136-705, Korea.Tel. 82-2-920-5578 Fax. 82-2-929-3796E-mail: urorad@gmail.com

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distri-bution, and reproduction in any medium, provided the original work is properly cited.

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of 34.2 mg/dL, serum creatinine of 0.97 mg/dL, white blood cell (WBC) count of 27400/μL, erythrocyte sedimentation rate of 31 mm/hr and C-reactive protein 157.16 mg/L, suggesting an acute infectious process. Urine analysis revealed pyuria (30–60 WBC/high power field) and urine culture was positive for Esch-erichia coli.

CT examination showed a large, multilocular cystic mass in right kidney and perirenal space with irregular and thick wall

and septa, extending into the right retroperitoneum, bare area and right psoas muscle. Focal enhancing solid portion was dem-onstrated at the cystic mass in the right kidney (Fig. 1A, B). There was no abnormality along the upper urinary collecting system and the bladder. The complicated cystic lesion was ini-tially considered most likely as an abscess involving right kidney and retroperitoneum. So, ultrasonography (US)-guided aspira-tion was performed to confirm the presence of turbid gray-col-

Fig. 1. Renal malakoplakia with wide retroperitoneal extension in a 78-year-old woman. Axial (A) and coronal (B) contrast enhanced CT scan shows a large multilocular cystic mass with irregular wall and septa (arrowheads) in right kidney and perirenal space. The mass extends into the right retroperitoneum, bare area and right psoas muscle. Focal enhancing solid portion is demonstrated in the right kidney (arrow). On follow-up CT scan (C) obtained after 4 months with antibiotic treatment, the complicated cystic le-sion is markedly reduced. And the enhancing solid portion is also decreased in size (curved arrow).

A B C

Fig. 2. Photomicrographs of malakoplakia. A. There are many scattered histiocytes (von Hansemann cells) containing intracytoplasmic lamellated basophilic inclusions, called Michaelis-Gutmann bodies (black arrows) (× 1000).B. A von Kossa stain highlights numerous Michaelis-Gutmann bodies (× 200).

A B

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ored pus, and percutaneous abscess drainage was attempted im-mediately. Escherichia coli were identified from the aspirated fluid, and the patient was given IV antibiotic therapy for 3 weeks. On follow-up CT, the complicated cystic lesion decreased in size, but the enhancing solid portion was present without inter-val change. Then, we performed US-guided biopsy for the en-hancing solid portion to exclude the possibility of malignancy. Diagnosis of malakoplakia was based on the numerous michae-lis-Gutmann bodies within the histiocytes on pathologic exami-nation (Fig. 2). Subsequently, the patient’s general condition had improved, and she was discharged after more than 3 weeks of continuous antibiotic therapy. On the latest CT scan, 4 months af-ter treatment, the enhancing solid portion was decreased in size (Fig. 1C).

DISCUSSION

Malakoplakia is a rare chronic granulomatous benign disease. It may affect any organ of the body but primarily affects the genitourinary tract (1). Other locations include the retroperito-neum, gastrointestinal tract, central nervous system, female geni-tal tract, lung, pleura, pancreas, spleen, lymph node, adrenal gland, and vertebra (1-3). Most patients have positive urine cul-tures, usually with Gram-negative bacteria and a predisposition to immunosuppression such as solid organ transplantation, au-toimmune disease requiring long-term steroid use, chemothera-py, malignancy, alcohol abuse and diabetes mellitus (1, 3).

Malakoplakia results from defective phagolysosomal activity with incomplete bacteria digestion, mostly Escherichia coli and Klebsiella, by macrophages and monocytes. Bacterial debris ac-cumulates in the cytoplasm of these cells and usually becomes mineralized. This leads to basophilic inclusion structures with surrounding clear halos i.e., Michaelis-Gutmann bodies, which are pathognomonic for diagnosis (1, 3, 5).

There is a peak incidence in the fifth to seventh decades at pre-sentation and a female predominance with a female to male ra-tion of 4:1 (1, 2). Even though the symptoms may vary accord-ing to the affected organ, malakoplakia is commonly associated with urinary tract infections, including acute renal failure in re-nal malakoplakia (3).

In most patients with malakoplakia, lesions are initially iden-tified at imaging studies in various clinical settings, including

an abdominal mass, hematuria, renal failure, bladder irritability or persistent urinary tract infection despite appropriate antibiot-ic therapy (1-5). Imaging features of malakoplakia are nonspe-cific and variable. Malakoplakia can present as a diffuse infiltra-tive disease, sharply demarcated solitary mass, or ill-defined solid masses. The lesion demonstrates variable echogenicity at US, and mildly enhanced, heterogeneous attenuation at CT. In the case of renal parenchymal malakoplakia, imaging studies com-monly demonstrate the enlarged, irregularly contoured kidneys and dedifferentiation of corticomedullary junction. Decreased excretion of contrast is more pronounced in cases with extensive parenchymal involvement. Parenchymal calcification is rare (1, 3, 7). Perinephric extension and renal vein thrombosis have been reported (1). Magnetic resonance imaging features include poorly defined multiple low signal intensity nodules on all se-quences with intervening fibrous stroma (3, 8). Focal renal le-sions are often misdiagnosed as a malignancy such as necrotic renal cell carcinoma. In imaging studies for renal malakoplakia, differential diagnosis includes xanthogranulomatous pyelone-phritis, local abscess, granuloma, lymphoma and primary or met-astatic tumors (3, 6).

Malakoplakia rarely extends to other organs. However, the presence of malakoplakia in retroperitoneal space is almost al-ways due to direct extension from an adjacent organ, mainly uri-nary tract malakoplakia (2). Hence, we could characterize our patient as having renal malakoplakia with wide retroperitoneal extension.

There is no established treatment for malakoplakia. However, there are treatment options including antibiotics, surgical exci-sion or a combination of both (2). Successful medical manage-ment has been reported with antimicrobial agents (4, 5). Malako-plakia is a highly treatable disease when detected in its early stage. Immunosuppressive drugs should be discontinued as far as possible (3). Because renal malakoplakia may mimic renal cell carcinoma on imaging studies, a percutaneous or an open bi-opsy helps to diagnose a treatable disease and prevent unneces-sary surgery.

In conclusion, renal malakoplakia should be considered in the differential diagnosis in patients with urinary tract infection, fever, abdominal pain, and renal mass like lesion, especially in patients that have a risk factor of immunosuppression. As shown in this case, renal malakoplakia can present as extensive retro-

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peritoneal mass and often be confused with malignancy.

REFERENCES

1. Wielenberg AJ, Demos TC, Rangachari B, Turk T. Malacopla-

kia presenting as a solitary renal mass. AJR Am J Roentgen-

ol 2004;183:1703-1705

2. Radin DR, Siskind B, Weiner S, Bernstein R, Ziprkowski M.

Retroperitoneal malacoplakia. Urol Radiol 1984;6:218-220

3. Zimina OG, Rezun S, Armao D, Braga L, Semelka RC. Renal

malacoplakia: demonstration by MR imaging. Magn Reson

Imaging 2002;20:611-614

4. Kajbafzadeh A, Baharnoori M. Renal malakoplakia simulat-

ing neoplasm in a child: successful medical management.

Urol J 2004;1:218-220

5. Yoon SY, Lee HJ, An JH, Kim SJ, Kim SW, Woo JH, et al. Re-

nal parenchymal malakoplakia presenting with abscesses

and hepatic extension misdiagnosed as a malignant tumor:

a case report. Korean J Med 2012;82:764-768

6. Cury J, Coelho RF, Franco M, Srougi M. Renal parenchymal

malacoplakia with pleural effusion. Clinics (Sao Paulo) 2007;

62:87-88

7. Dharmadhikari R, Crisp A. Sequential changes in sono-

graphic appearances of childhood renal malakoplakia pro-

gressing to end-stage renal failure. J Ultrasound Med 2006;

25:1219-1222

8. Kamishima T, Ito K, Awaya H, Mitchell DG. MR imaging of

bilateral renal malacoplakia after liver transplantation. AJR

Am J Roentgenol 2000;175:919-920

광범위한 후복막강 침범을 동반한 신 실질 연반증: 1예 보고

최수연1 · 성득제1 · 한나연1 · 박범진1 · 김민주1 · 심기춘1 · 조성범1 · 이유진2

연반증은 대식세포의 탐식작용 장애로 인해 발생하는 것으로 생각되는 드문 만성 염증성 질환이다. 연반증은 주로 요로계

를 침범하며, 대부분의 환자들은 면역 저하 요인을 가지고 있다. 장기간 스테로이드를 복용한 78세 여자 환자가 우측 옆구

리 통증을 호소하였다. CT에서 우측 신장과 후복막강에 걸쳐 큰 다방성의 낭성 종괴가 관찰되었으며, 일부 조영증강 되는

고형 성분이 보였다. 환자는 초음파 유도하에 고형 성분에 대해 조직검사를 시행 받았으며, 병리적으로 연반증으로 확인되

었다.

고려대학교 의과대학 안암병원 1영상의학과, 2병리과