AJR 2004; 183:1703-1705
© American Roentgen Ray Society
Malacoplakia Presenting as a Solitary Renal Mass
Aaron J. Wielenberg1,
Terrence C. Demos1,
Bhanu Rangachari1 and
Thomas Turk2
1 Department of Radiology, Loyola University Medical Center, 2160 S First Ave.,
Maywood, IL 60153.
2 Department of Urology, Loyola University Medical Center, Maywood, IL.
Received January 9, 2004;
accepted after revision February 7, 2004.
Address correspondence to T. C. Demos
(tdemos{at}lumc.edu).
Introduction
Malacoplakia, a rare granulomatous inflammatory disease characterized by
pathognomonic intracytoplasmic Michaelis-Gutmann bodies, was first reported as
a lesion of the urinary bladder in 1902. Until the 1950s, this disease was
thought to occur exclusively in the urinary tract. Malacoplakia, however,
affects many other organ systems including the gastrointestinal tract, bone,
lungs, lymph nodes, and skin. The urinary tract is most frequently involved,
and all parts of the urinary tract can be affected. In a 1981 review of 153
cases, 89 (58%) had involvement of the urinary tract and 63 (40%) had bladder
lesions. The next most common site was the kidney (16%)
[1]. Sixty-two cases of renal
involvement were found in a review published in 1993
[2]. Renal lesions are most
often multifocal and frequently involve both kidneys. We report a case of
malacoplakia in a 37-year-old man who presented with a complicated cystic
renal lesion that increased in size over the 2 years that he was monitored
using CT.
Case Report
A 37-year-old man with no significant medical history was referred for
evaluation of an enlarging cystic renal mass that had been followed for 2
years using CT. The patient initially presented for treatment of acute
bacterial prostatitis, which subsequently resolved with antibiotic therapy. An
initial CT study of the abdomen, performed for evaluation of persistent
microscopic hematuria after this episode, showed a 2-cm, predominantly
low-attenuation lesion with a septum located in the upper pole of the left
kidney (Figs. 1A and
1B). On CT 2 years later, the
lesion had increased in size and measured 2.8 cm in diameter. The lesion was
heterogeneous with an attenuation of 27 H (Figs.
1C and
1D). Because unenhanced images
were not obtained for either study, enhancement could not be determined.
Because this lesion not only was a complicated cystic lesion but had enlarged
in the interval, the patient underwent laparoscopic radical nephrectomy, which
was performed without complication. Subsequent CT and sonography of the
abdomen and urine cultures have remained normal at 1-year follow-up.
View larger version (94K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1A. —37-year-old man with solitary complex cystic renal mass on
initial examination. Initial contrast-enhanced CT scans of abdomen show 2-cm
cystic lesion in upper pole of left kidney. Slight thickening of cyst wall is
present.
|
|
View larger version (129K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1B. —37-year-old man with solitary complex cystic renal mass on
initial examination. Initial contrast-enhanced CT scans of abdomen show 2-cm
cystic lesion in upper pole of left kidney. Slight thickening of cyst wall is
present.
|
|
View larger version (118K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1C. —37-year-old man with solitary complex cystic renal mass on
initial examination. Contrast-enhanced CT scans obtained at 2-year follow-up
show interval increase in size; lesion now measures 2.8 cm.
|
|
View larger version (108K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1D. —37-year-old man with solitary complex cystic renal mass on
initial examination. Contrast-enhanced CT scans obtained at 2-year follow-up
show interval increase in size; lesion now measures 2.8 cm.
|
|
On gross examination, the lesion was multiloculated; measured 2.5 x
1.2 x 1.2 cm; had a smooth, thickened inner lining; and contained
grossly hemorrhagic fluid. Microscopic examination of the renal parenchyma and
calices showed well-delineated aggregates of histiocytes with intracellular
round, concentric, laminar, Michaelis-Gutmann bodies positive for anions of
calcium salts using von Kossa's stain. No microorganisms were present.
Discussion
Malacoplakia is a rare granulomatous inflammatory process that affects many
organ systems including the genitourinary tract, gastrointestinal tract, bone,
lungs, lymph nodes, and skin. Aside from the urinary tract, no sex
predominance is seen. The genitourinary tract is affected most often,
particularly in immunocompromised individuals. Disease of the genitourinary
system is most common in middle-aged women (female–male ratio, 4:1),
with an average age at presentation of more than 50 years
[1]. Most patients have some
form of immunosuppression, including suppression related to solid organ
transplants, autoimmune diseases requiring steroid use, or chemotherapy. Less
severe forms of immunosuppression, such as those associated with chronic
systemic diseases, malignancy, alcohol abuse, and poorly controlled diabetes,
also play a role [1,
2].
Malacoplakia is thought to result from inadequate intracellular killing of
phagocytosed bacteria by monocytes and macrophages, leading to the
accumulation of calcium and iron on bacterial glycolipid within cellular
phagolysosomes. Gram-negative bacteria are most often associated with
malacoplakia, with Escherichia coli found in more than two thirds of
lesions [1]. It is postulated
that the inadequate killing of bacteria is related to low levels of
intracellular cyclic guanine monoamine phosphatase that result in poor
microtubular function and lysosomal killing activity
[3]. The predilection of
specific bacteria for patients with differing sources of immunosuppression
(e.g., coliform bacteria in patients undergoing chemotherapy and
Rhodococcus equi in patients with AIDS) has led to speculation that
multiple mechanisms of inhibited killing may be involved in different patient
groups [4].
Grossly, lesions consist of soft, tan–yellow plaques and nodules,
usually less than 1 cm in diameter but ranging up to 3–4 cm in diameter,
with some progressing to fulgurating or sessile masses. Histologically, the
process is characterized by conglomerations of foamy histiocytes, or von
Hansemann cells, containing distinctive basophilic inclusions with surrounding
clear halos known as Michaelis-Gutmann bodies. These inclusions are
phagolysosomes filled with undigested bacterial fragments or even intact
bacteria that may calcify. Although not necessary for the diagnosis of
malacoplakia, Michaelis-Gutmann bodies are pathognomonic for the disease and
differentiate it from two similar processes—megalocytic interstitial
nephritis and xanthogranulomatous pyelonephritis—both of which lack the
characteristic intense periodic acid–Schiff staining
[5].
Lesions caused by malacoplakia initially are identified in most patients
because of imaging studies performed for a variety of reasons, including
bladder irritability, hematuria, renal failure, or persistent urinary tract
infection despite appropriate antibiotic therapy. Unexpected lesions also may
be shown on imaging studies performed for other reasons. Bladder lesions may
be shown as nonspecific solitary or multiple filling defects on imaging
studies. The trigone often is involved, and there may be associated ureteral
obstruction. Lesions in the collecting systems and ureters are most often
multiple but can be solitary. Most are 5 mm in diameter or smaller but on
occasion may be as large as several centimeters in diameter. Strictures of the
distal ureter resulting in hydronephrosis also have been reported.
The appearance of the affected kidney on imaging studies ranges from that
of a normal kidney to an enlarged, nonfunctioning kidney. Commonly, multiple
poorly defined renal lesions enlarging the kidney and often involving both
kidneys are present. The renal lesions can distort the pelvis and calices but
seldom cause obstruction. Perinephric extension and renal vein thrombosis have
been reported [1,
2]. Focal renal lesions on
sonography usually are poorly defined and hypoechoic. CT reflects the
pathologic range of renal involvement of multifocal disease involving one or
both kidneys. Most often, renal enlargement exists with poorly defined,
variably sized solid masses. Perinephric extension and renal vein thrombosis
are well shown. Parenchymal calcification is rare
[2,
6]. A unifocal renal lesion is
uncommon and can resemble a necrotic renal cell carcinoma, as in the case
presented here. Neovascularity is generally absent but has been reported with
unifocal disease [2,
6].
Treatment of malacoplakia depends on the extent of disease and the
underlying condition of the patient. Patients with bilateral or multifocal
disease most often are treated with antibiotics. Ciprofloxacin is a commonly
used agent in cases involving coliform bacteria, but rifampin, doxycycline,
trimethoprim sulfate, and even vancomycin also have been used
[7]. Bethanechol also has been
used to supplement antibiotic regimens. Contributing factors also are
addressed, such as stopping immunosuppressive therapy when possible and
relieving obstructions that contribute to urinary tract infections. Patients
with disease involving both kidneys or a transplanted kidney usually have a
survival rate of less than 6 months.
With unifocal disease, surgical excision is the treatment of choice, and
patients without other risk factors generally are cured after surgical
excision [6]. A patient has
been reported who had a complicated, unifocal cystic renal mass diagnosed as
malacoplakia on the basis of a fine-needle aspirate in whom the lesion
resolved after a 1-month course of antibiotic therapy
[8].
References
- Stanton MJ, Maxted W. Malacoplakia: a study of the literature and
current concepts of pathogenesis, diagnosis and treatment. J
Urol 1981;125:139
–146[Medline]
- Dobyan DC, Truong LD, Eknoyan G. Renal malacoplakia reappraised.
Am J Kidney Dis1993; 22:243
–252[Medline]
- Shabtai M, Anaise D, Frei L, et al. Malakoplakia in renal
transplantation: an expression of altered tissue reactivity under
immunosuppression. Transplant Proc1989; 21:3725
–3727[Medline]
- Hill GS, Droz D, Nochy D. The woman who loved well but not too
wisely, or the vicissitudes of immunosuppression. Am J Kidney
Dis 2001; 37:1324
–1329[Medline]
- Esparza AR, McKay DB, Cronan JJ, Chazan JA. Renal parenchymal
malacoplakia: histologic spectrum and its relationship to megalocytic
interstitial nephritis and xanthogranulomatous pyelonephritis. Am J
Surg Pathol 1989;13:225
–236[Medline]
- Schaeffner AJ. Infections of the urinary tract. In: Walsh PC, ed.
Campbell's urology. St. Louis, MO: Elsevier,2002
: 565–566
- Van der Voort HJ, ten Velden JA, Wassenaar RP, Silberbusch J.
Malacoplakia: two case reports and a comparison of treatment modalities.
Arch Intern Med1996; 156:577
–583[Abstract]
- Kapasi H, Robertson S, Futter N. Diagnosis of renal malacoplakia by
fine needle aspiration cytology: a case report. Acta
Cytol 1998;42:1419
–1423[Medline]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
Top
Introduction
Case Report
