Malakoplakia is a rare chronic granulomatous inflammatory condition resulting from defective macrophage response to bacterial (especially E. coli) infection. The bladder is the most commonly involved organ (58-75%). Pathologically characterized by Von Hansemann cells (large eosinophilic macrophages) and Michaelis-Gutmann bodies (calcified intracellular inclusions — laminated concentric structures containing iron and calcium). Michaelis-Gutmann bodies are pathognomonic. Occurs 4:1 more frequently in women than men. Immunosuppressed patients (organ transplant, HIV, diabetes) are high-risk. Clinically presents with hematuria, dysuria, and recurrent UTI. On imaging, appears as focal or multifocal plaque-like or nodular thickening of the bladder wall and may be confused with malignant tumor. Treatment uses antibiotics (fluoroquinolones, TMP-SMX) and immunomodulatory agents (bethanechol chloride, ascorbic acid).
Age Range
40-75
Peak Age
55
Gender
Equal
Prevalence
Rare
Malakoplakia pathogenesis is based on macrophages' inability to adequately digest bacteria (especially E. coli) within their lysosomes after phagocytosis. In normal phagocytic process, bacteria are completely broken down by lysosomal enzymes. In malakoplakia, due to defective cGMP metabolism and/or lysosomal enzyme deficiency (especially beta-glucuronidase), bacterial remnants accumulate within lysosomes. Calcium and iron salts precipitate on undigested bacterial remnants → concentrically laminated Michaelis-Gutmann (MG) bodies form. MG bodies show calcium positivity with Von Kossa stain and iron positivity with Perls Prussian blue stain. Von Hansemann cells are large eosinophilic macrophages filled with bacterial debris and MG bodies. This defective macrophage accumulation creates granulomatous inflammatory plaques and nodules in the bladder wall. Wall thickening and enhancement on imaging reflect vascularity of inflammatory granulation tissue. Calcium accumulation in MG bodies may rarely be visible as microcalcifications on CT. The role of immunosuppression is facilitating disease development by further impairing macrophage function — therefore transplant patients, HIV-positive individuals, and uncontrolled diabetes patients are at high risk.
Michaelis-Gutmann bodies, the pathognomonic finding of malakoplakia, require histological diagnosis; direct detection on imaging is mostly not possible. However, the combination of focal bladder wall thickening + immunosuppressed patient + recurrent UTI provides strong clinical clue. In rare cases, microcalcifications on thin-section CT may provide a clue.
Focal or multifocal plaque-like or nodular thickening of bladder wall in portal venous phase. Thickening usually at bladder base or posterior wall. Shows moderate enhancement. May be confused with malignant tumor. Perivesical fat stranding may accompany. Microcalcifications rarely visible (calcium in MG bodies).
Report Sentence
Focal plaque-like thickening of the bladder wall is observed; clinical context and risk factors should be evaluated; biopsy may be needed for differentiation between malakoplakia and tumor.
Focal thickening or plaque with intermediate signal intensity in the bladder wall on T2-weighted images. Internal structure usually homogeneous. Perivesical edema may appear T2 hyperintense. Muscularis propria usually preserved but may be invaded in advanced cases.
Report Sentence
Focal plaque with intermediate signal in bladder wall on T2.
Mild to moderate diffusion restriction may be observed in malakoplakia lesions on DWI. ADC values generally between 1.0-1.4 × 10⁻³ mm²/s, not at malignant level (<0.8). This finding is helpful for differentiation from urothelial carcinoma but biopsy required for definitive distinction.
Report Sentence
No malignant-level diffusion restriction identified in the lesion on DWI; inflammatory etiology should be considered.
Moderate enhancement of malakoplakia lesion on contrast-enhanced MRI. Enhancement pattern homogeneous or mildly heterogeneous. Perivesical inflammatory enhancement may accompany. Fat-sat T1 post-contrast sequences best evaluate enhancement.
Report Sentence
Moderate enhancement of malakoplakia lesion on contrast-enhanced images.
Focal thickening or plaque-like structure in bladder wall on B-mode US — hypoechoic or isoechoic. Smooth or mildly irregular contour. Minimal to moderate vascularity on Doppler. US findings are nonspecific and indistinguishable from urothelial carcinoma.
Report Sentence
Focal thickening of bladder wall on US; cystoscopy and biopsy recommended for differentiation between malakoplakia and tumor.
Microcalcifications within malakoplakia lesion on non-contrast CT in rare cases — due to calcium and iron accumulation in Michaelis-Gutmann bodies. Calcifications are very small and detectable only on thin-section CT (1-2 mm). This finding is specific for malakoplakia but very rarely seen.
Report Sentence
Microcalcifications in bladder wall thickening are observed, which may be consistent with Michaelis-Gutmann bodies in malakoplakia.
Criteria
Limited plaque-like lesion(s) in bladder wall. Most common form.
Distinct Features
Yellowish-brown soft plaques on cystoscopy. Regression with antibiotics. Focal wall thickening on CT/MRI.
Criteria
Widespread involvement of bladder wall. More common in immunosuppressed patients.
Distinct Features
Diffuse wall thickening, multiple plaques. High risk of confusion with malignant tumor. Clinically more aggressive course. Long-term antibiotic therapy required.
Criteria
Organ involvement outside bladder — kidney, retroperitoneum, GI tract, skin. Usually in setting of severe immunosuppression.
Distinct Features
Mass-like lesion in kidney with renal involvement (confused with malignant tumor). Soft tissue mass with retroperitoneal involvement. Poor prognosis with multiorgan involvement.
Distinguishing Feature
Urothelial carcinoma shows prominent diffusion restriction (ADC <0.8), early enhancement, stalk sign, and mucosal invasion; malakoplakia ADC >1.0, moderate enhancement, and usually intact mucosa. Clinically malakoplakia associated with recurrent UTI in immunosuppressed setting. Definitive distinction by biopsy.
Distinguishing Feature
Acute cystitis shows diffuse mucosal thickening; malakoplakia forms focal plaques or nodules. Cystitis resolves quickly with antibiotics; malakoplakia requires prolonged treatment. Malakoplakia generally shows chronic course.
Distinguishing Feature
SCC usually presents in setting of schistosomiasis with focal mass and prominent invasion; malakoplakia shows plaque-like thickening. Calcification may be widespread in bladder wall in SCC (schistosomiasis); microcalcifications very rare in malakoplakia.
Distinguishing Feature
Lymphoma shows marked diffusion restriction (ADC <0.7) and homogeneous submucosal mass; malakoplakia ADC >1.0 and plaque-like thickening. Intact mucosa similar in lymphoma; however ADC difference is distinguishing.
Urgency
routineManagement
medicalBiopsy
NeededFollow-up
6-monthMalakoplakia diagnosis must be confirmed by biopsy — MG bodies are pathognomonic. Treatment based on prolonged antibiotic therapy: fluoroquinolones (ciprofloxacin) or TMP-SMX preferred due to good macrophage penetration. Treatment duration generally 3-6 months. Immunosuppressive therapy should be reduced (if possible). Bethanechol chloride (cholinergic agent) may improve phagocytic capacity by increasing macrophage cGMP levels. Ascorbic acid may increase lysosomal enzyme activity. Surgery (TUR) may be needed in refractory cases. Prognosis generally good; however chronic and recurrence rate may be high in immunosuppressed patients.
Malakoplakia can clinically and radiologically mimic bladder carcinoma, making histological confirmation by biopsy mandatory. Michaelis-Gutmann bodies (PAS-positive, von Kossa positive calcified inclusions) are pathognomonic. Treatment includes addressing the underlying infection (long-term antibiotics — trimethoprim-sulfamethoxazole or quinolones) and modifying immunosuppression. Surgery is usually not needed. Prognosis is generally good but recurrence may occur in immunosuppressed patients. Rare cases may involve kidney, colon, and retroperitoneum.