Encrusted Cystitis

Encrusted cystitis is a chronic inflammatory disease of the bladder in which calcified deposits form on or in an ulcerated mucosa. It is caused by urease producing bacteria that raise urinary pH and precipitate struvite and calcium phosphate.

It occurs mainly in the immunosuppressed (kidney transplant recipients), after bladder or prostate surgery, with chronic catheterisation, radiotherapy, chemotherapy, neurogenic bladder, prolonged hospital stay and prior antibiotic exposure. Encrusted pyelitis can coexist.

Pathophysiology. Corynebacterium urealyticum is the classical organism, with Proteus, Klebsiella, Ureaplasma urealyticum and Mycoplasma hominis also reported.

Urease splits urea to ammonia, producing alkaline urine (pH over 7.5) and supersaturation with magnesium ammonium phosphate and calcium phosphate. Damaged mucosa, necrotic tissue and mucus act as a nidus, and the deposits embed in the bladder wall.

Dysuria, frequency, suprapubic pain, haematuria, passage of gravel or calcific debris, and recurrent cystitis with alkaline urine. Complications include blockage by debris with retention, bladder contracture, ureteric obstruction with hydronephrosis, and sepsis.

• Urine pH over 7.5 with persistent pyuria and routine culture often negative. Corynebacterium urealyticum grows slowly, needing enriched medium and prolonged incubation of 48 hours or more, so request this specifically. Add culture or PCR for Ureaplasma and Mycoplasma.
• CT shows linear calcification of the bladder wall. Plain film and ultrasound show echogenic wall thickening or calcified plaques.
• Cystoscopy: white or yellow plaques on an ulcerated, inflamed mucosa. Biopsy to exclude malignancy and tuberculosis.
• Creatinine, renal ultrasound for hydronephrosis, and drug levels when glycopeptides are given.

Differential diagnosis.

• Bladder calculus
• Bladder tumour with calcification
• Schistosomal cystitis
• Tuberculous cystitis
• Radiation cystitis
• Amyloidosis
• Calcified urachal remnant

• Systemic antibiotic against the urease producing organism. Corynebacterium urealyticum is resistant to most agents but susceptible to glycopeptides: vancomycin 15 mg/kg intravenously every 12 hours, adjusted to eGFR and trough or exposure levels (trough 10 to 20 mg/L), or teicoplanin by loading then daily dosing. Treat for about 2 to 4 weeks, directed by symptoms, urine pH and cystoscopic response. Avoid co-prescription of other nephrotoxins and monitor creatinine closely, especially with calcineurin inhibitors.
• Urine acidification: oral acidifiers have weak evidence. Acidifying bladder irrigation with a citric acid based solution through a catheter can dissolve encrustation.
• Endoscopic removal of encrusted plaques and stones by transurethral resection or holmium laser fragmentation, which is the central treatment with substantial burden. Send tissue for histology and culture.
• Urease inhibitor acetohydroxamic acid 250 mg orally every 8 hours (maximum 1.5 g daily) is an option where available. It is contraindicated in pregnancy and not used in significant renal impairment. Haemolytic anaemia and deep vein thrombosis are the main adverse effects.
• Treat the cause: remove catheters, reduce immunosuppression where safely possible, and relieve obstruction.
• Relapse is common, so continue to monitor.

Special groups. Transplant recipients need joint nephrology review, because glycopeptides are nephrotoxic and interact with calcineurin inhibitors, requiring level monitoring.

Monitoring. Urine pH and culture, creatinine and drug levels during treatment, and cystoscopy or CT at 4 to 6 weeks and then at 3 to 6 months. Renal ultrasound for hydronephrosis.

Referral and escalation. Refer to urology and infectious disease. Urgent referral for retention, sepsis or hydronephrosis.