[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Lower urinary tract and male genital system](https://durgical.com/en/general-pathology/areas/urinary-male/) › Cystitis and bladder metaplasias

# Cystitis and bladder metaplasias

- Lesion

Inflammation of the bladder is usually bacterial, but drugs, radiation, viruses and immune processes produce special forms and metaplasias.

Updated Nov 12, 2026

## Key points

- Bacteria: E. coli first, then Proteus, Klebsiella, Enterobacter; Staphylococcus saprophyticus in young women.
- Hemorrhagic cystitis: cyclophosphamide (acrolein), radiation, adenovirus, BK virus after transplant.
- Interstitial cystitis: chronic pelvic pain and urgency; Hunner ulcers with chronic inflammation and mast cells in some.
- Malakoplakia: soft yellow plaques; macrophages with Michaelis-Gutmann bodies (laminated calcified inclusions).
- Schistosoma haematobium: granulomas around eggs, squamous metaplasia, risk of squamous cell carcinoma.

## What it is

Acute cystitis is mostly caused by gut bacteria, especially Escherichia coli, ascending through the urethra; women, catheters, outlet obstruction and diabetes favour it. Chemotherapy with cyclophosphamide, radiation and adenovirus infection give hemorrhagic cystitis. Interstitial cystitis (bladder pain syndrome) is chronic pain with mucosal ulcers in some patients. Malakoplakia reflects defective killing of bacteria by macrophages, polypoid cystitis follows catheter irritation, and chronic irritation causes cystitis glandularis and cystica, squamous metaplasia and nephrogenic metaplasia.

## Structure

- Acute: red, edematous mucosa with neutrophils; may be hemorrhagic, suppurative or ulcerative.
- Chronic: thickened, red, friable mucosa with lymphocytes and fibrosis of the wall.
- Cystitis glandularis and cystica: nests of urothelium (Brunn nests) that become cystic or glandular; common and reactive.
- Squamous metaplasia: keratinizing squamous epithelium after chronic irritation; nephrogenic metaplasia: small tubules after injury, mimicking adenocarcinoma.
- Malakoplakia: sheets of foamy macrophages (von Hansemann cells) with Michaelis-Gutmann bodies.

## Forms of cystitis

| Form | Cause | Key feature |
| --- | --- | --- |
| [Bacterial cystitis](https://durgical.com/en/conditions/urinary-tract-infection/) | E. coli and other gut bacteria | Dysuria, frequency, pyuria |
| Hemorrhagic cystitis | Cyclophosphamide, radiation, adenovirus | Blood in the urine, hemorrhagic mucosa |
| [Interstitial cystitis](https://durgical.com/en/conditions/interstitial-cystitis/) | Unknown, chronic | Pain relieved by voiding; Hunner ulcers in some |
| Malakoplakia | Defective macrophage killing of bacteria (often E. coli) | Yellow plaques, Michaelis-Gutmann bodies |
| Polypoid cystitis | Catheters, irritation | Edematous polypoid mucosa that can mimic papillary tumour |

## Clinical notes

- Classic triad of cystitis: frequency, lower abdominal pain and dysuria.
- Asymptomatic bacteriuria needs treatment only in pregnancy and before urologic procedures.

## Memory aid

Bugs, drugs, rays and riddles: bacteria, cyclophosphamide, radiation and interstitial cystitis.

## Test yourself

Think of the answer, then tap the question to see it.

## Which drug is classically associated with hemorrhagic cystitis?

Cyclophosphamide, through its metabolite acrolein.

## What are Michaelis-Gutmann bodies?

Laminated, mineralized inclusions in macrophages, diagnostic of malakoplakia.

## Which parasite causes chronic cystitis that predisposes to squamous cell carcinoma?

Schistosoma haematobium.

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## Elsewhere in DurgiPedia

- [Metaplasia](https://durgical.com/en/general-pathology/metaplasia/)
- [Patterns of acute inflammation: serous, fibrinous, purulent, abscess, ulcer](https://durgical.com/en/general-pathology/patterns-of-acute-inflammation-serous-fibrinous-purulent-abscess-ulcer/)

## Connections

## Related 4

- [Acute pyelonephritis](https://durgical.com/en/general-pathology/acute-pyelonephritis/)
- [Other bladder tumours](https://durgical.com/en/general-pathology/other-bladder-tumours/)
- [Urothelial tumours: morphology, grade and stage](https://durgical.com/en/general-pathology/urothelial-tumours-morphology-grade-and-stage/)
- [Metaplasia](https://durgical.com/en/general-pathology/metaplasia/)

## Related conditions 6

- [Urinary tract infection (acute cystitis)](https://durgical.com/en/conditions/urinary-tract-infection/)
- [Interstitial cystitis (bladder pain syndrome)](https://durgical.com/en/conditions/interstitial-cystitis/)
- [Catheter-associated urinary tract infection](https://durgical.com/en/conditions/catheter-associated-urinary-tract-infection/)
- [Asymptomatic bacteriuria](https://durgical.com/en/conditions/asymptomatic-bacteriuria/)
- [Schistosomiasis](https://durgical.com/en/conditions/schistosomiasis/)
- [Acute pyelonephritis](https://durgical.com/en/conditions/acute-pyelonephritis/)

## Microorganisms 4

- [Escherichia coli](https://durgical.com/en/microbiology/escherichia-coli/)
- [Adenovirus](https://durgical.com/en/microbiology/adenovirus/)
- [Schistosoma mansoni / S. haematobium / S. japonicum](https://durgical.com/en/microbiology/schistosoma-mansoni-s-haematobium-s-japonicum/)
- [Staphylococcus saprophyticus](https://durgical.com/en/microbiology/staphylococcus-saprophyticus/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Acute Cystitis](https://www.ncbi.nlm.nih.gov/books/NBK459322/) (StatPearls (NCBI Bookshelf), 2024); [Interstitial cystitis: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000477.htm) (MedlinePlus, US National Library of Medicine, 2025).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/cystitis-and-bladder-metaplasias/