[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/) › Ureteral and bladder outlet obstruction

# Ureteral and bladder outlet obstruction

- Lesion

Stones, tumours, fibrosis or the prostate can block urine; the bladder muscle hypertrophies and the system above dilates.

Updated Nov 12, 2026

## Key points

- Intrinsic causes: stones, strictures, urothelial tumours, blood clots, fibroepithelial polyps.
- Extrinsic causes: pregnancy, pelvic tumours (cervix, rectum, prostate), endometriosis, retroperitoneal fibrosis.
- Retroperitoneal fibrosis: middle-aged men; drugs (ergot derivatives), IgG4-related disease, idiopathic.
- Bladder outlet obstruction: BPH in men, urethral valves in boys, strictures, neurogenic bladder.
- Trabeculated bladder with cellules and diverticula; residual urine favours infection and stones.

## What it is

Ureters run in the retroperitoneum and can be blocked from inside (stones, strictures, tumours, clots, fibroepithelial polyps), from their wall (neurogenic dysfunction) or from outside (tumours, pregnancy, endometriosis, fibrosis). Unilateral obstruction usually comes from proximal causes; bilateral from distal ones such as prostatic enlargement. Sclerosing retroperitoneal fibrosis encases the ureters in inflammatory fibrous tissue and is often part of IgG4-related disease. When the bladder outlet is obstructed, the detrusor hypertrophies, forms trabeculae and pouches, and finally decompensates.

## Structure

- Retroperitoneal fibrosis: plaque of dense fibrous tissue with lymphocytes, plasma cells (many IgG4-positive), eosinophils and obliterative phlebitis.
- Hypertrophied bladder: thick wall with prominent interlacing muscle bundles (trabeculae) and small outpouchings between them.
- Fibroepithelial polyp: loose vascular stroma covered by urothelium, often in children.

## Causes of obstruction by site

| Site | Causes | Pattern |
| --- | --- | --- |
| [Inside the ureter](https://durgical.com/en/conditions/kidney-stones/) | Stones, strictures, urothelial tumour, clots, fibroepithelial polyp | Usually unilateral |
| Outside the ureter | Pregnancy, pelvic tumours, endometriosis, retroperitoneal fibrosis | Unilateral or bilateral |
| [Bladder outlet](https://durgical.com/en/conditions/benign-prostatic-hyperplasia/) | BPH, prostate cancer, urethral valves, strictures | Bilateral hydronephrosis |
| [Bladder function](https://durgical.com/en/conditions/neurogenic-bladder/) | Spinal cord injury, diabetes, multiple sclerosis | Large or small, poorly emptying bladder |

## Clinical notes

- Retroperitoneal fibrosis presents with back pain and kidney failure from bilateral ureteral encasement.
- Urinary retention with overflow incontinence is a sign of chronic outlet obstruction.

## Memory aid

Inside, outside, at the gate or in the nerves: four places where urine stops.

## Test yourself

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

## What systemic disease is often behind retroperitoneal fibrosis?

IgG4-related disease.

## What happens to the bladder wall with chronic outlet obstruction?

The detrusor hypertrophies, forming trabeculae, cellules and diverticula.

## Why is bilateral obstruction usually distal?

Both ureters drain into the bladder, so one lesion of the bladder outlet or urethra blocks both kidneys.

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## Elsewhere in DurgiPedia

- [Hypertrophy: physiologic and pathologic](https://durgical.com/en/general-pathology/hypertrophy-physiologic-and-pathologic/)
- [Fibrosis in organs: TGF-β and the myofibroblast](https://durgical.com/en/general-pathology/fibrosis-in-organs-tgf-and-the-myofibroblast/)
- [Micturition and the bladder reflex](https://durgical.com/en/physiology/micturition-and-the-bladder-reflex/)

## Connections

## Related 5

- [Urinary tract obstruction and hydronephrosis](https://durgical.com/en/general-pathology/urinary-tract-obstruction-and-hydronephrosis/)
- [Benign prostatic hyperplasia](https://durgical.com/en/general-pathology/benign-prostatic-hyperplasia/)
- [Congenital anomalies of the ureter and bladder](https://durgical.com/en/general-pathology/congenital-anomalies-of-the-ureter-and-bladder/)
- [Hypertrophy: physiologic and pathologic](https://durgical.com/en/general-pathology/hypertrophy-physiologic-and-pathologic/)
- [Autoimmune pancreatitis: type 1 (IgG4-related) vs type 2](https://durgical.com/en/general-pathology/autoimmune-pancreatitis-type-1-vs-type-2/)

## Related conditions 8

- [Hydronephrosis and obstructive uropathy](https://durgical.com/en/conditions/hydronephrosis-and-obstructive-uropathy/)
- [Benign prostatic hyperplasia](https://durgical.com/en/conditions/benign-prostatic-hyperplasia/)
- [IgG4-related disease](https://durgical.com/en/conditions/igg4-related-disease/)
- [Neurogenic bladder](https://durgical.com/en/conditions/neurogenic-bladder/)
- [Acute urinary retention](https://durgical.com/en/conditions/acute-urinary-retention/)
- [Kidney stones (urolithiasis)](https://durgical.com/en/conditions/kidney-stones/)
- [Cervical cancer](https://durgical.com/en/conditions/cervical-cancer/)
- [Posterior urethral valves](https://durgical.com/en/conditions/posterior-urethral-valves/)

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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: [Obstructive uropathy: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000507.htm) (MedlinePlus, US National Library of Medicine, 2025).

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