[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/) › Congenital anomalies of the ureter and bladder

# Congenital anomalies of the ureter and bladder

- Lesion

Developmental errors of the ureters and bladder are common; the ones that matter block urine, let it flow backwards or leave open channels.

Updated Nov 12, 2026

## Key points

- UPJ obstruction: commonest cause of hydronephrosis in children; disorganized smooth muscle or excess collagen at the junction, sometimes a crossing vessel.
- Vesicoureteral reflux: short or absent intravesical tunnel; with infection it causes reflux nephropathy.
- Bladder exstrophy: defect of the lower abdominal wall and anterior bladder; chronic infection, glandular metaplasia and a higher risk of adenocarcinoma.
- Urachal remnants: patent urachus (urine from the umbilicus), cyst or sinus; adenocarcinoma can arise in them.
- Diverticula: congenital (a weak spot in the wall) or acquired (outlet obstruction); stasis, stones and infection.

## What it is

Anomalies of the ureter appear in a few percent of autopsies, most without symptoms. Ureteropelvic junction obstruction is the leading cause of hydronephrosis in infants and children. Duplicated and bifid ureters, ureteroceles and ectopic openings favour obstruction and reflux. In the bladder, diverticula, exstrophy and remnants of the urachus are the main lesions; vesicoureteral reflux, from a short intravesical course of the ureter, is the most important for kidney damage.

## Structure

- UPJ obstruction: dilated pelvis with a narrow junction; the muscle is disorganized and replaced by collagen.
- Diverticulum: pouch of mucosa through the muscle layer, with thin wall, often inflamed.
- Exstrophy: exposed bladder mucosa that becomes inflamed, ulcerated and metaplastic.
- Urachal remnant: a channel between the bladder dome and the umbilicus, lined by urothelium or glandular epithelium.

## Congenital anomalies of the ureter and bladder

| Anomaly | Problem | Consequence |
| --- | --- | --- |
| Ureteropelvic junction obstruction | Narrow, poorly propulsive junction | Hydronephrosis in infants; in adults more often in women, unilateral |
| Duplicated or bifid ureter | Two ureters from one kidney | Obstruction of the upper moiety, reflux into the lower |
| [Vesicoureteral reflux](https://durgical.com/en/conditions/vesicoureteral-reflux/) | Short intravesical tunnel | Pyelonephritis and reflux nephropathy |
| Bladder exstrophy | Open anterior bladder and abdominal wall | Infection, metaplasia, adenocarcinoma |
| Urachal anomalies | Persistent connection to the umbilicus | Umbilical leak, cyst infection, adenocarcinoma at the dome |

## Clinical notes

- Prenatal ultrasound often shows hydronephrosis; many cases of mild reflux resolve as the child grows.
- A cyst or mass at the bladder dome of an adult suggests a urachal lesion.

## Memory aid

Narrow at the top, short at the bottom, open at the front, open to the navel.

## Test yourself

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

## What is the commonest cause of hydronephrosis in infants and children?

Ureteropelvic junction obstruction.

## Which cancer arises in urachal remnants and exstrophic bladders?

Adenocarcinoma.

## Why does a short intravesical ureter cause reflux?

The bladder muscle cannot compress the ureter during voiding, so urine flows back toward the kidney.

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## Elsewhere in DurgiPedia

- [Duplicated ureter, UPJ obstruction and posterior urethral valves](https://durgical.com/en/embryology/duplicated-ureter-upj-obstruction-and-posterior-urethral-valves/)
- [Bladder exstrophy](https://durgical.com/en/embryology/bladder-exstrophy/)
- [Urachal anomalies: patent urachus, cyst and sinus](https://durgical.com/en/embryology/urachal-anomalies-patent-urachus-cyst-and-sinus/)
- [Bladder, urachus and urethra](https://durgical.com/en/embryology/bladder-urachus-and-urethra/)

## Connections

## Related 4

- [Congenital kidney anomalies](https://durgical.com/en/general-pathology/congenital-kidney-anomalies/)
- [Chronic pyelonephritis and reflux nephropathy](https://durgical.com/en/general-pathology/chronic-pyelonephritis-and-reflux-nephropathy/)
- [Ureteral and bladder outlet obstruction](https://durgical.com/en/general-pathology/ureteral-and-bladder-outlet-obstruction/)
- [Other bladder tumours](https://durgical.com/en/general-pathology/other-bladder-tumours/)

## Related conditions 4

- [Vesicoureteral reflux](https://durgical.com/en/conditions/vesicoureteral-reflux/)
- [Hydronephrosis and obstructive uropathy](https://durgical.com/en/conditions/hydronephrosis-and-obstructive-uropathy/)
- [Posterior urethral valves](https://durgical.com/en/conditions/posterior-urethral-valves/)
- [Acute pyelonephritis](https://durgical.com/en/conditions/acute-pyelonephritis/)

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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: [Vesicoureteral Reflux (VUR)](https://www.niddk.nih.gov/health-information/urologic-diseases/hydronephrosis-newborns/vesicoureteral-reflux) (NIDDK (National Institutes of Health), 2024); [Embryology, Kidney, Bladder, and Ureter - StatPearls - NCBI Bookshelf](https://www.ncbi.nlm.nih.gov/books/NBK547747/) (StatPearls Publishing (NCBI Bookshelf), 2023).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/congenital-anomalies-of-the-ureter-and-bladder/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/congenital-anomalies-of-the-ureter-and-bladder/