# Obstruction: A Normal Ultrasound Is Not Always the End

Watch urine output, sodium, potassium, and volume status for postobstructive losses. Functional recovery depends on the duration and severity of prior injury.

![Infographic: Obstruction: A Normal Ultrasound Is Not Always the End](https://urinenephrology.org/visual-reference/images/student-obstructive-uropathy.png?v=20261003c)

## Postrenal physiology

Obstruction raises urinary tract pressure and can impair filtration. The level, duration, laterality, and remaining functioning kidney determine clinical consequences.

## Look for the setting

Retention, stones, pelvic malignancy, instrumentation, and retroperitoneal fibrosis raise suspicion. Early or nondilated obstruction may lack prominent hydronephrosis.

## Match imaging to concern

Bladder assessment and ultrasound are useful first steps. Persistent suspicion may require cross-sectional imaging or urologic evaluation despite an unrevealing initial study.

## Relieve the blockage

Decompression and treatment of the cause are central. Infected obstruction requires urgent coordination; do not let prolonged diagnostic work delay necessary drainage.

## Consider fibrosis mechanisms

Retroperitoneal fibrosis can be idiopathic, related to IgG4 disease, malignant, or secondary to other conditions. Establish the diagnosis before assuming an inflammatory cause.

## Monitor after decompression

Watch urine output, sodium, potassium, and volume status for postobstructive losses. Functional recovery depends on the duration and severity of prior injury.

## Source lessons

- [obstructive uropathy student handout](https://urinenephrology.org/student-resources/uti/obstructive-uropathy-student-handout.html)

Read alongside the full lessons; the findings and decisions shown here require the stated clinical context.