# Toxic and Chronic Interstitial Nephropathies

Identify the exposure and the damaged transport process before labeling unexplained CKD as toxic nephropathy.

![Infographic: Toxic and Chronic Interstitial Nephropathies](https://urinenephrology.org/visual-reference/images/student-toxic-interstitial.png?v=20261003c)

## Build an exposure timeline

List prescriptions, over-the-counter analgesics, lithium, supplements/herbs, occupation, and possible metals. Record start/stop dates and prior kidney results. Product names are more useful than the label “natural.”

## Lithium: a concentrating defect

Polyuria and thirst during lithium therapy may reflect nephrogenic diabetes insipidus. Assess serum sodium, kidney function, lithium exposure/level when indicated, and water access. Abrupt water restriction can be dangerous.

## Proximal tubular toxins

Normoglycemic glycosuria, phosphate wasting, low bicarbonate, and nonalbumin proteinuria suggest proximal injury. Review implicated medicines or exposures and quantify deficits rather than treating an isolated low potassium result.

## Acute interstitial inflammation

A drug-related creatinine rise may occur with pyuria but without fever, rash, or eosinophilia. Remove a plausible culprit with the treating team and investigate alternatives; urine eosinophils do not confirm or exclude AIN.

## Chronic interstitial disease

A concentrating defect, modest proteinuria, and gradual GFR loss can accompany chronic interstitial injury. Ultrasound, family history, obstruction review, and targeted exposure testing help distinguish toxic, inherited, and structural causes.

## Choose evidence-based testing

Test for a specific metal or toxin only when exposure and clinical findings support it. Chelation has agent-specific indications and risks; do not infer a need for treatment from commercial provoked-urine testing.

## Source lessons

- [toxic nephropathies student handout](https://urinenephrology.org/student-resources/toxic-nephropathies/toxic-nephropathies-student-handout.html)

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