# Cancer Electrolyte Emergencies: Mechanism and Urgency

The diagnosis should follow this patient's physiology. Cancer type alone does not establish SIADH, hypercalcemia mechanism, or a specific tubular lesion.

![Infographic: Cancer Electrolyte Emergencies: Mechanism and Urgency](https://urinenephrology.org/visual-reference/images/mastery-onc-electrolytes.png?v=20261003c)

## Cancer creates several pathways

Tumor hormones, cell breakdown, obstruction, poor intake, gastrointestinal losses, and treatment toxicity can produce different electrolyte disorders.

## Recognize organ-threatening effects

Arrhythmia, seizures, encephalopathy, weakness, and rapidly changing kidney function require urgent assessment while the cause is investigated.

## Use the pattern to choose the workup

Low sodium requires tonicity, urine studies, medication review, and exclusion of adrenal insufficiency before SIADH attribution. High calcium requires PTH-guided evaluation. Rising potassium/phosphate with falling calcium and AKI raises tumor-lysis concern. Low magnesium after platinum exposure suggests a different tubular problem.

## Do not substitute the cancer name for a diagnosis

Small-cell lung cancer does not prove SIADH, and a bone lesion does not establish every cause of hypercalcemia. Stabilize the dangerous disturbance, then treat the mechanism supported by this patient’s tests. Monitor for treatment-induced shifts in the other electrolytes and changing renal clearance.

## Expect interacting abnormalities

Treating one ion can alter another. Follow acid–base status, renal clearance, volume tolerance, and the effects of repeated replacement.

## Avoid assumed frequency claims

The diagnosis should follow this patient's physiology. Cancer type alone does not establish SIADH, hypercalcemia mechanism, or a specific tubular lesion.

## Source lessons

- [cancer electrolyte emergencies review](https://urinenephrology.org/mastery/onconephrology/cancer-electrolyte-emergencies-review.html)

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