eGFR problem

Yes — what you’re describing can absolutely be from the contrast dye itself, not necessarily ongoing or progressive kidney damage from the prior chemotherapy.

Why contrast can temporarily lower eGFR:

IV contrast used in CT scans (iodinated contrast) can cause a temporary drop in kidney function, especially when:

Baseline eGFR is already low (typically < 45, and especially < 30–40).

There has been prior kidney stress (chemo, surgery, dehydration, age-related decline).

This phenomenon is often called contrast-associated acute kidney injury (CA-AKI). In many people:

eGFR drops within 24–72 hours after contrast.

Then slowly recovers over days to weeks.

Repeats with each exposure.

The key clue in your case is:

> eGFR falls after contrast, then rises again when contrast is stopped

That pattern strongly suggests a functional (temporary) injury, not ongoing structural kidney damage.

Role of chemotherapy:

Chemotherapy can cause permanent baseline kidney injury, which may explain why your eGFR never fully returned to normal.
However, chemo damage alone would not typically cause repeated up-and-down swings tied specifically to contrast exposure years later.

So in simple terms:

Chemo likely set the baseline.

Contrast dye is likely causing the recurrent dips.

Disadvantages of completely removing contrast dye.

The main downside is less diagnostic accuracy, depending on what doctors are looking for.

Without contrast, CT scans may:

Miss small tumors or early recurrences.

Be less accurate at distinguishing scar tissue vs cancer.

Provide less detail about lymph nodes and blood vessels.

That said, many follow-up cancer scans can still be done safely and effectively without contrast, or with alternatives.

Safer alternatives that are often used:

Doctors may consider:

Non-contrast CT (often acceptable for surveillance).

MRI (with or without gadolinium) — sometimes safer, sometimes not, depending on kidney function.

Ultrasound for certain organs.

Reduced contrast dose + aggressive hydration.

Longer intervals between contrast scans.

Important point:

Repeated contrast exposure when eGFR is already in the 30s increases the risk of:

Permanent kidney decline.

Progression to advanced CKD.

So your concern is very valid and medically reasonable.

Bottom line.

Yes, the contrast dye alone can be responsible for the repeated eGFR drops.

The recovery afterward suggests temporary injury, not worsening chemo damage.

Removing contrast slightly reduces imaging sensitivity but may significantly protect remaining kidney function.

This is a discussion worth having jointly with oncology, radiology, and nephrology.

Source's:

About Contrast-Related Kidney Injury:

1. NCBI / StatPearls — Contrast-Induced Nephropathy (overview) • Describes how contrast can cause acute kidney impairment after CT, usually peaking within 2–5 days and returning to baseline within ~2 weeks. It’s linked with pre-existing chronic kidney disease as a major risk factor.
https://www.ncbi.nlm.nih.gov/books/NBK448066/
2. National Kidney Foundation — “Contrast Dye and Your Kidneys” • Kidney.org explains that iodinated contrast in CT scans can cause acute kidney injury (AKI) especially in people with advanced CKD (low eGFR), diabetes, or dehydration.
https://www.kidney.org/kidney-topics/contrast-dye-and-kidneys
3. UCSF Radiology — CT Contrast & Kidney Function • Notes that pre-existing renal insufficiency is the most studied risk factor for contrast-induced kidney injury, and that contrast can transiently raise serum creatinine and lower eGFR after exposure.
https://radiology.ucsf.edu/patient-care/patient-safety/contrast/iodinated
About Temporary vs Permanent Effects:

4. UCSF — Post-contrast AKI Often Temporary • Describes that post-contrast acute kidney injury typically causes a transient kidney function decline that often returns to baseline within ~7–10 days and permanent damage is unusual.
https://radiology.ucsf.edu/patient-care/patient-safety/contrast/iodinated/adverse-effects-of-iodinated-contrast
Risk Depends on Kidney Function:

5. NCBI / Davenport Study (Risk by eGFR) • Describes how risk of contrast-associated AKI increases as baseline eGFR drops, especially below 30 mL/min/1.73 m²—though the exact causal role of contrast vs other factors is actively debated.
https://pubs.rsna.org/doi/abs/10.1148/radiol.2019192094
6. NCBI / Continued Debate on CI-AKI Risk • Some research suggests well-controlled studies show little risk of contrast itself causing AKI in many patients, especially with modern contrast media, though risk is still considered higher in severe CKD.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7808023/
Consensus Guidelines:

7. RSNA (Radiological Society) / Consensus Statement • Discusses that the risk of modern IV contrast in patients with reduced kidney function may not be as large as historically believed, and that necessary diagnostic imaging should not be delayed in many cases.
https://www.rsna.org/news/2020/january/contrast-media-consensus-statement
Summary of What These Sources Say:

A temporary rise in creatinine / drop in eGFR after contrast is well documented in people with reduced kidney function.

For many patients (especially with moderate CKD), kidney function usually returns to baseline over days to a couple of weeks.

Low baseline eGFR (especially < 30) increases risk for contrast-associated AKI.

Modern evidence suggests the true causal effect of contrast on long-term kidney function is less certain than historically thought, though risk still warrants clinical caution.

*For context, I want to share where my comments are coming from. I’ve spent more than 20 years independently investigating epidemiological data, scientific literature, and peer-reviewed medical research across a wide range of topics. My focus has always been on primary sources—original studies, systematic reviews, and consensus statements—rather than summaries, headlines, or anecdotal reports.

I make a point of cross-checking claims, understanding study design and limitations, and distinguishing between correlation, causation, and hypothesis. When evidence is incomplete or evolving, I try to say so clearly. When strong data exist, I rely on that rather than speculation or opinion.

I’m not here to persuade or argue, but to contribute information that is evidence-based, transparent, and open to correction if better data emerge. Thoughtful discussion grounded in reliable science benefits everyone, and that’s the spirit in which I participate here.