Kidney Injury After Cancer Treatment

Kidneys filter waste from blood, balance fluid, help control blood pressure, and manage salts such as potassium. Cancer treatment can harm them in several ways. Some damage comes on within hours and can be reversed. Some builds slowly and stays. Knowing which numbers to watch, and which warning signs cannot wait, protects the kidney function you still have.

MedlinePlus defines acute kidney failure as "the rapid (less than 2 days) loss of your kidneys' ability to remove waste and help balance fluids and electrolytes in your body." Clinicians usually call this acute kidney injury, or AKI.

The word injury covers a wide range. At one end is a small, silent rise in blood creatinine that only a lab test shows. At the other end is complete failure that needs dialysis.

The causes MedlinePlus lists fall into three patterns. All three are common during cancer treatment.

Less blood reaching the kidneys. MedlinePlus names very low blood pressure from burns, dehydration, bleeding, injury, septic shock, serious illness or surgery. It also lists blood clots in the vessels to the kidneys, and reduced flow from cholesterol emboli. During treatment the usual triggers are vomiting, diarrhea, fever, infection, and simply not drinking enough.

Direct damage to kidney tissue. MedlinePlus names medicines and toxins, including NSAIDs such as ibuprofen and naproxen, certain antibiotics, and the contrast dye used for some CT scans. Cisplatin belongs on this list. MedlinePlus warns that "cisplatin may cause serious kidney problems" and adds that "kidney problems may occur more often in older people." Kidney infection and autoimmune disease also damage tissue directly.

Blockage of urine flow. Urine that cannot leave the kidney backs up and raises pressure inside it. MedlinePlus lists urinary tract blockage among the causes of acute kidney failure, and a tumor pressing on the drainage path is one way it happens. Ask whether imaging has ruled out a blockage before anyone assumes the problem is only a drug.

Contact your care team the same day, or go to the emergency department, if you notice any of these. MedlinePlus lists them as symptoms of acute kidney failure.

• Passing much less urine than usual, or none at all.
• Swelling in the legs, ankles, or feet.
• Shortness of breath.
• Confusion, drowsiness, or any change in alertness.
• Seizures.
• Nausea and loss of appetite that will not settle.
• Bleeding that will not stop, easy bruising, or blood in urine or stools.
• A metallic taste in the mouth, or hiccups that will not stop.

Seizures and a drop in alertness are emergencies. Do not wait for the next scheduled clinic visit.

If you are on cisplatin, MedlinePlus tells patients to call the doctor right away for "decreased urination; swelling of the face, arms, hands, feet, ankles, or lower legs; or unusual tiredness."

Blood tests. Serum creatinine and blood urea nitrogen (BUN) are the two main waste products measured. Creatinine clearance estimates how much blood the kidneys clean each minute. Potassium and other electrolytes are checked at the same time, because a rising potassium level can affect the heart.

Estimated GFR. GFR stands for glomerular filtration rate, a measure of how well the kidneys filter. These cut-offs come from the National Institute of Diabetes and Digestive and Kidney Diseases, or NIDDK. A GFR of 60 or more is in the normal range. A GFR of less than 60 may mean you have kidney disease. A GFR of 15 or less is called kidney failure.

Urine tests. Urinalysis looks for blood, protein, and signs of infection. The urine albumin-to-creatinine ratio (uACR) measures protein leaking into urine. NIDDK states that 30 mg/g or less is normal, and more than 30 mg/g may be a sign of kidney disease.

Imaging. Ultrasound, X-ray, CT, or MRI can show a blockage.

Ask for the numbers, not just the word "normal." One creatinine value means little on its own. The trend across several results is what matters. NIDDK advises anyone with diabetes to have kidney tests every year. If you have high blood pressure, heart disease, or a family history of kidney failure, ask your provider how often you need testing.

Acute tubular necrosis (ATN) is damage to the cells lining the kidney tubules, the tiny filtering ducts inside the kidney. It is a frequent cause of acute kidney failure in hospital.

MedlinePlus lists several causes. One is lack of blood flow or oxygen to kidney tissue. Another is a medicine that is toxic to the kidneys, such as an aminoglycoside antibiotic or amphotericin. Contrast dyes are a third. Risk also rises after a blood transfusion reaction, an injury that damages muscle, low blood pressure lasting longer than 30 minutes, major surgery, and septic shock.

Its symptoms overlap with kidney failure. They include reduced or absent urine output, swelling, and nausea and vomiting. Alertness can also change, from drowsiness and confusion through to coma.

Recovery is slow but usual. MedlinePlus states that "ATN can last for a few days to 6 weeks or more" and that kidney function often returns to normal.

Treatment starts with removing the cause. That may mean stopping or changing a drug, treating an infection, giving fluid, or relieving a blockage.

MedlinePlus describes a diet that limits liquids to match urine output and that is high in carbohydrates and low in protein, salt, and potassium. Dialysis may be needed if potassium climbs to a dangerous level or if mental status worsens.

Some cancers are treated by removing kidney tissue. NCI describes nephrectomy, surgery to remove the whole kidney, as the most common treatment for Wilms tumor. Partial nephrectomy removes the tumor with a small margin of normal tissue and is also called renal-sparing surgery. NCI lists renal dysfunction among the late effects that childhood cancer survivors are monitored for.

If you have one kidney, or one and a fraction, every future decision about NSAIDs, contrast dye, and dehydration carries more weight. Say so at every new clinic.

MedlinePlus gives two rules. Keep conditions such as diabetes and high blood pressure under control. Avoid medicines and substances that are toxic to the kidneys.

Practical steps that follow from that advice:

• Take your current creatinine and GFR numbers to every new prescriber.
• Ask the pharmacist whether any dose needs adjusting for your kidney function.
• Ask before taking any NSAID, including ones sold without a prescription.
• Tell the radiology team about your kidney history before any scan that uses contrast.
• Ask what to do about fluids on days with vomiting, diarrhea, or fever.

• What was my creatinine and GFR before treatment, and what is it now?
• Which of my treatments is the most likely cause of the change?
• Is the drop from low blood flow, direct damage, or a blockage?
• Does my chemotherapy dose need to change because of my kidney function?
• Which of my other medicines and supplements should stop?
• Who owns my kidney follow-up: oncology, primary care, or nephrology?
• How much urine per day is too little for me, and when do I call?

• Acute kidney failure — MedlinePlus Medical Encyclopedia.
• Acute tubular necrosis — MedlinePlus Medical Encyclopedia.
• Cisplatin Injection — MedlinePlus.
• Chronic Kidney Disease Tests and Diagnosis — National Institute of Diabetes and Digestive and Kidney Diseases.
• Wilms Tumor and Other Childhood Kidney Tumors Treatment (PDQ) Patient Version — National Cancer Institute.