You are in: eMedicine Specialties > Nephrology > Drug- and Nephrotoxin-Associated Kidney Disorders Nephritis, RadiationArticle Last Updated: Jul 22, 2008AUTHOR AND EDITOR INFORMATIONAuthor: Eric P Cohen, MD, Professor of Medicine, Nephrology Fellowship Program Director, Department of Medicine, Division of Nephrology, Medical College of Wisconsin; Medical Director, Inpatient Dialysis Unit, Froedtert Hospital Eric P Cohen is a member of the following medical societies: American Society of Nephrology, Central Society for Clinical Research, and International Society of Nephrology Editors: Laura L Mulloy, DO, FACP, Professor of Medicine, Chief, Section of Nephrology, Hypertension and Transplantation Medicine, Glover/Mealing Eminent Scholar Chair in Immunology, Medical College of Georgia; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Ajay K Singh, MB, MRCP, MBA, Associate Professor of Medicine, Director of Dialysis, Department of Medicine, Harvard Medical School; Clinical Chief of Renal Division, Brigham and Women's Hospital; Rebecca J Schmidt, DO, FACP, FASN, Professor of Medicine, Section Chief, Department of Medicine, Section of Nephrology, West Virginia University School of Medicine; Vecihi Batuman, MD, FACP, FASN, Professor of Medicine, Section of Nephrology-Hypertension, Tulane University School of Medicine; Chief, Medicine Service, Southeast Louisiana Veterans Health Care System Author and Editor Disclosure Synonyms and related keywords: radiation nephritis, radiation nephropathy, kidney irradiation, ionizing radiation, kidney failure, renal failure, kidney injury, kidney damage, radionuclide therapy, body irradiation, bone marrow transplantation nephropathy, BMT nephropathy, radiation nephritis after bone marrow transplantation, radiation nephritis after BMT INTRODUCTIONBackgroundRadiation nephritis is kidney injury and impairment of function caused by ionizing radiation. It may occur after irradiation of one or both kidneys, and it may result in kidney failure. Classic radiation nephritis occurs after bilateral local kidney irradiation. It is a syndrome of chronic renal failure occurring months or years after renal irradiation.1 Acute radiation nephritis develops 6-12 months after irradiation, whereas chronic radiation nephritis develops years later. Radiation nephritis has also been discovered to cause chronic renal failure after bone marrow transplantation (BMT).2 In addition, the use of yttrium–90–tagged (90Y-tagged) somatostatin and other radionuclides for radionuclide therapy cause radiation nephritis when they are filtered by the kidneys and reabsorbed by the renal tubule epithelium or when blood-borne exposure to the kidney cells occurs.3 The term nephritis was commonly used in the past; however, because radiation nephropathy is not an inflammatory condition, the term nephropathy is probably more appropriate. For older reports, the term nephritis will be used. PathophysiologyRadiation nephritis is due to cellular injury caused by ionizing radiation. All components of the kidney are affected, including the glomeruli, blood vessels, tubular epithelium, and interstitium.4 In the case of local kidney irradiation or total-body irradiation, the injury is direct. In the case of injury by radionuclide therapy, a radioactive substance can injure the kidneys if its pharmacokinetics cause it to lodge in the kidney during a time when it is still a radioemitter. This is the case for the 90Y-tagged somatostatin, which has been used for treatment of neuroendocrine malignancies, and also for holmium-166–tagged (166Ho-tagged) phosphonate 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene phosphonic acid (DOTMP).5, 6 Oxidative injury to the DNA initiates injury to healthy tissue by ionizing radiation. This is a genotoxic injury. A cell with sufficient DNA injury eventually dies after several divisions. The delay in cell death may partially explain why radiation injury to healthy tissue is a delayed reaction. The detailed mechanism whereby the kidney cells and tissues malfunction after this injury remains poorly understood. In experimental models, ultrastructural damage to the glomerular endothelium is observed 3 weeks after a 10-Gy (1000-rad) dose of local kidney irradiation and neutrophil adherence to the endothelium occurs.4 By 6-10 weeks after the same dose, a wave of tubular epithelial cell death occurs. This is followed by interstitial scarring. The scarring tends to be most severe in the outer cortex, and it proceeds inward. The progression of these events is accelerated with higher doses of radiation. The earliest functional evidence of experimental radiation nephropathy is proteinuria, which is evident by 6 weeks in a radiation nephritis model with 17-Gy multifraction total-body irradiation. Azotemia and hypertension both are present by 12-15 weeks in the same model. The origin of the hypertension probably is similar to that of most experimental hypertension, though pressure-natriuresis curves have not been studied. Renin levels in systemic blood are normal or low, and blood and intrarenal angiotensin II levels are within the reference range (ie, not elevated). In clinical experience, radiation nephritis does not occur until months after the kidneys are exposed to sufficient ionizing radiation. Early data suggested that a dose of 20 Gy (2000 rads) given in multiple fractions over several weeks can cause radiation nephritis.1 Radiation nephritis after BMT (BMT nephropathy) occurs after a lower dose of irradiation than what was traditionally accepted. This dose is given over days, not weeks, to the whole body (total-body irradiation) and is accompanied by chemotherapy, which may account for the unexpectedly dramatic effect on the kidneys. Proteinuria is usual, though generally not in the nephrotic range. Azotemia and hypertension also develop. Anemia out of proportion to the degree of azotemia is a characteristic finding. Severe cases may be associated with a hemolytic- or uremic-like picture, with thrombocytopenia, microangiopathic hemolytic anemia, and a high blood level of lactate dehydrogenase (LDH). This last syndrome may be the result of severe endothelial injury. In the case of unilateral renal irradiation, progressive scarring of the irradiated kidney may occur, with severe hypertension related to renin release by the single irradiated kidney. FrequencyUnited StatesRadiation nephritis does not occur in all irradiated patients. In the large British series of classic radiation nephritis described by Luxton, only 20% of subjects developed radiation nephritis, though each received more than 2500 rads to the kidneys.1 The form of radiation nephritis in patients who receive BMT occurs in 10-20% of these patients. In a report from InternationalNo international variability is apparent in radiation nephritis, except as determined by the use of therapeutic irradiation. Mortality/MorbidityAs with other causes of chronic renal failure, radiation nephritis may be asymptomatic. When it sufficiently reduces kidney function, symptoms and signs of renal failure occur. End-stage renal disease and the need for dialysis or transplantation may develop. In patients with BMT nephropathy who are receiving dialysis, the survival rate is less than that of age-matched control subjects.7
RaceNo data on the racial variance of radiation nephritis have been published. SexNo confirmed sex-based differences in radiation nephritis have been reported. At the BMT unit of the Medical College of Wisconsin, BMT nephropathy has affected more women than men, but other centers have not had this experience. AgeNo age-based differences in susceptibility to classic radiation nephritis have been confirmed. However, in the case of BMT nephropathy, children appear to be more likely to develop this syndrome than adults. CLINICALHistory
Physical
Causes
DIFFERENTIALSChronic Renal Failure Hemolytic-Uremic Syndrome Hypertension Hypertension, Malignant Thrombotic Thrombocytopenic Purpura
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| Drug Name | Captopril (Capoten) |
|---|---|
| Description | Prevents conversion of angiotensin I to angiotensin II, potent vasoconstrictor, increasing levels of plasma renin and reducing aldosterone secretion. Clinically used for >20 y and is effective in experimental radiation nephropathy. May slow progression of renal failure by lowering intraglomerular pressure or other intrarenal mechanisms. Competitive ACE inhibitor. Reduces angiotensin II levels, decreasing aldosterone secretion. Dry cough common adverse effect of ACE inhibitors. If cough occurs with one ACE inhibitor, likely to occur with another; reasonable substitute if ACE inhibitor-induced cough occurs is an ARB, such as losartan, valsartan, or candesartan. |
| Adult Dose | 12.5 mg PO bid initially; may be increased to 25 mg PO tid |
| Pediatric Dose | Half that of adult dose; may be titrated upward as guided by response of blood pressure |
| Contraindications | Documented hypersensitivity; during pregnancy because may cause renal maldevelopment of fetus |
| Interactions | Concurrent potassium supplements may cause hyperkalemia; use with diuretics potentiates their antihypertensive effect; generally well tolerated |
| Pregnancy | D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus |
| Precautions | May elevate plasma potassium levels; causes dry cough in approximately 5% of patients; ACE inhibitors in general may cause modest anemia; angioedema, with swelling of lips and mouth, may occur |
| Drug Name | Enalapril (Vasotec) |
|---|---|
| Description | Competitive inhibitor of angiotensin-converting enzymes. Reduces angiotensin II levels, decreasing aldosterone secretion. Reduces systemic arterial blood pressure, reducing injury caused by elevated blood pressure. May slow progression of renal failure by lowering intraglomerular pressure or other intrarenal mechanisms. May be used qd or bid, which may improve compliance compared to tid medication, such as captopril. Dry cough common adverse effect of ACE inhibitors. If cough occurs with one ACE inhibitor, likely to occur with another; reasonable substitute if ACE inhibitor-induced cough occurs is an ARB, such as losartan, valsartan, or candesartan. |
| Adult Dose | 2.5 mg PO qd initially; may be up-titrated, not to exceed 20 mg bid, as guided by tolerance and blood pressure |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; during pregnancy because may cause renal maldevelopment of fetus |
| Interactions | Concurrent potassium supplements may cause hyperkalemia; NSAIDs may reduce hypotensive effects; hypotensive effects of ACE inhibitors may be enhanced with concurrent diuretics |
| Pregnancy | D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus |
| Precautions | May elevate plasma potassium level (especially in BMT nephropathy, in which hyperkalemia already possible); causes dry cough in approximately 5% of patients; angioedema, with swelling of lips and mouth, may occur with ACE inhibitors |
Antagonize the action of angiotensin II at the type 1 receptor, reducing systemic arterial blood pressure and blunting the intrarenal effect of angiotensin II. If ACE inhibitors cause cough, ARBs may be substituted.
| Drug Name | Losartan (Cozaar) |
|---|---|
| Description | Prototype ARB. Specific for type 1, as opposed to type 2, angiotensin receptor. May induce more complete inhibition of renin-angiotensin system than that of ACE inhibitors. Does not appear to affect bradykinin and is less likely to be associated with cough and angioedema. Use in patients unable to tolerate ACE inhibitors. In use for 10 y. |
| Adult Dose | 50 mg PO qd initially; dose may be increased to 100 mg PO qd |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity |
| Interactions | Concurrent potassium supplements may cause hyperkalemia |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Category D in second and third trimester of pregnancy; caution in unilateral or bilateral renal-artery stenosis |
| Drug Name | Valsartan (Diovan) |
|---|---|
| Description | Prodrug that directly antagonizes angiotensin II receptors. Displaces angiotensin II from AT1 receptor and may lower blood pressure by antagonizing AT1-induced vasoconstriction, aldosterone release, catecholamine release, arginine vasopressin release, water intake, and hypertrophic responses. May induce more complete inhibition of renin-angiotensin system than ACE inhibitors. Does not affect bradykinin, and is less likely to be associated with cough and angioedema. For use in patients unable to tolerate ACE inhibitors. |
| Adult Dose | 80 mg/d PO; may increase to 160 mg/d if needed |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; severe hepatic insufficiency; biliary cirrhosis or obstruction; primary hyperaldosteronism; bilateral renal-artery stenosis |
| Interactions | Potassium-sparing diuretics (eg, spironolactone, triamterene, amiloride), potassium supplements, or salt substitutes containing potassium may lead to increases in serum potassium |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Category D in second and third trimester of pregnancy; caution in hyperkalemia, suspected bilateral renal artery stenosis or solitary kidney with unilateral RAS |
Antihypertensive agents other than or in addition to ACE inhibitors and ARBs may be needed for blood pressure control in many subjects with hypertension and chronic renal failure. The same is true for subjects with radiation nephritis. No evidence indicates that one type of calcium channel blocker is preferred over another for radiation nephritis. However, one should avoid verapamil because use of this drug in a subject with hyperkalemia may cause atrial arrest.
| Drug Name | Nifedipine (Procardia) |
|---|---|
| Description | Like other calcium channel blockers, causes peripheral arterial vasodilation by inhibiting calcium influx across vascular smooth-muscle cell membranes. Long-acting formulations used for control of blood pressure. |
| Adult Dose | 30 mg PO qd initially; may increase dose to 120 mg PO qd |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity |
| Interactions | Caution with coadministration of any agent that can lower blood pressure, including beta-blockers and opioids; H2 blockers (cimetidine) may increase toxicity |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | May cause lower extremity edema; allergic hepatitis is rare |
Hyperkalemia may occur in subjects with BMT nephropathy, whether or not they are simultaneously taking ACE inhibitors or ARBs. For life-threatening hyperkalemia (plasma K > 6 mmol/L and/or ECG changes), emergency measures, such as intravenous glucose and insulin, are needed. For persistent, lesser degrees of hyperkalemia, a cation exchange resin may be needed to remove potassium by means of the gut.
| Drug Name | Sodium polystyrene sulfonate (Kayexalate) |
|---|---|
| Description | Given by mouth or retention enema. Exchanges approximately 2 sodium atoms for 1 potassium atom, which is lost in feces. |
| Adult Dose | 15-60 g PO qd, depending on plasma potassium level; often prepared in a suspension of 70% sorbitol, which acts as a laxative |
| Pediatric Dose | 1 g/kg PO in sorbitol q6h 2 g/kg PR in sorbitol as retention enema q6h |
| Contraindications | Documented hypersensitivity; hypernatremia |
| Interactions | Systemic alkalosis may occur if administered concurrently with magnesium hydroxide, aluminum carbonate or similar antacids, and laxatives |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Caution in patients who can be adversely affected by a small increase in sodium loads, such as those with severe hypertension, severe congestive heart failure, and marked edema; constipation, with possibility of fecal impaction, may occur; constipation should be treated with 70% sorbitol 10-20 mL q2h or prn to produce at least 1-2 watery stools daily |
Impaired potassium excretion in BMT nephropathy may be associated with low blood levels of aldosterone. In other causes of chronic renal failure with such aberrant potassium metabolism, use of a synthetic mineralocorticoid has been helpful.
| Drug Name | Fludrocortisone (Florinef) |
|---|---|
| Description | Mimics action of aldosterone, promoting sodium retention and potassium excretion. |
| Adult Dose | 0.1 mg PO qd |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; systemic fungal infections |
| Interactions | Antagonizes effects of anticholinergics; rifampin, hydantoins, and barbiturates decrease effects of fludrocortisone; decreases salicylate levels |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Sodium retention may lead to hypertension and edema formation, which may necessitate dose reduction of or addition of diuretic; glucocorticoid-type metabolic effects, such as peptic ulcer, hyperglycemia, or insomnia, may occur |
Anemia may occur in both radiation nephritis and BMT nephropathy, which has been associated with low blood levels of endogenous erythropoietin. Treatment of anemia with exogenous erythropoietin (EPO) may relieve symptoms of anemia.
| Drug Name | Epoetin (Epogen, Procrit) |
|---|---|
| Description | Glycoprotein is recombinant human erythropoietin (glycoprotein with 165 amino acids). Stimulates bone marrow RBC production. Abundant use in subjects who require chronic dialysis for end-stage renal disease. Given by IV or SC injection. |
| Adult Dose | 50 U/kg IV/SC, initially once or twice weekly |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; uncontrolled hypertension |
| Interactions | None reported |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Sufficient bodily iron stores needed for EPO to be effective (may require iron supplement); rapid rise in hematocrit may predispose patients to seizures, usually the result of uncontrolled hypertension; caution in porphyria, hypertension, or history of seizures; decrease dose if hematocrit increase exceeds 4% in any 2-wk period |
| Drug Name | Darbepoetin alfa (Aranesp) |
|---|---|
| Description | Erythropoiesis-stimulating protein closely related to erythropoietin. Mechanism of action similar to that of endogenous erythropoietin, which interacts with stem cells to increase RBC production. Differs from epoetin alfa (recombinant human erythropoietin) in that it contains 5 N-linked oligosaccharide chains, whereas epoetin alfa contains 3. Has longer half-life than epoetin alfa (may be administered weekly or biweekly). |
| Adult Dose | 0.45 mcg/kg IV/SC qwk initially; adjust dose (not to exceed 3 mcg/kg/wk) or frequency (eg, q2wk); to maintain target Hgb (not to exceed 12 g/dL); do not increase dose more than qmo Switching from epoetin alfa: Base dose on total weekly erythropoietin dose and frequency |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; uncontrolled hypertension |
| Interactions | None reported |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Elevation in Hgb > 1 g/dL/2 wk increases risk of MI, neurologic events (eg, seizures, stroke) and exacerbations of hypertension, CHF, thrombosis, ischemia, and edema; adverse effects include infection, hypertension, hypotension, myalgia, headache, and diarrhea (some of adverse events may be due to chronic renal failure or dialysis); severe skin rash may occur (rare) |
Control of hypertension in radiation nephritis and most chronic renal disease requires use of a diuretic. This is the clinical correlate of impaired natriuresis that exists in most forms of experimental hypertension. Additionally, diuretics facilitate potassium excretion.
| Drug Name | Hydrochlorothiazide (Esidrix, HydroDIURIL, Microzide) |
|---|---|
| Description | Acts on distal nephron to impair sodium reabsorption, enhancing sodium excretion. In use for >40 y and generally important agent for treatment of essential hypertension. |
| Adult Dose | 25 mg PO qd initially; may increase dose to 50 mg PO qd |
| Pediatric Dose | 1 mg/kg/d PO divided bid |
| Contraindications | Documented hypersensitivity; anuria or renal decompensation; because hydrochlorothiazide contains a sulfur atom, known allergy to sulfa drug may be accompanied by allergy |
| Interactions | Thiazides may decrease effects of anticoagulants, antigout agents, and sulfonylureas; thiazides may increase toxicity of allopurinol, anesthetics, antineoplastics, calcium salts, loop diuretics, lithium, diazoxide, digitalis, amphotericin B, and nondepolarizing muscle relaxants; diuretic response to thiazides may be blunted by nonsteroidal antiarthritic agents, such as ibuprofen |
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals |
| Precautions | As with all diuretics, should potentiate action of antihypertensive agents, especially ACE inhibitors or ARBs; as with other diuretics, may cause loss of potassium and, thus, hypokalemia, which may be beneficial in subjects with BMT nephropathy; after plasma creatinine is 2 mg/dL or higher, may no longer be effective to control fluid retention, and loop diuretic may be needed |
| Drug Name | Furosemide (Lasix) |
|---|---|
| Description | Acts on thick ascending limb of loop of Henle to enhance sodium, potassium, and chloride and water excretion. More potent than HCTZ and may be required for control of fluid retention in subjects with impaired renal function. |
| Adult Dose | 20 mg PO initially; may be increased to 3-4 mg/kg/d PO divided bid |
| Pediatric Dose | 2 mg/kg PO |
| Contraindications | Documented hypersensitivity; hepatic coma, anuria, and state of severe electrolyte depletion |
| Interactions | Metformin decreases concentrations; interferes with hypoglycemic effect of antidiabetic agents and antagonizes muscle-relaxing effect of tubocurarine; auditory toxicity appears to be increased with coadministration of aminoglycosides; hearing loss of varying degrees may occur; anticoagulant activity of warfarin may be enhanced when taken concurrently; increased plasma lithium levels and toxicity are possible when taken concurrently |
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals |
| Precautions | Loop diuretics potentiate action of antihypertensive drugs, especially ACE inhibitors or ARBs; may cause substantial urinary potassium loss and, thus, cause hypokalemia; loop diuretics may cause hypercalciuria |
| Media file 1: Evolution of the glomerular filtration rate (GFR) versus time in a case of nephropathy related to bone marrow transplantation (BMT). GFR may be approximated as 100/plasm creatinine on the Y axis and graphed versus time on the X axis. As is true in many cases of BMT nephropathy, the evolution appears to be biphasic, with an initial rapid decline in GFR, then a slower plateau phase. The patient whose data are shown here ultimately underwent kidney transplantation. | |
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| Media file 2: Photomicrograph of a kidney-biopsy sample in a case of nephropathy associated with bone marrow transplantation (periodic acid-Schiff stain). A glomerulus is in the center and is relatively hypocellular. Increased mesangial matrix is present. The glomerular basement membranes are thin; however, in some places, they are separated from the capillary lumens by a low-density matrixlike material. Interstitial fibrosis separates the tubules from each other. Arteriolar thickening and arteriolar hyalin both are present. | |
View Full Size Image | Media type: Photo |
Article Last Updated: Jul 22, 2008