Chronic Lead Nephropathy

Chronic lead nephropathy is a chronic tubulointerstitial kidney disease caused by prolonged lead exposure, with progressive tubular atrophy, interstitial fibrosis and reduced glomerular filtration. It arises after years of occupational exposure (battery recycling and informal lead smelting, paint removal, ceramics, soldering, mining), environmental exposure (leaded petrol legacy, contaminated soil and water, lead pipes, traditional medicines and cosmetics such as kohl), and drinking water or food contaminated by lead glazed pots.

Lead is stored in bone (about 90 percent in adults) with a half life of years to decades, so a latent period of 10 to 20 years often separates exposure from nephropathy.

Pathology is proximal tubular nuclear inclusion bodies in the acute phase, then interstitial fibrosis, with hyperuricaemia from reduced uric acid excretion (saturnine gout) and hypertension.

Blood lead levels at presentation may be modest because lead is stored in bone, so provocative testing is needed. Progression to end stage kidney disease is slow, and lead also accelerates other kidney disease.

• Often silent until chronic kidney disease is advanced: fatigue, nausea, anaemia, and hypertension.
• Gout in young or premenopausal patients with renal impairment, and gout resistant to treatment.
• Hypertension, hyperuricaemia.
• Extra renal lead toxicity: abdominal colic, constipation, blue gingival line, peripheral motor neuropathy (wrist drop), anaemia with basophilic stippling, cognitive impairment, infertility.
• Mild proteinuria (below 1 g per day), rarely a nephrotic picture.
• Red flags: rapidly rising creatinine, severe anaemia, encephalopathy, pregnancy.

• Occupational and environmental exposure history, including hobbies and home water supply.
• Blood lead level (current exposure; normal below 5 micrograms/dL; levels above 40 micrograms/dL warrant action) and zinc protoporphyrin (chronic exposure).
• Renal function: serum creatinine and eGFR; urine albumin to creatinine ratio; urine analysis showing low molecular weight proteinuria (beta-2-microglobulin).
• Serum uric acid (elevated out of proportion to GFR), potassium, phosphate, and blood pressure.
• Provocation test: calcium disodium EDTA 1 g intravenously over 1 hour (or 2 g intramuscularly in 2 divided doses) followed by a 24-hour urine lead; excretion over 600 micrograms in 24 hours (or a ratio of over 0.6 micrograms of lead per milligram of EDTA given) indicates an increased body lead burden. Used when blood lead is only mildly raised and renal function is below eGFR 60.
• K-shell X-ray fluorescence of bone lead (specialist centres) measures cumulative burden.
• Full blood count and film: basophilic stippling, microcytic hypochromic anaemia.
• Kidney biopsy only when the cause is unclear: tubulointerstitial fibrosis, nuclear inclusion bodies.
• Exclude hypertensive nephrosclerosis, analgesic nephropathy, diabetic nephropathy, cadmium and other heavy metal nephropathy, and chronic glomerulonephritis.

• Stop exposure first: remove the worker from lead work, test and treat the household, fix the water source and cookware.
• Chelation lowers body lead burden and slows loss of renal function when eGFR is 20 to 60 mL/min/1.73 m2 and the provocation test is positive: calcium disodium EDTA 1 g intravenously (in 250 mL of normal saline over 1 to 2 hours) three times a week for 3 months, repeated every 3 to 6 months while urinary lead after provocation stays raised. In eGFR below 20 give 1 g weekly (or at dialysis). Maintain hydration, monitor creatinine, calcium, zinc, phosphate and magnesium, and give EDTA only after lead exposure is stopped to avoid nephrotoxicity. Avoid the disodium edetate form (causes fatal hypocalcaemia).
• Succimer 10 mg/kg orally every 8 hours for 5 days then every 12 hours for 14 days, for blood lead over 45 micrograms/dL in patients who can take oral therapy; dose adjustment in renal impairment is limited, and monitor liver enzymes.
• Chronic kidney disease care: ACE inhibitor (enalapril 5 to 20 mg orally once daily, titrated; check potassium and creatinine at 1 to 2 weeks), target blood pressure below 130/80 mmHg, treatment of anaemia with iron and erythropoietin, phosphate control.
• Hyperuricaemia and gout: allopurinol 100 mg orally once daily increased by 100 mg every 2 to 4 weeks to a maximum of 300 to 600 mg daily to maintain serum urate below 360 micromol/L (reduce dose in renal impairment); colchicine 500 micrograms twice daily for 3 months when starting; avoid non-steroidal anti-inflammatory drugs.
• Dialysis and transplant when end stage; lead chelation can be combined with dialysis (EDTA given during the last hour of haemodialysis).
• Calcium 1000 mg and iron adequate in diet reduce gut lead absorption.
• Follow up: blood lead, creatinine, eGFR and urine albumin to creatinine ratio every 3 months; blood pressure each visit.
• Prevention: workplace lead monitoring (blood lead below 30 micrograms/dL for workers), pregnancy removal from exposure, and community abatement.