Alternate Names: Phenacetin nephritis; Nephropathy - analgesic

Causes and Risks: Analgesic nephropathy is one type of toxic injury to the kidney. It is usually a result of prolonged or chronic ingestion of analgesics, especially OTC medications that contain phenacetin or acetaminophen - oral and nonsteroidal antiinflammatory drugs (NSAIDs) including aspirin (see salicylates - oral) or ibuprofen. The ingestion may have been excessive, with as much as 2 or more kg (4 - 5 pounds) total medication ingested over a period of years, or about 3 pills per day for 6 years. This frequently occurs as a result of self-medication, often for some type of chronic pain.

Analgesic nephropathy occurs in about 4 out of 100,000 people, mostly women over 30 years old. The incidence has decreased significantly since phenacetin is no longer widely available in OTC preparations. Risk factors include use of OTC analgesics containing more than one active ingredient, chronic headache, chronic backache or musculoskeletal pain, pain with menstrual periods, emotional and/or behavioral changes, and history of dependent behaviors including smoking, alcoholism, and excessive use of tranquilizers. There may also have been a history of previous urinary tract infection (see UTI - acute), interstitial nephritis, renal calculi, prerenal azotemia, congestive heart failure, or blood volume depletion (such as dehydration).

The damage occurs within the internal structures of the kidney. There is interstitial nephritis and renal papillary necrosis, eventually leading to acute renal failure or chronic renal failure. The tissue of the kidney may slough off into the urine. There may be blood and pus in the urine with or without positive urine cultures or other signs of infection, and there may be minimal or no loss of protein in the urine.

Prevention: Follow the directions of the health care provider when using medications, including OTC medications. Do not exceed the recommended dose of medications without the supervision of the health care provider.

Symptoms:

• weakness
• fatigue
• increased urinary frequency or urgency
• blood in the urine
• flank pain or back pain, renal colic (occasional)
• decreased urine output
• decreased alertness
  • drowsiness
  • confusion, delirium
  • lethargy
• decreased sensation, numbness (especially of extremities)
• nausea, vomiting
• easy bruising or bleeding
• swelling, generalized

Signs and Tests: An examination may be unrevealing but may indicate interstitial nephritis or renal failure. The blood pressure may be elevated. There may be signs of fluid overload, including abnormal heart or lung sounds. Premature skin aging may be evident.

• A urine toxicology screen may be positive for salicylate.
• A urinalysis shows blood and white cells.
• A CBC may show anemia, with decreased number of red blood cells.
• A histology (examination) of sediment or tissue passed in the urine may show necrotic (dead) papillary tissue.
• An IVP (intravenous pyelogram) may show papillary necrosis (tissue death) or sloughed papillae in the renal pelvis or ureter.

Treatment: The primary goals of treatment are to prevent further damage and to treat any existing kidney failure. All suspect analgesics, particularly over-the-counter (OTC) medications, must be stopped.

Signs of kidney failure should be treated as appropriate to the extent and severity of the kidney failure. This may include dietary changes, fluid restriction, dialysis or kidney transplant, and other treatment.

Counseling, behavioral modification, or similar interventions may assist in developing alternative methods of chronic pain control.

Prognosis: The damage to the kidney may be acute and temporary, or chronic and long term.

Complications:

• acute renal failure
• chronic renal failure
• interstitial nephritis
• renal papillary necrosis (tissue death)
• urinary tract infections, chronic or recurrent
• hypertension
• transitional cell carcinoma of the kidney or ureter
• transitional cell carcinoma of the bladder

Call your health care provider if symptoms indicate analgesic nephropathy may be present, especially if there has been a history of use of analgesics.

Call your health care provider if blood or solid material is present in the urine, or if the urine output decreases.