Non-contrast-enhanced computerized tomography and analgesic-related kidney disease: report of the national analgesic nephropathy study

Analgesic Nephropathy–-A Painful Progression

One of the dreaded complications of long term analgesic intake is nephrotoxicity characterized by chronic interstitial nephritis and papillary necrosis. Much of the literature of its epidemiology dates back to 1960s and its impact on present day society is not well documented. Non steroidal anti inflammatory agents reduce pain by blocking prostaglandin generation. Prostaglandins have renal vaso dilatory effects in states of volume depletion to counteract the vasoconstrictive pressor hormones. Earlier analgesic tablets contained a mixture of aspirin, phenacetin and caffeine. Phenacetin and its metabolites have nephrotoxic potential and incidence of analgesic nephropathy was brought down in countries where it was banned. The concentration of phenacetin and its metabolite acetaminophen is increased at the tip of renal papilla due to counter current concentrating mechanism of the loop of henle. These are potent oxidants leading to cell injury due to lipid peroxidation, though their effects are normally counterbalanced by anti oxidant glutathione. Glutathione deficiency at the medulla can be precipitated by co ingestion of aspirin. The exact dose of analgesics which needs to be ingested is unclear but a daily ingestion of 5–8 tablets over 5 years results in clinical nephrotoxicity. The histopathology is one of chronic interstitial nephritis with renal fibrosis. Clinically the patient presents with polyuria, asthenia and anemia. The diagnosis is suspected in a patient with progressive chronic kidney disease without proteinuria. CT imaging of the kidneys show irregular scarred kidneys with papillary calcification and necrosis. Recently, COX-2 inhibitors are promoted as renal safe drugs, but may not be so given the multiple case reports of renal toxicity in post marketing surveys. The treatment of analgesic nephropathy includes discontinuation of offending drug, protein restricted diet, control of blood pressure and statins. In conclusion analgesic nephropathy is a preventable cause of chronic kidney disease and both the patients and treating physicians should be mindful of the potential nephrotoxcity of nonsteroidal anti inflammatory agents when administered for prolonged periods without monitoring renal function.

What do we know about chronic renal failure in young adults? I. Primary renal disease

Paediatric registries worldwide report that congenital abnormalities of the kidney and urinary tract (CAKUT) account for approximately 50% of end-stage renal failure and other congenital and familial diseases account for another 20% (together 70%). Does the same hold true for young adults? Almost nothing has been published about primary renal disease in adults who have reached end-stage before 30 years of age. I have reviewed the UK renal registry (2000-2006) and the United States Renal Data System (USRDS) data base (2005) to answer this question. While paediatric registries have reduced the number of children with 'no specific diagnosis' from 39% in 1976 to fewer than 5%, the adult registries still report rates of 20-27%, which rise to 28-36% when all unspecified groups, predominantly 'glomerulonephritis (GN) (histologically not examined)', are considered together. For UK data, this rise in 'no specific diagnosis' mirrors a fall in CAKUT to 26% for the age group 18-21 years. According to USRDS data, CAKUT falls from 31% for ages 0-19 years to only 5% for ages 20-30 years. Nephrologists probably under-diagnose CAKUT in young adult patients, and this diagnosis can account for many of the 30% that currently have no specified primary renal disease.

Over-the-counter analgesic use

Chronic analgesic nephropathy, particularly chronic interstitial nephritis and renal papillary necrosis, results from daily use for many years of mixtures containing at least two analgesics and caffeine or dependence-inducing drugs. Computed tomography scan can accurately diagnose this disease even in the absence of reliable information on previous analgesic use. The occasion to moderate regular use of aspirin and nonsteroidal anti-inflammatory drugs is without renal risk when renal function is normal. Paracetamol use is less clear although the risk is not great. The continued use of non-phenacetin-combined analgesics with or without nonsteroidal anti-inflammatory drugs is associated with faster progression toward renal impairment. As long as high-risk analgesic mixtures are available over the counter, analgesic nephropathy will continue to be a problem.

Non-phenacetin analgesics and analgesic nephropathy: clinical assessment of high users from a case-control study

BACKGROUND

A recent large-scale case-control study on analgesic nephropathy (SAN) [1] found no increased risk of end-stage renal disease (ESRD) in users of combined or single formulations of phenacetin-free analgesics. In a subgroup of 22 high users, however, a dose-dependent increased risk was found, which raised the question if these patients presented or not with analgesic nephropathy (AN).

METHODS

The individual questionnaires of this subgroup of high users were reviewed, and the total lifetime intake of different types of analgesics was calculated. For evidence of AN, the following data were considered: (1) the amount and type of analgesics consumed, (2) the cause of ESRD, as diagnosed by the nephrologist in charge of the patient and (3) renal imaging and other relevant laboratory data.

RESULTS

This group of ESRD patients consumed on average 7.8 kg of antipyretic analgesics (range 30.8-2.7 kg) over an average of 21.5 years (range 35-6 years). Single analgesics were exclusively used by 12 patients (54.5%) and combined analgesics by 5 patients (22.7%), while 5 patients used both. None of the patients was diagnosed as having AN, and a review of the questionnaires did not disclose evidence suggestive of AN. The possibility that, irrespective of AN, the analgesic (ab)use contributed to the progression of existing renal diseases cannot be answered in the absence of well-defined criteria. The data supporting the existence of such an analgesic-associated nephropathy (AAN) are, however, not consistent and most likely due to confounding by indication.

CONCLUSION

In a group of ESRD patients with high use of non-phenacetin analgesics, no evidence of AN was found. There is no evidence that (ab)use of analgesics or NSAIDs other than phenacetin leads to a pathologically or clinically defined renal disease that could be named AN or AAN.

Analgesic nephropathy and renal replacement therapy in Australia: trends, comorbidities and outcomes

BACKGROUND AND OBJECTIVES

This study examined age-specific incidence and prevalence of renal replacement therapy attributed to analgesic nephropathy from 1971 through 2005 and adjusted comorbidity prevalence and survival of patients who had analgesic nephropathy and were on renal replacement therapy (compared with control subjects without diabetes).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This retrospective cohort study, using data from the Australia and New Zealand Dialysis and Transplant registry, included all patients who were aged 35 to 84 yr and started long-term renal replacement therapy in Australia from 1971 through 2006.

RESULTS

Of 31,654 incident renal replacement therapy patients, 10.2% had analgesic nephropathy. Incidence and prevalence of renal replacement therapy attributed to analgesic nephropathy decreased earlier and faster among younger (age <55 yr) patients. Prevalence of analgesic nephropathy among 75- to 84-yr-old renal replacement therapy patients is still increasing. Compared with control subjects without diabetes, comorbidities (coronary artery, cerebrovascular, peripheral vascular, and chronic lung diseases) were more prevalent among patients with analgesic nephropathy at renal replacement therapy start. All-cause, cardiovascular, infection, and cancer mortality were higher among patients who had analgesic nephropathy and were on renal replacement therapy. For both comorbidities and mortality, the associations were stronger in younger patients.

CONCLUSIONS

Trends in renal replacement therapy attributed to analgesic nephropathy differed by age. Patients with analgesic nephropathy have more comorbidities and poorer survival on renal replacement therapy, especially among younger patients.

Analgesics use and ESRD in younger age: a case-control study

BACKGROUND

An ad hoc peer-review committee was jointly appointed by Drug Authorities and Industry in Germany, Austria and Switzerland in 1999/2000 to review the evidence for a causal relation between phenacetin-free analgesics and nephropathy. The committee found the evidence as inconclusive and requested a new case-control study of adequate design.

METHODS

We performed a population-based case-control study with incident cases of end-stage renal disease (ESRD) under the age of 50 years and four age and sex-matched neighborhood controls in 170 dialysis centers (153 in Germany, and 17 in Austria) from January 1, 2001 to December 31, 2004. Data on lifetime medical history, risk factors, treatment, job exposure and intake of analgesics were obtained in a standardized face-to-face interview using memory aids to enhance accuracy. Study design, study performance, analysis plan, and study report were approved by an independent international advisory committee and by the Drug Authorities involved. Unconditional logistic regression analyses were performed.

RESULTS

The analysis included 907 cases and 3,622 controls who had never used phenacetin-containing analgesics in their lifetime. The use of high cumulative lifetime dose (3rd tertile) of analgesics in the period up to five years before dialysis was not associated with later ESRD. Adjusted odds ratios with 95% confidence intervals were 0.8 (0.7 - 1.0) and 1.0 (0.8 - 1.3) for ever- compared with no or low use and high use compared with low use, respectively. The same results were found for all analgesics and for mono-, and combination preparations with and without caffeine. No increased risk was shown in analyses stratifying for dose and duration. Dose-response analyses showed that analgesic use was not associated with an increased risk for ESRD up to 3.5 kg cumulative lifetime dose (98 % of the cases with ESRD). While the large subgroup of users with a lifetime dose up to 0.5 kg (278 cases and 1365 controls) showed a significantly decreased risk, a tiny subgroup of extreme users with over 3.5 kg lifetime use (19 cases and 11 controls) showed a significant risk increase. The detailed evaluation of 22 cases and 19 controls with over 2.5 kg lifetime use recommended by the regulatory advisors showed an impressive excess of other conditions than analgesics triggering the evolution of ESRD in cases compared with controls.

CONCLUSION

We found no clinically meaningful evidence for an increased risk of ESRD associated with use of phenacetin-free analgesics in single or combined formulation. The apparent risk increase shown in a small subgroup with extreme lifetime dose of analgesics is most likely an indirect, non-causal association. This hypothesis, however, cannot be confirmed or refuted within our case-control study. Overall, our results lend support to the mounting evidence that phenacetin-free analgesics do not induce ESRD and that the notion of "analgesic nephropathy" needs to be re-evaluated.