NDT Advance Access originally published online on March 11, 2008
Nephrology Dialysis Transplantation 2008 23(5):1777-1778; doi:10.1093/ndt/gfn043
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Reply
Correspondence and offprint requests to: E-mail: pf.jana{at}seznam.czSir,
This is a very interesting case report with a valuable medical observation worth mentioning. We would like to thank Dr Jana and colleagues for their clinical accuracy of observation and the comments regarding our recent publication in NDT on radiographic appearance of lanthanum carbonate [1]. We previously reported that opacifications throughout the colon occurred after ingestion of lanthanum carbonate tablets in a 46-year-old woman with stage 5 chronic kidney disease (CKD) requiring chronic haemodialysis [1]. Therein we speculated that these opacifications are related to intestinal calcium–phosphate accumulations.
We agree with Jana et al. that, possibly, the radio-opaque structures we had documented throughout the colon in our patient are not the intestinal calcium–phosphate accumulations induced through the oral intake of lanthanum carbonate. According to their unique and thorough observation displaying a blister package of a lanthanum pill, it is likely to assume that radio-opacity of lanthanum itself causes such changes in the gut. However, it is difficult to distinguish whether the observed opacifications represent the high-contrast metallic-like substance lanthanum alone or whether they further include neighbouring calcium–phosphate conglomerates. A radiographic investigation of lanthanum pills in solutions with different phosphate and calcium concentrations in vitro may be useful to further study such issues.
The sixty-four-dollar question, however, is to resolve the radio-opacity of lanthanum. We have now further looked in the scientific literature and found, to our own surprise, that there was another previous medical use of lanthanum which had already answered the enigma of radio-opacity of lanthanum carbonate in patients with stage 5 CKD.
Conventional glass ionomer cement (GIC) is a kind of dental cement used for a variety of purposes in odontology [2]. Literally it is the generic name of a group of materials based on the reaction of silicate glass powder and polyalkeonic acid. The material acquires its name from its formulation of a glass powder and an ionomer that contains carboxylic acids [2]. These tooth-coloured anticariogenic materials were first designed in 1972 by Wilson and Kent [3] for use as restorative materials for anterior teeth but since they bond chemically to dental hard tissues and release fluoride for a relatively long period, their applications had expanded many fold [2]. Notably, calcium flouroaluminosilicate glass cements are X-ray transparent and are indistinguishable from caries under X-ray conditions. A clinician using X-rays to examine a crown would mistake a conventional GIC for the caries-dental decay.
Therefore, metal-reinforced GICs were first introduced in dental care in 1977 [2]. Cements containing barium, strontium as well as lanthanum glasses were designed as they had the advantage of increased radio-opacity. Mainly, the addition of silver amalgam alloy powder to conventional materials increased the physical strength of the cement and thereby provided radio-opacity [2]. However, a scientific controversy over the use of amalgams, which also contain mercury, started since then in the dental community. Though mercury itself is a potent neurotoxin, amalgam fillings are considered safe by most dentists. Recent random clinical trials have found no evidence of neurological harm associated with their use in children, examining a period of 5–7 years following treatment [4,5]. Still, some worry exists about the difficulties of conclusively excluding the possibility of neurological effects [6].
We would like to underline that lanthanum carbonate is a well-tolerated, effective drug to lower serum phosphate levels [7]. It already has shown significant promise in clinical trials in CKD patients [7]. Aluminium was the initial phosphorus binder used, but was replaced by calcium-containing binders because of the development of aluminium toxicity [7]. Unfortunately, many nephrologists feel threatened by the allegation that treatment with calcium-based phosphate binders e.g. calcium acetate or calcium carbonate may aggravate hypercalcaemia and induce coronary artery as well as cardiac calcification, thereby imposing a greater risk for cardiovascular mortality in CKD patients [7]. Therefore, the non-calcium/non-aluminium phosphate binder lanthanum carbonate is considered an efficient, probably safe medical alternative and widely used in clinical practice for the treatment of hyperphosphataemia in CKD patients [7].
The main message we wished to convey in our recent report was to keep in mind the disturbing abdominal radiographic appearance when oral lanthanum intake is present. The observation from Jana et al. adds valuable pathophysiologic insight into this fact. Nephrologic patients treated with lanthanum carbonate who need a diagnostic abdominal radiograph should intermittently discontinue their lanthanum carbonate intake to assure an adequate visualization and an unimpeachable diagnosis.
Conflict of interest statement. None declared.
1 Department of Nephrology 2 Department of Diagnostic Radiology, Medical School Hannover, Germany
References
- David S, Kirchhoff T, Haller H, et al. Heavy metal–rely on gut feelings: novel diagnostic approach to test drug compliance in patients with lanthanum intake. Nephrol Dial Transplant (2007) 22:2091–2092.
[Free Full Text] - Anusavice KJ. Phillips’ Science of Dental Material (2003).
- Wilson AD, Kent BE. A new translucent cement for dentistry. The glass ionomer cement. Br Dent J (1972) 132:133–135.[CrossRef][Web of Science][Medline]
- Bellinger DC, Trachtenberg F, Barregard L, et al. Neuropsychological and renal effects of dental amalgam in children: a randomized clinical trial. JAMA (2006) 295:1775–1783.
[Abstract/Free Full Text] - DeRouen TA, Martin MD, Leroux BG, et al. Neurobehavioral effects of dental amalgam in children: a randomized clinical trial. JAMA (2006) 295:1784–1792.
[Abstract/Free Full Text] - Needleman HL. Mercury in dental amalgam—a neurotoxic risk? JAMA (2006) 295:1835–1836.
[Free Full Text] - Persy VP, Behets GJ, Bervoets AR, et al. Lanthanum: a safe phosphate binder. Semin Dial (2006) 19:195–199.[CrossRef][Web of Science][Medline]
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