CASE 9395 Published on 25.06.2011

Radiographic appearance of lanthanum carbonate

Section

Abdominal imaging

Case Type

Clinical Cases

Authors

Dimitriou Ch, Marmareli P, Sdrolia A, Tzeliou V, Karvelis A, Fountoulakis G.
Radiology Department, General Hospital of Kastoria, Greece

Patient

60 years, male

Categories
Area of Interest Colon ; No Imaging Technique
Clinical History
A 60-year-old male patient with end-stage renal disease (ESRD) on peritoneal dialysis for the past 5 years, presented with lower back pain.
Imaging Findings
The plain X-ray of the lumbar spine revealed degenerative changes and scoliosis. Multiple intense radiopaque structures of varying size were also seen, incidentally, in the region of the colon.
Additional clinical history: The patient had not undergone radiographic examination of the abdomen with the use of contrast agent recently. However, he received lanthanum carbonate (Fosrenol), one tablet three times daily (750mg each tablet, a total of 2250mg) for the treatment of hyperphosphatemia for six months.
Discussion
Lanthanum carbonate is a novel calcium- and aluminum- free phosphate binder that is used for the treatment of hyperphosphataemia in patients with ESRD. Oral administration of this drug inhibits the absorption of phosphate from food by forming highly insoluble lanthanum-phosphate complexes which are excreted in the feces. This has as a result the reduction of serum phosphate level [1].
Lanthanum is a rare earth metal with the atomic number 57, which is close to that of Barium (56). The affinity of lanthanum for phosphate is above 97%. Lanthanum binds phosphate optimally at ph 3-5 (of the gastric fluid in the stomach) and retains binding activity at ph 1-7. Lanthanum carbonate is virtually non-absorbed (systemic absorption is only 0.00005%) and exhibits low aqueous solubility (practically insoluble in water) [2].
The total daily dose of Fosrenol should be divided and taken with or immediately after meals. The recommended initial daily dose is 1500mg and it should be titrated every 2-3 weeks until an acceptable serum phosphate level is reached. Dosage of 1500-3000mg daily usually is required to reduce serum phosphate level below 6mg/dl. Tablets should be chewed completely before swallowing. Intact tablets should not be swallowed.
Initial reports implicated intestinal calcium-phosphate accumulation as responsible for the characteristic radiopaque finding. However, lanthanum itself was subsequently found to be radiopaque and the reason for the radiopaque appearance [3]. Even without calcium and phosphate, lanthanum is itself radiopaque.
On computed tomography images, this drug may cause strong beam-hardening artefacts which may be mistakenly interpreted as foreign bodies. Because of these artefacts, the CT images are degraded and difficult to evaluate [4]. To achieve a non-obscured abdominal image on the radiological examinations, treatment with lanthanum carbonate should be discontinued and changed to a different phosphate binder several days before the radiological examination of the abdomen.
Given the increasing usage of lanthanum carbonate in patients with ESRD in clinical practice, every physician must be aware of the typical radiographic appearance, in order to avoid false diagnosis, unnecessary radiological and endoscopic examinations and of course, inappropriate management . Finally, due to this characteristic radiopaque finding, one can evaluate the patient's compliance to lanthanum carbonate [2, 5].
Differential Diagnosis List
Typical radiographic appearance of lanthanum carbonate.
Foreigh bodies
Contrast agents
Final Diagnosis
Typical radiographic appearance of lanthanum carbonate.
Case information
URL: https://www.eurorad.org/case/9395
DOI: 10.1594/EURORAD/CASE.9395
ISSN: 1563-4086