Marrow visualization on renal scintigraphy: An often-overlooked finding in azotemic patients

Delayed perfusion and enhanced hepatobiliary uptake are recognized findings on ^99mTc-mercaptoacetyltriglycine (^99mTc-MAG3) scintigraphy in patients with renal insufficiency. Less well appreciated is the finding of bone marrow visualization. This study was performed to determine the frequency of this sign and to try to determine its association with laboratory parameters. Methods: We retrospectively studied medical records and the results of renal scans performed on 170 patients from June to December 2009 at the Montefiore Medical Center. Among them we identified 167 patients who fulfilled our inclusion criteria for participation in this study. Prominent individual vertebrae and sacroiliac joints were categorized as bone marrow visualization. A lack of radiotracer activity in individual vertebrae or in the sacroiliac joints was categorized as bone marrow nonvisualization. The studies were interpreted by 2 nuclear medicine physicians who were unaware of the laboratory and clinical data. Results: The 167 patients fulfilling our inclusion criteria were divided into 2 groups: group 1 (n = 20), with visualization, and group 2 (n = 147), without visualization. The mean creatinine level in group 1 was higher than that in group 2 (3.2 vs. 1.1, P = 0.001). There was no difference in mean hematocrit and hemoglobin between the 2 groups. None of the patients with a creatinine level less than 1.5 mg/dL had bone marrow visualization, whereas bone marrow was visualized in 44% of patients with a creatinine level greater than 1.5 mg/dL. There was no definite correlation between the intensity of marrow activity and the level of creatinine. Conclusion: Bone marrow often may be visualized on early images of ^99mTc-MAG3 renal scans of azotemic patients. The etiology needs further clarification. Enhanced marrow perfusion, an increased blood concentration of ^99mTc-MAG3, and marrow hyperplasia secondary to associated anemia or hemolysis are possible causes.