Single-photon emission CT using (99m)Tc-dimercaptosuccinic acid (DMSA) for characterization of suspected renal masses

Abstract

Objective: A retrospective analysis of the clinical utility of (99m)Tc-dimercaptosuccinic acid (DMSA) single photon emission CT (SPECT) for characterization of suspected renal masses.

Methods: 15 patients who had undergone (99m)Tc-DMSA SPECT were identified, and 13 patients also had SPECT/CT. (99m)Tc-DMSA uptake in the renal lesion was characterized semiquantitatively. Other imaging tests, histology and clinical data were available for correlation.

Results: (99m)Tc-DMSA was not taken up in all five renal masses with histological confirmation of malignancy (uptake 7-19% of normal renal tissue); in two further masses, which were clinically likely to be malignant; and in one indeterminate mass (lack of sufficiently long follow-up). No renal malignancy was identified in any of the seven patients whose renal masses had normal (99m)Tc-DMSA uptake (41-130%).

Conclusion: Although caution with regard to applying those results in clinical practice must be advised, owing to the retrospective nature of this report and the small number of patients included, it seems that (99m)Tc-DMSA SPECT shows a clinically useful diagnostic accuracy for distinguishing true renal masses (which in many cases require surgery) from pseudomasses.

Advances in knowledge: (99m)Tc-DMSA SPECT is a clinically useful adjunct test for characterization of suspected renal masses.

Figure 1.

A 79-year-old male presented with haematuria. A renal mass was seen on ultrasound. CT showed a 31-mm right lower pole renal mass with hypoenhancement (arrow). ^99mTc-dimercaptosuccinic acid single-photon emission CT showed very little tracer uptake in the lesion (approximately 9% of normal renal parenchyma). The patient remained on CT surveillance for 9 months, but then underwent a nephrectomy and a 28-mm clear-cell carcinoma was found.

Figure 2.

A 66-year-old male had a history of prostate cancer and transitional cell cancer of the bladder and presented with haematuria. CT showed a 30-mm isoenhancing renal mass in the right kidney centrally (top row, arrow), which had increased in size from 3 years ago, as well as a 15-mm cystic right upper pole lesion (bottom row, arrow) with heterogeneous enhancement. ^99mTc-dimercaptosuccinic acid single-photon emission CT showed very little tracer uptake in either lesion (approximately 7% of normal renal parenchyma). Biopsy of the central lesion revealed clear-cell carcinoma. As the patient was unfit for surgery, he underwent radiofrequency ablation (RFA) treatment of the larger lesion. The upper pole lesion was in an unfavourable position for RFA and continues to grow. The patient is now being reconsidered for nephrectomy.

Figure 3.

An 84-year-old male had a history of melanoma 3 years ago and presented with right abdominal pain. Ultrasound examination showed a focal solid mass extending into the renal sinus fat of the left kidney with appearances consistent with a hypertrophied column of Bertin. However, this was of an unusually large size and therefore was further evaluated with a renal mass protocol CT scan. This showed inhomogeneous enhancement within the mass consistent with a central renal tumour (arrow). ^99mTc-dimercaptosuccinic acid single-photon emission CT showed very little tracer uptake in the lesion (approximately 11% of normal renal parenchyma). The overall interpretation was of a likely renal cell cancer, but it was considered unsuitable for radiofrequency ablation, and the patient opted for surveillance. There was no change on CT after 6 and 12 months.

Figure 4.

A 61-year-old male had a history of transitional cell carcinoma of the bladder. An ultrasound scan of the kidneys was normal 4 years ago. A 14-mm lesion at the lower pole of the right kidney had been noted on a CT scan a year ago and was felt to represent a pseudomass of spared renal parenchyma with adjacent renal scarring (arrow), but a solid renal mass was difficult to exclude on both ultrasound and CT evaluation. Laparoscopic approach for nephrectomy was felt to be difficult. ^99mTc-dimercaptosuccinic acid (DMSA) single-photon emission CT showed that the lesion had uptake similar to normal renal parenchyma (approximately 84%). No further follow-up was undertaken, and the patient is alive 29 months after his ^99mTc-DMSA scan.

Figure 5.

A 62-year-old female had a history of right nephrectomy for Stage I renal cancer 4 years ago. An ultrasound scan 9 months ago showed a focal solid projection into the renal sinus thought likely to represent a hypertrophied column of Bertin (left image, arrow). In view of the previous history of renal malignancy, a CT scan and ^99mTc-dimercaptosuccinic acid (DMSA) scan were performed for confirmation of normal renal parenchyma. The CT scan is consistent with a column of Bertin (centre image, arrow). The ^99mTc-DMSA single-photon emission CT/CT was performed on the GE Millenium VG with Hawkeye (GE Healthcare, Chalfort St Giles, UK), giving comparably low CT image quality, but the corresponding sections confirm uptake similar to normal renal parenchyma consistent with a column of Bertin (right images). A repeat ultrasound scan 20 months later was unchanged, and no further imaging has been undertaken. The patient is alive 7 years after the DMSA scan.