Comparison of radionuclide scrotal blood-pool index versus gonadal venography in the diagnosis of varicocele

The purpose of our study was to assess the value of a radionuclide scrotal blood-pool index (SBPI) in diagnosing and grading clinical and subclinical varicocele. Methods: Scrotal scans were performed on 1360 infertile patients. Thirty fertile patients with a normal scrotum on palpation served as controls. The patients' red blood cells were labeled in vivo by administration of stannous ions of pyrophosphate followed by the intravenous administration of ^99mTc-pertechnetate. The scans initially were inspected visually and, when bilateral varicocele was excluded, a computerized analysis of the ratio of the blood-pool activity in each hemiscrotum (SBPI) permitted accurate grading of the varicocele. A subgroup of 224 patients was selected randomly and had gonadal venography. The results of physical examination, scrotal scan, gonadal venography and semen analysis were compared. Results: Normal values of SBPI (0.9-1.1) were derived from the control group. There was a 93.5% correlation between palpation and SBPI grade in diagnosing palpable varicocele. When compared to gonadal venography, subclinical varicocele was demonstrated by scrotal scan in 54.8% of infertile male patients with abnormal semen analysis, normal female partners and no other cause of infertility. Of these patients, 32.6% had, unexpectedly, Grade 2 or 3 varicocele. Right and bilateral varicocele were demonstrated three times as often by scrotal scan than by palpation. SBPI was accurate in diagnosing recurrent varicocele but there was a low correlation (61.1%) between SBPI and gonadal venography grade. There was a high correlation between SBPI grade and sperm analysis grade. Conclusion: SBPI grading of varicocele was validated as an accurate, quantitative and noninvasive method of grading varicocele, equivalent to the grading system by palpation in a large group of infertile patients. The main contribution of SBPI was in detecting and grading subclinical varicocele in infertile patients with no other cause of infertility. SBPI also was accurate in diagnosing but not in grading recurrent varicocele.