Objective To describe findings and outcomes of 331 bilateral inferior petrosal sinus sampling (BIPSS) procedures performed in 327 patients evaluated for Cushing disease (CD).

Materials and methods The radiology department's electronic database was searched to identify all BIPSS procedures (1990–2013). Electronic medical records were used to identify demographics, laboratory, procedural, surgical and pathologic findings.

Results A total of 331 BIPSS procedures were performed in 327 patients (254 F, 73 M), mean age 41 (range 7–81) years. The overall technical success rate was 88% for bilateral cannulation, though nearly two-thirds of the technical failures had unilateral sampling that diagnosed CD. Of the 331 BIPSS procedures, 40 were performed without, and 291 with stimulation by Acthrel or desmopressin. Sensitivity was 89–94% for unstimulated BIPSS, 96% for stimulated BIPSS, and 77% for MRI. BIPSS lateralization was accurate in about half of patients, compared with 75% accuracy for MRI. Mean inferior petrosal sinus (IPS):peripheral adrenocorticotropic hormone ratio was 17.3 (SE 1.8) at baseline, and 99.2 (SE 14.8) at 3 min, with decreasing values over time. All patients with follow-up after surgical resection for centralizing BIPSS were reported to be cured, with cortisol levels significantly decreased from 19 to 4 μg/dL (p<0.0001). Complications from BIPSS were rare, including groin hematoma (2.5%), but no thromboembolic complications were seen.

Conclusions BIPSS remains the ‘gold standard’ for diagnosing CD. Stimulation with Acthrel or desmopressin is key to increasing specificity. When only one IPS can be successfully cannulated, results may still be diagnostic. BIPSS findings cannot be used to accurately lateralize lesions within the pituitary.