Localizing an occult Insulinoma by Selective Calcium Arterial Stimulation Test: First ever experience and a new dimension to diagnosis in Pakistan.

Insulinomas are rare, usually benign, solitary tumours accounting for 60% of islet cell tumours. These tumours can be difficult to localize preoperatively due to their small size. We present a challenging case of a 40 year old male with frequent hypoglycaemic spells and endogenous hypoglycaemia who presented as a diagnostic dilemma. Patient had an occult insulinoma with inconclusive CT Abdomen, MRI Abdomen and Octreotide scan. The final localization of the tumour was made by selective arterial calcium stimulation testing (SCAT), done for the first time in Pakistan at Aga Khan University Hospital. This was followed by successful distal pancreatectomy as localizd by SACT yielding a well differentiated neuroendocrine tumour. After surgery patient made a robust recovery with no further hypoglycaemic symptoms. Hence successful localization and management of occult insulinomas can be challenging but can be achieved with the advent of newer invasive modalities.