Which patients with ischaemic priapism require further investigation for malignancy?

Ischaemic priapism (IP) is characterised by a persistent, painful penile erection lasting for >4 h. Many causes of IP have been identified including haematological dyscrasias (particularly, sickle cell disease), drugs and rarely malignancy. There are also a large proportion of men, in which no aetiology is identified. Identification of men at risk for malignancy provides a diagnostic challenge to the clinicians looking after these patients. All cases of IP between 2007 and 2017 at a single tertiary andrology unit were identified. The case notes and electronic records of these patients were reviewed to identify cases of malignant priapism. Men with idiopathic IP were used as a control group for comparative statistics. In total, 412 men with IP were identified, 202 of which had idiopathic IP. Within this group, the prevalence of malignant priapism was 3.5% (n = 11). MP secondary to local invasion or penile metastases occurred in seven of the 11 men (bladder × 3, prostate, lung, urethral and chondrosarcoma of the pelvis). MP secondary to haematological malignancy occurred in the remaining four (chronic myeloid leukaemia  ×  2, chronic lymphocytic leukaemia, and myelodysplasia). IP was the initial presentation of malignancy in seven of the patients (64%). An abnormally low haemoglobin value (reference range 130-180 g/dl) was found in 82% (n = 9) of the men with MP. The mean haemoglobin value in men with MP was 109.64 ± 20.30 g/dl compared to the control of 131.87 ± g/dl. This difference was considered highly significant p = 0.0046. Men with MP also appear to have a very poor prognosis with an 18-month mortality of 64% (n = 7). Malignancy is a rare and important cause of IP. A low haemoglobin is a predictor of malignancy and warrants further investigation in IP.