a persistent, painful erection of the penis unaccompanied by sexual excitation or desire.

When normal erection occurs, the sides and the bottom of the penis, the corpora cavernosa and the corpus spongiosum, respectively, become engorged with blood so that the penis enlarges, hardens, and assumes an erect position. The major symptom of priapism is pain and tenderness in the enlarged portions. There may be a short period during the onset when pleasurable sensations are felt, but this quickly gives way to constant pain. In only about 25 percent of the cases can the cause be identified. The causes are generally classified as nervous or mechanical disorders. The nervous disorders may be in the spinal nerves or in the peripheral nerves that lead to the reproductive tract. Syphilitic involvement of the nervous system can cause cases of priapism that may be prolonged for years; most instances of the disorder last only a few hours, days, or weeks.

Not all cases involve the full penis. Sometimes only the corpora cavernosa are engorged. When the corpus spongiosum is also erect, serious urinary difficulties may result. The urethra, which is the duct for urine excretion, runs down the middle of the corpus spongiosum. Constant prolonged restriction of the tube can lead to retention of urine in the bladder. In some cases catheterization (mechanical drainage) can relieve the buildup. If urine retention is not relieved, urine can back up into the kidneys, with serious kidney disease as a result.

Among mechanical causes of priapism are obstructions such as large blood clots or tumours in the penis. In rare cases, chronic priapism may result from exceptionally prolonged and rough copulation. It is caused by a blood clot (thrombosis) in the vein that releases the blood from the penis. It is distressing, lasting for days or weeks, and it generally leaves the affected person permanently impotent. The penis is at first tensely erect and painfully tender. After several days, there is gradual lessening of tension and pain; the organ may remain semierect for weeks before it gradually returns to a flaccid state. In this prolonged period the erectile tissue of the penis is replaced by nonfunctioning fibrous scar tissue, so that the sufferer is rendered impotent. This type of priapism may be helped by early treatment with anticoagulant drugs or by drainage with large needles inserted into the erectile tissue.

Children have been known to have brief episodes of priapism from full bladders, local irritation, or prolonged masturbation. Disorders such as inflammation of the urethra, calcium stones in the urethra, infections of the prostate gland, or rectal parasites can also cause the condition. More prolonged cases arise from congenital syphilis, leukemia, or sickle cell anemia. Male infants and toddlers are not exempt, but in most cases the sufferer is older.

Ordinarily, treatment is directed toward the cause. Usually only when abscesses or tumours are involved is the penis surgically opened.