The seminal vesicles (also called vesicular glands, or seminal glands) are a pair of two convoluted tubular glands that lie behind the urinary bladder of some male mammals. They secrete fluid that partly composes the semen. The vesicles are 5–10 cm in size, 3–5 cm in diameter, and are located between the bladder and the rectum. They have multiple outpouchings which contain secretory glands, which join together with the vas deferens at the ejaculatory duct. They receive blood from the vesiculodeferential artery, and drain into the vesiculodeferential veins. The glands are lined with column-shaped and cuboidal cells. The vesicles are present in many groups of mammals, but not marsupials, monotremes or carnivores. Inflammation of the seminal vesicles is called seminal vesiculitis, most often is due to bacterial infection as a result of a sexually transmitted disease or following a surgical procedure. Seminal vesiculitis can cause pain in the lower abdomen, scrotum, penis or peritoneum, painful ejaculation, and blood in the semen. It is usually treated with antibiotics, although may require surgical drainage in complicated cases. Other conditions may affect the vesicles, including congenital abnormalities such as failure or incomplete formation, and, uncommonly, tumours. The seminal vesicles have been described as early as the second century AD by Galen, although the vesicles only received their name much later, as they were initially described using the term from which the word prostate is derived.
Stones or cysts that become infected, or obstruct the vas deferens or seminal vesicles, may require surgical intervention.Seminal vesiculitis (also known as spermatocystitis) is an inflammation of the seminal vesicles, most often caused by bacterial infection. Symptoms can include vague back or lower abdominal pain; pain of the penis, scrotum or peritoneum; painful ejaculation; blood in the semen on ejaculation; irritative and obstructive voiding symptoms; and impotence. Infection may be due to sexually transmitted infections, as a complication of a procedure such as prostate biopsy. It is usually treated with antibiotics. If a person experiences ongoing discomfort, transurethral seminal vesiculoscopy may be considered. Intervention in the form of drainage through the skin or surgery may also be required if the infection becomes an abscess. The seminal vesicles may also be affected by tuberculosis, schistosomiasis and hydatid disease. These diseases are investigated, diagnosed and treated according to the underlying disease.Benign tumours of the seminal vesicles are rare. When they do occur, they are usually papillary adenomas and cystadenomas. They do not cause elevation of tumour markers, and are usually diagnosed based examination of tissue that has been removed after surgery. Primary adenocarcinoma of the seminal vesicles, although rare, constitutes the most common malignant cancer of the seminal vesicles; that said, the majority of malignant cancers affecting the vesicles are lesions that have extended into the vesicles from nearby parts of the body. When adenocarcinoma occurs, it can cause blood in the urine, blood in the semen, painful urination, urinary retention, or even urinary obstruction.