Webster's New World Medical Dictionary

spiral fracture
See 
fracture, torsion.
spirochete
A microscopic bacterial organism in
the Spirochaeta family that has a worm-like, spiral-
shaped form and wiggles vigorously when viewed
under a microscope. Treponema pallidum, the cause
of syphilis, is a particularly well-known spirochete.
spleen
An organ that is located in the upper-left
part of the abdomen, not far from the stomach, that
produces lymphocytes, which are important ele-
ments in the immune system. The spleen is the
largest lymphatic organ in the body. The spleen also
filters blood, serves as a major reservoir for blood,
and destroys blood cells that are aged (or abnor-
mal, as in the case of sickle cells).
spleen, ruptured
Rupture of the capsule of the
spleen that is a potential catastrophe and requires
immediate medical and surgical attention. Splenic
rupture permits large amounts of blood to leak into
the abdominal cavity, and it is severely painful and
life threatening. Shock, and ultimately death, can
result. Patients typically require immediate surgery.
Rupture of a normal spleen can be caused by
trauma, such as an accident. If an individual’s
spleen is enlarged, as is frequent in mononucleosis,
most physicians will not allow participation in
major contact sports or other activities because
injury to the abdomen could be catastrophic.
splenectomy
An operation to remove the spleen.
splenic artery
A large and critically important
artery within the abdomen that arises from a branch
off the aorta called the celiac trunk. The splenic
artery supplies blood not only to the spleen but also
to the esophagus, stomach, duodenum, liver, and
pancreas. See also 
aorta; artery.
splenic fever
See 
anthrax.
splenomegaly
Abnormal enlargement of the
spleen. Splenomegaly is a sign of an underlying con-
dition, such as severe liver disease, leukemia, or
mononucleosis. Patients with splenomegaly should
avoid activities that risk trauma to the abdomen,
including contact sports, because of risk of bleeding
from the injured spleen.