Dr. Ahmed Saleem
FICMS
TUCOM / 3rd Year / 2015
CYSTS, SINUS AND FISTULA
Cysts
The word cyst is derived from the Greek word meaning ‘bladder’. The pathological term ‘cyst’ means a
swelling consisting of a collection of fluid in a sac which is lined by epithelium or endothelium.
Definitions
True cysts: are lined by epithelium or endothelium.
False cysts (pseudocysts): Walled-off collections of fluid as a result of exudation or degeneration,
not lined by epithelium are not regarded as true cysts, e.g. pseudocyst of pancreas, cystic
degeneration in a tumor.
Teratomas are tumors composed of various parenchymal cell types representative of more than one
germ cell layer. They arise from totipotential cells capable of forming endodermal, ectodermal, and
mesenchymal tissues and can have both benign and malignant forms. Such tumors typically occur in
testis or ovary, or rarely midline embryonic rests.
Dermoid is a loose term given to cysts lined by epidermal epithelium occurring in various parts of
the body.
Teratomatous dermoids are found in the ovary, testis, retroperitoneum, superior mediastinum
and the presacral area. Malignant change (carcinomatous or sarcomatous) can occur.
The sequestration dermoid is due to displacement of epithelium along embryonic fissures during
closure, e.g. skin. Sites include outer and inner borders of orbit, midline of the body, and
anterior triangle of neck (brachial cyst).
Implantation dermoids may follow puncture wounds, commonly of the fingers, when living
epithelial cells are implanted beneath the surface.
A sebaceous cyst starts with the obstruction of a sebaceous gland (Retention cyst), but this is
followed by the down-growth and the accumulation of desquamated epidermal cells, thus turning it
into an epidermoid cyst and
although surgeons often refer to it as sebaceous cyst because it appears to
contain sebum, this is a misnomer and the substance is actually keratin.
A classification of cysts
I – Congenital:
The sequestration dermoid.
Tubuloembryonic (tubulodermoid) cysts occur in the track of an ectodermal tube used in
development, e.g. a thyroglossal cyst from the thyroglossal duct.
Cysts of embryonic remnants arise from embryonic tubules and ducts which normally disappear or
are only present as remnants, e.g. cysts of the urachus and the vitellointestinal duct.
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II – Acquired:
Implantation dermoids.
Retention cysts. Due to the blocking of a glandular or excretory duct, e.g. ranula (salivary gland).
Distension cysts. Due to the distension of closed cavities as a result of exudation or secretion, e.g.
thyroid or ovarian cysts; hydrocele, ganglia.
Cystic tumors. For example, cystadenoma, cystadenocarcinoma of ovary.
Parasitic cysts. For example, hydatid cysts (Taenia echinococcus).
Pseudocysts. Due to necrosis of hemorrhage with liquefaction and encapsulation, e.g. necrotic
tumors, cerebral softening, or coalescence of inflammatory fluid collections, e.g. pseudocyst of
pancreas.
Clinical Presentation
Smooth, spherical, soft and fluctuant when palpated in two planes with the fingers at right angles to
each other.
If tense contents, may produce pain in the cyst or surrounding tissue.
If the fluid is clear, the swelling will transilluminate.
Ultrasound and aspiration of contents are methods of determining whether a given swelling is cystic
and may differentiate a cyst from a lipoma.
May compress surrounding tissues.
May produce pain if complications supervene. They are also subject to infection, torsion if on a
pedicle, hemorrhage, and calcification.
Sinuses and Fistulas
A sinus is a blind epithelial track, lined by granulation tissue which extends from a free surface into
the tissues, e.g. pilonidal sinus.
A fistula is an abnormal communication between two epithelial surfaces. It is lined by granulation
tissue and colonized by bacteria, e.g. fistula-in-ano, pancreaticocutaneous, colovesical,
vesicovaginal.
Causes
Specific disease, e.g. Crohn’s.
Abscess formation and spontaneous drainage, e.g. diverticular abscess discharging into vagina with
fistula formation.
Penetrating wounds.
Iatrogenic (e.g. anastomotic leak discharging via wound).
Neoplastic.
Persistence of a fistula is due to the following
Presence of foreign material, e.g. suture/bone in a sinus.
Distal obstruction of the viscus of origin.
Continuing active sepsis, e.g. TB.
Epithelialization of the track.
Chronic inflammation, e.g. Crohn’s.
Malignancy in the track.
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Investigation
Establish the extent by sinography/fistulogram. MRI scan is often helpful.
Treatment
Principles of sinus treatment:
Ensure adequate drainage, laying it open and remove granulations.
Remove septic material, foreign bodies.
Biopsy sinus wall if concern over underlying diagnosis.
Loose packs may be used to help drainage.
Principles of fistula treatment:
Treat any sepsis, fluid imbalances, and poor nutrition if associated.
Ensure good drainage to prevent fistula extension.
Identify the anatomy, use examination under anesthetic (EUA) or imaging if required.
Biopsy the fistula if concern over underlying diagnosis.
Definitive treatment requires:
Excision of the organ of origin or closure of the site of origin.
Removal of chronic fistula track and surrounding inflamed tissue.
Closure of “recipient” organ if internal or drainage of external site if to skin.
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