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Home Departments Dermatology Hygroma (Hydroma)

Hygroma (Hydroma)


Hygromas develop over pressure points due to repeat trauma.

They are commonly seen in large/giant breeds over point of olecranon in the elbow or calcaneous in the hock. The reason for this breed predilection is because of the following reasons:

* Large or giant breeds with higher bodyweight.
* Environmental factors, i.e. sleeping on cement, wood or brick.
* Concurrent orthopaedic problems resulting in stiffness rising and lying down.

A hygroma is a fluid-filled cavity surrounded by dense fibrous connective tissue occurring over the lateral aspect of the bony prominence e.g. the olecranon or the tuber calcanei. Caused by chronic trauma, they often occur bilaterally as non-painful swellings, however, they can also occur singly. Most hygromas occur in young (i.e., 6 to 18 months old), large-breed dogs, before a protective callus forms over the bony prominence; however, they may occur in older animals with neuromuscular disease. Hygromas vary in size, becoming larger and thicker with repeated trauma. They are usually sterile initially, but bacteria may be introduced during aspiration. Infected hygromas are painful. Small, non-painful hygromas are cosmetic problems that persist if not treated. Hygromas also occur over other bony prominences (i.e., tuber calcanei, greater trochanter, tuber coxae, tuber ischium, external occipital protuberance, thoracic vertebral dorsal spinous processes).

PATHOGENESIS

Summary

Repeat mild trauma over bony prominences.

Cause

* Protective response to pressure induced ischemia, necrosis and inflammation.
* May develop with other concurrent orthopaedic problems secondarily to increased trauma if difficulty laying down.
* Histologically characterized by cystic spaces surrounded by dense walls of granulation tissue, the inner layer consisting of a dense layer of fibroblasts.
* Initially soft, fluid-filled swellings may become abscesses or granulomas - especially if secondarily infected.

Pathophysiology

* Hygromas develop after repeat trauma-induced necrosis and inflammation over pressure points.
* Known as false or acquired bursae.
* Time course
* Chronic disease with insidious onset.
* Months to years.

Signs: soft, fluid-filled subcutaneous swelling over bony prominences.

Diagnosis: signs, history, and biopsy.

Treatment: conservative, occasionally surgical resection required.

Prognosis: generally good, although rarely resolves spontaneously.

DIAGNOSIS

Pathway

Swelling located over bony prominences.

History

Soft swelling over bony prominence.

Clinical

* Variable size, soft, fixed subcutaneous swelling over bony prominence, commonly olecranon of the elbow.
* Generally no systemic illness, no lameness, no pain on palpation.
* Often bilateral.
* May become secondarily infected leading to erythema and discharge.
* Ancillary

Cytopathology

* Fine needle aspiration of mass produces clear cystic fluid.
* Useful for ruling out presence of neoplasia.

Histopathology

* Examination following surgical removal shows cystic spaces with dense walls of granulation tissue.
* Cystic spaces often lined with fibroblasts.
* May show evidence of infection or granulomas if chronic lesions.
* Diagnostic criteria
* Discriminatory

History.

Clinical signs.

Definitive

Histopathology.

Differential

* Abscess.
* Granuloma.
* Cutaneous neoplasia
* Synovial neoplasia
* Lipoma (usually not bilateral, hygroma often bilateral).

Postmortem

Histopathology

Histology reveals cystic spaces surrounded by walls of granulation tissue, flattened fibroblast inner layer.

TREATMENT

The primary treatment for elbow hygromas is elimination of repeated elbow trauma (i.e., soft, padded bed and padded elbow bandage). A spica-type bandage may be needed to prevent slippage. Aspiration of the hygroma is of little benefit and may introduce bacteria. Although surgery should be avoided if possible, development of a fibrous capsule or infection may necessitate it. Infection requires drainage and administration of appropriate antibiotics. Prolonged drainage may be obtained by placement of Penrose drains into the hygroma. The advantage of this technique is that the Protective callus is preserved. Penrose drains should not be used on ulcerated hygromas. For non-ulcerated (infected or sterile) hygromas, prepare the limb for aseptic surgery and make several dorsal and ventral stab wounds into the hygroma cavity. Probe the cavity, breaking down fibrous septum, and lavage it. Place multiple Penrose drains into the hygroma secure them. Apply a non-adhesive bandage to absorb drainage and prevent trauma. Change the bandage daily. Remove drains when drainage becomes minimal and scar tissue adherence occurs (i.e., 2 to 3 weeks). Continue to bandage the elbow for at least one week after drain removal, or until healing is complete.

Occasionally, hygromas are surgically excised when fibrous tissue, fistulae, or infection develops without a large fluid-filled cavity. The naturally Protective callus is removed during excision and postoperative management is often complicated. Incisions may dehisce and ulcerate, bandages are difficult to maintain, and recurrence is common. Wounds that dehisce may not heal. Small hygromas can be excised and the defect closed by undermining and advancing tissue until skin edge can be approximated with interrupted sutures. The cavity lining should be debrided and ravaged and Penrose drains placed before closure.

Excision of fibrous tissue is unnecessary. Suturing is completed by positioning the sutures medial or lateral to the olecranon. The limb should be bandaged for a minimum of 4 weeks. An external coaptation splint is put which protects and pads the elbow.


Single element

* Environmental changes, padded bedding, e.g. foam rubber pads, air mattress, straw.
* Localized padding using loose, padded bandages for 2-3 weeks initially.

Multi-element

Surgical removal:

* If response to initial attempts at padding is poor, severe lesions may need extensive drainage, extirpation or skin grafting techniques.
* Surgery often encounters extensive hemorrhage and wound dehiscence is a common complication of surgery.
* Drainage of non-ulcerated lesions involves stab incisions proximal and distal to the hygroma.
* Use finger to break down loculi before placing Penrose drain.
* Multi-element for hygromas not responding to drainage
* Excise ulcerated area of skin.
* Reconstruct using advancement flap for small defects, or pedicle direct flap from lateral thorax for extensive lesions.
* Wound dehiscence is a common complication of surgery if excessive residual tension or repeated trauma.

Monitoring

* Keep bandage dry and change regularly for first 2 weeks. Continue to dress for a further 3 weeks.,
* Infection is common sequelae to drainage if not performed aseptically.
* Wound dehiscence is a common complication of surgery.

After drainage

* Keep bandaged for 5-6 weeks, changing regularly every 3-4 days whilst still draining.
* Remove surgical drains once dry at 2-3 weeks. Restrict movement whilst bandaged.

After surgery

* If pedicle graft used, support limb in sling along thoracic wall for 2 weeks, changing wound dressings when wet.
* Second surgery to cut free graft and suture donor and recipient sites, then bandage for further 3 weeks.

PREVENTION

Control

* Advise owner to provide soft, padded bedding.
* Prophylaxis
* Avoid bedding on hard materials.

CONSEQUENCES

Prognosis

* Early lesions often respond well to loose bandaging.
* Surgical treatment often has poor results as trauma is ongoing and wound complications common.

Response criteria

* Conservative treatment of early lesions should result in protective callus formation after padded bandages for 3 weeks.
* Surgically drained lesions should be dry in 3 weeks, then remove bandages at 6 weeks and return patient to padded environment.
* Surgically reconstructed lesions will need strict confinement with limb supported in sling whilst graft takes, then a further 3 weeks of bandage support.

Failures

* Infection is common sequelae to aspiration, surgical drainage and reconstruction.
* Wound dehiscence due to pressure and trauma to tissues following treatment.
* Recurrence of hygroma following drainage if environment not adequately padded
 

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