“In addition to the speed at which they move, these sea urchins are clever and sensitive with their spines. When approached, the long sharp little spears all move and aim their points at the approaching body until the animal is armed like a Macedonian phalanx….The prick of one of the points burned like a bee sting”
The Log from the Sea of Cortez
John Steinbeck, 1941
Case Report:
A twenty-eight year old male presented to the emergency department with the chief complaint of right foot pain and malaise. The patient had been surfing in Southern California two days prior, and a short time after leaving the water noted an aching pain in his right heel exacerbated by walking. Upon inspecting his own foot the patient noted a number of puncture wounds where sea urchin spines had entered his heel. The patient tried to remove the spines with tweezers but those attempts were largely unsuccessful.
Physical exam revealed a healthy Caucasian male in no apparent distress. The vital signs were within normal limits, with a temperature of 99.8 F. The pupils were equal, round, and reactive. The cardiovascular exam was unremarkable. The reflexes were 2+ and symmetric throughout. There were no parasthesias or dysesthesias, and motor strength was normal. The heel pad of the right foot contained six closely spaced puncture wounds which were black in color. There was local tenderness, but no erythema, swelling or drainage.
AP and lateral radiographs of the foot were obtained and showed one 1 cm spine embedded in the heel. Under local anesthesia an attempt was made to remove the spine, but only small fragments were removed. The patient was discharged with a prescription for lbuprophen 600 mg. as well as instructions for partial weight bearing as tolerated. After one week’s duration the patient was completely symptom free.
Introduction:
Of the injuries inflicted by marine animals on surfers, sea urchin injuries are among the most common. Direct contact with the sharp and brittle spines of sea urchins often results in multiple, clustered puncture wounds, often containing retained spines which can prove difficult to remove. Some species of sea urchins are also venomous and can deliver a nasty sting to boot.
Sea urchins belong to the class Echinoidea, and the phylum Echinodermata. There are 750 known species which are divided into five orders and a number of families. They are ubiquitous creatures whose habitat includes all oceans in a wide range of latitudes and depths ranging from zero to 600 feet.1 Sea urchins are nocturnal, feeding on dead and decaying marine fauna at night and hiding in crevices between rocks or within reefs during the daylight hours.
They are composed of a globular, radially symmetrical, hard calciferous shell surrounded by sharp spines and covered by a darkly pigmented epithelium. The base of a sea urchin spine is concave enabling it to articulate on a small tubercle located on the body, like a ball and socket joint. Like the exoskeleton, the spines are composed mostly of calcium carbonate and magnesium carbonate, and are covered by epithelium.2 A nerve ring around the base of each spine is controlled in such a way that when one spine is stimulated, its neighbors point towards it as a protective mechanism which results in the characteristic grouping of puncture wounds.
The spines may be of three different types and are of variable length. The most common type, found on non venomous sea urchins are straight and solid.The spines of venomous urchins, like a hypodermic needle are long, straight, hollow spines which secrete venom from a gland at their tip. These are typified by the Black sea urchin Diadema setosum found widely distributed through the Indo-Pacific whose spines may be over a foot in length. Another venomous type of spine known as pedicellariae, are specialized short, delicate spines with three-pronged fangs used for motility and grasping. In some species these too may contain venom secreting glands located at their distal tip. These spines may be torn off the urchin and remain attached to the victim while continuing to inject venom into the skin. Usually only one type of venom secreting spine is present on a given species.
Pathophysiology, Diagnosis, and Treatment:
Injuries from sea urchins can be classified into five different types: puncture wounds; envenomations; granulomatous reactions; synovitis; and allergic reactions. By far the most common of these is the simple non-venomous puncture wound. Most of these wounds will heal spontaneously with gradual absorption, or extrusion of retained spine fragments. These wounds are most commonly seen on the plantar and palmar aspects of the feet and hands. They often cause a significant amount of burning pain which typically resolves within hours of injury, although tenderness at the site of injury often lasts up to a week.
In patients presenting for medical treatment, it is important to identify the number and location of embedded spines because this will determine the treatment strategy. The black or purple pigment left behind in a puncture wound often causes a tattooing of the victim’s skin but does not always indicate the presence of an embedded spine.3 Plain film radiography using soft tissue technique with A.P. and lateral views is usually sufficient given the relative radioopacity of calcium carbonate.4 Occasionally additional tangential views, MRI, or ultrasound may be useful diagnostic aids in the event that the initial plain films are negative.5,1
Spine Removal
The management of spines that are not in joints or near neurovascular bundles is conservative. Spines that are protruding from the skin or are easily accessible should be removed withsplinter forceps. Those that are deeply embedded or not easily removed should be left in place. Avoid the temptation to “dig a little deeper” as these efforts usually cause more harm than good. As noted above, most spines, if left alone, will eventually get absorbed or extruded without treatment.
Formal surgical exploration is reserved for spines which causing synovitis, granulomas, or chronic pain. Puncture wounds should be copiously irrigated with saline, and then covered with a dry protective dressing. Oral analgesics are usually sufficient for pain control.
Folk remedies include urinating on wounds or applying vinegar, as well as putting on shoes and running in order to break up spines which have entered the feet. However, none of these treatments are supported by the literature or recommended by the author.
Infections
Due to the low likelihood of infection. prophylactic antibiotics should not be routinely prescribed, but oral Ciprofloxacin, or Trimethoprim/Sulfamethoxazole (Bactim) should be given to patients who are immunocompromised, or who have liver disease, especially those with increased serum iron levels.3
Infected wounds should be cultured using aerobic and anaerobic isolators, and the laboratory should be notified that a marine organism is suspected as these bacteria may require special culture media to promote optimal growth. Vibrio vulnificans presents the most serious threat to life and limb, and is best treated with parenteral Imipenem. A more common infection in the fingers or hand is the indolent “shuckers thumb” characterized by an erysipeloid reaction and caused by erysiplothrix rhusopathidiae which is sensitive to Penicillin, and Cephalexin. As in all puncture wounds,tetanus prophylaxis must be current.
Envenomation
In general, sea urchin venom is more potent in the tropical species especially during their reproductive cycle. The venom of Tripneustes gratilla found in the Red Sea has been characterized as pink, opalescent, and protenaceous, containing polypeptides from 20,000 to 78,000 in molecular weight. It is a heat labile toxin (completely inactivated at 50 C0 for five minutes) that releases histamines, and is hemolytic, cardiotoxic, and neurotoxic.6, 7 The tropical species Toxopneustes is noted to have a particularly potent venom, and there have been a few case reports of paralysis and death from its sting.
Local symptoms of envenomation are immediate and severe burning or aching pain at the site of the sting. This may be later accompanied by erythema, swelling, and an aching sensation. Systemic symptoms range from dizziness, lightheadedness, and parasthesias to aphonia, paralysis, coma, and death.
Pedicellariae that are visible should be shaved off with shaving cream and a razor blade to prevent continued envenomation of the patient. Immersion of the affected limb in hot water is often very effective in decreasing pain at the site of the sting, possibly because it causes denaturation of toxic proteins. If pain returns after the patient removes the limb from hot water, the treatment should be repeated, being careful not to cause thermal injury. Treatment of systemic symptoms is supportive, with no specific antivenin available. In a murine model, antihistamines did not alter LD 50 of envenomation from Tripneustes.6
Delayed Complications
Cutaneous granulomas are the most common delayed sequelae of sea urchin injuries. These pink or purple lesions are typically are seen on the hands or feet and form from two months to a year post injury. They are less than five mm. in diameter, painless and sterile, with keratotic surfaces. Superficial granulomas of the palmar surface of the hand are commonly umbilicated.8 If they occur in deeper tissues they may erode adjacent structures, particularly bone and tendons. Paracentrotus lividus, found in European waters may cause painful small tense cystic lesions of the hands which may be very bothersome. If the cysts are crushed, escape of their contents into surrounding tissue often reproduces the burning pain of the original injury.15
Histologically, the granulomas are composed of epithelioid cells and multinucleated giant cells surrounded by lymphocytes.22 Occasionally, small fragments of foreign material are found within the granulomas. They are non-caseating, and described by many Pathologists as sarcoidal. It remains unclear why a minority of individuals develop granulomas. Most authors feel that they are due to an immunologic response to the epithelial covering or slime of the spine, as the calcium carbonate skeleton is immunologically inert. Although one case was possibly due to a mycobacterial infection, acid fast bacilli are usually not present in cultures or pathological specimens.16 The granulomas may gradually flatten and become replaced with scar tissue, however surgical excision often yields the best and most immediate results. There is some controversy in the literature with regards to the use of steroid injections for treatment of granulomas or painful cysts. Most authors feel that this treatment is of no significant benefit. A systemic illness consisting of arthralgias, low grade fever and malaise presenting a month after injury has been described in one case. The symptoms resolved completely after excision of granuloma and embedded spines.9
Penetration of spines into joint spaces causes a large effusion acutely, and can often lead to a destructive arthritis and synovitis from the inflammatory reaction they elicit. Cases have been reported involving the interphalyngeal joints, the knee, and the ankle. Often, surgical removal of the offending spines in a timely manner results in complete reversal of symptoms of pain and stiffness, and a rapid return to normal function. Cracchiolo and Goldberg note that the synovial fluid had a white cell count of approximately 10,000 with a lymphocitic predominance. Synovial membrane biopsy reveals acute and chronic inflammatory changes as well as the presence of giant cells.9
Untreated, spines which become embedded in the interphalyngeal joints have resulted in chronic fusiform swelling, pain and such erosion of articular surfaces as to make amputation the treatment of Choice.16 A similar case resulting in amputation through the proximal interphatyngeal joint that was initially thought to be caused by a sea urchin, instead was found to be caused by an annelid worm, or “sea mouse” (family Aphroditidae).10
Recently, a classic delayed type hypersensitivity reaction to the spines of Diadema has been described.11,12 This allergic response is manifest by a locally erythematous, intensely puritic rash that may contain grouped vesicles and is seen ten days after exposure to antigen found on this sea urchin. Treatment with both oral and topical steroids is successful in reducing the itching and rash, but some residual hyperpigmentation may remain. In one case, skin patch testing using ground spines was preformed to confirm the relationship between rash and sea urchin. Since patients may develop this allergic response without prior exposure to sea urchins, it is hypothesized that sensitization occurs at the time of injury, and there is a subsequent reaction to residual antigen in the skin.
Prevention:
As a general safety measure is always safer to swim or paddle ones board than it is to wade in shallow water. Booties offer some measure of protection, but can occasionally be penetrated by spines. Steel shanked “reef walker” type booties are best, but may be impractical for high performance surfing. Obviously the handling of sea urchins is not to be recommended, but if harvesting or collecting these animals, heavy protective gloves should be worn.
Conclusion:
Surfers are at high risk for sea urchin injuries, particularly to the plantar aspect of the foot. Management is conservative in the vast majority of cases, as removal is difficult, and spines left in place will gradually get dissolve or or extruded. Spines that have entered joint space should be surgically removed by and experienced surgeon so as to avoid reactive arthritis or synovitis. Tender granulomas, which can form weeks to months post injury should also be excised. Envenomations are best treated with immersion in non-scalding hot water.
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