Laboratory Studies
Laboratory tests should be obtained if the diagnosis is uncertain to exclude alternative diagnoses (eg, acute abdomen, myocardial infarction [16] ). The authors recommend the following, as appropriate:
-
Complete blood cell count
-
Cardiac markers (eg, troponin)
-
Pregnancy test when applicable
-
Comprehensive metabolic profile
-
Lipase
-
Urinalysis
-
Creatine kinase
Laboratory studies also may be necessary to evaluate for end-organ damage following widow spider envenomation.
It is common for the creatine kinase and peripheral white blood cell count to be elevated following widow spider envenomations.
Imaging Studies
Consider performing an acute abdominal series or an abdominal CT scan if the diagnosis is unclear in a patient presenting with abdominal pain.
Patients with focal neurologic deficits in the setting of severe hypertension following widow envenomation may require neuroimaging (eg, head CT).
Other Tests
Skin testing variably may predict immediate hypersensitivity to antivenom and may influence the decision regarding its administration. Antivenom-induced anaphylaxis may be more life-threatening than the envenomation itself.
Obtain an electrocardiogram in patients with comorbid conditions such as hypertension, coronary artery disease, and congestive heart failure, and in patients with chest pain or respiratory symptoms.
-
Black widow spider (Latrodectus mactans) and offspring. Photo by Sean Bush, MD.
-
Female black widow spider guarding an egg case; species Latrodectus mactans. By Chuck Evans (mcevan). [CC BY 2.5 (https://creativecommons.org/licenses/by/2.5)], courtesy of Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Black_Widow_Spider_07-04-20.jpg).
-
Female black widow spider, Latrodectus mactans, in the process of spinning her web on a tree branch. Note the characteristic red hourglass located on her inferior abdominal surface. This marking can vary in coloration from yellowish to shades of orange and red and, at times, white. The female’s body is an overall shiny jet-black in color. This spider was found on a farm in the US state of Georgia. By James Gathany (http://phil.cdc.gov/phil/) [Public domain], courtesy of Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Black_widow_spider_9854_lores.jpg).
-
A redback spider (Latrodectus hasseltii) female, found in suburban Sydney, New South Wales, Australia. By Toby Hudson [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], courtesy of Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Latrodectus_hasseltii_close.jpg).
-
Young female Latrodectus tredecimguttatus; photo taken in Croatia by K. Korlevic. No machine-readable author provided. Kork~commonswiki assumed (based on copyright claims). [Public domain], via Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Latrodectus_tredecimguttatus_female.jpg).
