Teaching Case

A 24-year-old male, with no known comorbidities presented to our emergency department with severe pain in the right foot after an unknown snake bite approximately 7days back. Routine lab investigations showed an extremely prolonged PTINR and aPTT.

CT scan of the abdomen showed an oval-shaped well defined hyperdense lesion along the anterior aspect of the left lobe of the liver causing scalloping (measures approximately 11cm x 5.9cm x 6cm). (Figure 1a). There was no significant post-contrast enhancement or active contrast leak within the lesion. (Figure 1b).

Moderate high-density ascites was noted. (Figure 2,3).

Background:

Snakebite envenoming remains a life-threatening health problem and an acute medical emergency, particularly in rural areas. The prognosis depends on factors including bite location, bite angle, bite duration, size of the snake, condition of glands and teeth, age/weight/health status of the victim, activity of victim post-bite [1,2].

Snake venom is mixtures of protein families and enzymes. Based on their effects, snake venom can be classified as hemotoxic, neurotoxic or cytotoxic [1]. Snakes of the Viperidae family have hemotoxic venoms that can disrupt the coagulation cascade and the hemostatic system. Hemotoxic snake venoms contain procoagulant proteases resulting in the consumption of clotting factors resulting in consumptive coagulopathy [1]. This can occur within minutes to several hours or days [3]. Even in severe cases little change in prothrombin time, activated partial thromboplastin time, fibrinogen levels is observed [2].

Clinical Perspective:

Generally, the presence of two puncture wounds indicates a bite by a poisonous snake. Local manifestations include burning, bursting or throbbing pain, local swelling, bruising, blistering and necrosis [1,4].

Systemic features of hemotoxic venom include DIC which occurs primarily due to direct endothelial damage, secondarily due to clotting defects and hemolysis. The first systemic hemorrhagic signs can be seen after several days if treatment is delayed [4], include rare manifestations like visceral bleeding which usually occurs in the abdomen (pancreas, peritoneum, spleen, liver). Cerebral/gastrointestinal/ respiratory haemorrhages are also less frequent [4].

Acute renal failure can occur as an early or late complication and is primarily caused by microthrombotic vascular occlusion, shock and nephrotoxic effects of hemoglobinuria/ myoglobinuria.

Other systemic complication include ARDS probably due to direct effect of venom on pulmonary vascular endothelium [3].

Imaging Perspective:

Diagnostic imaging is used to rule out visceral haemorrhage in suspected cases of systemic envenomation.

Ultrasonography may help in diagnosing internal bleeding. Ultrasound findings include free fluid in peritoneal cavity with fine echoes, solid organ hematoma, intra-abdominal/ parietal hematoma, pleural/pericardial effusion [5,6].

A computed tomography angiogram help assess the site of active contrast extravasation. Other additional reports have included intramural hematoma in the alimentary tract with active contrast extravasation into the peritoneal cavity, thrombosis of the internal iliac vessels, occlusion of the superior mesenteric artery and ischemic colitis with colonic stricture [5].

Outcome:

Early administration of ASV, antibiotics, proper management of complications like sepsis, DIC, ARF, and proper ventilator management for ARDS to reduce the mortality and morbidity.

Additional reported cases of hepatic artery embolization, splenic artery embolization and splenectomy to treat hemoperitoneum from snakebite [5].

Teaching Points:

Imaging generally plays a limited role in snakebite cases but plays an important role in cases with coagulopathy effect in abdomen, other organs and systemic complications for diagnosis and further treatment.