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Key Features

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Essentials of Diagnosis
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  • Transient pruritic rash after exposure to freshwater

  • Fever, urticaria, arthralgias, cough, lymphadenitis, and eosinophilia

  • Weight loss, anorexia, hepatosplenomegaly, or hematuria

  • Eggs in stool, urine, or rectal biopsy specimens

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General Considerations
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  • Caused by several species of Schistosoma flukes

    • Schistosoma japonicum, Schistosoma mekongi, and S mansoni involve the intestines

    • Schistosoma haematobium involves the urinary tract

  • Infection is caused by free-swimming larvae (cercariae), which emerge from certain species of freshwater snails

  • The cercariae penetrate human skin, migrate to the liver, and mature into adults, which then migrate through the portal vein to lodge in the bladder veins (S haematobium), superior mesenteric veins (S mekongi and S japonicum), or inferior mesenteric veins (S mansoni)

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Demographics
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  • S japonicum and Smekongi are found in eastern and southeastern Asia

  • S mansoni is found in tropical Africa, the Caribbean, and parts of South America

  • S haematobium is found in Africa

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Clinical Findings

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  • Much of the population in endemic areas is infected but asymptomatic

  • Only heavy infections produce symptoms

  • Schistosomiasis progresses in three distinct phases: acute, chronic, and advanced disease

  • The cercarial penetration may cause a maculopapular, pruritic rash, comprising discrete, erythematous, raised lesions that vary in size from 1 cm to 3 cm

  • Acute schistosomiasis (Katayama syndrome)

    • Can last from days to weeks

    • Can include fever, malaise, cough, diarrhea, hematuria, and right upper quadrant pain

  • Chronic stages of gastrointestinal disease are characterized by

    • Hepatic fibrosis

    • Portal hypertension

    • Splenomegaly

    • Ascites

    • Bleeding from esophageal varices

  • Chronic stages of genitourinary tract disease may result in

    • Obstructive uropathy

    • Stones

    • Infection

    • Bladder cancer

    • Fistulas

    • Anemia due to chronic hematuria

  • Terminal hematuria in children from an endemic region is a red flag for urinary schistosomiasis

  • Spinal cord granulomas and paraplegia due to egg embolization into the Batson plexus have been reported

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Diagnosis

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Laboratory Findings
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  • Diagnosis is made by finding the species-specific eggs in

    • Feces (S japonicum, S mekongi, S mansoni, and occasionally S haematobium)

    • Urine (S haematobium and occasionally S mansoni)

  • If no eggs are found, concentration methods should be used

  • Because the shedding of eggs can vary, three specimens should be obtained.

  • Urine specimens should be collected between 10 AM and 2 PM to coincide with the timing of maximal egg secretion

  • Testing should wait until 2 months after the last known freshwater contact as this is the time required for worms to start producing eggs following infection

  • Serologic may be helpful in making the diagnosis in patients who are not excreting eggs

  • Peripheral eosinophilia is common, and eosinophils may be seen in urine

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Diagnostic Procedures
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  • A rectal biopsy may reveal S mansoni and should be done if other specimens are negative

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