Paragonimiasis misdiagnosed as liver abscess: A case report

Abstract

BACKGROUND

Paragonimiasis is a typical food-borne zoonotic disease. Hosts acquire Paragonimus infection through the ingestion of raw or undercooked crayfish and crab. The clinical manifestations of the disease are varied, and it is often misdiagnosed or missed. The diagnosis of paragonimiasis should be considered comprehensively. Praziquantel is the first choice for treatment, and albendazole can be used in combination with repeated courses in severe cases.

CASE SUMMARY

We report a case of liver paragonimiasis that was misdiagnosed as an abscess. The patient presented with fatigue and poor appetite for 2 months, and was diagnosed with liver abscess in the local hospital. After 6 months, the patient visited our hospital because of recurrent abdominal pain and was diagnosed with liver paragonimiasis based on epidemiological history, clinical presentations, and laboratory findings. He was treated with praziquantel (25 mg/kg) three times a day for 3 days; however, the symptoms still presented after treatment. He was treated with oral praziquantel and albendazole for one further course. Follow-up suggested that the treatment was effective and the symptoms improved.

CONCLUSION

The combination of albendazole and praziquantel may improve the therapeutic efficacy of paragonimiasis.

Key Words: Liver paragonimiasis, Liver abscess, Misdiagnosis, Albendazole, Praziquantel, Case report

Core Tip: We report a case of paragonimiasis that was misdiagnosed as liver abscess. The patient was treated with praziquantel and albendazole. Follow-up examinations suggested that the treatment was effective.

INTRODUCTION

Paragonimiasis is a lung fluke disease that is prevalent mainly in Asia, Africa and South America. The morbidity in China is about 1.71%[1]. The occurrence of paragonimiasis in the liver, brain, spinal cord, subcutaneous tissue, muscle and orbital foci is rare[2,3]. The clinical and radiological symptoms of liver paragonimiasis are atypical, which definitive diagnosis difficult. We report a case of liver paragonimiasis misdiagnosed as an abscess and a literature review to provide a reference for this disease.

CASE PRESENTATION

Chief complaints

The patient was admitted to our hospital because of recurrent wandering epigastric.

History of present illness

On November 25, 2021, a 55-year-old male who was admitted to our hospital because of recurrent wandering epigastric pain, with symptoms of fatigue, poor appetite and other symptoms for 6 months. The abdominal pain was located in the subxiphoid and the right epigastric region, which was paroxysmal. The nature of the pain was not clear, and the pain was aggravated by consumption of meat and relieved by exhaustion of gas.

History of past illness

The patient had a history of hypertension and coronary heart disease but denied any other medical history. He was admitted to a local hospital on April 7, 2021, due to fatigue and poor appetite for 2 months. Physical examination showed no abnormality. Routine blood analysis in the local hospital showed an absolute leukocyte count of 10.28 × 10⁹/L, absolute eosinophil count of 2.51 × 10⁹/L, with a percentage of 24.40%, erythrocyte sedimentation rate (ESR) 63mm/h, γ-glutamyltransferase 93.4 U/L, alkaline phosphatase 152.7 U/L, albumin/globulin ratio 1.12. Abdominal ultrasound revealed a space-occupying lesion in the right lobe of the liver. Abdominal contrast-enhanced computed tomography (CT) showed an abscess in the right lobe of the liver (Figure 1A). Contrast-enhanced magnetic resonance imaging (MRI) showed a 6.2 cm × 4.2 cm mass with an abnormal signal in the right lobe of the liver. No enlarged lymph nodes were observed in the abdominal cavity or retroperitoneum (Figure 1B and C). The local hospital considered a diagnosis of liver abscess. Cefoperazone and sulbactam were given as anti-infective treatment for 2 weeks, and the patient was discharged after symptoms such as malaise and poor appetite improved.

Figure 1 Abdominal enhanced computed tomography and magnetic resonance imaging. A: In April 2021, abdominal enhanced computed tomography (CT) of the right lobe of the liver showed a mass of low density; B: In April 2021, magnetic resonance imaging (MRI) in the coronal position showed an uneven flaky shadow in the liver parenchyma; C: In April 2021, MRI T1-weighted imaging (T1WI) showed that the lesion in the right lobe of the liver was mildly intensified; D: In November 2021, chest CT showed small nodular foci in the middle lobe of the right lung; E: In November 2021, abdominal MRI showed a bunch of grapes sign in T1WI in the right lobe of the liver; F: In March 2022, abdominal CT indicated that the lesion was smaller than before.

Personal and family history

The patient had no significant personal or family history.

Physical examination

The findings of the physical examination were within normal limits.

Laboratory examinations

Laboratory analyses revealed admission tests for Mycobacterium tuberculosis IgM antibody and tuberculin were negative. Anti-extractable nuclear antigen peptide profile and anti-neutrophil cytoplasmic antibodies were normal. Routine blood analysis showed a leukocyte count of 13.89 × 10⁹/L, absolute eosinophil count of 8.03 × 10⁹/L, percentage of eosinophils 57.8%, and percentage of neutrophils 32.2%. Routine urinalysis showed weakly-positive proteinuria. Routine stool examination showed no abnormality. ESR was 49 mm/h. Liver function tests showed albumin 32.74 g/L, globulin 43.24 g/L, and albumin/globulin ratio 0.76. Peripheral blood cell morphology demonstrated 51% eosinophils, the rest were normal. Bone marrow biopsy showed active myeloproliferative activity with 25.5% eosinophils. Microscopic fecal analysis showed: no liver fluke, hookworm, tapeworm or other eggs.

Imaging examinations

Imaging revealed that Chest CT showed a small nodular focus in the middle lobe of the right lung (Figure 1D). Abdominal MRI showed a bunch of grapes sign. TI-weighted imaging (WI) and T2WI showed signal foci in the right lobe of the liver, with blurred borders and enlarged scope, and a small amount of peritoneal effusion (Figure 1E). The bunch of grapes sign is characteristic of paragonimiasis.

FINAL DIAGNOSIS

The patient's personal history was pressed again, he reported a history of eating raw crab in childhood, so further improved the paragonimus intradermal test suggested strong positivity, which supported the diagnosis of liver paragonimiasis. Definitive clinical diagnosis of liver paragonimiasis was based on recurrent abdominal pain for 6 months, childhood history of eating raw crab, routine blood tests indicating increased eosinophils, bunch of grapes sign on liver MRI, and positive lung fluke intradermal test.

TREATMENT

He was treated with praziquantel tablets (25 mg/kg) for 3 days, and discharged with relief of abdominal pain.

OUTCOME AND FOLLOW-UP

On December 27, 2021, the patient was admitted to hospital again with abdominal pain, accompanied by weakness and fatigue, and the symptoms of abdominal pain were the same as before. Admission blood tests showed a white blood cell count of 14.03 × 10⁹/L and an absolute eosinophil value of 6.02 × 10⁹/L. Repeated lung fluke intradermal test still suggested strong positivity. Praziquantel (25 mg/kg) was given orally three times a day for 3 days, and albendazole 1 g orally twice daily for 2 days. A follow-up review in March 2022 showed that peripheral blood leukocytes and eosinophils returned to normal, and abdominal CT (Figure 1F) suggested shrinkage of the lesion. There were no further symptoms such as abdominal pain and fatigue.

DISCUSSION

In China, paragonimiasis is mainly caused by Paragonimus skrjabini and Paragonimus westermani. Adult Paragonimus parasitize human lungs, and the eggs are discharged with sputum through the mouth or digestive tract along with feces. The eggs develop into sporocysts and cercariae. The cercariae enter freshwater crayfish and crab to form metacercariae. People are infected by eating raw or undercooked freshwater crayfish or crab that contain metacercariae. Metacercariae form in the intestinal tract as juvenile worms, which travel through the intestinal tract to abdominal organs, across the diaphragm and into the lungs, where they mature to adults[4]. Pathogenicity is mainly due to the mechanical damage caused by the migration of juvenile worms, and the immunopathological response induced by their metabolites. The disease has been reported in northeastern China, Zhejiang, Sichuan and Guangdong. Similar to the epidemiological trend of other infectious diseases, the prevalence of paragonimiasis has decreased in intensity in traditionally infected areas. New emerging areas of infection continue to appear, which results in decreased alertness of medical personnel in the traditional infected areas. Personnel in the new areas of infection have insufficient knowledge of the clinical characteristics of the disease, which is the reason for the high rate of misdiagnosis. The clinical manifestations of paragonimiasis are not specific, which makes it easier to misdiagnose as liver abscess or cancer, which can lead to delayed treatment or unnecessary surgery, with serious sequelae.

Paragonimiasis be divided into thoracic-pulmonary, liver, cutaneous, cerebrospinal and mixed types. Some patients only show eosinophilia in the peripheral blood and have no obvious clinical symptoms, which is known as cryptic paragonimiasis among which the thoracic–pulmonary type is the most common. However, extrapulmonary paragonimiasis rarely involves the liver³. Liver paragonimiasis is clinically characterized by migration of worms and damage to the liver and patients may present with symptoms such as abdominal distension, abdominal pain, nausea, vomiting, fatigue, poor appetite, and fecal blood. The site of abdominal pain is not fixed, and ascites and liver enlargement may also occur, with characteristic imaging manifestations such as a bunch of grapes or tunnel appearance. MRI of liver paragonimiasis has the following characteristics[4-6]: (1) Foci are round, irregular, or strip-shaped, and some foci have a typical a bunch of grapes or tunnel appearance; and (2) Foci are isointense or hypointense in T1WI and hyperintense or hypointense in T2WI. Dynamic enhancement scans show patchy or ring-shaped enhancement in the arterial and portal phases, and the lesion is isointense in the delayed phase. In our case, MRI showed a bunch of grapes sign, which was consistent with the typical manifestations of low signal intensity in T1WI, high signal intensity in T2WI, and mild enhancement during the arterial phase of dynamic enhanced scanning. The diagnosis of paragonimiasis begins with the etiological examination of eggs found in sputum or feces, but the positive rate with this method is only 11.7%[7], and skin, cerebrospinal fluid and stools do not contain eggs, so this test cannot be relied upon. Eosinophilia is not specific for diagnosis of paragonimiasis, and some hematological and allergic diseases can cause the same changes. Therefore, the diagnosis of paragonimiasis needs to be combined with epidemiological history, clinical manifestations, and auxiliary examination results[1,2,5]: (1) Epidemiological history, mainly for eating raw crab and freshwater crayfish; (2) Allergic lesions caused by paragonimiasis migration, and the corresponding signs, symptoms and imaging manifestations, such as CT or MRI with a bunch of grapes or tunnel signs and other characteristic changes; (3) Blood, body fluids, leukocytes and eosinophils increased and exclude blood diseases and other parasitic infections; (4) Positive circulating antibody to Paragonimus; (5) Immunodiagnostic tests, such as intradermal test, ELISA, and complement fixation test; and (6) Finding eggs by etiological or pathological examination. For differential diagnosis of liver paragonimiasis and abscess: Most pyogenic hepatic abscesses are usually solitary, and coalesce to form a large abscess cavity, especially without treatment, which results from the disintegration and necrosis of hepatic tissues by suppurative infection. The walls of liver abscesses are non-homogeneously thickened, obviously enhanced and are accompanied by apparent hyperemia reaction and edema of surrounding liver tissues. However, inflammation and hyperemia of surrounding liver tissues in liver paragonimiasis are not common on arterial or portal-phase enhanced CT or MRI[6]. The reasons for the misdiagnosis of liver abscess in this case are as follows: (1) Shiyan residents mostly live near rivers and ditches and have the habit of eating raw crabs, while the overall incidence of paragonimiasis is low, there is no local large-scale epidemiological survey information, and the prevention and control departments do not have sufficient epidemiological knowledge and insufficient popularisation of science; (2) Clinicians, imaging physicians, and medical staff lack an understanding of the clinical characteristics of paragonimiasis. The incidence of hepatic type is low and its clinical and imaging manifestations are often atypical; (3) The medical history was taken cursorily, omitting information such as eating habits and dietary history; (4) Abnormal results of auxiliary examinations were not given enough attention, such as, increased eosinophil counts were ignored in the initial diagnosis; and (5) Lack of etiological evidence made diagnosis more difficult.

The drug of choice for the treatment of paragonimiasis is praziquantel, and albendazole can also be used[8]. Praziquantel has the advantages of a short course of treatment, low toxicity, and high efficacy[9]. Its specific course of treatment should be based on the clinical manifestations, eosinophils, and changes in hepatic function. For severe liver paragonimiasis with a long course, the dose and course of praziquantel should be increased or in combination with albendazole[10]. Literature shows that the combination of albendazole and praziquantel may improve the therapeutic efficacy due to higher concentration of both active drugs[11]. In addition, it has been confirmed that the therapeutic effect of the combination of the two drugs can improve schistosomiasis, neurocysticercosis, parenchymal brain cysticercosis, hydatid disease and other parasitic diseases[12-14]. In this study, the treatment effect of praziquantel alone was poor; when combined with albendazole, the patient's condition improved, follow-up examinations suggested that the treatment was effective. This provides a new idea for cases with poor treatment effect to praziquantel alone. In this case, the poor therapeutic response was because the patient had liver paragonimiasis, with a small amount of peritoneal effusion. The condition was complicated and the course of the disease was long, which caused recurrence. Clinical manifestations, eosinophils, and imaging tests are the leading indicators for evaluating treatment efficacy. Eosinophils will decrease or return to normal after treatment, which can be used as an indicator for efficacy evaluation. Intradermal test for paragonimiasis antigen has a high positivity rate. However, it may still be positive after the disease is cured, so it cannot be used to evaluate the efficacy of the treatment.

Paragonimiasis is a food-borne parasitic infectious disease with wide distribution and diverse clinical manifestations, which is easily misdiagnosed. On the one hand, health education should be carried out to raise public awareness of the prevention of paragonimiasis, and prevention can be achieved by not eating raw or undercooked crayfish and crab[15]. On the other hand, clinical knowledge of paragonimiasis should be strengthened, especially for liver paragonimiasis, which has a lower incidence, to improve diagnosis and treatment, reduce the rate of misdiagnosis and missed diagnosis, avoid progression of the disease, and reduce complications.

CONCLUSION

The diagnosis of paragonimiasis should be considered comprehensively. Praziquantel is the first choice for treatment, the combination of albendazole and praziquantel may improve the therapeutic efficacy of paragonimiasis. This provides a new idea for cases with poor treatment effect to praziquantel alone.

ACKNOWLEDGEMENTS

We would like to acknowledge all members of the department of General Practice and Pulmonary and Critical Care Medicine, Taihe Hospital, Hubei University of Medicine.