Hydatid cyst of the psoas: case report and review of literature

Abstract

Introduction:

Hydatid disease (HD) is a parasitic pathology that remains endemic in Morocco and poses a public health problem. Its location in the psoas muscle is a rare entity. We report this case highlighting the diagnostic challenges, therapeutic modalities as well as prognosis.

Case Presentation:

We report the case of a 40-year-old male patient without a notable pathological history, referred to our department for management of a paravertebral hydatid cyst mass with fluid density and scalloping on the verteral body on thoraco-abdomino-pelvic computed tomography scan. After a pretherapeutic assessment, the patient underwent an exploratory laparotomy which objective a deep right laterovertebral mass. The patient underwent a resection of the protruding dome, lavage using hydrogen peroxide and drainage of the residual cavity. The patient recovered well and was discharged 5 days later on albendazole 10 mg/kg/d. The anatomopathological analysis of the specimen confirmed the diagnosis of hydatid cyst. The evolution was satisfactory for the patient with a recall of 6 months.

Discussion:

Hydatidosis is an anthropozonosis caused by the larval form of Echinococcus granulosus. It can reach the psoas muscle by great circulation. The diagnosis of HD in the psoas is often difficult. Biology and imaging confirm the diagnosis and the standard treatment remains surgery.

Conclusion:

HD of the psoas is a rare entity. The diagnosis is based on biology and imaging, and radical treatment is surgery.

HIGHLIGHTS

• Hydatid disease (HD) is a rare entity that remains endemic in pastoral communities.

• HD diagnosis is often difficult and based on biology and imaging.

• Standard treatment of HD of the psoas is surgery.

Introduction

The hydatid cyst or hydatidosis is an anthropozoonosis due to the development in humans of the larval form of the Taenia Echinococcus granulosus. It is endemic and constitutes a real public health problem in Mediterranean countries and notably in Morocco. Isolated muscle localization is an unusual entity even in endemic countries. Its frequency would be 1–3% of all localizations1. In the world literature, a few clinical cases of hydatid cyst of the psoas muscle have been described2. This case has been reported following the SCARE criteria3.

Case report

We report the case of a 40-year-old male patient without a notable pathological history. The patient consulted in the emergency for low back pain and paresthesia of the right lower limb, evolving for 2 months with no fever, or any other associated abdominal or extra-abdominal signs. The patient reports regular contact with dogs. Abdominal examination finds right lumbar pain with a soft abdomen.

Biological assessment with hydatid serologies by indirect hemagglutination technique was positive. Thoracic-abdominal-pelvic computed tomography (CT) scan revealed a paravertebral formation adjacent to the right diaphragmatic pillar, hypodense with fluid density measuring 69×39 mm, containing a septum and scalloping on the vertebral body of D12 (Fig. 1).

Figure 1.

Enhanced abdominopelvic computed tomography scan showed a right hypodense paravertebral formation (arrow).

The patient was hospitalized in our department for surgical operation. Exploratory surgery via median laparotomy revealed a deep stationary right laterovertebral hydatid cyst that was difficult to reach. Critical anatomical elements such as spinal neurons and paravertebral vessels were respected. The patient underwent resection of the protruding dome with lavage using hydrogen peroxide and drainage of the residual cavity.

Macroscopic and microscopic examinations of the specimen confirmed the diagnosis of the hydatic cyst. The postoperative phase was simple, and the patient was put on albendazole 10 mg/kg/d. The course was good with no recurrence after 6 months of follow-up after surgery.

Discussion

Hydatidosis is an anthropozonosis caused by the larval form of E. granulosus, a small tapeworm parasitizing, in its adult state. The digestive tract of the dog constitutes the definitive host. The infestation of the dog is done by digestive way and would be secondary to the consumption of parasitized viscera, notably the liver and the lungs of the intermediate host the sheep. The latter, constituting the main reservoir of Echinococcus Taenia, gets contaminated by the dog’s excrement containing the eggs of the parasite. Man is only an intermediate accidental host; he gets infected either directly by contact with the parasitized dog or indirectly by ingestion of soiled food. Man constitutes an epidemiological dead end4.

All localizations of hydatidosis have been described. In 90% of cases, it affects the liver and the lung. This distribution can be explained by the dissemination of the parasite and the blood flow of the portal circulation. The eggs of the Echinococcus Taenia ingested by human release in the intestine, the embryohexacante. The latter crosses the intestinal mucous membrane mucosa and enters the portal circulation. Its size and its plasticity allow it to pass everywhere. The portal current carries this embryo towards the first barrier which is the liver where it stops in six times out of 10, otherwise, through the suprahepatic veins, the parasite reaches the inferior vena cava, the right heart, and then the lung which constitutes the second barrier where it is retained three times out of 10. One time out of 10, the embryohexacante crosses the two barriers, finds itself in the great circulation, and can be lodged in any part of the body5. Muscle sites account for only 1–3% of all hydatid cyst locations2. This is due, on the one hand, to the degree of vascularization of the tissues and to the muscular contractions which prevent the development of the larva and, on the other hand, to the lactic acid richness of the muscle which would prevent the growth of the hydatid6.

The diagnosis of hydatid cyst of the psoas muscle is often difficult. It can be disclosed by lumbar pain with homolateral paresthesia as in our case, sign of compression of nerve branches passing through the psoas region. Some cysts may be revealed by complications such as nerve, urinary, or vascular compression, or by a superinfection by way of hematogenous route, which can lead to sepsis, sometimes severe7. Imaging is essential for diagnosis and pretherapeutic assessment. Ultrasound is an innocuous first-line examination with an estimated diagnostic reliability of 96%. The ultrasound appearance reproduces the stages of Gharbi’s classification and the stage of the disease8. A CT study is necessary in deep locations such as the psoas. The CT scan allows an easy diagnosis with more precise topographical assessment.

The biological workup brings a certain to the diagnosis of hydatidosis, especially in the case of diagnostic problems, and remains of major interest in follow-up after treatment. Hypereosinophilia is inconstant and is only of interest in the orientation of the diagnosis. Biology is essentially limited to hydatid serology. It is of great diagnostic value when it is positive. Its negativity does not eliminate the diagnosis of hydatid cyst given the significant proportion of false negatives, which varies according to the location of the cyst6 hence the need for a comparison between the clinic, imaging, and biology.

In addition to its role in diagnostic confirmation, hydatid serology allows to follow the posttherapeutic evolution of the hydatid cyst, to formulate a prognosis and to detect secondary hydatidosis at an early stage. Thus, any elevation in the 6 months following the operation is synonymous with recurrence or unnoticed hydatid localization. Qualitative and quantitative methods are difficult to interpret, however, western blot and immunoblot are more sensitive and specific9.

According to the latest WHO-IWGE recommendations on the treatment of HD, the choice of treatment is based on the type of cyst, its size, location, and the presence/absence of complications, resulting in the choice of one of the following options: percutaneous treatment, surgery, anti-infective drug treatment, or watch and wait.

Surgery is the standard in the treatment of hydatid cyst of the psoas, but other alternatives have been studied such as percutaneous drainage of the cyst – puncture, aspiration, injection of hypertonic saline and absolute alcohol, and reaspiration10.

The open approach can be extraperitoneal through a lumbar incision or transperitoneal through median laparotomy. Radical treatment is based on total pericystectomy. However, adhesions to the vascular-nervous elements, association with vertebral involvement may make this complete resection difficult or even dangerous11. In these cases, resection of the protruding dome with lavage and drainage may be sufficient. Intraoperatively, the use of drapes soaked in hypertonic saline solutions, oxygenated water, or 10% betadine has been used to surround the cyst before opening the cavities. These scolicides kill the daughter cysts and thus prevent propagation10. Antiparasitic treatment with mebendazole and albendazole is commonly used when surgery is not feasible with curative intent (such as for bony localization) or when patients are not suitable for surgery, and as prophylaxis against recurrence4. Albendazole is used at a dose of 400 mg orally, twice daily, for 1–5 months for adults and at a dose of 15 mg/kg/d (maximum 800 mg) for children for 1–6 months10.

Although mortality directly due to echinococcosis is very low, it can cause very debilitating morbidity. A mortality rate of between 0.29 and 0.6% has been reported. The recurrence rate of this disease remains high, on the order of 10%10.

Conclusion

Isolated hydatid cyst of the psoas remains a rare entity. Diagnosis is based essentially on ultrasound and CT scan, with biology providing additional information. The standard of treatment is surgery and frequently associated with antiparasitic therapy. Even if mortality is low, the recurrence rate in HD remains high.

Ethical approval

None.

Sources of funding

None.

Authors’ contribution

M.M. has written the article, consulted the patient, prescribed all of the tests and prepared the patient for surgery, and participated in the surgery. A.R.: has helped in writing the article and data collection. N.K. and C.R.: data collection. T.B. and B.S.: supervised the writing of the manuscript. T.E.H.: has supervised the writing of the paper, and had been the lead surgeon of the case.

Conflicts of interest disclosure

The authors declare that they have no financial conflict of interest with regard to the content of this report.

Research registration unique identifying number (UIN)

None.

Guarantor

Mhand Mohammed.

Consent

Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Provenance and peer review

Not commissioned, externally peer-reviewed.