INTRAMUSCULAR HYDATID CYST
A CASE REPORT AND LITERATURE REVIEW

Abu Salem O.T.
Irbid, Jordan

Introduction:

Enchinococus granulosus is endemic in many parts of the world where sheep and cattle are raised with the help of dogs. Dogs are the principal host and sheep are the most common intermediate host, Dogs acquire the infestation by ingesting hydatid scolices from infected sheep organs. The parasite develops into a tapeworm in the dog intestine and tapeworm eggs are then excreted in dog feces and transmitted to humans via the fecal-oral route. Ingested eggs develop into hydatid cysts in the intermediate host to complete the life cycle of the parasite. The patient in this study lived next to a sheep ranch.

In humans the infestation is usually localized in the liver and lungs, and rarely involves the brain, heart, bone, or other organs(6). However, a review of the English medical literature also revealed cases involving the musculature of the chest wall (2), the abdominal wall(3), the pectoralis major(1), Sartorius(10) and sternomastoid muscles(2) although it has been suggested that muscle provides a poor environment for the parasite because of the presence of lactic acid(2). This report presents an unusual case of an intramuscular infestation of Echinococcus in a 48-year-old man.

Case Report:

A 48-year-old man had a two-month history of a painless, enlarging mass in the left thigh. He had no history of fever or prior trauma. His medical history included treated and cured pulmonary tuberculosis.

A physical examination (Figure 1) revealed a painless multicystic lesion, about 6 by 8 cm, fixed to the deep tissue, with a smooth surface in the region of left quadriceps femoris muscle (Figures 1a, 1b). There was no redness, increased warmth or lymphadenopathy. The left hip and knee region had a full range of movement. Distal pulses were equal in both lower limbs. The remainder of the physical examination was unremarkable.

(Figure 1a)	(Figure 1b)
The figure above shows multicystic lesions, non-tender about 6 by 8cm, fixed with smooth surfaces in the region of left quadriceps femorus. There is no redness, increased warmth, or lymphadenopathy the distal pulses were equal in both lower limbs.

Laboratory tests included a complete blood count, electrolytes, alkaline phosphatase, bilirubin and an indirect hemagglutination test, the results of all of which were normal. A bone isotope scan was also normal.

A skin test for tuberculosis using purified protein derivative was normal. X-rays of the left thigh showed a soft tissue mass in the region of the left quadriceps femoris muscle. Magnetic resonance imaging (Figures 2a, 2b) revealed a multicystic lesion consisting of three cysts each about 6 by 8cm within the substance of the left quadriceps femoris muscle, extending from the lower pelvis to the left knee.

(Figure 2a)	(Figure 2b)
The figure above magnetic resonance imaging revealed a multicystic lesions extending from the lower pelvis down to the left knee region each about 6 by 8 cm, within the substance of the left quadriceps femorus muscle.

Based on clinical and radiographic data, the mass was believed to be a soft tissue tumor. At operation there were found (Figures 3a, 3b) encapsulated, multi cystic cavities within the substance of left quadriceps muscle, each filled with about 200 ml of clear fluid and lined with a white membrane. The cyst linings were excised, the cavity was thoroughly irrigated with hypertonic saline (5%) and the wound was closed.

(Figure 3a)	(Figure 3b)
The above operative finding showed encapsulated, multicystic cavities filled with about 200ml of clear fluid in each cyst located within the substance of left quadriceps muscle, the cavity was lined with a white membrane containing hydatid daughter cysts.

Histopathology confirmed the diagnosis of Echinococcus granulosus infestation. The patient was maintained on albendazaole (800mg) daily for three months and remained asymptomatic with no evidence of recurrence.

Discussion:

Pre-operative recognition of an Echinococcus infestation is critical as Echinococcus granulosus infestations are best treated by complete excision of the intact cyst. It may be impossible to excise a large cyst en bloc, in which case the cyst is drained intra-operatively, irrigated with a scolecidal agent such as hypertonic saline and then excised. (Figures 3a, 3b). Inadvertent cyst rupture releases viable scolices which may enter the circulation, disseminate to distant organs and reproduce asexually to form additional cysts(11). The likelihood of recurrent infestation is increased after rupture of the parent cyst(7). In addition, leakage of cyst contents may cause anaphylactic shock (5). Thus, excision of an intact cyst is usually curative whereas cyst rupture may be fatal.

The purpose of the present report is to alert the reader to this rare infestation so that open biopsy will be avoided. Percutaneous needle biopsy is also not recommended because of the possibility of introducing scolices into the needle tract. The recommended treatment of Echinococcus is complete excision of the cyst lining and thorough irrigation of the cyst cavity with hypertonic saline to decrease the risk of recurrence.

Summary:

Intramuscular Echinococcus infestation is rare, it is important to reach a preoperative diagnosis because of the propensity for recurrence and dissemination. Intramuscular infestation may mimic a soft tissue tumor, leading to inappropriate cyst rupture with the attendant risks of anaphylaxis and dissemination to other organs.

References:

1. Abdel-Khaliq, R.A., & Othman, Y.: Hydatid cyst of pectoralis major Muscle, Acta chir, Scand. 152: 469, 1986.

2. Alvarez-Sala, R., and Caballero, P.:E. cyst as a cause of chest wall tumor (Letter) and Ann. thorac. Surg. 43: 689, 1987.

3. Baig, M.A. misgar, M.S., & Brijmojan, B: Primary E. cyst of the internal oblique muscle. Int. surg. 60: 562, 1975.

4. Freedman, A.N.: Muscular hydatidosis: A case report & review of the literature Car. J. Surg. 17: 232, 1974.

5. Heinze, J. Junginger, W., Muller, G., and Gaebel, G. Anaph. Shock during extirpation of an E.G. cyst of the thigh. Anesthesist 36: 659, 1987.

6. Little, J.M.: Hydatid disease of Royal Albert Hospital, 1964- 1974. Med. J. Awst. 1: 903, 1976.

7. Mottaghian, H., & Farrokh, S.: Post Operative recurrence of Hydatid disease. Br.J. Surge 65: 237, 1978.

8. Naik R.S. and Naik V.L Hydatid cyst in the sternomastoid muscle, J. Indian Med. Assoc. 79: 57,1982

9. Plorcte, J.J, and Ramsey, P. G.: Echinococciasis. In petersdorf, P.G. Adams, R.D., Braunwall, E., Isselbacher, K. Martin. J., and Wilson, J. (eds): Harrson’s principles of internal Medicine, St. Louis, Mcgraw- Hill, 1983, pp 1237/1238.

10. Rask, M.R., & Latting, G.J: Primary intramuscular hydatidosis of the sartorius: Report of acase. J Bone joint surg. 52A: 582, 1970.

11. Schiller, C.F.: Complication of Echinococus cyst rupture, JAMA 195: 158, 1966.

12. Wani, N.A, & Shah, I.A.: Hydatid cyst in muscles, J. Indian Med, Assoc. 84: 385, 1986.