Hydatid Cyst Disease (Echinococcosis)

Hydatid cyst disease or echinococcosis is a parasitic infection caused by the Echinococcus tapeworm larvae. Of the seven recognized species, Echinococcus granulosus and Echinococcus multilocularis , which cause cystic echinococcosis (CE) and alveolar echinococcosis (AE), respectively, pose clinically significant and potentially lethal public health risks. Human infection occurs after incidental ingestion of the parasite eggs from the stool of infected animals. Most of these cysts are solitary and occur in either the liver or the lungs. Although the cysts displace healthy tissue, the primary infection is typically asymptomatic unless rupture or mass effect occurs. Definitive diagnosis for most cases is by imaging with ultrasound or computed tomography (CT), although immunodiagnostic assays can be a useful adjunct in both primary diagnosis and follow-up. Surgery has the potential to remove the cysts and lead to complete cure; however, successful eradication requires the entire elimination of the parasite without intraoperative contamination or compromise of affected organ systems. Alternatively, the puncture, aspiration, injection, and reaspiration (PAIR) procedure has emerged as a less invasive treatment option in patients with CE who present high surgical risks because of underlying pathophysiology or who are remote from surgical care facilities.

A 58-year-old woman presents with gradual worsening of abdominal pain and distention. She lives on a sheep ranch in Turkey, in the home in which she grew up. For approximately a year, she has noticed increased abdominal girth and early satiety. In recent months, her abdomen has begun to ache around the clock, without any discernible relation to meals or time of day. Her bowel movement pattern is unchanged.

On examination, she is found to be a short woman in no acute distress. Her exam is unremarkable except for her abdomen, which is protuberant, especially in the right upper quadrant, where she reports tenderness on palpation without a rebound phenomenon. By percussion, her liver seems to be markedly enlarged. Routine bloodwork is unremarkable.

Ultrasonography of the right upper quadrant reveals a large, well-circumscribed, complex cystic mass involving most of the right lobe of the liver. Innumerable spheres are present within this mass, all of which have an echodensity suggestive of water. CT imaging confirms this finding ( Fig. 45.1A ) and demonstrates that the mass abuts and impinges on the inferior vena cava. The diagnosis of multicystic echinococcosis (World Health Organization [WHO] class CE2) is made. The patient confirms that there are always sheepdogs on her ranch and that they are fed the uncooked entrails of sheep after they have been harvested. She is told that she probably acquired this infection years earlier from consuming food soiled with the feces of her sheepdogs.

Treatment is indicated because she is symptomatic. PAIR is not appropriate because the cyst contains many daughter cysts. Complete surgical resection is not possible because of the size and location of the lesion. She is treated with antiparasitic medications (praziquantel and albendazole) for 4 weeks and then undergoes palliative surgery: the mother cyst is carefully entered via a small incision surrounded by sponges soaked in hypertonic 15% saline (see Fig. 45.1B ). Liquid and solid cyst contents are removed, the cyst is instilled with hypertonic saline for 10 min that is then removed, and the case is concluded. No hemodynamic instability concerning for anaphylaxis is noted. Direct microscopic examination of cyst debris (“sand”) reveals hooklets and viable protoscolices of Echinoccocus granulosus (see Fig.45.1C ). Postoperatively, the patient reports feeling substantial relief from abdominal bloating and pain. She continues to receive antiparasitic medications for the next 4 months, which she tolerates well except for mild leukopenia. She remains symptomatically improved at 2 years of follow-up. She states that her sheepdogs have all been dewormed, and they are no longer fed offal on her ranch.