This article describes the case of a 64-year-old man whose thigh swelling was a subcutaneous hydatid cyst.
He presented to the hospital with a complaint of swelling on the right medial thigh. According to him, the swelling was one year old and was gradually increasing in size. However, he did not report any pain associated with the swelling, nor did he complain of a fever or any other significant symptoms.
Relevant Examination Suggests a Cyst
On examination, doctors noticed a painless swelling on the inner side of the patient’s right thigh. Additionally, it was mobile with a fluctuating nature. The features suggested a cyst. Hence, doctors performed an ultrasound, which revealed a hydatid cyst. Other investigations came out normal except for ESR, which came out slightly elevated. The patient denied being operated on for a cyst. He also denied having any associated liver problems.
Treatment for Subcutaneous Hydatid Cyst
After making a final diagnosis based on examination and ultrasonic findings, doctors decided to surgically explore and excise the cyst. Therefore, they prepared the patient for surgery and proceeded under spinal anaesthesia. After dissecting through the skin and subcutaneous layers, they injected hypertonic saline into the cyst as a standard protocol. This kills the live parasites inside the cyst. Next, they carefully excised the cyst and irrigated the whole area with iodine.
Histopathology of the cyst confirmed a hydatid cyst. Doctors started the patient on a three-month course of albendazole to prevent recurrence. However, no swellings were noted elsewhere in the body. Furthermore, the patient did not report any symptoms of recurrence during his follow-up period.
Subcutaneous Hydatid Cyst: What Do We Know About It?
Hydatid disease is a parasitic disease caused by Echinococcus granulosus. This parasite divides its life cycle into two parts. It grows in intermediate hosts like cattle and occasionally human beings and matures inside definitive hosts like dogs and wolves (more commonly dogs). Whatever the case, it usually affects the liver, and if it goes on to affect any other organ, it involves the lungs. Subcutaneous involvement, as in our case, on the medial aspect of the thigh, is extremely rare.
Subcutaneous disease occurs in two forms: primary and secondary. Secondary disease refers to a cyst that happens in relation to another cyst, say in the liver or lung, through hematogenous or regional spread. In primary disease, however, the subcutaneous cyst is the sole cyst in the body, with no primaries elsewhere.
The mechanisms of development of a primary subcutaneous hydatid cyst are very unique and still not fully known. Humans develop a cyst after ingesting the parasitic larvae in contaminated food or water. The larvae penetrate the gut wall and enter the portal circulation. That’s how they reach the liver. In the liver, they form primarily with cysts. Hence, in most cases where hydatid cysts involve organs other than the liver, a primary cyst resides in the liver. The second most common site for these cysts remains the lungs.
Although doctors have seen cysts in the brain as well, they all stem from a primary hepatic cyst and then spread the parasite through blood. Cysts residing solely in the subcutaneous tissue remain an etiological dilemma.