A rare presentation of filariasis in abdominal wall of child

Clinical History

A 6-year-old girl presented with a painless swelling of the lower anterior abdominal wall, which had gradually increased in size over the past 6 months. Physical examination revealed a soft, well circumscribed, non-tender, non-erythematous swelling extending from the supra-pubic region to the vulva, including the right gluteal region. An ultrasound examination was performed.

Imaging Findings

Trans-abdominal ultrasound revealed multiple cystic lesions in the supra-pubic region, which extended to the vulva, postero-medial aspect of the right upper thigh and the right gluteal region (Fig. 1).
Subsequent MR revealed multiple, ill-defined, non-capsulated cystic lesions in the subcutaneous plane of lower anterior abdominal wall extending to the vulva, postero-medial aspect of right upper thigh and the right gluteal region. The lesions were hypointense on T1-W and hyperintense on T2-W sequences, with no intramuscular/peritoneal extension. (Fig. 2, 3, 4, 5, 6a and 6b).
Follow-up ultrasound revealed anechoic tubular channels, which failed to show colour flow on Doppler imaging (Fig. 7). Multiple, linear, dangling, echogenic, undulating structures with persistent twirling motion were noted within these anechoic channels, which strongly suggested a diagnosis of lymphedema of filarial origin (so-called "filarial dance"). (Fig. 8, 9 - video 1).
US-guided Fine Needle Aspiration Cytology of the lesion on light microscopy revealed live microfilariae of Wuchereria bancrofti.

Discussion

Filariasis is a neglected endemic infectious disease, most commonly caused by Wuchereria bancrofti in the tropical and subtropical regions of the world. It is also known as elephantiasis. Elephantiasis of filarial origin is the most common cause of disability in the world. Out of 120 million people infected with filariasis, 1/3rd are Indians, 1/3rd Africans and remaining 1/3rd are Southeast Asians [1].
The infective larvae penetrate the skin by mosquito bite and migrate into the lymphatic system, where they develop into adult parasites, which cause obstruction, progressive dilation and impairment in contractility of lymphatics, with dysfunction of unidirectional valves [2].
The common presentations of lymphatic filariasis are subclinical microfilaraemia, hydrocele, acute adenolymphangitis, lymphocele, filariasis of breast, chyluria or groin lymphadenovarix. Rare presentations include lesions in the thyroid gland [3], vulva [6], salivary glands [8], intra-oral [9], vitreous [10] and intra-abdominal masses [4], retroperitoneal cysts [5], thoraco-abdomino-pelvic lymphangiectasia [7]. Skin changes mimicking hyperkeratosis, thickening of the subcutaneous tissues, secondary infection and scarring may be found in chronic cases.
Filarial origin elephantiasis involving the anterior abdominal wall is a very rare entity.
The method of detection of microfilaria in a night-time blood specimen has been replaced by filarial antigen measurement in daytime blood samples.
Ultrasound is the only non-invasive imaging modality that can show live adult filarial worms; the “Filarial dance" sign. This sign indicates the active release of microfilariae into the lymphatic vessels and is a reliable marker of active infection [11]. It is therefore ideal for post-therapy follow-up. Colour Doppler imaging helps to distinguish from haemangiomata and venolymphatic malformations.
Ultrasound guided FNA from the anechoic channels of the lesion is helpful for the detection of microfilaria even in asymptomatic patients.
MRI in conjunction with lymphangioscintography is a useful complementary technique to accurately depict lymphatic insufficiency of the peripheral lymphatic system and the extent of involvement before surgery [12].
Medical treatment consists of high dose mebendazole and subsequent cycles of diethylcarbamazine (drug of choice). Sadly, around 40 million people are disfigured and incapacitated by this disease [1]. Failure of medical management requires surgical intervention with surgical resection, reconstruction and physiological drainage procedures that attempt to reconstruct lymphatic drainage by introducing distant/local pedicle or microsurgery to bypass the obstruction in the lymphatics and reestablish lymphatic flow. Anastomoses of transected lymph nodes to the veins has also been carried out [13].

Elephantiasis of filarial origin in the anterior abdominal wall is a very rare entity and a conventional investigation like ultrasound can play a key role in diagnosis.

Differential Diagnosis List

Final Diagnosis

Abdominal wall filariasis with vulval, gluteal and thigh extension.

URL:	https://www.eurorad.org/case/12210
DOI:	10.1594/EURORAD/CASE.12210
ISSN:	1563-4086