We report our experience of two cases of refractory cellulitis caused by peripheral micro-arteriovenous fistulas (AVFs) in the lower extremity. The micro-AVFs were so small that they could not be located accurately; further, the patients’ symptoms differed markedly from those previously reported for AVF. AVF is known to cause ischemic symptoms. In contrast, micro-AVF causes congestive symptoms and remains undetected in the majority of patients. Identification of this pathology is crucial to enable effective treatment by the ligation of the incompetent perforator vein that increases venous hypertension, leading to congestive symptoms.