Endometriosis is a common condition where tissue similar to the lining of the uterus, called the endometrium, grows outside the uterine cavity. This misplaced tissue responds to hormonal changes, leading to inflammation and pain. Umbilical endometriosis is an extremely rare manifestation of this disease, involving the growth of this tissue directly in or around the belly button, or umbilicus. Classified as extra-pelvic endometriosis, meaning it occurs outside of the pelvic organs, this form is also known as Villar’s nodule.
The Pathology of Umbilical Endometriosis
Umbilical endometriosis is a rare form of extra-pelvic endometriosis, accounting for only about 0.5% to 1% of all cases. The exact mechanism by which endometrial tissue arrives at the umbilicus is not fully understood, but several theories explain its pathogenesis. One leading idea is the coelomic metaplasia theory, which suggests that cells already present in the abdominal lining transform into endometrial tissue.
Another explanation is the theory of lymphatic or hematogenous spread, where endometrial cells travel to the umbilical area through the bloodstream or lymphatic system. This spread is often favored when umbilical endometriosis occurs alongside the more common pelvic form of the disease. The condition is classified as either primary, occurring spontaneously without prior surgery, or secondary, developing following a surgical procedure.
The secondary form is attributed to the iatrogenic transplantation theory, suggesting that endometrial cells are accidentally implanted into the umbilical surgical incision or port site during a procedure like a C-section or laparoscopy. For the primary, spontaneous form, the migration of endometrial cells from the pelvic cavity, possibly channeled by the anatomical remnants of the umbilical fold, is a strong hypothesis. Once established, this ectopic tissue behaves like the uterine lining, thickening and bleeding in response to the menstrual cycle’s hormones.
Identifying Clinical Symptoms
The most characteristic sign of umbilical endometriosis is a firm, palpable mass or nodule within or near the umbilicus. This lesion typically ranges from a few millimeters to a few centimeters in diameter. The nodule may display distinct discoloration, often appearing bluish, brownish, purple, or dark, due to the presence of old blood within the lesion.
The defining feature suggesting a diagnosis is the cyclical nature of the discomfort and changes, known as catamenial symptoms. Patients frequently report pain and tenderness in the umbilical mass that intensifies just before or during their menstrual period. This cyclic pain is often accompanied by swelling of the nodule and, in some cases, slight bleeding or discharge from the umbilicus.
These cyclical symptoms are reported in over 80% of cases. The symptoms are a direct result of the misplaced endometrial tissue reacting to hormonal fluctuations, causing the nodule to swell and bleed into the surrounding area. Because the umbilical mass can sometimes be mistaken for other conditions like a hernia or melanoma, recognizing the correlation between the symptoms and the menstrual cycle is important for proper identification.
Confirmatory Diagnostic Methods
The diagnostic process begins with a detailed patient history, focusing on the cyclical nature of any umbilical pain, swelling, or bleeding. A thorough physical examination assesses the size, texture, and discoloration of the umbilical nodule. These physical findings, coupled with a strong link between symptoms and the menstrual cycle, often lead a clinician to suspect umbilical endometriosis.
Non-invasive imaging techniques are used to characterize the lesion and rule out other potential causes of an umbilical mass. An ultrasound or magnetic resonance imaging (MRI) scan provides information about the lesion’s depth, size, and relationship to the underlying abdominal wall structures. These studies help distinguish the endometriotic nodule from other differential diagnoses, such as a hernia, lipoma, or malignant tumor.
While imaging and clinical history are highly suggestive, the definitive diagnosis of umbilical endometriosis requires a histological examination. This involves obtaining a tissue sample through a biopsy or, more commonly, analyzing the entire excised nodule after surgical removal. Confirmation is achieved when the tissue analysis reveals the presence of both endometrial glands and stroma outside of the uterus.
Treatment Strategies
The primary treatment for umbilical endometriosis is complete surgical removal, known as wide local excision. The goal of this surgery is to remove the entire endometriotic lesion along with a margin of healthy surrounding tissue to prevent recurrence. Surgical excision often provides a complete cure for the umbilical manifestation of the disease and is considered the standard of care.
The excision procedure is typically followed by a histopathological examination to confirm the diagnosis and ensure that the entire nodule was removed. In some cases, the surgeon may also inspect the peritoneal cavity, often using laparoscopy, as up to one-quarter of patients with umbilical endometriosis may also have concurrent pelvic endometriosis. Surgical reconstruction of the abdominal fascia may be performed after removal of the mass to ensure structural integrity.
Medical management, primarily involving hormonal suppression, is a secondary option used to manage symptoms. Medications such as oral contraceptives, progestins, or gonadotropin-releasing hormone (GnRH) analogs can reduce the size of the lesion and suppress cyclical pain by inhibiting hormonal stimulation of the ectopic tissue. While hormonal therapy offers symptom relief, it is not considered curative, and surgical removal remains necessary for definitive resolution.