Symptoms
Internal intussusception may be asymptomatic, but common symptoms include:
Fecal leakage
Sensation of obstructed defecation (tenesmus). Pelvic pain. Rectal bleeding.Recto-rectal intussusceptions may be asymptomatic, apart from mild obstructed defecation. "interrupted defaecation" in the morning is thought by some to be characteristic.Recto-anal intussusceptions commonly give more severe symptoms of straining, incomplete evacuation, need for digital evacuation of stool, need for support of the perineum during defecation, urgency, frequency or intermittent fecal incontinence.It has been observed that intussusceptions of thickness ≥3 mm, and those that appear to cause obstruction to rectal evacuation may give clinical symptoms. Cause
There are two schools of thought regarding the nature of internal intussusception, viz: whether it is a primary phenomenon, or secondary to (a consequence of) another condition. Some believe that it represents the initial form of a progressive spectrum of disorders the extreme of which is external rectal prolapse. The intermediary stages would be gradually increasing sizes of intussusception. The folding section of rectum can cause repeated trauma to the mucosa, and can cause solitary rectal ulcer syndrome. However, internal intussusception rarely progress to external rectal prolapse.Others argue that the majority of patients appear to have rectal intussusception as a consequence of obstructed defecation rather than a cause, possibly related to excessive straining in patients with obstructed defecation. Patients with other causes of obstructed defecation (outlet obstruction) like anismus also tend to have higher incidence of internal intussusception. Enteroceles are coexistent in 11% of patients with internal intussusception.
It represents late sequelae of lipodermatosclerosis where the skin has lost its nutrient blood flow. Lipodermatosclerosis,  an indurated plaque in the medial malleolus. Malignancy, malignant degeneration being a rare but important complication of venous disease since tumors that develop in the setting of an ulcer tend to be more aggressive. Pain, a feature of venous disease often overlooked and commonly undertreated. Anxiety
Depression
Inflammation
Cellulitis

Causes
The most common cause of chronic venous insufficiency is reflux of the venous valves of superficial veins. This may in turn be caused by several conditions:

Deep vein thrombosis (DVT), that is, blood clots in the deep veins. Chronic venous insufficiency caused by DVT may be described as postthrombotic syndrome. DVT triggers an inflammatory response subsequently injuring the vein wall. Superficial vein thrombosis. Phlebitis
May–Thurner syndrome. This is a rare condition in which blood clots occur in the iliofemoral vein due to compression of the blood vessels in the leg. The specific problem is compression of the left common iliac vein by the overlying right common iliac artery. Many May-Thurner compressions are overlooked when there is no blood clot. More and more of them get nowadays diagnosed and treated (by stenting) due to advanced imaging techniques.Deep and superficial vein thrombosis may in turn be caused by thrombophilia, which is an increased propensity of forming blood clots.Arteriovenous fistula (an abnormal connection or passageway between an artery and a vein) may cause chronic venous insufficiency even with working vein valves.