lower anterior resection, often performed for colorectal cancer), radiotherapy directed at the rectum, and inflammatory bowel disease can cause scarring, which may result in the walls of the rectum becoming stiff and inelastic, reducing compliance. Reduced rectal storage capacity may lead to urge incontinence, where there is an urgent need to defecate as soon as stool enters the rectum, where normally stool would be stored until there was enough to distend the rectal walls and initiate the defecation cycle. Tumors and strictures also may impair reservoir function. Conversely, increased rectal volume (megarectum), may cause fecal loading and overflow FI. Reduced rectal sensation may be a contributory factor. If the sensory nerves are damaged, detection of stool in the rectum is dulled or absent, and the person will not feel the need to defecate until too late. Rectal hyposensitivity may manifest as constipation, FI, or both. Rectal hyposensitivity was reported to be present in 10% of people with FI. Pudendal neuropathy is one cause of rectal hyposensitivity, and may lead to fecal loading/impaction, megarectum and overflow FI. Normal evacuation of rectal contents is 90-100%. If there is incomplete evacuation during defecation, residual stool will be left in the rectum and threaten continence once defecation is finished. This is a feature of people with soiling secondary to obstructed defecation. Obstructed defecation is often due to anismus (paradoxical contraction or relaxation failure of the puborectalis). : 38  Whilst anismus is largely a functional disorder, organic pathologic lesions may mechanically interfere with rectal evacuation.
This is an uncommon cause in general, but is commonly seen in victims of nuclear disaster.Cases of psychogenic purpura are also described in the medical literature, some claimed to be due to "autoerythrocyte sensitization". Other studies suggest the local (cutaneous) activity of tissue plasminogen activator can be increased in psychogenic purpura, leading to substantial amounts of localized plasmin activity, rapid degradation of fibrin clots, and resultant bleeding. Petechial rash is also characteristic of a rickettsial infection. Etymology and pronunciation
The word purpura () comes from Latin purpura, "purple", which came from ancient Greek πορφύρα. Purpura is a mass noun naming the condition or state, not the name of an individual spot (thus there is no *pupurum, *purpura or *purpura, *purpurae count declension). See also
Bruise, which is a hematoma caused by trauma
Petechia, which is a small type of hematoma (<3 mm)
Ecchymosis, which is a large type of hematoma (>1 cm)
Purpura secondary to clotting disorders
Purpura hemorrhagica in horses
Pigmented purpuric dermatosis
Schamberg disease (progressive pigmentary purpura)

References
External links

Evaluating the Child with Purpura from American Academy of Family Physicians