<prompt> Per rectum examination is not a useful test for diagnosis ofAnal fissureHemorrhoidPilonidal sinusRectal ulcer  <response>: PILONIDAL SINUSDISEASE Jeep Bottom; Drivers Bottom Pilus--hair; Nidus--nest It is epithelium lined tract, situated sho distance behind the anus, containing hairs and unhealthy diseased granula- tion tissue. It is due to penetration of hairs through the skin into subcutaneous tissue. It forms granulomaunhealthy granulation tissue in the deeper plane. It is of infective origin and occurs in sacral region between the buttocks, umbilicus, axilla. Other indications of per rectal examination are:Carcinoma rectum, Stricture rectum, Polyps, BPH and carcinoma prostate, Secondaries in the rectovesical pouch Blumer shelf, Sphincter tone, Pelvic abscess is felt as boggy swelling, to feel the internal opening of anal fistulas, in bimanual palpation of the bladder or pelvic tumours, in acute abdominal conditions--it reveals dilated empty rectum with tenderness.Reference : page 967 and 952 SRBs manual of surgery 5th edition 