Pilondial Cyst and Sinus
A pilondial cyst is a fairly common, probably congenital, abnormality located in the midline superficial to the coccyx or the lower sacrum. Look for the opening of a sinus tract. This opening may exhibit a small tuft of hair and be surrounded by a halo or erythema. Although pilonidal cysts are generally asymptomatic, except perhaps for slight drainage, abscess formation and secondary sinus tracts may complicate the picture.
External Hemorrhoids (Thrombosed)
External hemorrhoids are dilated hemorrhoidal veins that originate below the pectinate line and are covered with skin. They seldom produce symptoms unless thrombosis occurs. This causes acute local pain that increases with defacation and siting. A tender, swollen, bluish, ovoid mass is visible at the anal opening.
Internal Hemorrhoids (Prolapsed)
Internal hemorrhoids are enlargements of the normal vasicular cushions located above the pectinate line. Here, they are not usually palpable. Sometimes, especially during defacation, internal hemorrhoids may cause bright-red bleeding. They may also prolapse through the anal canal and appear as reddish, moist, protruding masses, typically located in one or more of the positions illustrated.
Prolapse of the Rectum
On straining for a bowel movement, the rectal mucosa, with or without its muscular wall, may prolapse through the anus, appearing as a donut or rosette of red tissue. A prolapse involving only mucosa is relatively small and shows radiating folds. When the entire bowel is involved, the prolapse is larger and covered by centrically circular folds.
Anal Fissure
An anal fissure is a very painful oval ulceration of the anal canal, found commonly in the midline posteriorly, less commonly in the midline anteriorly. There may be a swollen "sentinel" skin tag just below it. Gentle seperation of the anal margins may reveal the lower edge of the fissure. The sphincter is spastic; the examination is painful. Local anesthesia may be required.
Polyps of the Rectum
Polyps of the rectum are fairly common. Variable in size and number, they can develop on a stalk (pedunculated) or lie on the mucosal surface (sessile). They are soft and may be difficult or impossible to feel even when in reach of the examining finger. Proctoscopy and biopsy are needed for differentiation of benign from malignant lesions.
Rectal Shelf
Widespread peritoneal metastases from any source may develop in the area of the peritoneal reflection anterior to the rectum. A firm to hard nodular rectal "shelf" may be just palpable with the tip of the examining finger. In a woman, this shelf of metastatic tissue in the rectouterine pouch, behind the cervix and the uterus.
Anorectual Fistula
An anorectal fistula is an inflammatory tract or tube that opens at one end into the anud or rectum and at the other end into the skin surface or into another viscus. An abscess usually antedates such a fistula. Look for the fistulous opening or openings anywhere in the skin or around the anus.