Diseases of the Colon, Rectum and Anus

inflammatory diseases of the colon, colonic diverticular disease, other lesions of the colon



Rectal Infections

Gonococcal Proctitis

Gonorrheal proctitis in men is almost always the result of anal intercourse; in women, most cases are believed to be caused by genitoanal spread. Most patients with rectal gonorrhea have no symptoms and are discovered only by the meticulous tracing of sexual contacts and by having a high index of suspicion. To differentiate gonorrheal proctitis from other ulcerative diseases, Gram staining and selective culturing of the purulent exudate must be performed. The symptoms associated with gonorrheal proctitis are similar to those of other forms of ulcerative proctitis and include rectal burning and itching, purulent anal discharge, and blood and mucus in the stools. Barium enema examination is normal in most patients with gonorrheal proctitis. Infrequently, mucosal edema and ulceration confined to the rectum can be demonstrated. Gonorrheal proctitis responds promptly to specific antibiotic therapy.

Herpes Simplex

Anorectal herpes is a sexually transmitted disease in whic vesicles or ulcerations may be seen in the genital ar perianal areas, and erythema, friability, and discrete focal ulcerations may be noted on sigmoidoscopy. Barium enema examinations may demonstrate aphthous ulcer plaquelike erosions, and deep collar-button ulceratior in the rectum, at times extending to involve the sigmoi colon.

Lymphogranuloma Venereum

Lymphogranuloma venereum is a sexually transmitte chlamydial infection that is especially common in th tropics. The rectum is the first and usually the only portion of the colon involved. Invasion and blockage of rectal lymphatics, combined with secondary infectior lead to rectal edema with cellular infiltrate in the submucosa and muscularis. In the early stages of the disease the bowel is spastic and irritable and has boggy an edematous mucosa and multiple shaggy ulcers. Fistula and sinus tracts of varying lengths are frequently present.

The hallmark of lymphogranuloma venereum is the development of a rectal stricture in the chronic stage of the disease. These strictures are usually long and tubular, beginning just above the anus and varying in radiographic appearance from a short, isolated narrowing to a stenotic segment up to 25 cm long. The mucosa is irregular, with multiple deep ulcers; the lumen can be so narrow that it resembles a thin string. The portion of normal colon proximal to the stricture is usually dilated, has a loss of haustration, and gradually tapers in a smooth, conical fashion. In a patient with a rectal stricture, the demonstration of fistulas and sinus tracts communicating with perirectal abscess cavities, the lower vagina, or perianal skin should suggest a diagnosis of lymphogranuloma venereum.

gonococcal proctitis · yhs-fh_lsonsw · torqued pelvis and abdomen ·

Hemorrhoids

Internal hemorrhoids can produce single or multiple rectal filling defects that simulate polyps. The proper diagnosis can easily be made by inspection or direct vision through the anoscope.

Metastases of the Colon

Metastases to the colon can arise from direct invasion, intraperitoneal seeding, or hematogeneous or lymphangitic spread. Direct invasion of the colon from a contiguous primary tumor indicates a locally aggressive lesion that has broken through fascial planes. In men, the most common primary tumor is advanced prostatic carcinoma, which spreads posteriorly across the rectogenitai septum. The most frequent presentation of prostatic carcinoma metastatic to the colon is a long, asymmetric annular stricture that often has irregular scalloped margins caused by intramural tumor nodules or by edema infiltrating the bowel wall. A large, smooth concave pressure defect on the anterior aspect of the rectosigmoid due to metastases occasionally may be severe enough to obstruct the colon. Invasion of the anterior rectal wall produces a fungating, ulcerated mass that closely simulates primary rectal carcinoma. In women, direct invasion from a noncontiguous primary tumor is usually related to a pelvic mass arising in the ovary or uterus. Invasion of the bowel wall produces a mass effect that is often of great length and does not demonstrate overhanging margins. An associated desmoplastic reaction causes angulation and tethering of mucosal folds and can even lead to the development of an annular stricture.

Carcinomas of the stomach and pancreas are noncontiguous primary tumors that can spread to the colon along mesenteric reflections. Primary carcinoma of the stomach (usually s “irrhous) extends down the gastrocolic ligament to involve the transverse colon along its superior haustral border. Pancreatic carcinomas spread downward through the transverse mesocolon to predominantly involve the inferior aspect of the transverse colon. Both lesions cause fixation and nodularity of the transverse’colon; progressive involvement can lead to circumferential colonic narrowing.
Figure 24.64. Carcinoma of the breast metastatic to the colon. A CT scan shows circumferential thickening (arrowheads) of the colonic wall and associated omental metastases (arrow;. (From Mauro and Koehler;50 with permission from the publisher.:
Primary abdominal malignancies can extend into the peritoneal cavity and shed tumor cells into ascitic fluid. The serosa! bowel metastases caused by this intraperitoneal seeding reflect the predictable course of malignant ascites that is determined by mesenteric reflections, peritonea! recesses, and the forces of gravity and negative intra-abdominal pressure. In more than half the cases, intraperitoneal metastases grow in the region of the pouch of Douglas (the lower extension of the peritoneal reflection between the rectosigmoid and the urinary bladder at the level of the lower-second to upper-fourth sacral segments), where they produce a nodular mass or the characteristic pattern of fixed transverse parallel folds. Spread of tumor along the distal small bowel mesentery in the right lower quadrant can cause a smooth or tabulated extrinsic mass indenting the medial and inferior borders of the cecum below the level of the ileocecal valve. Involvement of the sigmoid mesocolon is usually localized to the superior border and typically incites an intense desmoplastic reaction leading to tethering or retraction of folds. When seen en face on double-contrast studies, this tethering appears to be projected through the colonic lumen as transverse folds that do not completely cross the lumen of the colon (striped colon).

The hematogenous spread of tumor, especially due to carcinoma of the breast, tends to cause thickening and rigidity of a long segment of colon. This pattern, which is due to densely cellular submucosal metastatic deposits, simulates a primary infiltrating scirrhous carcinoma. At times, metastatic breast carcinoma can mimic primary inflammatory colitis and produce such radiographic findings as mucosal thickening, nodular masses, multiple and eccentric strictures, and spiculations.

Computed tomography can demonstrate mural and mesenteric masses and stretching of colonic loops due to metastases to the colon. This modality can also be of value in differentiating a primary colonic tumor from secondary spread of pancreatic or gastric carcinoma.

Other Tumors of the Colon

Lipomas of the colon appear radiographically as circular or ovoid, sharply defined, smooth filling defects in the barium column. A pathognomonic diagnostic feature of lipomas is their changeability in size and shape during the course of a barium enema examination. Because these tumors are extremely soft, their configuration can be altered by palpation and extrinsic pressure. Thus a malleable lipoma that appears round or oval on filled films characteristically becomes elongated (sausage- or banana-shaped) on postevacuation films in which the colon is contracted.

Other spindle cell tumors (leiomyoma, fibroma, neurofibroma) are rare in the colon. Malignant spindle cell tumors are extremely rare. They tend to be much larger and more irregular than their benign counterparts, although differentiation between benign and malignant submucosal tumors can be extremely difficult.

Megacolon

Acquired Megacolon

In Chagas’ disease, destruction of the colonic myenteric plexuses by the protozoan Trypanosoma cruzi causes striking elongation and dilatation, especially of the rectosigmoid and descending colon. Acquired megacolon in adults can also be found in patients with severe neurologic or psychologic disorders and in patients with abnormal colonic motility (myxedema, infiltrative diseases such as amyloidosis and scleroderma, narcotic drugs).

Chronic constipation and acquired megacolon may be caused by mechanical obstruction (e.g., carcinoma, stricture) or be of functional origin, as in bedridden elderly patients or persons with improper bowel habits. Plain abdominal radiographs may demonstrate a tremendously dilated, tortuous colon and rectum filled with a large fecal residue.

Psychogenic megacolon, which has its onset later in childhood than Hirschsprung’s disease, is characterized by huge dilatation of a feces-filled rectum, often with distension of the entire colon. Unlike aganglionic megacolon, psychogenic megacolon results in no narrowed segment, and a rectal biopsy discloses the normal complement of ganglion cells in Auerbach’s plexus.

 

Fecal Impaction

 

The incomplete evacuation of feces over a prolonged period can result in the formation of a fecal impaction, a large, firm, immovable mass of stool in the rectum that may cause large bowel obstruction. Fecal impactions most commonly develop in elderly, debilitated, or sedentary persons. They can occur in patients who have been inactive for long periods (e.g., because of myocardial infarction, traction), in narcotic addicts, in patients on large dosages of tranquilizers, and in children with megacolon or psychogenic problems.

The symptoms of fecal impaction usually consist of vague rectal fullness and nonspecific abdominal discomfort. A common complaint is overflow diarrhea, the uncontrolled passage of small amounts of watery and semi-formed stools around a large obstructing impaction. In elderly, bedridden patients, it is essential that this overflow phenomenon be recognized as secondary to fecal impaction rather than perceived as true diarrhea.

Plain radiographs of the pelvis are usually diagnostic of fecal impaction. The fecal mass within the rectum typically appears as a mottled soft tissue density containing multiple small, irregular iucent areas that reflect pockets of gas within the mass. Contrast studies demonstrate a large, irregular intraluminal mass that can occasionally be confused with colonic malignancy. For fecal impaction to be confirmed as the cause of large bowel obstruction, an enema of water-soluble contrast material should be used instead of barium; hypertonic contrast medium draws fluid into the bowel and can aid in breaking up the fecal mass.

megacolon symptoms in adults · mega colon in adults · treatment of megacolon in adults ·

Volvulus of the Colon

Because torsion of the bowel usually requires a long, movable mesentery, volvulus of the large bowel most frequently involves the cecum and sigmoid colon. The transverse colon, which has a short mesentery, is rarely affected bv volvulus.

Cecal Volvulus

The ascending colon and cecum may have a long mesentery as a fault or rotation and fixation during the development of the gut. This situation predisposes to volvulus, with the cecum twisting on its long axis. It should be stressed, however, that only a few patients with a hypermobile cecum ever develop cecal volvulus. Other factors (colonic ileus, distal obstruction as in sigmoid carcinoma, pregnancy, and chronic cecal retention) have been implicated as precipitating causes.

in cecal volvulus, the distended cecum tends to be displaced upward and to the left, though it can be found anywhere within the abdomen. A pathognomonic sign ot cecal volvulus is a kidnev-shaped mass representing a twisted cecum, with the torqued and thickened mesentery mimicking a renal pelvis. A barium enema examination is usually required for definite confirmation of the diagnosis. This study demonstrates obstruction of the contrast column at the level of the stenosis, with the tapered edge of the column pointing toward the site ot torsion.

 

Sigmoid Volvulus

A long, redundant loop of sigmoid colon can undergo a twist on its mesenteric axis and form a closed-loop obstruction. In sigmoid volvulus, the greatly inflated sigmoid loop appears as an inverted-U-shaped shadow that rises out of the pelvis in a vertical or oblique direction and can even reach the level of the diaphragm. The affected loop appears devoid of haustral markings and has a sausage or balloon shape. On supine radiographs, there are often three dense, curved lines running downward and converging toward the point of stenosis. These lines appear to end in a small tumorlike density that corresponds to the twisted mesenteric loop. The central and most constant line is a dense midline crease produced by the two walls of the torqued loop lying pressed together. The other two lines, less frequently seen, are made up of the outer margins of the closed loop joined with the medial walls of the cecum on the right and the descending colon on the left. When a barium enema examination is performed on a patient with sigmoid volvulus, the flow of contrast material ceases at the obstruction, and the rectum becomes distended. The lumen tapers toward the site of stenosis, and a pathognomonic bird’s beak is produced.

As with any colonic obstruction, prompt decompression of sigmoid volvulus is necessary to prevent bowel ischemia and perforation. Fluoroscopic or sigmoido-scopic guidance of a rectal tube is often therapeutic and is the preferred form of initial treatment if there are no signs of vascular compromise. Tube decompression allows time for medical stabilization of the patient and is the only viable approach to the patient who is at high risk for surgery. Because there is a high recurrence rate of sigmoid volvulus (up to 80 percent), resection of the redundant sigmoid is often necessary.

volvulus of colon · hypermobile cecum · cecal volvulus cecum survival rate with heart patients ·

Endometriosis

Endometriosis is the presence of heterotopic foci of endometrium in an extrauterine location. Endometriosis involving the bowel primarily affects those segments that are situated in the pelvis, especially the rectosigmoid colon. Because endometriosis is usually clinically apparent only when ovarian function is active, most women who are symptomatic from endometriosis are between 20 and 45 years of age. The typical gastrointestinal complaint is abdominal cramps and diarrhea during the menstrual period.

Growth of endometrial tissue in the wail of the bowel may produce an eccentric intramural filling defect simulating a flat saddle cancer. In contrast to primary colonic malignancy, the underlying mucosal pattern in endometriosis usually remains intact or is pleated because of secondary fibrosis. Endometriosis can aiso present as a constricting lesion simulating annular carcinoma. Radiographic findings favoring endometriosis are an intact mucosa, a long lesion with tapered margins, and the absence of ulceration within the mass. Repeated shedding of endometrial tissue and blood into the peritoneal cavity can lead to the development of dense adhesive bands causing extrinsic obstruction of the bowel.

Lymphoma of the Colon

Although the gastrointestinal tract is the most common location of primary extranodal lymphoma, the colon is the segment of gut that is least often affected. Localized lymphoma can appear as a single, smooth or lobulated polypoid mass that is radiographically indistinguishable from polypoid carcinoma. Unlike carcinoma, localized lymphoma tends to be unusually bulky and to extend over a longer segment of the colon. Diffuse submucosal infiltration can produce multiple nodules simulating familial polyposis, or irregular thumbprinting suggesting ischemic colitis. Lymphoma occasionally appears as an area of localized narrowing simulating annular carcinoma. Subserosal lymphoma may develop a large ex-tracolonic component that displaces adjacent abdominal structures. Multiple subserosal masses may mimic mesenteric metastases.

 

Carcinoid Tumors of the Colon

Almost all nonappendiceal carcinoid tumors of the colon arise in the rectum. The vast majority are small (under 1 cm), solitary, and asymptomatic. Most are found only incidentally on barium enema or sigmoidoscopic examination. Rectal carcinoids develop metastases in about 10 percent of cases, have a significantly better prognosis than the more proximal colonic lesions, arid are usually cured by simple local excision. The size of the lesion is closely correlated with the aggressiveness of the tumor, and the survival rate is associated with the size. Small colonic carcinoids (< 1 cm) rarely invade locally or metastasize to the liver. In contrast, larger lesions (> 2 cm) are often locally aggressive and invade the muscularis, extending beyond the serosa into adjacent tissues. Unlike ileal tumors, carcinoids of the colon and rectum rarely give rise to the carcinoid syndrome.

Although colonic carcinoids arise from the submucosa, they most frequently present radiographically as polypoid protrusions into the lumen. Large ulcerating lesions can produce rectal bleeding, intussusception, or obstruction. Rarely, rectal carcinoids appear as infiltrating or annular lesions indistinguishable from adenocarcinoma.

Colonic carcinoids elsewhere than in the appendix and rectum are extremely rare. These tumors tend to be relatively large, often have a prominent extramural component, and have a higher malignant potential than rectal carcinoids.

carcinoid extending to the submucosa · carcinooid tumors of the colon ·

Intestinal Polyposis Syndromes

The intestinal polyposis syndromes are a diverse group of conditions that differ widely in the histology of the pftlyps, the incidence of extracolonic polyps, extra-abdominal mahifestations, and the potential for developing malignant disease. An intestinal polyposis be suspected when a polyp is demonstrated in a young person, when multiple polyps are found in any person, or when carcinoma of the colon is found in a patient under 40 years of age. If one of the hereditary forms of intestinal polyposis is diagnosed, the patient’s immediate family should be studied so that a potentially fatal disease is not missed in its premalignant stage.

 

Familial Polyposis

Familial polyposis is an inherited disease (autosomal dominant) characterized by multiple adenomatous polyps almost exclusively limited to the colon and rectum. The polyps are not present at birth but tend to appear in childhood and adolescence. They may cause diarrhea or rectal bleeding, though many patients with familial polyposis are asymptomatic and their condition is only discovered during routine investigation of relatives of a patient known to have the disease. There is no evidence of extra-intestinal involvement.

On barium enema examination, the polyps appear as sessile or pedunculated lesions scattered throughout the colon. Although the rectum and left colon are involved more frequently than the right colon, myriads of polyps often blanket the entire length of the colon. With diffuse disease, the colon can appear to be “poorly prepared”; however, in familial polyposis the true adenomatous polyps remain fixed in position with palpation, unlike retained fecal material, which is usually freely movable.

Because patients with familial polyposis have virtually a 100 percent risk of developing carcinoma of the colon or rectum, total colectomy is usually recommended at the time of diagnosis.

Gardner’s Syndrome

Gardner’s syndrome is an inherited disorder (autosomal dominant) in which diffuse colonic polyposis is associated with bony abnormalities and soft tissue tumors. Osteomas are common, especially in the paranasal sinuses. Sebaceous cysts and subcutaneous fibromas, leiomyomas, and lipomas are often seen. Exostoses and cortical thickening can involve the long bones and ribs. Dental abnormalities are not infrequent and include odontomas, extra teeth, unerupted teeth, and a propensity toward numerous caries.

The distribution and appearance of the adenomatous polyps in Gardner’s syndrome are indistinguishable from the pattern in familial polyposis. The polyps are almost always limited to the colon and rectum; extracolonic polyps occasionally occur in the small bowel and stomach. Like patients with familial polyposis, patients with Gardner’s syndrome have almost a 100 percent risk of developing carcinoma of the colon or rectum. Therefore, a total colectomy is recommended. In addition, patients with Gardner’s syndrome appear to have a predilection toward small bowel malignancies, particularly in the pancreaticoduodenal region.