Screening methods for colon cancer depend on detecting either precancerous changes such as certain kinds of polyps or on finding early and thus more treatable cancer. The extent to which screening procedures reduce the incidence of gastrointestinal cancer or mortality depends on the rate of precancerous and cancerous disease in that population. gFOBT (guaiac fecal occult blood test) and flexible sigmoidoscopy screening have each shown benefit in randomized clinical trials. Evidence for other colon cancer screening tools such as iFOBT (immunochemical fecal occult blood test) or colonoscopy is substantial and guidelines have been issued by several advisory groups but does not include randomized studies.

In 2009 the American College of Gastroenterology (ACG) suggest that colon cancer screening modalities that are also directly preventive by removing precursor lesions should be given precedence, and prefer a colonoscopy every 10 years in average-risk individuals, beginning at age 50. The ACG suggests that cancer detection tests such as any type of FOB are an alternative that is less preferred, and if a colonoscopy is declined, the FIT (fecal immunochemical test, or iFOBT) should be offered instead. Two other recent guidelines, from the US Multisociety Task Force (MSTF) and the US Preventive Services Task Force (USPSTF), while permitting immediate colonoscopy as an option, did not categorize it as preferred. The ACG and MSTF also included CT colonography every five years, and fecal DNA testing as considerations. All three recommendation panels recommended replacing any older low-sensitivity, guaiac-based fecal occult blood testing (gFOBT) with either newer high-sensitivity guaiac-based fecal occult blood testing (hs gFOBT) or fecal immunochemical testing (FIT). MSTF looked at six studies that compared high sensitivity gFOBT (Hemoccult SENSA) to FIT, and concluded that there was no clear difference in overall performance between these methods.

The American College of Gastroenterology has recommended the abandoning of gFOBT testing as a colorectal cancer screening tool, in favor of the fecal immunochemical test. Though the FIT test is preferred, even the guaiac FOB testing of average risk populations may have been sufficient to reduce the mortality associated with colon cancer by about 25%. With this lower efficacy, it was not always cost effective to screen a large population with gFOBT.

If colon cancer is suspected in an individual (such as in someone with an unexplained anemia) fecal occult blood tests may not be clinically helpful. If a doctor suspects colon cancer, more rigorous investigation is necessary, whether or not the test is positive.

In 2006, the Australian Government introduced the National Bowel Cancer Program which has been updated several times since; targeted screening will be done of all Australians aged over 50 to 74 by 2017–2018. Cancer Council Australia recommended that FOBT should be done every two years. Gradually government fund disbursement meant that some people are not yet eligible for the national program and should pay for a FOBT by themselves.

The Canadian Cancer Society recommends that men and women age 50 and over have a FOBT at least every 2 years.

In colon cancer screening, using only one sample of feces collected by a doctor performing a digital rectal examination is discouraged.

The use of the M2-PK Test is encouraged over gFOBT for routine screening as it may pick up tumors that are both bleeding and non bleeding. It is able to pick up 80 percent of colorectal cancer and 44 percent for adenoma > 1 centimeter, while gFOBT picks up 13 to 50 percent of colorectal cancers.

An extensive literature has examined the clinical value of FOBT in iron deficiency anemia.

Anemia is a common complication of blood in the stool, especially when there is a large amount of blood or bleeding occurs over a long period of time. Anemia is also commonly associated with an iron deficiency, due to the importance of iron in the formation of red blood cells (RBCs). When anemia is diagnosed as a result of blood in the stool, vitamins that are important for RBC formation (folate, vitamin B12, and vitamin C) are frequently prescribed in order to ensure that all the materials are available for those cells that are made.

The tests that are considered to evaluate of the passage of blood in the stool are based on the characteristics of bleeding (color, quantity) and whether or not the person passing blood has a low blood pressure with elevated heart rate, as opposed to normal vital signs. The following tests are combined to determine the causes of the source of bleeding.

- Digital rectal exam (DRE) and fecal occult blood test (FOBT)

- Colonoscopy

- Anoscopy

- Esophagogastroduodenoscopy (EGD)

- Capsule endoscopy

- CT Scan

Melena is defined as dark, tarry stools, often black in color due to partial digestion of the RBCs.

Hematochezia is defined as bright red blood seen in the toilet either inside of, or surrounding the stool.

Hematochezia is typically presumed to come from the lower portion of the GI tract, and the initial steps of diagnosis include a DRE with FOBT, which if positive, will lead to a colonoscopy. If the person has a large amount of blood in their stool, an EGD test may be necessary. If no source of active bleeding is found on these examinations, a capsule endoscopy may be performed, in order to more closely examine the small bowel, which cannot be seen with the other types of studies. With melena, a DRE with FOBT is often also performed, however the suspicion for a source from the upper GI tract is higher, leading first to the use of EGD with the other tests being required if no source is identified. The anoscopy is another type of examination, which can be used along with a colonoscopy, which exams the rectum and distal portion of the descending colon.

Diagnosis is achieved mainly by plain and contrasted radiographical and ultrasound imaging. Colonic marker transit studies are useful to distinguish colonic inertia from functional outlet obstruction causes. In this test, the patient swallows a water-soluble bolus of radio-opaque contrast and films are obtained 1, 3 and 5 days later. Patients with colonic inertia show the marker spread throughout the large intestines, while patients with outlet obstruction exhibit slow accumulations of markers in some places. A colonoscopy can also be used to rule out mechanical obstructive causes. Anorectal manometry may help to differentiate acquired from congenital forms. Rectal biopsy is recommended to make a final diagnosis of Hirschsprung disease.

It is important to note that both barium enema and colonoscopy are contraindicated during acute episodes of diverticulitis, as the barium may leak out into the abdominal cavity, and colonoscopy can cause perforations of the bowel wall.

Several methods have been developed to identify the disorder but there are difficulties with all of them. Fecal bile acid quantification is unpleasant for both the patient and laboratory. Diagnosis of bile acid malabsorption is easily and reliably made by the SeHCAT test. This nuclear medicine test involves two scans a week apart and so measures multiple cycles of bile acid excretion and reabsorption. There is limited radiation exposure (0.3 mSv). Retention of SeHCAT at 7 days is normally above 15%; values less than 15%, 10% and 5% predict respectively mild, moderate and severe abnormal retention and an increasing likelihood of response to bile acid sequestrants. This test is not licensed in the USA, and is underutilized even where it is available.

Older methods such as the C-glycocholic breath test are no longer in routine clinical use.

Measurement of 7α-Hydroxy-4-cholesten-3-one, a bile acid precursor, in serum, shows the increased bile acid synthesis found in bile acid malabsorption. This test is an alternative diagnostic means when available. Fasting blood FGF19 values may have value in the recognition of the disease and prediction of response.

Currently, there are two tests for evaluating BAM in the U.S. One test, currently available only for research purposes, measures serum levels of the marker 7α-hydroxy-4-cholesten-3-one (C4), a downstream product of CYP7A1. Plasma C4 levels increase when bile acid synthesis increases, and C4 levels are substantially elevated in BAM patients with a sensitivity and specificity of 90 percent and 79 percent, respectively. C4 levels have also been shown to correlate well with SeHCAT retention. This makes fasting serum C4 attractive as a screening test for BAM, although it can produce false-positives and false-negatives in patients who have liver disease or are taking statins.

The second test, which can now be clinically ordered, is the fecal bile acid excretion test. It quantifies individual and total bile acids in a 48-hour stool collection. Increased total fecal bile acids are seen in patients with chronic functional diarrhea and higher levels of CA and CDCA are associated with IBS-D.

A clinical validation involving 94 healthy volunteers, 60 patients with IBS-D and 28 patients with IBS with constipation (IBS-C) found that the sum of CA and CDCA concentrations above 3.7 percent were indicative of IBS-D with 72 percent sensitivity and 90 percent specificity. In addition, the upper limit of normal total fecal bile acid excretion over the 48 hours has been defined.

Bile acid malabsorption is common in Crohn's disease but not always recognised. Most patients with previous ileal resection and chronic diarrhea will have abnormal SeHCAT tests and can benefit from bile acid sequestrants.

Patients with primary bile acid diarrhea are frequently misdiagnosed as having the irritable bowel syndrome as clinicians fail to recognize the condition. When SeHCAT testing is performed, the diagnosis of primary bile acid diarrhea is commonly made. In a review of 18 studies of the use of SeHCAT testing in diarrhea-predominant irritable bowel syndrome patients, 32% of 1223 patients had a SeHCAT 7-day retention of less than 10%, and 80% of these reported a response to cholestyramine, a bile acid sequestrant.

Estimates of the population prevalence taken from this review suggest that 1% of the adult population could have primary bile acid diarrhea (Type 2 bile acid malabsorption).

There may be signs of septic shock. A physical examination reveals abdominal tenderness and possible loss of bowel sounds. An abdominal radiography shows colonic dilation. White blood cell count is usually elevated. Severe sepsis may present with hypothermia or leukopenia.

Diagnosis of angiodysplasia is often accomplished with endoscopy, either colonoscopy or esophagogastroduodenoscopy (EGD). Although the lesions can be notoriously hard to find, the patient usually is diagnosed by endoscopy. A new technique, pill enteroscopy, has been a major advance in diagnosis, especially in the small bowel which is difficult to reach with traditional endoscopy. With this technique a pill that contains a video camera and radio transmitter is swallowed, and pictures of the small intestine are sent to a receiver worn by the patient. Recently, multiphase CT angiography (without positive oral contrast) has been shown to play a promising role in the diagnoses of small and large bowel angiodysplasia, especially when associated with active hemorrhage

Angiodysplasiae in the small bowel can also be diagnosed and treated with double-balloon enteroscopy, a technique involving a long endoscopic camera and overtube, both fitted with balloons, that allow the bowel to be accordioned over the camera.

In cases with negative endoscopic findings and high clinical suspicion, selective angiography of the mesenteric arteries is sometimes necessary, but this allows for interventions at time of the procedure. An alternative is scintigraphy with red blood cells labeled with a radioactive marker; this shows the site of the bleeding on a gamma camera but tends to be unhelpful unless the bleeding is continuous and significant.

A high-fiber diet and fiber supplements are advisable to prevent constipation. The American Dietetic Association recommends 20–35 grams each day. Wheat bran has been shown to reduce intra colonic pressure.

The US National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says foods such as nuts, popcorn hulls, sunflower seeds, pumpkin seeds, caraway seeds, and sesame seeds have traditionally been labeled as problem foods for people with this condition; however, no scientific data exists to prove this hypothesis. The seeds in tomatoes, zucchini, cucumbers, strawberries, raspberries, and poppy seeds, are not considered harmful by the NIDDK.

One study found that nuts and popcorn do not contribute positively or negatively to patients with diverticulosis or diverticular complications.

Reducing opiate-based medication (when possible, tolerable, and safe; prescription medication changes should be done under the supervision of a physician), and adequate intake of liquids (water) and dietary fiber and daily exercise.

Distal or sigmoid, fecalomas can often be disimpacted digitally or by a catheter which carries a flow of disimpaction fluid (water or other solvent or lubricant). Surgical intervention in the form of sigmoid colectomy or proctocolectomy and ileostomy may be required only when all conservative measures of evacuation fail.

Ultrasonography and doppler sonography are useful to detect appendicitis, especially in children. Ultrasound can show free fluid collection in the right iliac fossa, along with a visible appendix with increased blood flow when using color Doppler, and noncompressibility of the appendix, as it is essentially a walled off abscess. Other secondary sonographic signs of acute appendicitis include the presence of echogenic mesenteric fat surrounding the appendix and the acoustic shadowing of an appendicolith. In some cases (approximately 5%), ultrasonography of the iliac fossa does not reveal any abnormalities despite the presence of appendicitis. This false negative finding is especially true of early appendicitis before the appendix has become significantly distended. In addition, false negative findings are more common in adults where larger amounts of fat and bowel gas make visualizing the appendix technically difficult. Despite these limitations, sonographic imaging in experienced hands can often distinguish between appendicitis and other diseases with similar symptoms. Some of these conditions include inflammation of lymph nodes near the appendix or pain originating from other pelvic organs such as the ovaries or Fallopian tubes.

MRI use has become increasingly common for diagnosis of appendicitis in children and pregnant patients due to the radiation dosage that, while of nearly negligible risk in healthy adults, can be harmful to children or the developing fetus. In pregnancy, it has been found to be more useful during the second and third trimester, particularly as the enlargening uterus displaces the appendix, making it difficult to find by ultrasound. The periappendiceal stranding that is reflected on CT by fat stranding on MRI appears as increased fluid signal on T2 weighted sequences. First trimester pregnancies are usually not candidates for MRI, as the fetus is still undergoing organogenesis, and there are no long-term studies to date regarding its potential risks or side effects.

Possible treatments include:

- In stable cases, use of laxatives and bulking agents, as well as modifications in diet and stool habits are effective.

- Corticosteroids and other anti-inflammatory medication is used in toxic megacolon.

- Antibiotics are used for bacterial infections such as oral vancomycin for "Clostridium difficile"

- Disimpaction of feces and decompression using anorectal and nasogastric tubes.

- When megacolon worsens and the conservative measures fail to restore transit, surgery may be necessary.

- Bethanechol can also be used to treat megacolon by means of its direct cholinergic action and its stimulation of muscarinic receptors which bring about a parasympathetic like effect.

There are several surgical approaches to treat megacolon, such as a colectomy (removal of the entire colon) with ileorectal anastomosis (ligation of the remaining ileum and rectum segments), or a total proctocolectomy (removal of colon, sigmoid and rectum) followed by ileostomy or followed by ileoanal anastomosis.

In the United States screening is typically recommended between the age of 50 and 75 years. For those between 76 and 85 years of age the decision to screen should be individualized. A number of screening methods can be used including stool based tests every 3 years, sigmoidoscopy every 5 years and colonoscopy every 10 years. For those at high risk, screenings usually begin at around 40. It is unclear which of these two methods is better. Colonoscopy may find more cancers in the first part of the colon but is associated with greater cost and more complications. For people with average risk who have had a high-quality colonoscopy with normal results, the American Gastroenterological Association does not recommend any type of screening in the 10 years following the colonoscopy. For people over 75 or those with a life expectancy of less than 10 years, screening is not recommended. It takes about 10 years after screening for one out of a 1000 people to benefit.

In Canada, among those 50 to 75 at normal risk, fecal immunochemical testing or FOBT is recommended every two years or sigmoidoscopy every 10 years. Colonoscopy is less preferred.

Some countries have national colorectal screening programs which offer FOBT screening for all adults within a certain age group, typically starting between age 50 and 60. Examples of countries with organised screening include the United Kingdom, Australia and the Netherlands.

The treatment of fecal impaction requires both the remedy of the impaction and treatment to prevent future recurrences. Decreased motility of the colon results in dry, hard stools that in the case of fecal impaction become compacted into a large, hard mass of stool that cannot be expelled from the rectum.

Various methods of treatment attempt to remove the impaction by softening the stool, lubricating the stool, or breaking it into pieces small enough for removal. Enemas and osmotic laxatives can be used to soften the stool by increasing the water content until it is soft enough to be expelled. Osmotic laxatives such as magnesium citrate work within minutes - 8 hours for onset of action, and even then they may not be sufficient to expel the stool.

Osmotic laxatives can cause cramping and even severe pain as the patient's attempts to evacuate the contents of the rectum are blocked by the fecal mass. Polyethylene glycol (PEG 3500) may be used to increase the water content of the stool without cramping; however, since it may take 24 to 48 hours for it to take effect, it is not well suited to cases where the impaction needs to be removed immediately due to risk of complications or severe pain. Enemas (such as hyperosmotic saline) and suppositories (such as glycerine suppositories) work by increasing water content and stimulating peristalsis to aid in expulsion, and both work much more quickly than oral laxatives.

Because enemas work in 2–15 minutes, they do not allow sufficient time for a large fecal mass to soften. Even if the enema is successful at dislodging the impacted stool, the impacted stool may remain too large to be expelled through the anal canal. Mineral oil enemas can assist by lubricating the stool for easier passage. In cases where enemas fail to remove the impaction, polyethylene glycol can be used to attempt to soften the mass over 24–48 hours, or if immediate removal of the mass is needed, manual disimpaction may be used. Manual disimpaction may be performed by lubricating the anus and using one gloved finger with a scoop-like motion to break up the fecal mass. Most often manual disimpaction is performed without general anaesthesia, although sedation may be used. In more involved procedures, general anaesthesia may be used, although the use of general anaesthesia increases the risk of damage to the anal sphincter. If all other treatments fail, surgery may be necessary.

Individuals who have had one fecal impaction are at high risk of future impactions. Therefore, preventative treatment should be instituted in patients following the removal of the mass. Increasing dietary fiber, increasing fluid intake, exercising daily, and attempting regularly to defecate every morning after eating should be promoted in all patients.

Often underlying medical conditions cause fecal impactions; these conditions should be treated to reduce the risk of future impactions. Many types of medications (most notably opioid pain medications, such as codeine) reduce motility of the colon, increasing the likelihood of fecal impactions. If possible, alternate medications should be prescribed that avoid the side effect of constipation.

Given that all opioids can cause constipation, it is recommended that any patient placed on opioid pain medications should be given medications to prevent constipation before it occurs. Daily medications can also be used to promote normal motility of the colon and soften stools. Daily use of laxatives or enemas should be avoided by most individuals as it can cause the loss of normal colon motility. However, for patients with chronic complications, daily medication under the direction of a physician may be needed.

Polyethylene glycol 3350 can be taken daily to soften the stools without the significant risk of adverse effects that are common with other laxatives. In particular, stimulant laxatives should not be used frequently because they can cause dependence in which an individual loses normal colon function and is unable to defecate without taking a laxative. Frequent use of osmotic laxatives should be avoided as well as they can cause electrolyte imbalances.

If the condition does not improve, the risk of death is significant. In case of poor response to conservative therapy, a colectomy is usually required.

Fecal impaction and attempts at removal can have severe and even lethal effects, such as the rupture of the colon wall by catheter or an acute angle of the fecaloma (stercoral perforation), followed by septicemia. A small fecalith is one cause of both appendicitis and acute diverticulitis. It may also lead to stercoral perforation, a condition characterized by bowel perforation due to pressure necrosis from a fecal mass or fecaloma.

Aspirin and celecoxib appear to decrease the risk of colorectal cancer in those at high risk. Aspirin is recommended in those who are 50 to 60 years old, do not have an increased risk of bleeding, and are at risk for cardiovascular disease to prevent colorectal cancer. It is not recommended in those at average risk. There is tentative evidence for calcium supplementation, but it is not sufficient to make a recommendation. Vitamin D intake and blood levels are associated with a lower risk of colon cancer.

The Rome III Criteria for functional constipation must include two or more of the following and present for the past three months, with symptoms starting for at least 6 months prior to diagnosis.

- Straining during defecation for at least 25% of bowel movements

- Lumpy or hard stools in at least 25% of defecations

- Sensation of incomplete evacuation for at least 25% of defecations

- Sensation of anorectal obstruction/blockage for at least 25% of defecations

- Manual maneuvers to facilitate at least 25% of defecations

- Fewer than 3 defecations per week

- Loose stools are rarely present without the use of laxatives

- There are insufficient criteria for irritable bowel syndrome

A physical examination should involve at least an abdominal exam and rectal exam. Abdominal exam may reveal an abdominal mass if there is significant stool burden and may reveal abdominal discomfort. Rectal examination gives an impression of the anal sphincter tone and whether the lower rectum contains any feces or not. Rectal examination also gives information on the consistency of the stool, the presence of hemorrhoids, blood and whether any perineal irregularities are present including skin tags, fissures, anal warts. Physical examination is done manually by a physician and is used to guide which diagnostic tests to order.

Screening for colonic polyps as well as preventing them has become an important part of the management of the condition. Medical societies have established guidelines for colorectal screening in order to prevent adenomatous polyps and to minimize the chances of developing colon cancer. It is believed that some changes in the diet might be helpful in preventing polyps from occurring but there is no other way to prevent the polyps from developing into cancerous growths than by detecting and removing them.

According to the guidelines established by the American Cancer Society, individuals who reach the age of 50 should perform an occult blood test yearly. Colon polyps as they grow can sometimes cause bleeding within the intestine, which can be detected with the help of this test. Also, persons in their 50s are recommended to have flexible sigmoidoscopies performed once in 3 to 5 years to detect any abnormal growth which could be an adenomatous polyp. If adenomatous polyps are detected during this procedure, it is most likely that the patient will have to undergo a colonoscopy. Medical societies recommend colonoscopies every ten years starting at age 50 as a necessary screening practice for colon cancer. The screening provides an accurate image of the intestine and also allows the removal of the polyp, if found. Once an adenomatous polyp is identified during colonoscopy, there are several methods of removal including using a snare or a heating device. Colonoscopies are preferred over sigmoidoscopies because they allow the examination of the entire colon; a very important aspect, considering that more than half of the colonic polyps occur in the upper colon, which is not reached during sigmoidoscopies.

It has been statistically demonstrated that screening programs are effective in reducing the number of deaths caused by colon cancer due to adenomatous polyps. While there are risks of complications associated with colonoscopies, those risks are extremely low at approximately 0.35 percent. For comparison, the lifetime risk of developing colon cancer is around 6 percent. As there is a small likelihood of recurrence, surveillance after polyp removal is recommended.

Fecal vomiting, also called feculent vomiting and stercoraceous vomiting is a kind of vomiting wherein the material vomited is of fecal origin. It is a common symptom of gastrojejunocolic fistula and intestinal obstruction in the ileum. Fecal vomiting is often accompanied by an odor of feces on the breath and other gastrointestinal symptoms, including abdominal pain, abdominal distension, dehydration, and diarrhea. In severe cases of bowel obstruction or constipation (such as those related to Clozapine-treatment) fecal vomiting has been identified as a cause of death.

Fecal vomiting occurs when the bowel is obstructed for some reason, and intestinal contents cannot move normally. Peristaltic waves occur in an attempt to decompress the intestine, and the strong contractions of the intestinal muscles push the contents backwards through the pyloric sphincter into the stomach, where they are then vomited.

Fecal vomiting can also occur in cats.

Fecal vomiting does not include vomiting of the proximal small intestine contents, which commonly occurs during vomiting.