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.

Gastroscopy, or endoscopic evaluation of the stomach, is useful in chronic cases of colic suspected to be caused by gastric ulcers, gastric impactions, and gastric masses. A 3-meter scope is required to visualize the stomach of most horses, and the horse must be fasted prior to scoping.

Laparoscopy involves inserting a telescoping camera approximately 1 cm in diameter into the horse's abdomen, through a small incision, to visualize the gastrointestinal tract. It may be performed standing or under general anesthesia, and is less invasive than an exploratory celiotomy (abdominal exploratory surgery).

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.

The main diagnostic tools are blood tests, X-rays of the abdomen, CT scanning, and/or ultrasound. If a mass is identified, biopsy may determine the nature of the mass.

Radiological signs of bowel obstruction include bowel distension and the presence of multiple (more than six) gas-fluid levels on supine and erect abdominal radiographs.

Contrast enema or small bowel series or CT scan can be used to define the level of obstruction, whether the obstruction is partial or complete, and to help define the cause of the obstruction.

According to a meta-analysis of prospective studies by the Cochrane Collaboration, the appearance of water-soluble contrast in the cecum on an abdominal radiograph within 24 hours of oral administration predicts resolution of an adhesive small bowel obstruction with a pooled sensitivity of 97% and specificity of 96%.

Colonoscopy, small bowel investigation with ingested camera or push endoscopy, and laparoscopy are other diagnostic options.

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.

Fetal and neonatal bowel obstructions are often caused by an intestinal atresia, where there is a narrowing or absence of a part of the intestine. These atresias are often discovered before birth via an ultrasound, and treated with using laparotomy after birth. If the area affected is small, then the surgeon may be able to remove the damaged portion and join the intestine back together. In instances where the narrowing is longer, or the area is damaged and cannot be used for a period of time, a temporary stoma may be placed.

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.

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.

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).

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.

The psychiatric (DSM-IV) diagnostic criteria for encopresis are:

1. Repeated passage of feces into inappropriate places (e.g., underwear or floor) whether voluntary or unintentional

2. At least one such event a month for at least 3 months

3. Chronological age of at least 4 years (or equivalent developmental level)

4. The behavior is not exclusively due to a physiological effect of a substance (e.g., laxatives) or a general medical condition, except through a mechanism involving constipation.

The DSM-IV recognizes two subtypes: with constipation and overflow incontinence, and without constipation and overflow incontinence. In the subtype with constipation, the feces are usually poorly formed and leakage is continuous, and this occurs both during sleep and waking hours. In the type without constipation, the feces are usually well-formed, soiling is intermittent, and feces are usually deposited in a prominent location. This form may be associated with oppositional defiant disorder (ODD) or conduct disorder, or may be the consequence of large anal insertions, or more likely due to chronic encopresis that has radically desensitized the colon and anus.

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.

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.

Various modalities of diagnosis are available:

- Cystoscopy

- Colonoscopy

- Poppy seed test

- Transabdominal ultrasonography

- Abdominopelvic CT

- MRI

- Barium enema

- Bourne test

- Cystogram

A definite algorithm of tests is followed for making the diagnosis.

Many pediatricians will recommend the following three-pronged approach to the treatment of encopresis associated with constipation:

1. cleaning out

2. using stool softening agents

3. scheduled sitting times, typically after meals.

The initial clean-out is achieved with enemas, laxatives, or both. The predominant approach today is the use of oral stool softeners like Movicol, Miralax, Lactulose, mineral oil, etc. Following that, enemas and laxatives are used daily to keep the stools soft and allow the stretched bowel to return to its normal size.

The child must be taught to use the toilet regularly to retrain his/her body. It is usually recommended that a child be required to sit on the toilet at a regular time each day and 'try' to go for 10–15 minutes, usually soon (or immediately) after eating. Children are more likely to be able to expel a bowel movement right after eating. It is thought that creating a regular schedule of bathroom time will allow the child to achieve a proper elimination pattern. Repeated voiding success on the toilet itself helps it become a releasor stimulus for successful bowel movements.

Alternatively, when this method fails for six months or longer, a more aggressive approach may be undertaken using suppositories and enemas in a carefully programmed way to overcome the reflexive holding response and to allow the proper voiding reflex to take over. Failure to establish a normal bowel habit can result in permanent stretching of the colon. Certainly, allowing this problem to continue for years with constant assurances that the child "will grow out of it" should be avoided.

Dietary changes are an important management element. Recommended changes to the diet in the case of constipation-caused encopresis include:

1. reduction in the intake of constipating foods such as dairy, peanuts, cooked carrots, and bananas

2. increase in high-fiber foods such as bran, whole wheat products, fruits, and vegetables

3. higher intake of water and liquids, such as juices, although an increased risk of tooth decay has been attributed to excess intake of sweetened juices

4. limit drinks with caffeine, including cola drinks and tea

5. provide well-balanced meals and snacks, and limit fast foods/junk foods that are high in fats and sugars

6. limit whole milk to 500 mL (16.9 ounces) a day for the child over 2 years of age, but do not completely eliminate milk because children need calcium for bone growth and strength.

The standard behavioral treatment for functional encopresis, which has been shown to be highly effective, is a motivational system such as a contingency management system. In addition to this basic component, seven or eight other behavioral treatment components can be added to increase effectiveness.

The two key features of obstructed defecation are:

1. An inability to voluntarily evacuate rectal contents

2. Normal colonic transit time

A 5 item questionnaire was validated for diagnosis and grading of obstructed defecation syndrome. The parameters were:

1. Excessive straining

2. Incomplete rectal evacuation

3. Use of enemas and/or laxatives

4. Vaginal-anal-perineal digitations (needing to press in the back wall of the vagina or on the perineum to aid defecation)

5. Abdominal discomfort and/or pain

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.

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.

Pain relief is administered concomitantly to the treatment of the primary disease causing tenesmus. Methadone has been shown to be an effective pain-reliever.

These may reveal congestion and edema (swelling) of the distal rectal mucosa, and in 10-15% of cases there may be a solitary rectal ulcer on the anterior rectal wall. Localized inflammation or ulceration can be biopsied, and may lead to a diagnosis of SRUS or colitis cystica profunda. Rarely, a neoplasm (tumour) may form on the leading edge of the intussusceptum. In addition, patients are frequently elderly and therefore have increased incidence of colorectal cancer. Full length colonoscopy is usually carried out in adults prior to any surgical intervention. These investigations may be used with contrast media (barium enema) which may show the associated mucosal abnormalities.

SRUS is commonly misdiagnosed, and the diagnosis is not made for 5–7 years. Clinicians may not be familiar with the condition, and treat for Inflammatory bowel disease, or simple constipation.

The thickened lining or ulceration can also be mistaken for types of cancer.

The differential diagnosis of SRUS (and CCP) includes:

- polyps

- endometriosis

- inflammatory granulomas

- infectious disorders

- drug-induced colitis

- mucus-producing adenocarcinoma

Defecography, sigmoidoscopy, transrectal ultrasound, mucosal biopsy, anorectal manometry and electromyography have all been used to diagnose and study SRUS. Some recommend biopsy as essential for diagnosis since ulcerations may not always be present, and others state defecography as the investigation of choice to diagnose SRUS.

Obstructed defecation may be a cause of incomplete evacuation of stool. Normal emptying of rectal contents is 90-100%. <90% evacuation could be defined as incomplete evacuation. Incomplete evacuation is also one of the factors implicated in the cause of fecal leakage.