Descending Colon: Function and Associated Conditions

Located Below the Transverse Colon and Above the Sigmoid Colon

Medically reviewed by Jay N. Yepuri, MD

The descending colon is one part of the colon. It is around 4 to 6 inches, or 10 to 15 centimeters (cm), long. The entire colon is about 5 feet long and is divided into five parts. The descending colon is the third main section of the colon and connects to the transverse colon and sigmoid colon.

Many health conditions can affect the descending colon, including inflammatory bowel disease (IBD), colon cancer, colonic perforation, and diverticulitis.

This article will cover descending colon anatomy and function, conditions that affect the descending colon, diagnosis, treatment, and more.

Descending Colon Anatomy and Function 101

The colon is part of the large intestine, which contains the following sections:

• Appendix

• Cecum

• Colon

• Rectum

The colon helps the body absorb water and nutrients from food by expelling waste. It is made up of muscle and is located below the stomach.

The Colon

The colon makes up most of the large intestine. It is connected to the small intestine and contains five segments, which are:

• The cecum, or the pouch which is the beginning of the colon

• The ascending colon, or the second part of the colon, starting at the cecum

• The transverse colon, located across the abdomen, is the longest and most movable part of the colon. It connects to the descending colon at the splenic flexure.

• The descending colon, or the part of the colon that stores stool before it reaches the sigmoid colon

• The sigmoid colon, or the final part of the colon, that meets the upper part of the rectum
  

The descending colon is part of the retroperitoneal organ—the anatomical space behind the peritoneum (abdominal lining) containing the ascending and descending colon and the rectum.

It is located in the left lumbar (back) abdomen region and passes in front of and down the left kidney area. The descending colon sits on the left side of the large intestine next to the splenic fixture (the sharp bend in the colon) and ends by joining the sigmoid colon. It falls behind the peritoneum–the tissue lining the abdominal wall and covering the abdominal organs.

The primary job of the descending colon is to hold stool (solid waste) that eventually makes its way to the rectum for a bowel movement. It also assists in absorbing water and electrolytes from digestive materials, leading to the formation of feces. 

Gastrocolic reflex

The gastrocolic reflex is activated when the colon is filled with digested food. The activation initiates peristalsis—wavelike contractions that help move food through the digestive tract. This process helps food waste travel from the descending colon to the rectum.

All parts of the colon are made up of four separate layers—serosa, muscularis, submucosa, and mucosa. They also have individual physical features, including the following:

• Epiploic (fat-filled) pouches

• Appendices (small pouches of the peritoneum filled with fat)

• Teniae coli (longitudinal ribbons of smooth muscle)

• Haustrations (small pouches that give the colon a segmented appearance)

The colon contains gut flora (bacteria and other microbes), including Bifidobacteria and Lactobacillus. These microbes assist in digesting food and protecting the lining of the gut. An imbalance in gut flora can lead to the growth of less beneficial microbes and may result in diarrhea or severe digestive health conditions.

Associated Descending Colon Conditions

Pain in the abdomen might indicate a problem caused by your colon. It can be caused by a number of conditions that affect the colon, including constipation, diarrhea, a redundant colon, irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), colitis, diverticular disease, colonic perforation, and colon cancer.

Constipation and Diarrhea

According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), you are constipated if you have the following:

• Fewer than three bowel movements a week

• Stools that are hard, dry, lumpy, or difficult or painful to pass

• Bowel movements that feel incomplete

Stool travels from the ascending colon to the transverse colon, the descending colon, and finally, the sigmoid colon before reaching the rectum for a bowel movement. The descending colon is one of the last two stops, so if you are constipated, hard stools may lead to left-sided descending colon pain.

Diarrhea refers to loose, watery stools three or more times a day. It is a symptom of many chronic conditions, including irritable bowel syndrome and inflammatory bowel disease. Diarrhea causes abdominal pain and cramping, which can affect the descending colon.

Redundant Colon

This condition refers to a longer-than-normal colon, especially in the descending colon. The colon may also have additional twists or loops in it. If symptoms are felt, they may include bloating, constipation, and impacted fecal matter.

A redundant colon might lead to sigmoid volvulus, a twisting of the sigmoid colon.

Colon Polyps

Colon polyps are clumps of cells that grow in the colon; most are harmless. Removal of small polyps during a routine colonoscopy can reduce cancer risk.

It is unlikely you will experience symptoms with polyps, but larger polyps can cause the following:

• Bowel habit changes

• Stool color changes

• Iron deficiency anemia

• Pain

• Rectal bleeding

You should see a healthcare provider for abdominal pain, bloody stools, and bowel habit changes that last a week or longer.

Familial Adenomatous Polyposis (FAP)

Familial adenomatous polyposis is a rare, inherited condition that causes hundreds to thousands of polyps to form in the colon and rectum. While much rarer, FAP may occur from a spontaneous gene mutation.

If untreated, these polyps can become cancerous. They become extremely large and need surgical removal so they do not become cancerous.

IBS

IBS is a common disorder of the gastrointestinal (GI) tract. It may cause descending colon pain, especially if you are constipated, have diarrhea, or experience abdominal pain and bloating.

IBD

"Inflammatory bowel disease" is an umbrella term for disorders that cause chronic inflammation in the tissues of the digestive tract. This includes ulcerative colitis (inflammation of the colon and rectum) and Crohn's disease (inflammation of tissues in the digestive tract, including the colon).

Common IBD symptoms are:

• Diarrhea

• Rectal bleeding

• Abdominal pain

• Bloating

• Fatigue

• Weight loss

Read Next: Ulcerative Colitis vs. Crohn's Disease: What's the Difference?

Colitis

Colitis is inflammation of the colon. Ulcerative colitis, pseudomembranous colitis, and ischemic colitis are colitis types.

The inflammation of the colon can lead to pain throughout the entire colon. Other symptoms include diarrhea, rectal bleeding, and the urgent need to have a bowel movement.

Related: Causes and Risk Factors of Inflamed Colon

Diverticular Diseases

Diverticulosis and diverticulitis are diverticular diseases. In diverticulosis, diverticula (small bulging pouches) develop in the intestinal lining. These often do not produce symptoms. Diverticulitis occurs when the pouches become inflamed. This may cause abdominal pain.

When these conditions affect your colon, they cause pouches in the mucosa and submucosa that bulge through the muscular layers of the colon.

Colonic Perforation

A colonic perforation is a hole in the colon's lining. It is sometimes called a bowel or gastrointestinal (GI) perforation. If a GI perforation affects the colon, it can affect any part of it, including the descending colon.

Symptoms of a colonic perforation include abdominal pain and cramping, which can be severe, abdominal bloating, swelling and tenderness, fever, chills, nausea, and vomiting.

Colon Cancer

Colon cancer is cancer that starts in the colon. Symptoms of colon cancer include:

• Abdominal pain

• Blood in the stool

• Constipation

• Diarrhea

• Fatigue

• Weight loss
  

Detecting Colon Cancer Early

Most people with early-stage colon cancer will not experience symptoms, especially early on. Routine screenings, such as stool tests and colonoscopies, are vital.

Most colon cancers occur on the left in the descending and sigmoid parts of the colon. They will start in the mucosa, the innermost colon lining consisting of the cells that make and release mucus. If these cells change, they create colon polyps. Over time, polyps can become cancerous, but this takes many years.

Symptoms of Descending Colon Pain

Without diagnostic testing, it is difficult to know what is causing symptoms and pain related to the descending colon. The descending colon is located on the left side of the body, and pain can be felt on the left side of the abdomen or back, but it can also radiate across the abdomen and back.

If there is a problem of the descending colon (i.e., inflammation or blockage), you may experience pain and additional symptoms, such as:

• Abdominal cramping or stomachache

• Abdominal gas and bloating

• Constipation

• Diarrhea

Testing to Diagnose Descending Colon Pain

Abdominal pain causes are numerous, so there is no single test alone that can confirm a colon problem. Your doctor will utilize multiple diagnostic tools to determine the source of your symptoms.

Diagnostic testing for descending colon pain might include:

• Physical exam: A physical exam may involve looking for lumps or tender areas in the abdomen. A digital rectal exam, in which the healthcare provider inserts a lubricated, gloved finger in the rectum, can also check for masses, blood, and other signs or symptoms of a colon problem.

• Colonoscopy: A colonoscopy looks directly at the colon and diagnoses health problems affecting the colon. It uses a colonoscope—a tube with a light and camera—inserted in the rectum to examine the colon and other abdominal organs.

• Lab tests: Your healthcare provider may request blood work to check levels of different types of blood cells (red and white), hemoglobin (protein found in red blood cells), and platelets (cell fragments that form clots). Biopsy samples may be taken during a colonoscopy and sent to a lab for testing.

• Stool tests: A stool test might be ordered to look for blood or changes in the feces. Such changes might indicate a colon problem.

A Glance at Descending Colon Treatment

Contact your healthcare provider if you experience abdominal pain that does not resolve within a day or two and is not related to an acute (short-term) health condition.

Other symptoms that warrant reaching out to your healthcare provider include:

• Recurrent diarrhea or constipation

• Significant weight loss

• Black or bloody stools
  

Takeaway

Getting in to see your provider quickly is especially important if you have a family history of colon cancer or a personal or family history of colon polyps, including adenomatous polyposis.

Treatment for your descending colon pain will depend on the underlying cause. In general, treatment approaches may include:

• Wait and watch

• Lifestyle changes

• Medication

• Resection (surgical removal of a section of the colon)

• Removal

Wait and Watch

A redundant colon generally does not require treatment. Most people can have a good quality of life without any needed surgical intervention.

Colon polyps may not need treatment and may go away on their own. For people with FAP, small polyps are removed during a colonoscopy exam, and they will need to be monitored with regular colonoscopies.

Lifestyle Changes

Having a redundant colon may increase constipation, but this can be resolved by consuming a high-fiber diet. Examples of high-fiber foods include beans, lentils, whole grains, fruits, and vegetables.

Mild IBS can be controlled by reducing stress and managing lifestyle and diet. Diet changes include avoiding food triggers, staying hydrated, and eating high-fiber foods. Lifestyle changes include regular exercise and getting enough sleep.

Diet can also help manage IBD. This includes eating a healthy and balanced diet, avoiding foods that add stomach inflammation, and staying hydrated to keep symptoms of the conditions at bay.

Treatment for colitis includes lifestyle changes to manage flare-ups (exacerbations) of the condition. Such changes may include avoiding foods that worsen symptoms and limiting stress.

Mild diverticular disease can be managed at home with a clear liquid diet with solids added gradually as symptoms improve.

Medication

Acute constipation and diarrhea can be treated with over-the-counter (OTC) medicines, including laxatives and antidiarrheals, respectively. If these symptoms become chronic, you should contact a healthcare provider to determine the source of the symptoms.

IBS treatments include OTC and prescription drugs, depending on your symptoms and severity. Prescription options may include:

• Medications to manage bowel spasms (anticholinergic drugs)

• Pain relievers for severe abdominal pain and bloating

• Prescription antidiarrheals

• Medicines designed to treat IBS, including Lotronex (alosetron) and Xifaxan (rifaximin).

Related: Medications for Diarrhea-Predominant Irritable Bowel Syndrome (IBS-D)

Medications to treat IBD include:

• Anti-inflammatory drugs (to bring down inflammation)

• Immunosuppressant drugs (suppress the immune system to stop inflammation before it starts)

• Antibiotics (fight bacterial infections)

• Biologics (to counteract proteins that lead to inflammation)

A healthcare provider may prescribe medicines to manage specific symptoms, including pain and diarrhea.

Medication for colitis involves anti-inflammatory medicines, immunosuppressive drugs, pain medications, antibiotics, and iron supplements.

Medication prescribed for diverticular disease will depend on symptom severity. For example, oral antibiotics can treat mild cases, while severe cases may require intravenous antibiotics (through a vein).

Colon cancer can be treated with medicines that can be given by mouth or directly into the bloodstream, called systemic therapies. This may include chemotherapy, immunotherapy, and targeted therapy drugs.

Resection

If you experience sigmoid volvulus due to having a redundant colon, you will need a sigmoidoscopy procedure to untwist the colon. If a sigmoid volvulus returns, you may need a partial colectomy. Surgery might include colostomy, creating a new abdominal wall hole. The stool will then be collected in a bag outside the body.

Surgery for diverticular disease is typically related to disease complications, such as bowel obstruction or puncture. It may involve removing the diseased parts of the colon and reconnecting the healthy sections (bowel resection). In some cases, a bowel resection includes a colostomy.

In most cases, a colonic perforation will require surgical repair using an endoscopy, but this may not be an option for everyone. Some people may need an open bowel resection and a colostomy.

Read Next: 6 Types of Colectomy Surgery

Removal

Surgical treatment for large polyps or polyps related to FAP is often done laparoscopically (small incisions and few stitches), although there are some instances in which a part of the colon may need to be removed. Surgery will not cure FAP, and polyps may continue to form in the remaining parts of the colon. You also may need additional surgeries later on.

Some people with IBD may need surgery to remove damaged parts of the colon and rectum. Fortunately, surgery is rarely needed these days thanks to newer treatments that have reduced disease complications and the need for surgical intervention.

Surgery is often the main treatment for early-stage colon cancer. The type of surgery will depend on the cancer stage, where the cancer is located in the colon, and surgical goals. Surgical options include local excision or a procedure to remove polyps, colectomy (removal of part or all of the colon), and surgery to remove the cancer and blockages related to the cancer. 

Related: How Colon Cancer Is Treated

Summary

The descending colon is the second to last section of the colon, sitting between the transverse colon and sigmoid colon on the left side of the body. It stores food remains before they pass through to the sigmoid colon and the rectum for elimination.

Many different health conditions can affect the descending colon, including a redundant colon, colon polyps, inflammatory bowel disease, and colon cancer. Treatment for colon conditions may include lifestyle changes, medications, and resection and removal surgeries. Some conditions may not require treatment, and your provider will want to monitor your condition with routine colonoscopies.

Pain in the left part of the abdomen might indicate a problem with the descending colon. Still, because abdominal pain is a symptom of many conditions, contacting your healthcare provider for a diagnosis is vital. This is especially important if you have a family history of colon cancer or a personal or family history of colon polyps, including adenomatous polyposis.

Read the original article on Verywell Health.