Conditions & Treatments


Gastroenterologist in Orange County, CA

Dr. Kevin Ashby is a board-certified, UCLA fellowship-trained gastroenterologist in Orange County with decades of experience treating a variety of acute and chronic digestive disorders in adults. He offers advanced treatments and minimally invasive procedures to help you get back to living your best life.

Get the advanced, effective care you need from a highly respected doctor you can trust. Call the office of Dr. Kevin Ashby today at (949) 238-8050 or request an appointment online. He sees patients in Irvine, Laguna Hills, and Foothill Ranch, California.

Common Gastroenterology Conditions

Dr. Ashby treats a spectrum of GI conditions, including those that affect the upper GI tract (esophagus, stomach, and duodenum [first part of the small intestine]) and lower GI tract (small intestine, large intestine [colon], rectum, and anus). He offers effective treatment for conditions such as:

Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome is a common disorder of the digestive system that often includes symptoms such as bloating, gas, abdominal pain, constipation, and diarrhea for a prolonged period of time.

Although the underlying causes are not well understood, it is more common in women and appears to be associated with many factors, including emotional stress. While there is no cure for IBS, symptoms may be managed with medications along with diet and lifestyle changes.

GERD, Heartburn, and Acid Reflux

GERD is a digestive disorder in which stomach contents and acids travel back up the esophagus (the tube that moves food from your throat to your stomach) causing heartburn or acid indigestion. GERD can be prevented and is typically treated with lifestyle changes and medications. If ignored, however, GERD can result in serious medical complications.

Abdominal Pain

Many gastrointestinal conditions can cause abdominal pain, including functional disorders such as constipation, diarrhea, and IBS, as well as inflammatory bowel disease (Crohn’s disease and ulcerative colitis). Dr. Ashby is an expert in diagnosing causes of abdominal pain. He will work to correctly diagnose and treat the causes of your abdomnal pain.

Gallbladder Disease/Gallstones

Gallbladder disease occurs when inflammation or gallstones block the flow of bile from the gallbladder. Bile is a fluid that breaks down fat during the digestive process. An imbalance of bile components can cause the formation and accumulation of gallstones. When this happens, the gallbladder can become painful and inflamed.

Treatment depends on the severity of your symptoms. Some people may not need any treatment at all while others may require surgery to remove the gallbladder and gallstones.

Hiatal Hernia

Ahiatal hernia occurs when a portion of the stomach bulges into the chest area through an opening for the esophagus known as the hiatus, which can cause abdominal discomfort and heartburn.

This common GI condition is treated with lifestyle changes and medications.

Colon Cancer (Colorectal Cancer)

Colorectal cancer is a cancer located in the colon (the large intestine) and/or the rectum (the end of the digestive tract). It develops from colon polyps, or small growths on the inside lining of the large intestine. Colon polyps are easily detected and removed during a colonscopy.

Colorectal cancer treatment depends on the stage of the cancer. The surgical removal of cancer is the primary treatment for colon cancer. Advanced cancers may need additional treatments such as radiation or chemotherapy. Early detection and treatment is key to a successful outcome.

Stomach Cancer

Stomach cancer occurs when cells in the stomach grow abnormally and out of control. It most frequently occurs in men over 40 years old, although it relatively rare in the United States. Treatment for stomach cancer depends on the stage and location of the cancer. Surgery to remove the cancer cells is the primary treatment, along with radiation therapy and chemotherapy.

Peptic Ulcers

A peptic ulcer is a sore in the lining of the stomach (gastric ulcer) or the first part of the small intestine (duodemal ulcer). Ulcers form from an imbalance between the acids and pepcin enzymes that break down food in the upper GI tract, which causes the stomach or intestinal lining to become inflamed and weak.

People who use nonsteroidal anti-inflammatory medications (NSAIDS) such as aspirin, ibuprofen, and naproxen for long periods of time are more likely to get peptic ulcers. Some ulcers may not need treatment while others may require lifestyle changes or medications. If an ulcer bleeds, you may need an upper GI endoscopy or surgery to stop it.


Constipation is a disorder in which bowel movments become difficult or infrequent. It may be casued by a poor diet, poor bowel habits, physical inactivity, and older age. While uncomfortable, constipation is rarely linked to a serious medical condition. Constipation is treated with diet and lifestyle changes, and in some cases, medications.


Diarrhea is a condition in which bowel movements become watery and loose. It is usually caused by a viral infection such as the stomach flu, bacterial infection, or an underlying medical condition. Most cases of diarrhea are treated at home and resolve in a few days.


Common Treatments for GI Disorders

When treating a GI condition, Dr. Ashby’s goal is to restore his patients’ digestive health as quickly and efficiently as possible. When appropriate, he will do so with minimally invasive diagnostic testing and procedures, some of which can be done in our office. Other procedures may need to be performed on an outpatient basis at an endoscopy center or as an inpatient at the hospital. Explore the topics below to learn more.


A colonoscopy is a nonsurgical outpatient procedure that uses a scope (a long, thin tube with a light and a viewing instrument) to view the inside lining of the colon (large intestine) and rectum. Most frequently used as a screening tool for colon polyps or colon cancer, a colonoscopy may also be used to identify digestive or inflammatory disease.

During the procedure, Dr. Ashby can obtain a tissue sample or biopsy, remove colon polyps, or perform specialized laser surgeries. Download colonoscopy prep forms here.

Upper Endoscopy

An upper gastrointestinal (GI) endoscopy, also called an esophagogastroduodenoscopy (EGD), is a nonsurgical outpatient procedure that uses a scope (a long, thin tube with a light and a viewing instrument) to view the esophagus, stomach, and duodenum (first part of the small intestine). It allows a gastroenterologist to examine the inside of the upper GI tract for bleeding, tumors, polyps, diseases, and other digestive disorders.

During the procedure, Dr. Ashby can obtain a tissue sample or biopsy, treat bleeding, or remove polyps or obstructions. Download endoscopy prep form here.

Capsule Endoscopy

This outpatient procedure allows a gastroenterologist to visualize the small intestine. It involves swallowing a small capsule that contains a tiny camera and light source that takes pictures of your small intestine as it travels through your GI tract.

Capsule endoscopy can help detect gastrointestinal (GI) bleeding, Crohn's disease, iron-deficiency anemia, small bowel tumors, small bowel injury due to nonsteroidal anti-inflammatory use, and malabsorption disorders such as celiac disease.

Flexible Sigmoidoscopy

A flexible sigmoidoscopy is a nonsurgical outpatient procedure that uses a scope (a long, thin tube with a light and a viewing instrument) to view the inside lining of the rectum and lower section of the colon. It allows a gastroenterologist to examine the lower GI tract for cancer, polyps, hemorrhoids, and other digestive disorders.

During the procedure, Dr. Ashby can obtain a tissue sample or biopsy any remove polyps.


ERCP, which stands for endoscopic retrograde cholangiopancreatography, is an outpatient procedure performed during an upper endoscopy. It is used to view, diagnose, and treat problems in the bile ducts, pancreas, liver, and gallbladder, such as tumors, pancreatitis, pancreatic cancer, or gallstones.

Hydrogen and Urea Breath Tests

A hydrogen breath test is used to detect lactose intolerance (the inability to digest lactose, the sugar found in milk) or bacterial overgrowth in the small intestine. A urea breath test is used to detect Helicobacter pylori (H. pylori), a bacteria found in the stomach that can cause peptic ulcers. These tests are done in our office.

Esophageal Manometry (Motility Testing)

Esophageal manometry (also known as a motility test or study) is performed to see if the esophagus (the tube that moves food from your throat to your stomach) is contracting and relaxing properly. It is typically performed to help diagnose GERD or swallowing problems.

pH Impedance Testing

This test is considered the gold standard for diagnosing GERD. It may also be referred to as esophageal pH monitoring or 24-hour ambulatory reflux monitoring. For a 24-hour period, you will wear a thin, flexible, disposable probe that is inserted through the nose and throat into the esophagus and connected to a monitoring device.

During this time, the test measures how much stomach acid backs up into the esophagus, how long it stays there, and the strength of your stomach acid. The probe is removed the following day and the data is downloaded from the monitoring device. Dr. Ashby will analyze the data to help make a diagnosis.


Words from our patients

  • Google

    "I have been seeing Dr Ashby and his staff for nearly two years! He is very knowledgeable, professional, and importantly caring."

    Duke H.
  • Google

    "This is a Doctor who doesn't stop treating you when leave his office. He has called on weekends and hoildays just to make sure I was ok. We need more like this doctor."

    Dale M.
  • Yelp

    "Beyond EXCELLENT. Dr. Ashby is very conscientious. He followed up with me via phone and text several times [even after hours] relative to changes in my condition."

    Wayne V.
  • Healthgrades

    "Dr. Ashby made me feel comfortable, was knowledgeable and explained everything he thought and his recommendations. Very professional and personable."

    Brenda M.
  • Yelp

    "Dr. Ashby is the best doctor I have ever been to. He is extremely nice and caring. He explains everything to you and soothes your concerns."

    Nancy M.
  • Healthgrades

    "What a wonderful doctor. Called on a holiday to see how I was treated in the office. Could not believe it. Easy to talk to and very happy I found Dr. Ashby."

    Martin S.