Dr. John Clemmons, MD

Dr. John Clemmons Gastroenterologist

Dr. John Clemmons is a board-certified gastroenterologist providing diagnostic, preventive, and procedural care for conditions affecting the digestive system.

His clinical work includes the evaluation of abdominal pain, acid reflux, swallowing difficulties, changes in bowel habits, rectal bleeding, gastritis, haemorrhoids, pancreatic disease, and other gastrointestinal concerns. He also provides endoscopic care for patients who require a closer examination of the oesophagus, stomach, small intestine, colon, bile ducts, or pancreas.

Dr. Clemmons practises in Houston, Texas. His professional background includes internal medicine, gastroenterology, and advanced interventional endoscopy.

Patients comparing Houston digestive health physicians may also read about Dr. Shabbir Husain Jamali’s gastroenterology care.

Doctor Information

Name: Dr. John Benjamin Clemmons Jr., MD
Specialty: Gastroenterology
Additional Clinical Focus: Advanced interventional endoscopy
Board Certification: Gastroenterology
Medical School: Virginia Commonwealth University School of Medicine
Residency: Internal Medicine, VCU Health
Practice: John B. Clemmons Jr. MD, P.A.
Primary Location: Houston, Texas
Hospital Affiliations: HCA Houston Healthcare Medical Center and Houston Methodist Hospital
NPI Number: 1518997477
Accepting New Patients: Yes, according to current public provider listings
Telehealth: Patients should confirm current availability directly with the practice

About Dr. John Clemmons

Dr. Clemmons earned his medical degree from Virginia Commonwealth University School of Medicine. He then completed postgraduate residency training through VCU Health before continuing into gastroenterology.

Gastroenterologists receive specialised training in conditions involving the digestive tract and related organs. These include the oesophagus, stomach, small intestine, colon, rectum, liver, gallbladder, bile ducts, and pancreas.

Dr. Clemmons’s professional profile also lists advanced interventional endoscopy. This area of gastroenterology involves specialised procedures that may be used to diagnose or treat more complex digestive, pancreatic, or biliary conditions.

A patient may visit Dr. Clemmons because of a new digestive symptom, an abnormal laboratory result, a recommendation for colorectal cancer screening, or a condition that has not improved with initial treatment.

His role may include reviewing symptoms, examining the patient, ordering blood or stool tests, interpreting imaging, prescribing medicine, performing endoscopy, and coordinating treatment with another specialist when necessary.

Gastroenterology Services

Dr. Clemmons may evaluate and manage concerns such as:

• Abdominal pain
• Acid reflux and heartburn
• Gastritis
• Difficulty swallowing
• Nausea and vomiting
• Constipation
• Diarrhoea
• Rectal bleeding
• Haemorrhoids
• Irritable bowel syndrome
• Diverticular disease
• Inflammatory bowel disease
• Colon polyps
• Unexplained anemia
• Pancreatic conditions
• Gallbladder and bile-duct disorders
• Abnormal liver tests
• Colorectal cancer screening

The appropriate evaluation depends on the location, duration, and severity of symptoms.

Some patients may only need an office assessment and basic testing. Others may require endoscopy, colonoscopy, imaging, biopsy, or a specialised procedure.

Abdominal Pain Evaluation

Abdominal pain can originate from several organs and may have many possible causes.

Dr. Clemmons may ask:

• Where the pain occurs
• When it began
• Whether it is constant or intermittent
• Whether eating affects it
• Whether bowel movements change it
• Whether nausea or vomiting is present
• Whether fever has occurred
• Whether weight has changed
• Whether bleeding is present
• Which medicines are being taken

Possible digestive causes include gastritis, acid reflux, ulcers, gallstones, pancreatic inflammation, constipation, infection, diverticular disease, or irritable bowel syndrome.

Testing may involve blood work, stool studies, ultrasound, CT imaging, upper endoscopy, or colonoscopy.

The goal is to identify the cause rather than repeatedly treating pain without a clear diagnosis.

Acid Reflux and GERD

Gastroesophageal reflux disease, commonly called GERD, occurs when stomach contents repeatedly move back into the oesophagus.

Symptoms may include:

• Heartburn
• A sour or bitter taste
• Regurgitation
• Burning behind the breastbone
• Throat irritation
• Hoarseness
• Chronic cough
• Symptoms after meals
• Symptoms that worsen while lying down
• Difficulty swallowing

Dr. Clemmons may review meal patterns, medicine use, symptom frequency, and previous treatment.

Care may include adjustments to eating habits, acid-reducing medicine, or further testing.

Upper endoscopy may be considered when symptoms continue despite treatment or occur with swallowing problems, bleeding, anemia, vomiting, or unexplained weight loss.

Gastritis

Gastritis describes inflammation or irritation of the stomach lining.

Possible symptoms include:

• Upper abdominal discomfort
• Burning pain
• Nausea
• Bloating
• Reduced appetite
• Vomiting
• Indigestion
• Dark stool when bleeding occurs

Possible causes include infection with Helicobacter pylori, regular use of certain pain medicines, alcohol exposure, autoimmune disease, or severe physical illness.

Dr. Clemmons may recommend blood tests, stool testing, breath testing, medication review, or upper endoscopy.

Treatment depends on the cause and may involve acid-reducing medicine, antibiotics for confirmed infection, or changes to medicines that irritate the stomach.

Difficulty Swallowing

Difficulty swallowing is also called dysphagia.

A patient may feel that food moves slowly, becomes stuck, or causes discomfort while passing through the throat or chest.

Possible causes include:

• Oesophageal narrowing
• Inflammation caused by reflux
• Abnormal muscle movement
• Allergic inflammation
• Scar tissue
• A growth or mass
• Neurological disease

Dr. Clemmons may use upper endoscopy to examine the oesophagus and determine whether a visible narrowing, inflammation, or structural problem is present.

Additional swallowing or motility testing may be needed when the symptoms appear to involve muscle movement rather than a physical blockage.

Upper Endoscopy

Upper endoscopy uses a flexible camera to examine the upper digestive tract.

The examination may include the:

• Oesophagus
• Stomach
• First part of the small intestine

It may be recommended for:

• Continuing heartburn
• Swallowing difficulty
• Upper abdominal pain
• Nausea or vomiting
• Suspected ulcer
• Unexplained anemia
• Signs of digestive bleeding
• Abnormal imaging
• Monitoring an established condition

Small tissue samples may be collected during the procedure.

A biopsy does not automatically mean cancer is suspected. Tissue may also be tested for inflammation, infection, allergic disease, or other changes.

Peptic Ulcer Disease

A peptic ulcer is an open sore in the lining of the stomach or upper small intestine.

Possible symptoms include:

• Burning upper abdominal pain
• Discomfort related to meals
• Nausea
• Bloating
• Reduced appetite
• Dark stool
• Anemia
• Vomiting blood

Common causes include H. pylori infection and regular use of certain anti-inflammatory pain medicines.

Testing may involve upper endoscopy, breath testing, stool testing, or biopsy.

Treatment depends on the cause and may include acid-reducing medicine, antibiotics, and changes to medicines that increase ulcer risk.

Colonoscopy

Colonoscopy uses a flexible camera to examine the colon and rectum.

Dr. Clemmons may recommend colonoscopy for:

• Colorectal cancer screening
• Rectal bleeding
• Changes in bowel habits
• Persistent diarrhoea
• Unexplained constipation
• Abdominal pain
• Iron-deficiency anemia
• Previous colon polyps
• Abnormal imaging
• A family history of colorectal cancer

During the procedure, polyps may be removed and tissue samples may be collected.

Removing certain precancerous polyps can reduce the likelihood that they will later develop into colorectal cancer.

Colorectal Cancer Screening

Colorectal cancer screening aims to identify cancer early or detect precancerous growths before cancer develops.

Available screening methods may include:

• Colonoscopy
• Stool-based testing
• Other tests selected according to medical need

The most suitable method depends on age, symptoms, family history, previous polyps, earlier screening results, and personal risk factors.

Patients should tell Dr. Clemmons if a parent, sibling, or child has had colorectal cancer or advanced colon polyps.

Family history may change when screening should begin and how often it should be repeated.

Colon Polyps

Colon polyps are growths that form on the inner lining of the colon.

Many polyps do not cause symptoms and are found during routine screening.

During colonoscopy, Dr. Clemmons may:

• Identify polyps
• Remove suitable growths
• Collect tissue for laboratory analysis
• Mark an area requiring later treatment
• Recommend a follow-up schedule

The timing of the next colonoscopy depends on the number, size, type, and laboratory features of the removed polyps.

Not every polyp becomes cancer, but removing certain types can prevent future disease.

Rectal Bleeding

Rectal bleeding may appear as bright-red blood, darker blood mixed with stool, or black stool.

Possible causes include:

• Haemorrhoids
• Anal fissures
• Colon polyps
• Diverticular bleeding
• Inflammatory bowel disease
• Infection
• Ulcers
• Colorectal cancer
• Bleeding from higher in the digestive tract

The colour and amount of blood can provide useful information, but appearance alone cannot confirm the cause.

Dr. Clemmons may recommend laboratory testing, examination, colonoscopy, or upper endoscopy depending on the bleeding pattern and the patient’s medical risks.

Haemorrhoid Care

Haemorrhoids are swollen veins in or around the anus and rectum.

Symptoms may include:

• Bright-red bleeding
• Anal itching
• Swelling
• Discomfort
• A tender lump
• Irritation during bowel movements

Constipation and repeated straining can make symptoms worse.

Initial care may include improving stool consistency, increasing appropriate fibre intake, reviewing hydration, and using selected medicines.

Further treatment may be considered when bleeding, swelling, or discomfort continues.

Other conditions can also cause rectal bleeding, so patients should not assume that haemorrhoids are always responsible.

Constipation

Constipation may involve hard stool, infrequent bowel movements, straining, or a feeling of incomplete emptying.

Possible causes include:

• Low fibre intake
• Inadequate fluid intake
• Reduced physical activity
• Medicine
• Thyroid disorders
• Diabetes
• Pelvic floor problems
• Irritable bowel syndrome
• Narrowing in the colon
• Neurological conditions

Dr. Clemmons may review the patient’s diet, medicine, bowel pattern, and associated symptoms.

Testing may be needed when constipation begins suddenly, continues despite treatment, or occurs with bleeding, anemia, weight loss, or significant pain.

Chronic Diarrhoea

Diarrhoea that continues or repeatedly returns may have several causes.

These include:

• Infection
• Medicine side effects
• Food intolerance
• Irritable bowel syndrome
• Inflammatory bowel disease
• Celiac disease
• Microscopic colitis
• Pancreatic disease
• Thyroid disorders
• Previous digestive surgery

Dr. Clemmons may order blood tests, stool studies, colonoscopy, biopsy, or other investigations.

Patients can help by recording how often symptoms occur, whether they follow particular foods, and whether blood, fever, weight loss, or nighttime symptoms are present.

Irritable Bowel Syndrome

Irritable bowel syndrome, commonly called IBS, is associated with abdominal discomfort and changes in bowel habits.

Symptoms may include:

• Cramping
• Bloating
• Constipation
• Diarrhoea
• Alternating bowel patterns
• Urgency
• A feeling of incomplete emptying

IBS can affect daily life but does not usually cause visible damage to the digestive tract.

Diagnosis involves reviewing the symptom pattern and checking for signs that point to another condition.

Treatment may include dietary adjustments, fibre management, medicine, and care directed toward constipation or diarrhoea.

Diverticular Disease

Diverticula are small pouches that can form in the wall of the colon.

Their presence is called diverticulosis. Many patients have no symptoms.

Diverticulitis develops when one or more pouches become inflamed or infected.

Possible symptoms include:

• Lower abdominal pain
• Fever
• Tenderness
• Nausea
• Constipation
• Diarrhoea
• Changes in bowel habits

Testing may include CT imaging and laboratory studies.

Treatment depends on symptom severity and whether an abscess, obstruction, perforation, or another complication is present.

A colonoscopy may be recommended after recovery in selected patients.

Inflammatory Bowel Disease

Inflammatory bowel disease includes Crohn’s disease and ulcerative colitis.

These conditions cause continuing inflammation within the digestive tract.

Possible symptoms include:

• Persistent diarrhoea
• Rectal bleeding
• Abdominal pain
• Urgency
• Weight loss
• Tiredness
• Anemia
• Reduced appetite

Diagnosis may involve blood tests, stool testing, colonoscopy, biopsy, and imaging.

Treatment is selected according to the location and severity of inflammation, earlier response to therapy, and risk of complications.

Patients may require continuing laboratory monitoring and repeat endoscopy to assess disease control.

Pancreatic Disease

Dr. Clemmons’s public profiles list significant experience involving pancreatic disease.

The pancreas produces digestive enzymes and hormones that help control blood sugar.

Pancreatic conditions may cause:

• Upper abdominal pain
• Pain spreading toward the back
• Nausea
• Vomiting
• Unexplained weight loss
• Greasy or difficult-to-flush stool
• Abnormal pancreatic enzymes
• Changes in blood sugar
• Yellowing of the skin or eyes

Evaluation may include blood testing, CT imaging, MRI, endoscopic ultrasound, or other specialised procedures.

The correct investigation depends on the symptom pattern and the suspected condition.

Pancreatitis

Pancreatitis is inflammation of the pancreas.

Possible symptoms include:

• Significant upper abdominal pain
• Pain extending toward the back
• Nausea
• Vomiting
• Fever
• Abdominal tenderness
• Difficulty eating

Possible causes include gallstones, alcohol exposure, high triglycerides, medicine, injury, or structural conditions involving the pancreatic ducts.

Some cases require hospital treatment.

After the acute illness improves, additional testing may be needed to identify the cause and reduce the risk of recurrence.

Gallbladder and Bile-Duct Conditions

The gallbladder stores bile produced by the liver. The bile ducts carry bile into the small intestine.

Gallstones or narrowing may block the normal flow of bile.

Possible symptoms include:

• Upper-right abdominal pain
• Pain after meals
• Nausea
• Vomiting
• Fever
• Yellowing of the skin or eyes
• Dark urine
• Pale stool
• Abnormal liver tests

Ultrasound, CT imaging, MRI, or advanced endoscopic procedures may be used during evaluation.

Some conditions require surgery, while others may be treated through an endoscopic procedure.

Advanced Interventional Endoscopy

Advanced interventional endoscopy uses specialised instruments and imaging techniques to diagnose or treat selected digestive conditions without traditional open surgery.

Depending on the diagnosis and Dr. Clemmons’s current procedural services, this area may involve evaluation of:

• Pancreatic disease
• Bile-duct obstruction
• Gallstones within the bile duct
• Digestive-tract narrowing
• Complex polyps
• Internal bleeding
• Abnormal imaging findings
• Selected cysts or masses

The exact procedure should be confirmed directly with the practice because advanced endoscopic services vary by physician, hospital, and clinical setting.

Endoscopic Ultrasound

Endoscopic ultrasound combines a flexible endoscope with ultrasound imaging.

It can produce detailed images of structures near the digestive tract, including the:

• Pancreas
• Bile ducts
• Gallbladder
• Oesophageal wall
• Stomach wall
• Nearby lymph nodes

It may be considered when ordinary imaging does not provide enough information.

In selected cases, a needle can be guided through the endoscope to collect a tissue or fluid sample.

ERCP

Endoscopic retrograde cholangiopancreatography, commonly called ERCP, is a specialised procedure used mainly to treat conditions involving the bile ducts or pancreatic ducts.

It may be used to:

• Remove bile-duct stones
• Open a narrowed duct
• Place a temporary stent
• Collect samples
• Treat selected leaks
• Improve blocked bile flow

ERCP has important benefits but also carries risks, including inflammation of the pancreas, bleeding, infection, and perforation.

It is normally recommended when the expected benefit is greater than the procedural risk.

Unexplained Anemia

Iron-deficiency anemia may sometimes result from slow blood loss within the digestive tract.

Dr. Clemmons may investigate anemia when a patient has:

• Low haemoglobin
• Low iron levels
• Tiredness
• Weakness
• Shortness of breath
• Dark stool
• Visible bleeding
• No clear non-digestive cause

Evaluation may include colonoscopy, upper endoscopy, laboratory testing, or examination of the small intestine.

Finding the source is important because replacing iron alone may not correct continued blood loss.

Preparing for Colonoscopy

A clean colon is essential because retained stool can hide polyps or other abnormalities.

Preparation may involve:

• Following dietary instructions
• Drinking a prescribed bowel-cleansing solution
• Adjusting selected medicines
• Avoiding food during the stated period
• Arranging transportation
• Informing the office about medical conditions

Patients should tell the practice if they use:

• Blood thinners
• Diabetes medicine
• Insulin
• Iron supplements
• Weight-management injections
• Medicines affecting bowel movements
• Other prescriptions requiring special instructions

Patients should not stop prescribed medicine unless the procedural or prescribing team provides clear directions.

Preparing for Upper Endoscopy

Patients undergoing upper endoscopy are normally asked to avoid food and drink for a specified period.

They should provide information about:

• Current medicines
• Blood thinners
• Diabetes treatment
• Allergies
• Previous reactions to sedation
• Heart or lung conditions
• Sleep apnoea
• Earlier digestive procedures

Transportation is commonly required when sedation is used because the patient should not drive afterward.

Sedation and Monitoring

Endoscopic procedures are often performed with sedation to improve comfort.

The medical team may monitor:

• Heart rate
• Blood pressure
• Breathing
• Oxygen level
• Response to sedation

Patients should follow all fasting and medication instructions carefully.

They should also arrange for a responsible adult to provide transportation and follow the discharge instructions after the procedure.

Biopsy and Laboratory Testing

During endoscopy or colonoscopy, Dr. Clemmons may collect a small tissue sample.

A biopsy may help diagnose:

• Inflammation
• Infection
• Celiac disease
• Microscopic colitis
• Barrett’s oesophagus
• Precancerous changes
• Cancer
• Other digestive conditions

Patients usually do not feel the biopsy being taken from inside the digestive tract.

Results are reviewed after the laboratory examines the tissue. Follow-up recommendations depend on the findings.

Preparing for a Gastroenterology Appointment

Patients can prepare by bringing:

• A current medicine list
• Previous colonoscopy reports
• Earlier endoscopy reports
• Biopsy or pathology results
• Recent blood tests
• Stool-test results
• Imaging reports
• Hospital discharge documents
• A list of allergies
• Family history of digestive disease
• Questions about testing or treatment

It is helpful to explain when symptoms began, how often they occur, and whether meals or bowel movements affect them.

Patients should also mention rectal bleeding, black stool, unexplained weight loss, swallowing difficulty, jaundice, or continuing vomiting.

Coordinated Digestive Care

Digestive conditions sometimes require cooperation between several healthcare professionals.

Dr. Clemmons may coordinate with:

• Primary care physicians
• General surgeons
• Colorectal surgeons
• Liver specialists
• Pancreatic specialists
• Oncologists
• Radiologists
• Pathologists
• Nutrition professionals
• Other gastroenterologists

Coordination is particularly important when a patient has pancreatic disease, bile-duct obstruction, abnormal imaging, significant bleeding, or a condition requiring both endoscopic and surgical care.

Patients may also compare digestive services with Dr. Ramakrishna Chava’s gastroenterology profile.

Patient-Centered Gastroenterology

Dr. Clemmons provides digestive healthcare based on each patient’s symptoms, medical history, family risk, test results, previous treatment, and screening needs.

His clinical work may include abdominal pain evaluation, reflux treatment, colonoscopy, upper endoscopy, colorectal cancer screening, polyp removal, pancreatic assessment, bile-duct care, and advanced interventional endoscopy.

Patients should confirm current appointment availability, accepted insurance plans, procedure locations, hospital participation, telehealth options, and referral requirements directly with John B. Clemmons Jr. MD, P.A.