10 Differential Diagnosis for Your IBS Patients: Part 1

Irritable bowel syndrome (IBS) is a condition affecting the stomach and the intestines. IBS is a common disorder present in 10-15% of people in the US. It is more common in women, but anyone can be affected.

The main symptoms of IBS are cramping, bloating, changes in the appearance of bowel movements, abdominal pain, gas, diarrhea, and constipation. It is a problem that lasts lifelong and is certainly challenging to manage. A small proportion of people with IBS present with severe symptoms. Most of the symptoms can be managed through changes in diet, lifestyle, and stress management, while more severe symptoms can be treated with medication.

Visiting a doctor is crucial if you experience a constant change in bowel habits or other symptoms of IBS. Severe symptoms such as weight loss, diarrhea at night, rectal bleeding, iron deficiency anemia, unexplained vomiting, and pain not relieved by passing gas or a bowel movement may indicate a more severe condition such as colon cancer.

[signup]

10 Differential Diagnosis for IBS: Part 1

As a Functional Medicine or Integrative Medicine practitioner, it's important to know differential diagnoses for IBS and how to rule them out. This is the first part of a two-part series with five differential diagnoses for IBS to consider. Please don't forget to check Part 2!

Inflammatory Bowel Disease

Inflammatory Bowel Disease (IBD) includes two conditions: Crohn's disease and Ulcerative Colitis. The colon is inflamed in ulcerative colitis affecting the colon's inner lining, while in Crohn's disease, the inflammation goes deeper into the intestinal wall. Also, Crohn's disease can involve the small intestine and the large intestines.

Key Stand-Out Symptoms of IBD

The main symptoms of IBD are:

• Persistent diarrhea
• Abdominal pain
• Rectal bleeding/bloody stools
• Weight loss
• Fatigue
• Mouth sores

Key Lab Test Markers For Diagnosis of IBD

IBD is diagnosed through a combination of endoscopy in Crohn's disease or colonoscopy in Ulcerative Colitis. Imaging studies, such as contrast radiography, magnetic resonance imaging, and computed tomography, are used for diagnostic purposes, too.

Laboratory testing is also crucial for evaluating IBD, monitoring disease activity, and screening for complications. The following are important tests:

Comprehensive metabolic panel (CMP): used to assess dehydration, malnutrition, and gallbladder/liver dysfunction. The CMP in an Ulcerative Colitis patient can reveal hypoalbuminemia, hypokalemia, hypomagnesemia, and elevated alkaline phosphatase.

Complete Blood Count (CBC): The test measures the total amount and proportion of different types of blood cells. A high count of leukocytes may indicate infection. Both IBD and IBS can be misdiagnosed as other conditions such as appendicitis, diverticulitis, and chronic gut infections. A CBC count can help to rule out if there is an ongoing infection in the patient.

C-reactive protein (CRP): this test can quantify levels of systemic inflammation.

Erythrocyte sedimentation rate (ESR): this test can also quantify levels of systemic inflammation. The CRP and ESR tests are commonly used to detect inflammation caused by various factors such as infection, autoimmune disorders, and others. The CRP test detects the presence of C-reactive protein, a plasma protein produced in response to inflammation or infection. In contrast, ESR measures the inflammation level in the body. Both tests typically show elevated results during acute inflammation. However, their response patterns differ. CRP increases quickly following an infection or inflammation onset and returns to normal within a week if the condition is resolved. In contrast, ESR increases slowly and remains elevated for longer.

Stool Tests For IBD Evaluation Include:

Fecal Leukocytes Stain: leukocytes indicate immune activity; the presence and precise increased numbers of leukocytes in the gastrointestinal tract can be a sign of IBD pathology

Calprotectin: This test measures the amount of calprotectin in the stool, quantifies baseline disease severity, and monitors patient response to treatment. Fecal calprotectin is a highly sensitive non-invasive marker for distinguishing between inflammatory bowel diseases (IBD) and functional disorders.

Lactoferrin: is another marker of inflammation and leukocyte activity in the intestines and is often elevated during IBD flares.

Cholecystitis

Cholecystitis involves inflammation of the gallbladder, a small organ in the abdomen. The gallbladder holds the bile that's released into the small intestine. Sometimes, gallstones can block the tube leading out of the gallbladder and cause cholecystitis. Bile duct problems, tumors, serious illnesses, and certain infections can cause cholecystitis.

Key Stand-Out Symptoms of Cholecystitis

Symptoms of cholecystitis include:

• Pain in the abdomen
• Tenderness over your abdomen when it's touched
• Pain that spreads to the back or right shoulder
• Nausea
• Gas
• Vomiting
• Fever
• Diarrhea

Key Lab Test Markers For Diagnosis of Cholecystitis

Lab tests for Cholecystitis evaluation include:

Liver tests: These are blood tests that measure liver enzymes such as alkaline phosphatase (ALP), alanine transaminase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), and bilirubin. Abnormal Liver Function Tests (LFTs) are strong predictors of the presence of common bile duct stones in patients with Acute Cholecystitis.

Pancreas function tests: To detect a blockage of the pancreatic duct by measuring the levels of blood's amylase or lipase to see inflammation of the pancreas.

CBC: The test measures the total amount and proportion of different types of blood cells. A high count of leukocytes may indicate infection.

Comprehensive Hormone Panel: This test may help the physician to understand the cause of cholecystitis. Women have double the chances of developing gallstones compared to men. Extra estrogen increases cholesterol and slows gallbladder emptying. The DUTCH test is an extensive hormone panel that looks for metabolites of sex hormones.

Cholesterol Balance Test: measures markers of cholesterol production and gastrointestinal cholesterol absorption. Too much cholesterol has been linked to gallstones which can lead to cholecystitis.

Lipid Panel: This test can help identify metabolic syndrome, a known cause of gallbladder disease.  

Stool Tests for Cholecystitis Evaluation Include:

A comprehensive stool test can help the physician to identify dysbiosis, fat absorption, pancreatic enzyme production, pathogens, and much more for an accurate picture of your gastrointestinal health. All of these factors can contribute to gallbladder disease.

Bile acid diarrhea (BAD) causes chronic diarrhea. It is characterized by an excess of bile acids in the colon that are not adequately absorbed, resulting in increased colonic motility and secretion of extra water.

Bile Acid Diarrhea

Bile acid diarrhea (BAD) causes chronic diarrhea. It is characterized by an excess of bile acids in the colon that are not adequately absorbed, resulting in increased colonic motility and secretion of extra water.

Key Stand-Out Symptoms of Bile Acid Diarrhea

Bile Acid Diarrhea symptoms include:

• Watery diarrhea
• Gas and gas pain
• Abdominal bloating
• Frequent bowel movements
• Painful stomach cramps
• Urgency and difficulty holding bowel movements in
• Fatty stools
• Indigestion

Long-term symptoms may include:

• Dehydration
• Dizziness
• Nausea
• Headaches
• Weight gain
• Weight loss
• Fatigue

Key Lab Test Markers For Diagnosis of Bile Acid Diarrhea

Three main diagnostic tests are available for the diagnosis of Bile Acid Diarrhea:

Bile Acids 48-Hour in Feces Test: Helps to evaluate patients with symptoms related to BAD. Bile acids are mostly reabsorbed in healthy individuals' intestines, and only 5% are excreted in feces. Impaired absorption of bile acids in the intestines leads to an excess of bile acids in the colon that can be detected in feces.

The 7AC4, Bile Acid Synthesis in Serum Test: Serum concentrations of 7alpha-hydroxy-4-cholesten-3-one (7aC4) are elevated in patients with BAD and can be used as a surrogate marker to the timed fecal collection.

Serum C4: Complement C4 is a biomarker of hepatic bile acids synthesis.

Microscopic Colitis

Microscopic colitis is a condition with an inflammation of the large intestine, causing watery diarrhea. The name microscopic colitis refers to the need for a microscopic examination of the colon tissue to identify it. The alterations in the tissue cannot be detected with regular imaging, such as with a colonoscopy or flexible sigmoidoscopy.

Three different subtypes of microscopic colitis have been described:

Collagenous colitis: where a thick layer of collagen develops in the colonic tissue

Lymphocytic colitis: where the white blood cells increase in colon tissue

Incomplete microscopic colitis: where there is a mix of both lymphocytic and colitis.

Key Stand-Out Symptoms of Microscopic Colitis

The main symptoms of microscopic colitis are:

• Abdominal pain, bloating, or cramps
• Nausea
• Chronic watery diarrhea
• Fecal incontinence
• Dehydration
• Weight loss

These symptoms may come and go frequently, and sometimes they resolve independently.

Key Lab Test Markers For Diagnosis of Microscopic Colitis

The most appropriate way to rule out microscopic colitis is by examining a tissue biopsy of the colon under a microscope. Additionally, two laboratory tests are used:

Comprehensive Stool Test: this test is used to rule out a possible infection as the cause of persistent watery diarrhea.

CBC: The test measures the total amount and proportion of different types of blood cells. A high count of leukocytes may indicate infection. The test is also used to look for signs of anemia.

Celiac Disease

Celiac disease (CD) refers to an immune-mediated condition where there is a reaction in the small intestine against gluten, a protein found in rye, wheat, and barley. The immune reactivity against gluten can cause tissue damage to the inner layer of the intestines and impair the absorption of nutrients. CD has no cure. But, for individuals suffering from this disease, a strict gluten-free diet is essential to treat the symptoms and ensure the healing of the intestines.

Key Stand Out Symptoms of Celiac Disease

The main symptoms associated with CD are:

• Diarrhea after eating gluten-containing foods
• Body weight loss
• Fatigue
• Anemia
• Vomiting
• Bloating
• Nausea
• Constipation

Key Lab Test Markers For Diagnosis of Celiac Disease

There are different laboratory tests for the differential diagnosis of Celiac Disease:

The Celiac Disease Profile: This a serum test that measures six antibodies that are known markers of celiac disease: Anti-tTG IgA, Anti-tTG IgG, Anti-DGP IgA, Anti-DGP IgG, Anti-Gliadin IgG, and Anti-Gliadin IgA. Note: tTG= Tissue transglutaminase, DGP= deamidated gliadin peptides

Genetic testing of HLA-DQ2: The test detects mutations in the gene HLA-DQ2 that could raise the risk of celiac disease. Close to 95% of patients with CD have an HLA-DQ2 alteration.

Genetic testing of HLA-DQ8: The test detects mutations in the gene HLA-DQ8 that could raise the risk of celiac disease.

Tissue Transglutaminase IgA: This test measures IgA antibodies to tissue transglutaminase. It is helpful for the diagnosis of possible celiac disease.

Anti-Endomysial (EMA) IgA: This is a serum test that measures the presence of endomysial antibodies (EMA). These autoantibodies cause your intestines to swell in response to gluten exposure.

Summary

Irritable Bowel Syndrome is a common condition characterized by bloating, abdominal pain, and changes in bowel habits. But, these symptoms can also be caused by other conditions such as Celiac Disease, Inflammatory Bowel Disease, Cholecystitis, Microscopic Colitis, Bile Acid Diarrhea, Hypothyroidism, Hyperthyroidism, Lactose or Fructose Intolerance, Small Intestinal Bacterial Overgrowth, or Gastritis.  

By conducting a differential diagnosis, functional medicine practitioners can exclude these other possible causes and confirm a diagnosis of IBS. This helps to ensure that patients receive the correct treatment and management plan for their specific condition, which can improve their quality of life and alleviate their symptoms.

In this first part, we discussed the background, symptoms, and laboratory tests for the differential diagnoses of Celiac Disease, Inflammatory Bowel Disease, Cholecystitis, Microscopic Colitis, and Bile Acid Diarrhea. Remember to check part two, where we discuss Hypothyroidism, Hyperthyroidism, Lactose or Fructose Intolerance, Small Intestinal Bacterial Overgrowth, and Gastritis.